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Carlos E. Cordova
The Lakes of the Basin of Mexico Dynamics of a Lacustrine System and the Evolution of a Civilization
The Lakes of the Basin of Mexico
Carlos E. Cordova
The Lakes of the Basin of Mexico Dynamics of a Lacustrine System and the Evolution of a Civilization
Carlos E. Cordova Department of Geography Oklahoma State University Stillwater, OK, USA
ISBN 978-3-031-12732-8 ISBN 978-3-031-12733-5 (eBook) https://doi.org/10.1007/978-3-031-12733-5 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland
Preface
On November 3, 1519, Spanish conquistador Hernan Cortes and his army reached a mountain pass in the Sierra Nevada from where they contemplated a valley with of lakes and insular settlements in them. They were the first Europeans to see Anahuac, the Aztec name of the Basin of Mexico (La Cuenca de México) or the Valley of Mexico (El Valle de México). What Cortés and his army saw was an aquatic landscape with its mountainous surroundings, where several civilizations have flourished in the past. The last of them was a civilization that had grown in strong connection with aquatic environments to the point of transforming them for agriculture and habitation. Unfortunately, the incompatibility of the Spanish economic activities and mindset led to the gradual disappearance of the lakes and most of the vestiges of the cultures that inhabited them. Nevertheless, the lakes of the Basin of Mexico have attracted the interest of scholars from a variety of disciplines such as archaeology, geology, history, geography, and biology. Despite a good number of scientific and historical research, our knowledge of the former lakes is limited and sometimes based on isolated facts and assumptions without corroboration. Such assumptions have led to the belief that the former lakes were static bodies of water, which contrasts with the highly dynamic hydrological system far from the romanticized landscape that is often portrayed in the mainstream media, social media outlets, museums, popular literature, and, unfortunately, also in some scholarly publications. Certainly, the lakes and their civilizations that lived in them, especially during the Postclassic period, were grandiose, but not in the romanticized way they are often. The aquatic environment was generous, but the reality of living in an aquatic environment was a different one and not the idyllic environment often depicted in the media and popular literature. In this book, I present the case on how complex the lakes were in terms of their ever-changing dynamics and abrupt surprises, which was a challenge to its settlers. Thus, as the title Dynamics of a Lacustrine System and the Evolution of a Civilization denotes, the lakes were dynamic hydrological systems, and the ancient societies and civilizations of the Basin of Mexico evolved with them.
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After decades of research on the long-term history of the former lakes of the Basin of Mexico and the societies that interacted with them, I have decided to put together information drawn from a variety of sources and corroborate them across different various disciplines and integrate them into a critical and comprehensive view. With the collected information, I attempt to elaborate on synthetic models that first explain the functioning of the ancient lakes (i.e., lacustrine dynamics) and second explain the integration of human-made features and economies within the lacustrine dynamics. Despite the focus on the evolution of human societies living in the Basin of Mexico in the past few millennia, I consider important to look to the natural history of lakes as far back as the Late Pleistocene. Furthermore, I consider that even looking at tectonic and volcanic events in deep geological times is important to understand the geologic legacies that influenced the use of the lakes in recent times. The book is divided into 3 parts and 15 chapters. The first part (Chaps. 1, 2, 3, 4, 5 and 6) presents a historical introduction to the study of the Basin of Mexico and its lakes, the sources, and resources for studying the former lakes, the modern environmental context, and an overview of geological aspects necessary to understand the evolution of the lakes of the Basin of Mexico. The second part (Chaps. 7, 8, 9 and 10) focuses directly on the geography and the natural and cultural dynamics of the former lakes, including a model that explains the short- and long-term functioning of the lakes. This model serves as the basis to describe historical facts described in the subsequent chapters. The third part (Chaps. 11, 12, 13, 14 and 15) discusses the evolution of the lakes in the context of cultural changes. Although the discussion follows a chronological order, from the time of hunter-gatherer societies to the present, it focuses on the particular issues or facts that need proper or alternative interpretations. Although most of the chapters constitute a review of results and hypotheses produced by past research, the main contribution of the volume is the creation of three interpretive models of the evolution of the lakes in relation to human development. Thus, models produced here constitute a dynamic natural model (Chap. 8), a basic dynamic cultural-natural model for lake appropriation (Chap. 10), a specific model to explain the adaptation of human societies (Chap. 12), and an environmental model to explain the origin and development of Mexico-Tenochtitlan (Chap. 13). The models proposed here are idealized and diagrammatic. In some cases, they may represent a guide for future research, in others, the conceptual framework for computer simulation models of hydrological and environmental processes in space and time. With that said, I expect that the treatment of the subjects and issues in this book and the interpretive models I propose serve as the basis for future research. I would like to make clear that this volume is intended only for archaeologists, geologists, geographers, historians, interested in the subject, but also engineers, city planners, and nature enthusiasts who would like to inform themselves on the variety of topics concerning the natural and cultural history of the Lakes of the Basin of Mexico. Likewise, I recommend the book to those interested in the broad topics relevant to global environmental issues, especially related to the geological evolution of lacustrine basins, shallow lake dynamics, and evolution of human societies
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in lakes and aquatic environments. Consequently, given the multidisciplinary nature of this book, a large number of technical words, especially in geosciences, appear. Although I have added explanations in some of them throughout the book, I strongly encourage readers to search any technical terms on the Web. Stillwater, OK, USA Carlos E. Cordova
Notes on Usage, Place Names, and Chronology
Throughout the book, I use the name “Basin of Mexico” (i.e., Cuenca de México) instead of the more popular, but less academically used, “Valley of Mexico” (i.e., Valle de México). To avoid repetitions of the term, I use the full name Basin of Mexico at the beginning of each section, and subsequently refer to it just as “the Basin.” Likewise, the term Desagüe appears very often in the book. The term desagüe translates as “draining” or “drainage,” but its use here in capital letters encapsulates the four-century long effort to desiccate or drain the lakes out of the Basin. Particular works of relevant importance to the Desagüe would be left in Spanish, for example, Gran Canal del Desagüe, Tajo de Nochistongo, and Túnel de Tequixquiac, among others. In such case, terms like “tajo” and “tunel” would appear in the glossary at the end of the book. The names of local and traditional objects, techniques, and abstract concepts in Spanish and Nahuatl include terms such as chinampa, tlatel, embarcadero, and tequesquite, among others. They have been included in a glossary at the end of the book. However, in many cases, short explanations follow the first mention of the term in the text. A considerably large number place names in Spanish and Nahuatl appear in this book. Place names in Nahuatl are particularly problematic because their spellings vary in the literature and old maps. For example, Texcoco (the name of the city and the lake) is often spelled “Tetzcoco,” or” Tetzcuco.” Therefore, I use the official spelling used in the INEGI maps, unless I am transcribing a direct quotation from a document, in which case the name will appear as in the original. In some cases, given the historic context, I use the original Nahuatl names, followed by the Hispanicized official name in parentheses. Examples are Huitzilopochco (Churubusco), Atlacolohuayan (Tacubaya), and Tlacopan (Tacuba), which are the original Aztec names. The names of the lakes in the literature and on maps have changed over time (cf. Chap. 7). The general use here is the modern one to refer to the former lakes: Zumpango, Xaltocan, Texcoco (or Mexico-Texcoco), Xochimilco, and Chalco (see,
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e.g., the maps in the figures in Chap. 1). However, like in the case of place names, other names may be used when citing documents or reproducing maps. The use of archaeological periods refers to the chronology discussed in Chap. 2, Table 2.2 and Fig. 2.1. Archaeological periods and their divisions are capitalized (e.g., Late Aztec). Whenever it is convenient, ceramic phases (ceramic complexes in Fig. 2.1) are used. In these cases, Colonial (1521–1821) and Independent (1821– present) are capitalized when they are followed by period as to give continuity to usage of capital letters for previous chronological periods.
Acknowledgments
There are so many people and institutions that I would like to thank that I am sure some may have been left out. First, I would like to thank Dr. Jose Lugo Hubp, my undergraduate and master’s advisor at UNAM, to whom I dedicate this book. I am also indebted to my friends and colleagues Lorenzo Vazquez-Selem and Jose Juan Zamorano, both from the Institute of Geography-UNAM, and Federico Mooser for introducing me to the Quaternary of the Basin of Mexico. I would like also to mention the encouragement and support of the late Dr. Karl W. Butzer, my PhD advisor at the University of Texas. My special thanks to archaeologist Luis Morett-Alatorre (University of Chapingo), who has been very supportive of my research in many ways and from whom I learned a great deal in matters of field research, archaeology, and history. The same goes for Dr. Charles Frederick, a collaborator and a friend who shares my interest in geoarchaeology and the Basin of Mexico. I am also indebted for comments and cooperation in this project to the late Dr. Jeff Parsons (University of Michigan). Other persons to whom I am indebted for their collaboration, suggestions, and comments are Lorena Gamez (INAH), Miguel Medina-Jaén (INAH), Guillermo Acosta (IIA-UNAM), Emily McClung (IIA-UNAM), Christopher Morehart (Arizona State University), Dr. Teresa Rojas-Rabiela (CIESAS), and many other colleagues with whom I have exchanged ideas and suggestions. I would also like to thank Frances Griffin for her support in improving the manuscript of this book. I am thankful to the staff at the archives at the Archivo Técnico del Consejo de Arqueologia del INAH, and mainly to José (Pepe) Ramirez for his guidance and suggestions, and to the staff of the Archivo y Biblioteca Angel Garcia Cook of Salvamento Arqueologico for their help and support during the long hours of archival research. I thank also the staff of the Nettie L. Benson Latin American Collection in Austin, Texas, for their support. From a personal point of view, I am also grateful to Frances Griffin for her help with proofreading, and to the people of Balanced Coffee Company in Stillwater for their hospitality during the long hours of writing.
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Contents
Part I The Lakes: Approaches and Records of Their Past and Present 1
Basin of Mexico and Its Lakes: Approaches and Research Questions�������������������������������������������������������������������������������������������������� 3 1.1 Defining a Regional Research Subject���������������������������������������������� 3 1.2 Scientific and Humanistic Approaches �������������������������������������������� 6 1.2.1 The Development of a Scientific Approach�������������������������� 6 1.2.2 The Emerging Interest in the Past ���������������������������������������� 8 1.2.3 Archaeology, Anthropology, and Ethnohistory�������������������� 9 1.2.4 Hydrology and Hydraulics���������������������������������������������������� 10 1.2.5 Geosciences and Civil Engineering�������������������������������������� 11 1.2.6 Quaternary Geology and Geoarchaeology���������������������������� 12 1.2.7 Paleoecology and Paleolimnology���������������������������������������� 13 1.2.8 Cultural Ecology ������������������������������������������������������������������ 13 1.2.9 Environmental History���������������������������������������������������������� 14 1.2.10 Ecology and Conservation���������������������������������������������������� 15 1.3 Persistent Views Regarding the Former Lakes���������������������������������� 16 1.3.1 Unfounded Paradigms���������������������������������������������������������� 16 1.3.2 The Configuration of the Former Lakes on Maps���������������� 17 1.3.3 A View from the City Versus a View from the Lakes ���������� 19 1.4 Thematic Research Questions���������������������������������������������������������� 20 1.4.1 The Evolution and Geographic Characteristics of the Prehistoric Lakes�������������������������������������������������������� 21 1.4.2 Long- and Short-Term Lacustrine Dynamics ���������������������� 21 1.4.3 Lake Dynamics and Human Appropriation of Lacustrine Spaces ������������������������������������������������������������ 22 1.4.4 The Origin and Evolution of Tenochtitlan and Its Hydraulic System������������������������������������������������������ 22 1.4.5 The Lakes During the War of Conquest�������������������������������� 23 1.4.6 Spanish and Independent Mexican Attitudes Toward the Lakes ������������������������������������������������������������������������������ 23 xiii
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Resources for Reconstructing the Ancient Lakes���������������������������������� 25 2.1 Diverse Sources of Information�������������������������������������������������������� 25 2.2 The Archaeological Record�������������������������������������������������������������� 25 2.2.1 The Preceramic Period���������������������������������������������������������� 25 2.2.2 The Ceramic Period�������������������������������������������������������������� 28 2.2.3 Recovery of the Archaeological Record ������������������������������ 30 2.2.4 Archaeology in the Urbanized Areas������������������������������������ 34 2.2.5 The Artifactual Record of Past Aquatic Lifeways���������������� 36 2.3 The Historical and Ethnohistorical Record�������������������������������������� 38 2.3.1 Codices and Representations of Lacustrine Geography ������ 38 2.3.2 Chronicles and Descriptions of Daily Life �������������������������� 39 2.3.3 Written Documents and Cartographic Sketches ������������������ 40 2.3.4 Historical Landmarks and Historical Photography�������������� 43 2.4 The Modern Environment and the Ethnographic Record ���������������� 44 2.4.1 Features in the Modern Landscape as Clues to the Past ������ 44 2.4.2 The Ethnographic Record and Ethnoarchaeology���������������� 45 2.5 GIScience, Virtual Realities, and Modeling�������������������������������������� 45 2.5.1 GIS and Remotely Sensed Imagery�������������������������������������� 45 2.5.2 Virtual Realities of the Past�������������������������������������������������� 46 2.5.3 Modeling Past Environments and Their Processes �������������� 46
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Geographic Context and the Modern Environment ���������������������������� 49 3.1 General Physiographic Background ������������������������������������������������ 49 3.1.1 Location and Major Landforms�������������������������������������������� 49 3.1.2 Topographic Characteristics of the Lacustrine Basins���������� 51 3.2 Climate���������������������������������������������������������������������������������������������� 54 3.2.1 General Climatic Patterns ���������������������������������������������������� 54 3.2.2 Temperatures������������������������������������������������������������������������ 56 3.2.3 Precipitation and Moisture Balance�������������������������������������� 57 3.2.4 Wind Patterns������������������������������������������������������������������������ 59 3.3 Hydrology ���������������������������������������������������������������������������������������� 60 3.3.1 The Current Drainage System���������������������������������������������� 60 3.3.2 The Modern Hydrological Record and the Former Lake Basins�������������������������������������������������������������������������� 62 3.4 Regional Ecosystems and Soils�������������������������������������������������������� 64 3.4.1 Vegetation Communities and Floristic Composition������������ 64 3.4.2 Fauna������������������������������������������������������������������������������������ 66 3.4.3 Soils and Landscapes������������������������������������������������������������ 66 3.5 Lacustrine Flora and Fauna�������������������������������������������������������������� 68 3.5.1 Aquatic, Subaquatic, and Halophytic Vegetation������������������ 68 3.5.2 Fish���������������������������������������������������������������������������������������� 70 3.5.3 Amphibians and Reptiles������������������������������������������������������ 72 3.5.4 Aquatic Avifauna������������������������������������������������������������������ 72 3.5.5 Other Living Forms in the Aquatic Environments���������������� 73
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Geological Evolution of the Lacustrine Basins�������������������������������������� 75 4.1 The Geological Record �������������������������������������������������������������������� 75 4.1.1 Stratigraphic Sequences�������������������������������������������������������� 75 4.1.2 Deep Cores���������������������������������������������������������������������������� 76 4.1.3 Medium-Depth Cores����������������������������������������������������������� 78 4.1.4 Shallow-Depth Cores������������������������������������������������������������ 80 4.1.5 Subsurface Cores and Exposures������������������������������������������ 80 4.1.6 Lithostratigraphic Chronologies ������������������������������������������ 81 4.1.7 Surface Geology and Tectonic Structures���������������������������� 82 4.1.8 Geotechnical Records ���������������������������������������������������������� 83 4.2 The Tectonic and Volcanic Background�������������������������������������������� 85 4.2.1 The Basin of Mexico in the Regional Tectonic Context ������ 85 4.2.2 Summarized Sequence of Geologic Events�������������������������� 88 4.3 Formation and Integration of the Lacustrine Basins������������������������ 89 4.3.1 Tectonic Evolution Models and Biogeographic Patterns������ 89 4.3.2 The Origin and Integration of the Pleistocene Endorheic Basins������������������������������������������������������������������ 91 4.4 Geological Legacies in the Lacustrine Realm���������������������������������� 93 4.4.1 The Legacy of Deep Faulting������������������������������������������������ 93 4.4.2 The Volcanic Legacy������������������������������������������������������������ 94 4.4.3 Minerals in the Lacustrine Basins���������������������������������������� 95
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Recent Sediments and Landforms���������������������������������������������������������� 97 5.1 Sediments, Landforms, and Their Interpretation������������������������������ 97 5.1.1 The Lacustrine Basins in the Quaternary������������������������������ 97 5.1.2 Geomorphic Features in the Lacustrine Realm�������������������� 98 5.2 Sedimentation in the Lacustrine Basins�������������������������������������������� 99 5.2.1 Lacustrine and Palustrine Sediments������������������������������������ 99 5.2.2 Gaps and Disturbance of Lacustrine Stratigraphic Sequences������������������������������������������������������������������������������ 103 5.3 Lakeshore and Transitional Environments���������������������������������������� 106 5.3.1 Beach and Other Lakeshore Deposits ���������������������������������� 106 5.3.2 Fluvial Environments and Their Stratigraphic Sequences���� 112 5.3.3 Fluvio-lacustrine Deposits���������������������������������������������������� 114 5.4 Pedogenesis and Soil Patterns in the Dry Lakebeds ������������������������ 119
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Lacustrine Change in the Late Quaternary������������������������������������������ 123 6.1 Chronological Schemes�������������������������������������������������������������������� 123 6.1.1 Stratigraphic and Chronological Schemes in the Quaternary of the Basin of Mexico���������������������������� 123 6.1.2 The Impact of Absolute Chronologies���������������������������������� 124 6.1.3 Tephrochronology ���������������������������������������������������������������� 125 6.2 Paleolimnological Research in the Basin of Mexico������������������������ 128 6.2.1 Research Localities �������������������������������������������������������������� 128 6.2.2 Paleolimnological Research�������������������������������������������������� 130 6.2.3 Multiproxy Paleolimnological Reconstructions ������������������ 130
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6.3 Background for Paleoclimatic Change �������������������������������������������� 134 6.3.1 Correlation Across Paleoclimatic Records���������������������������� 134 6.3.2 Glacial Chronologies and Lacustrine Changes �������������������� 137 6.3.3 Vegetation Changes Around the Lakes �������������������������������� 139 6.3.4 Paleosols and Paleoclimatic Change������������������������������������ 140 6.3.5 High-Resolution Records������������������������������������������������������ 140 Part II The Lakes: Geography and Environmental Dynamics 7
Geographic Sketch of the Historic Lakes������������������������������������������ 145 A 7.1 Cartographic Representations of the Lakes�������������������������������������� 145 7.1.1 The Former Lakes in Modern Maps ������������������������������������ 145 7.1.2 Cartographic References for Reconstructing the Ancient Lakes ������������������������������������������������������������������������������������ 146 7.2 An Ever-Changing Lacustrine Geography���������������������������������������� 150 7.2.1 The Lakes and Their Changing Shorelines �������������������������� 150 7.2.2 Connected or Disconnected Lakes?�������������������������������������� 151 7.2.3 Lagos or Lagunas?���������������������������������������������������������������� 153 7.2.4 Shifting Names and Shifting Lakes�������������������������������������� 155 7.3 A Geography of the Historic Lakes�������������������������������������������������� 157 7.3.1 The Lacustrine Complex������������������������������������������������������ 157 7.3.2 The Northern Lakes: Zumpango and Xaltocan�������������������� 159 7.3.3 Lake Texcoco������������������������������������������������������������������������ 162 7.3.4 The Southern Lakes: Chalco and Xochimilco���������������������� 164 7.3.5 Recapping on the Geographic Nature of the Former Lakes�������������������������������������������������������������� 166
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Models of Lacustrine Dynamics and Environments ���������������������������� 167 8.1 Conceptual Framework and Methodological Approaches���������������� 167 8.1.1 Characterization of the Basin of Mexico’s Lacustrine Systems �������������������������������������������������������������������������������� 167 8.1.2 Approaches to Reconstructing the Dynamics of Vanished Lakes ���������������������������������������������������������������� 168 8.2 Shallow Lacustrine Systems ������������������������������������������������������������ 169 8.2.1 General Characteristics of Shallow Lakes���������������������������� 169 8.2.2 Wind, Currents, and Waves: A Model���������������������������������� 173 8.2.3 Effects of Storms and Seiches���������������������������������������������� 175 8.2.4 Fluvio-Lacustrine Environments: Deltaic Systems�������������� 176 8.3 Natural Features in the Lacustrine Realm���������������������������������������� 182 8.3.1 Islands, Shoals, and Tulares�������������������������������������������������� 182 8.3.2 Mudflats, Saltflats, Marshes, and Swamps���������������������������� 183 8.3.3 Inlets (Esteros)���������������������������������������������������������������������� 183 8.3.4 Springs���������������������������������������������������������������������������������� 185 8.4 Ecological Expression of Depositional Environments���������������������� 185 8.4.1 Geomorphological and Ecological Diversity Across the Former Lake Basins�������������������������������������������������������� 185
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8.4.2 Low-Gradient Littoral Environments������������������������������������ 187 8.4.3 High-Gradient Littoral Environments���������������������������������� 188 8.4.4 Mid-Lake Environments ������������������������������������������������������ 188 8.5 Dynamics of the Basin’s Lacustrine Complex���������������������������������� 189 8.5.1 Physico-Geographical Factors���������������������������������������������� 189 8.5.2 Seasonal, Interannual, Decadal, and Centennial Lacustrine Dynamics������������������������������������������������������������ 190 9
Cultural Features in the Lacustrine Realm ������������������������������������������ 195 9.1 Cultural Features: Environmental Context and Basic Structures������ 195 9.1.1 The Lacustrine Context of Human-Made Features�������������� 195 9.1.2 The Palisaded Enclosure as a Basic Construction Feature������������������������������������������������������������ 196 9.2 Tlateles, Platforms, and Complex Insular Settlements �������������������� 197 9.2.1 The Concept of Tlatel in the Lacustrine Context of the Basin of Mexico���������������������������������������������������������� 197 9.2.2 From Tlatel and Platform to Insular Complexes������������������ 198 9.2.3 Tlateles and Salt-Production ������������������������������������������������ 199 9.2.4 Archaeological Examples of Tlateles ���������������������������������� 199 9.3 Chinampas���������������������������������������������������������������������������������������� 206 9.3.1 Definition and Description���������������������������������������������������� 206 9.3.2 Types of Chinampas�������������������������������������������������������������� 210 9.3.3 Chinampa Fields in the Context of Other Features�������������� 212 9.4 Canals and Embarcaderos���������������������������������������������������������������� 214 9.4.1 Canals and Their Purposes���������������������������������������������������� 214 9.4.2 Embarcaderos (Dockings)���������������������������������������������������� 215 9.5 Dikes, Dams, and Causeways ���������������������������������������������������������� 215 9.5.1 Features and Functions �������������������������������������������������������� 215 9.5.2 Features Associated with Dikes and Causeways������������������ 219 9.6 Tools, Human Power, and Construction Materials �������������������������� 219 9.6.1 Tools and Human Power ������������������������������������������������������ 219 9.6.2 Lacustrine Raw Materials ���������������������������������������������������� 220 9.6.3 Non-lacustrine Materials������������������������������������������������������ 221
10 Models of Lacustrine Features and Settlement Development�������������� 223 10.1 A Classification of Cultural Lacustrine Features���������������������������� 223 10.1.1 Theoretical and Conceptual Framework �������������������������� 223 10.1.2 Feature Typology by Setting and Type of Construction���� 224 10.2 Types of Features: Models and Examples�������������������������������������� 228 10.2.1 Tlateles Based on Geomorphic Setting ���������������������������� 228 10.2.2 Tlateles and Platforms Based on Construction Type�������� 232 10.2.3 Canals�������������������������������������������������������������������������������� 234 10.2.4 Embarcaderos�������������������������������������������������������������������� 237 10.2.5 Types of Chinampas by Setting���������������������������������������� 237 10.2.6 Types of Chinampas by Construction ������������������������������ 240 10.2.7 Dikes, Causeways, and Bordos ���������������������������������������� 241
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10.3 Processes of Lacustrine Appropriation and Control ���������������������� 243 10.3.1 Complexes of Cultural Features in the Lakes of the Basin of Mexico������������������������������������������������������ 243 10.3.2 Processes of Cultural Development and Control of Freshwater Lakes���������������������������������������������������������� 243 10.3.3 Processes of Cultural Development and Control of Saline Lakes������������������������������������������������������������������ 246 10.3.4 Water Compartments in the Agricultural Development of Saline and Brackish Lakes�������������������������������������������� 247 Part III Lacustrine Systems in the Evolution of Civilization 11 From the Upper Pleistocene to the Agricultural Beginnings �������������� 251 11.1 The Lakes Through the Upper Pleistocene and Holocene�������������� 251 11.1.1 The Lakes Before the Appearance of Humans in the Basin������������������������������������������������������������������������ 251 11.1.2 From MIS 6 to MIS 2�������������������������������������������������������� 252 11.1.3 The Last Glacial Maximum���������������������������������������������� 252 11.1.4 The Deglaciation and the Younger Dryas�������������������������� 253 11.1.5 Early and Middle Holocene Environments ���������������������� 254 11.2 Lakes, Megafauna, and Early Humans in the Basin ���������������������� 255 11.2.1 Megafaunal Sites �������������������������������������������������������������� 255 11.2.2 Pleistocene Human Occupations in the Basin of Mexico�������������������������������������������������������������������������� 258 11.2.3 Preceramic Human Remains and Sites ���������������������������� 259 11.2.4 Rock Promontories and Early Humans in the Lacustrine Realm���������������������������������������������������� 261 11.3 Preceramic Societies Around the Lakes������������������������������������������ 263 11.3.1 Archaeological Findings and Their Chronology�������������� 263 11.3.2 Environmental Change and the Path to Sedentarism and Agriculture������������������������������������������������������������������ 268 12 The Lakes During the Agricultural Era������������������������������������������������ 271 12.1 Climatic Changes, Lake Levels, and Settlements �������������������������� 271 12.1.1 Millennial and Centennial Climatic Changes ������������������ 271 12.1.2 Trends in Atmospheric Moisture and Lake-Level Fluctuations ���������������������������������������������������������������������� 273 12.2 Volcanism and Ecological Change�������������������������������������������������� 274 12.2.1 Volcanic Events and Population in the Holocene�������������� 274 12.2.2 The Xitle Eruption and Its Impact on Cuicuilco’s Surrounding Landscape���������������������������������������������������� 275 12.3 The Formative Period���������������������������������������������������������������������� 279 12.3.1 The Lakes and the Earliest Agricultural Villages�������������� 279 12.3.2 Lacustrine Settlements Through the Formative Period���� 279 12.3.3 The Terminal Formative-Classic Transition Viewed from the Lakes������������������������������������������������������������������ 282
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12.4 The Classic and Postclassic Periods ���������������������������������������������� 284 12.4.1 The Lacustrine Geography of the Basin of Mexico During the Classic Period������������������������������������������������� 284 12.4.2 The Lakes During the Epiclassic and Early Postclassic Periods������������������������������������������������������������������������������ 285 12.4.3 Lacustrine Settlement Expansion During the Middle and Late Postclassic Periods�������������������������� 287 12.5 Patterns of Long-Term Appropriation of Lacustrine Environments���������������������������������������������������������������������������������� 288 12.5.1 Settlement Patterns Across the Lacustrine Realm������������ 288 12.5.2 The Late Postclassic Appropriation of Lacustrine Spaces�������������������������������������������������������������������������������� 290 13 Late Aztec Settlement, Hydraulic Management, and Environment���� 293 13.1 Prevailing Views and Questions About Tenochtitlan���������������������� 293 13.1.1 The Environmental Significance of Tenochtitlan�������������� 293 13.1.2 Historical Sources ������������������������������������������������������������ 294 13.1.3 The Ethnohistory and Archaeology of Tenochtitlan and Its Surroundings �������������������������������������������������������� 294 13.1.4 Research Questions ���������������������������������������������������������� 295 13.2 The Original Landscape of Tenochtitlan���������������������������������������� 298 13.2.1 The Elusive “Primitive” Islands���������������������������������������� 298 13.2.2 Historical Sources and Archaeological Records �������������� 300 13.2.3 The Original Landscape of Tenochtitlan Through Toponyms�������������������������������������������������������������������������� 302 13.2.4 The Stratigraphy Below the City�������������������������������������� 302 13.2.5 Geophysical and Geotechnical Research Studies ������������ 303 13.3 Hydraulic Technology, Floods, Navigation, and Agriculture �������� 304 13.3.1 Water Flows Across the City and Its Surroundings���������� 304 13.3.2 The Dikes of Nezahualcoyotl and Ahuitzotl �������������������� 305 13.3.3 Infrastructure in the Shadow of Large Dikes and Causeways������������������������������������������������������������������������ 308 13.3.4 The Chinampa Systems in the Western Part of Lake Texcoco���������������������������������������������������������������� 309 13.3.5 The Lacustrine Landscape Beyond Tenochtitlan�������������� 311 13.4 The Development of Tenochtitlan as an Environmental Dynamic Process���������������������������������������������������������������������������� 312 13.4.1 A Dynamic Environmental Model������������������������������������ 312 13.4.2 Long-Term Changes in the Evolution of the City ������������ 313 13.4.3 Seasonal Hydraulic Dynamics in the Context of Long-Term Lake-Level Changes���������������������������������� 316 14 The Lakes After 1519: War, Floods, and Drainage������������������������������ 319 14.1 The Lacustrine Landscapes of the War of Conquest���������������������� 319 14.1.1 The Strategic Importance of Insular Settlements�������������� 319 14.1.2 A Battlefield Geography (1519–1521)������������������������������ 320
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14.1.3 Lacustrine Dynamics and Features in the Chronicles of the Conquest ���������������������������������������������������������������� 322 14.1.4 The Brigantines and the Naval Battle of Lake Texcoco���� 324 14.2 Dynamic Lakes, Floods, and Drainage ������������������������������������������ 327 14.2.1 A Non-Lacustrine Society Settles on the Lake ���������������� 327 14.2.2 The Colonial Desagüe Projects ���������������������������������������� 330 14.2.3 The Desagüe After Independence ������������������������������������ 331 14.3 The Desiccation of the Lakes in Retrospect ���������������������������������� 332 14.3.1 The Prediction and Realization of an Ecological Disaster������������������������������������������������������������������������������ 332 14.3.2 Water Management or Drainage? A History of Adaptive Decisions ������������������������������������������������������ 334 15 Lacustrine Systems and Societies in the Basin of Mexico�������������������� 337 15.1 The Lakes of the Basin of Mexico�������������������������������������������������� 337 15.1.1 The Overall Picture of the Lacustrine Realm�������������������� 337 15.1.2 Lake Texcoco�������������������������������������������������������������������� 338 15.1.3 Lakes Chalco and Xochimilco������������������������������������������ 339 15.1.4 Lakes Xaltocan and Zumpango���������������������������������������� 339 15.1.5 The Good, the Bad, and the Ugly of the Lakes���������������� 340 15.2 The Development of a Lacustrine Culture and Technology ���������� 341 15.2.1 Lacustrine Subsistence������������������������������������������������������ 341 15.2.2 The Development of Wetland Agriculture������������������������ 342 15.2.3 Lakes as Marginal Land and the Postclassic Demographic Phenomenon ���������������������������������������������� 342 15.2.4 Environmental and Technological Thresholds������������������ 343 15.2.5 The Origin and Development of Tenochtitlan������������������ 345 15.3 Prospects for Research on the Lakes of the Basin of Mexico�������� 346 Glossary������������������������������������������������������������������������������������������������������������ 351 References �������������������������������������������������������������������������������������������������������� 355 Index������������������������������������������������������������������������������������������������������������������ 379
Part I
The Lakes: Approaches and Records of Their Past and Present
Chapter 1
Basin of Mexico and Its Lakes: Approaches and Research Questions
1.1 Defining a Regional Research Subject The Basin of Mexico (La Cuenca de Mexico), also known by many of its residents as the Valley of Mexico (El Valle de Mexico), is a closed basin encased in the volcanic highlands of south-central Mexico. Its original Aztec name, Anahuac (the place next to water), characterizes the lakes as its most important geographic feature (Fig. 1.1), a designation that seems to make no sense today as the lakes practically disappeared and were replaced by urban and rural development. The disappearance of the lakes occurred gradually during the past five centuries, through the process of draining known locally as the desagüe, a scheme that took the waters of the lake out of the basin through canals and tunnels across the lowest mountains surrounding the basin to the north. The purpose of the desagüe projects developed by the Spanish colonial government and later by independent Mexican state is to protect Mexico City from flooding. This measure contrasted with the previous management of the lake by Aztec predecessors who managed to control the waters of the lake to enable it for the development of human habitation and farming. Today, the urban sprawl of Mexico City’s metropolitan area and surrounding cities occupies large parts of the dry lakebeds (Fig. 1.1), leaving only a few remnants of the former lakes, mostly wetlands, and series of artificial bodies of water (Fig. 1.2). The Basin of Mexico, where Mexico City, the largest city in the country and among the third largest in the world, and several other important towns (e.g., Pachuca, Texcoco, Chalco, Cuautitlan, and Apan) are located, straddles portions of the territory of five states (Fig. 1.1). Combining the urban and rural populations, the basin is home to 21 million inhabitants, which is nearly 16.5 % of the country’s total. Thus, given its historical, political, and economic importance, the Basin of Mexico has received a great deal of scholarly attention, reflected in publications in history, archaeology, geology, geography, civil engineering, and environmental © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5_1
3
1 Basin of Mexico and Its Lakes: Approaches and Research Questions
Gulf of Mexico
Pacific Ocean
W 99° 45’ 00”
4
Hid
Mé
alg
o
xic
Basin of Mexico
o
L. Tecocomulco L. Zumpango Hidalgo Tlaxcala
L. Xaltocan
Mé xic
o
ala xc Tla ico x Mé
Mé
N 19° 24’ 10”
Ciudad de México
N
0
L.Texcoco xic o
Puebla
L.Xochimilco L.Chalco 5
10
15
20
kilometers
Approximate extension of the former lakes in late prehistoric times Hydrological divide of the Basin of Mexico Mexico City metropolitan area and adjacent urban areas in the early twenty first century Mexico-Tenochtitlan in the early sixteenth century, now Mexico City’s historic center. State boundaries
Fig. 1.1 The Basin of Mexico, the former lakes, and the urban sprawl
science. However, despite the number of publications on diverse scholarly subjects, there is little integration of the information obtained in the different scientific and humanistic fields. The information produced by separate fields rarely crosses disciplinary boundaries, a problem that has existed for a long time. During the middle decades of the twentieth century, many scholars of the fields of anthropology and archaeology pointed to the problem of lack of integration and cooperation among researchers of various fields. Regarding this issue, Ola Apenes explains: The Valley of Mexico offers, from various points of view, numerous attractions for scientific study. To a geologist, [the Valley] presents a unique case of a closed basin which has filled in through volcanic activity and sedimentation. An archaeologist sees in it a long sequence of cultures, whose beginnings are still to be discovered. A historian finds in this valley the scene of the development of the political and military might of the Aztec Empire and the dramatic encounter between the cultures of the Old and New Worlds. For a biologist a unique world exists in it, especially in the lacustrine environment. Ethnographers and folklorists have here a kind of human way of life adapted to the special conditions offered by this extraordinary land. The most interesting aspect that seems ahead of its time is the allusion to the idea that ‘these studies within the various branches of science could increase in value if they could be coordinated’ (Apenes 1947: 11).
5
1.1 Defining a Regional Research Subject SYMBOLS
N
Original lakes Permanent lacustrine body Semi-permanent, seasonal lacustrine body Limits of Lake Texcoco Federal Zone
1
Lake Zumpango
Lake Xaltocan
Area of chinampas (active and abandoned), canals, and managed wetlands Aztec dike and causeway of Tlahuac El Caracol de Sosa Texcoco (former evaporation basin)
Extent of original lakes based on map by C. Niederberger-Betton (1987)
REMAINING LACUSTRINE BODIES 7
Mexico-Tenochtitlan
6 11 12
5
Lake Zumpango
8
1. Lake Zumpango
9 10
Lake Texcoco 2. L. Nabor Carrillo 3. L. Reguladora Churubusco 4. L. El Fusible 5. L. Reguladora Cola de Pato 6. L. Casa Colorada 7. L. Sosa Texcoco 8. L. Ciénega de San Juan 9. L. Xalapango 10. L. Texcoco Norte 11. L. Bosque San Juan de Aragon 12. L. Alameda Norte
2
4 3
Lake Texcoco
13
Lake Xochimilco
14 15
Lake Xochimilco 0
5 Km
Origin Natural, remains of original or incidental Artificial
10
16
17 18 19
Lake Chalco
13. Canal de Cuemanco 14. Parque Ecologico Lago de Xochimilco 15. Remains of former L. Xochimilco
Lake Chalco 16. L. de Xico 17. New Lake Chalco 18. Unnamed lake 19. L. de S. Pablo Tezompa
Fig. 1.2 Remaining bodies of water and wetlands in the beds of the former lakes of the Basin of Mexico
Ola Apenes tried to convey idea that archaeology needs to collaborate with various scientific fields to take on problems concerning the human history of the Basin of Mexico, an aspect that was not an issue among his colleagues at the time. However, in the subsequent decades, increasing collaboration between archaeologists and geologists resulted in several meaningful projects targeting questions regarding the human-environmental history of the lakes, thus making interdisciplinary research indispensable in archaeological projects. Nevertheless, a few independent projects in geosciences and engineering produced information that rarely falls in the radar of archaeologists studying the societies that inhabited the lacustrine realm. In the context of the efforts across multiple disciplines to understand a regional subject (the Basin of Mexico), this book attempts an integrative view of processes
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1 Basin of Mexico and Its Lakes: Approaches and Research Questions
at different time scales that provide us with a picture of how the region and its peoples evolved into the modern scene. For this reason, this chapter addresses some of the objectives and interests of each group of scientific fields in relation to the natural and cultural history of the Basin of Mexico. In addition to focusing on the natural dynamics and history of the lakes of the Basin, this book draws on the scholarship that has surrounded the history of the Basin of Mexico. Therefore, this chapter attempts to place the study of the lacustrine systems within the historical context of the scientific and humanistic scholarship of the whole Basin of Mexico.
1.2 Scientific and Humanistic Approaches 1.2.1 The Development of a Scientific Approach The Spanish brought to the colonies a form of scientific inquiry stemming from the European Renaissance during the sixteenth and early seventeenth centuries (Alcina- Franch 1988). In the New Spain, this influence came in different forms, through the founding of universities and through studies carried out by missionaries and engineers commissioned by the Spanish Crown. The universities and missionaries were mainly concerned with the human world and to a lesser extent on physical science, and the engineers with pragmatic solutions to environmental problems using the science of the time. The Universidad Real y Pontificia de México, created by a decree signed by Emperor Charles V in 1551, officially opened in Mexico City in 1553, becoming the first university in the New World. Molded after the University of Salamanca, Spain, it focused on teaching aspects of philosophy, philology, and law (Carreño 1961). However, some of the faculty became interested in aspects of the local, physical, and cultural world. One of its most renowned philosophers, Fray Alonso de la Vera Cruz, wrote Physica Speculatio in 1557, the first scientific treatise published in the Americas (Beauchot 2011). Pragmatic studies concerning the lakes during the sixteenth and seventeenth centuries focused primarily on ways of draining them out of the basin, a matter that became the centuries-long process of draining the lakes (i.e., the desagüe). One of the earliest figures in this effort was Enrico Martinez, who came to Mexico with the title of Kings’s Cosmographer, a position that meant not only the use of cosmography, but also meteorology, geology, hydrology, and engineering, and in general solving problems of practical nature. However, as attested by his writings in his Repertorio de los Tiempos e Historia Natural de la Nueva España (Martinez 1948), Enrico Martinez had a profound interest in explaining natural phenomena through observation and means of rational thinking in the philosophical context of his time. Other figures such as Adriaan Boot, also appointed by the Crown, contributed to the knowledge of the lakes, as well as other figures commissioned to the desagüe after Martinez’s death, notably the Jesuit Andrés de San Miguel (Candiani 2014; Gurría-Lacroix 1978).
1.2 Scientific and Humanistic Approaches
7
Despite these scholarly developments, it was not until the European Enlightenment brought to the Americas interest in science as a form of inquiry in the modern sense of science (Alcina-Franch 1988). The transition to a more scientific view of the world, which occurred in the later decades of the eighteenth century, is clear in many of the articles in Gaceta de Literatura (Newspaper of Literature), a periodical compiled and published by José Antonio de Alzate y Ramírez (1737–1799). The periodical included his writings and those of other figures interested in aspects of the natural and cultural aspects of the country. Remarkably, Alzate’s writings reveal scientific interest in several fields, much like his Anglo-American contemporary Benjamin Franklin. Hydrology and hydraulics were among Alzate’s scientific interests in many cases concerned the Basin of Mexico’s lakes, of which he wrote extensively in various papers in his Gaceta. Although not always practical or technically achievable, he presented to the authorities several proposals for draining the lakes and reducing the floods (Candiani 2014). In a broader academic context, the later decades of the eighteenth century saw the development of a systematic view of science and engineering. Because of applications to economic development, specialized institutions sponsored by the viceroyalty government appeared, as is the case of the Colegio de Minería founded in 1793 (Uribe-Salas 2015). Thus, the nineteenth century began to see the organization of science in its modern form. The work of Alexander Humboldt, who visited New Spain in 1804 and published extensively on the country, also contributed to local interest in many aspects of nature. During his visit, Humboldt traveled widely in the Basin of Mexico, where he recovered information relevant to physical aspects of the former lakes, geology, volcanic activity, flora and fauna, and archaeology, and which he formally discussed in his Political Essay of the Kingdom of New Spain (Humboldt 1811). After the consummation of independence (1821), European science in Mexico began to have a significant impact on the organization of scientific societies and schools, as many Mexican intellectuals traveled to Europe to study. The idea of scientific societies, academies, and institutes arrived in Mexico at the time that existing universities were creating numerous departments and faculties that specialized in particular branches of the sciences (Saldaña and Azuela 1994). In terms of regional studies, the Sociedad Mexicana de Geografia y Estadistica (established in 1836) had an impact as a support group on the development of studies concerning mapping as well as studies of natural and cultural aspects of the country, specifically on the Basin of Mexico. Among other scientific societies, the Sociedad Científica Antonio Alzate (established in 1884) was one of the most respected organizations that devoted large amount of research to topics including engineering, natural sciences, and humanities. Many studies on problems related to floods and the sinking of the ground in the city published in the society’s papers influenced the perspective of scientists, humanists, and engineers of the time. As for the lakes of the Basin of Mexico, the usual works of the desagüe projects required feasibility studies. Thus, sponsored mostly by the government, several studies began to produce quantitative and qualitative information, including historical information on the former lakes (cf. Chap. 2). Among the eminent names who
8
1 Basin of Mexico and Its Lakes: Approaches and Research Questions
contributed to the knowledge of the Basin and its lake are Manuel Orozco y Berra (1816–1881), Joaquín García Icazbalceta (1824–1894), Antonio García Cubas (1832–1912), and Francisco Díaz Covarrubias (1833–1889). Manuel Orozco y Berra made a significant contribution to the cartography of the former lakes, as he collected an immense number of maps, which are now available at the Mapoteca Manuel Orozco y Berra at the headquarters of the National Meteorological Observatory in Tacubaya. The development of scientific and humanistic interest in the Basin of Mexico diversified into discrete academic fields, some of which are of special interest for topics related to the natural and cultural history of the Basin’s lakes. The following section summarizes the main achievements concerning the lakes as a background to defining the main questions and research problems tackled in the subsequent chapters of this book.
1.2.2 The Emerging Interest in the Past Catholic missionaries exploring the history of the pre-conquest world collected numerous historical narratives and myths, mostly because doing so was necessary to understand the former culture and religion of the new converts, an idea brought forth initially by Fray Pedro de Gante (1480–1576) and Bernardino de Sahagun (León-Portilla 1999; Kieckens 1880). Arriving in Mexico in 1524 and 1529, respectively, Gante and Sahagún witnessed the initial cultural shock between the two cultures; they not only saw the remains of the temples of Tenochtitlan as the Aztec city was being destroyed to give way to the Spanish city. Subsequent arrivals, notably Fray Toribio de Benavente Motolinia (1482–1569), Fray Geronimo de Mendieta (1525–1604), and Fray Juan de Torquemada (1557–1624) recorded the history of the Aztec culture and the historical developments of the first century after the Spanish Conquest (Torquemada 1975; Mendieta 1980; Motolinia 1990). Their histories have important passages concerning the histories of the lakes of the Basin of Mexico. Church ministers and missionaries, who oversaw the colleges, focused on the formation of Hispanicized native priests and intellectuals, some of whom later wrote important documents that today constitute the keystone of the knowledge about Mexico’s pre-conquest past. Hernando Alvarado Tezozomoc (1525–1608), Fernando Alva Ixtilxochitl (1568–1648), and Domingo Anton Muñoz de Chimalpahin Cuauhtehuanitzin (1579–1600) are among the few main contributors who contributed to the aspects of the history and geography of the Basin of Mexico. The Spanish faculty teaching at these colleges also carried out research on various subjects, from linguistics to natural history and ancient culture. As a faculty member at the College of the Santa Cruz of Tlatelolco, Fray Bernardino de Sahagún (1499–1590) taught while researching aspects of the land, its peoples, and its history (León-Portilla 1999). In so doing, he gathered a wealth of information that he published in his General History of the Things of New Spain,
1.2 Scientific and Humanistic Approaches
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also known as the Florentine Codex, which is one of the main sources of information on how humans interacted with the Basin’s lakes and its resources. It is important then to mention that the work of Sahagún, along with those of other missionaries and Hispanicized native intellectuals, will be the basis of a field that today we know as Mexican ethnohistory. Substantial interest in Mexico’s past, and particularly the pre-Columbian past, did not begin to grow until the end of the seventeenth century, and more properly in the eighteenth century, particularly between the American-born Spanish, whose interest in Mexico’s past reflected the nascent idea of national identity (Vela 2014). This class, locally known as criollos (i.e., American-born Spanish), would lead the Independence movement in the following century. Among these criollo scholars are Carlos de Sigüenza y Góngora (1645–1700), Francisco Javier Clavijero (1645–1700), and José Antonio Alzate y Ramírez (1731–1799), all of whom collected antiquities and historical documents. Their work constituted the basis for the future systematic history of pre-Hispanic Mexico. It is worth mentioning the contributions of non-Spanish foreigners who came to the country to study different aspects of geography, such as Alexander von Humboldt (1769–1589), who made relevant observations on the lakes at the time of his visit (1803–1804) and set the basis for reconstructions of the lakes in pre-Conquest times. In so doing, Humboldt stirred interest in many fields such as history, archaeology, and in particular the ancient geography of the Basin of Mexico and its lakes. During the nineteenth century, particularly after the country achieved its independence in 1821, Mexican scholars began studying documents such as codices and maps, many of which were held in various European cities. Historical facts extracted from the documents necessitated corroboration that could be obtained by excavating ancient monuments, thus marrying the idea of history and archaeology (Bernal 1979). However, archaeological work in the nineteenth century had a long way to go to careful excavations that produced significant information about Mexico’s past societies (Vela 2014). Although a number of publications on the antiquities of the country appeared in Mexico and abroad, in some cases, articles referring archaeological finds appeared in numerous journals, including those of the Sociedad Mexicana de Geografía y Estadística and the bulletins of the Sociedad Científica Antonio Alzate.
1.2.3 Archaeology, Anthropology, and Ethnohistory The establishment of archaeology as a defined field of study and as a state-sponsored enterprise developed through the first half of the twentieth century. It reached its zenith as a scientific field in the 1930s and 1940s, when it became important in the post-revolutionary efforts to strengthen the indigenous past as part of a Mexico’s national identity (Vela 2014). However, concerning studies in the Basin of Mexico, research projects focused only on major archaeological sites. Notable in this case is the systematic study and restoration of monuments in Teotihuacan, in which Manuel
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1 Basin of Mexico and Its Lakes: Approaches and Research Questions
Gamio (1883–1990) played a key role, as well as in other important sites in the Basin notably Cuicuilco, Copilco, and Azcapotzalco (Vela 2014). One aspect that pushed the study of monuments and sites in the second half of the century was the rapid expansion of cities, which undoubtedly uncovered hidden antiquities, thus creating the need for and expansion of salvage archaeology. However, since 1960s more research in the countryside around the metropolis in the form of archaeological surveys, produced a better understanding of the archaeological landscapes and changes in settlement patterns. The surveys produced information that led to views of the Basin and its lakes under the lens of landscape archaeology (e.g., Armillas 1971) and an ecological view of cultural development (Sanders et al. 1979; Parsons 2008). The number of written and pictorial documents collected during the Colonial period led to the development of ethnohistory, a historical discipline with strong links to anthropology and archaeology. Ethnohistory has a strong basis on the collection of information by Spanish missionaries and Hispanicized scholars (see Sect. 1.2.2). which contributed to the reconstruction of the lacustrine past of the Basin including historical events, building of hydraulic infrastructure, and natural phenomena (floods, droughts, volcanic eruptions), as well as daily life in the aquatic realm during pre-Hispanic and early colonial times. Archaeology and more properly anthropological archaeology in the Americas relies heavily on ethnographic information. This is no exception in Mexico, where several studies of traditional modern cultures are the basis for interpretation of archaeological data and ethnohistoric information. Research on resource exploitation by traditional communities has added more information on various aspects of social organization and labor investment. Worth of mention are studies of chinampa agriculture and related activities (e.g., Rojas-Rabiela 1974), fishing and collection of resources (Albor-Ruiz 2017; Parsons 2006), and salt production (Parsons 2001), among many other studies.
1.2.4 Hydrology and Hydraulics During the Late Aztec Period, particularly in the fifteenth and early sixteenth centuries, numerous hydraulic structures were constructed such as dikes, sluices, and canals in the lakes of the Basin. Many of these structures were destroyed during the war of conquest or fell in disrepair afterwards as efforts were concentrated in the building of Spanish Mexico City. Thus, the city was unprotected when successive catastrophic flooding events through the decades of the mid-1500s. Thus, the administration called for an engineering solution, which came first as protecting the city with dams and later with draining the lakes (Candiani 2014; Mundy 2015). Draining the lakes out of the Basin was the solution thought of by the colonial authorities and later by republican governments to keep the city safe from flooding, an exhaustive and lengthy process that involved engineers, local and foreign. This
1.2 Scientific and Humanistic Approaches
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long-term process produced a wealth of information useful for understanding the nature of the ancient lakes (Candiani 2014; Gurría-Lacroix 1978; Lemoine-Villicaña 1978; Rojas-Rabiela 1974). Among the early figures who documented the works leading to the drainage of the lakes during the early colonial times were Fernando Gudiel, Enrico Martinez, and Adriaan Boot, Andrés de San Miguel, and Ignacio Castera. After independence in the nineteenth century, a strong scientific interest in the desagüe developed among scientists, engineers, geographers, and historians. Engineers Francisco de Garay and Tito Rosas, in particular, produced research documents and maps that today constitute an important basis for understanding the ancient lakes and the Basin of Mexico in general (Auvinet et al. 2017). The final stage of the desagüe materialized at the turn of the twentieth century with the construction of the Gran Canal and the Tajo de Nochistongo, which finally permitted the drainage of most of the lakes. However, although it solved the flooding problem for some time, it brought numerous other environmental issues, some of which were predicted by Fernando Altamirano (1895), who pointed to possible changes in microclimates, increase in dust storms, and adverse effects on the health of the city’s inhabitants that the draining of Lake Texcoco would bring to the city. Certainly, such problems affect the city and the Basin to this day, with the additional problem that as the city expands and sinks heavy rains flood some neighborhoods. Thus, searching for solutions for these problems has brought geoscientists and engineers to develop new research that provides information on the lacustrine past.
1.2.5 Geosciences and Civil Engineering Interest in the geological processes that formed the Basin of Mexico has a long history go back to the late Colonial period. Although interest in geology remained primarily in mining, an activity that was not important in the Basin, some aspects of the formation of the Basin of Mexico were touched upon in Antonio’s Alzate’s Gazeta de Literatura (see above). However, systematic studies on the geological evolution of the Basin did not begin until the second half of the nineteenth century. Some of these studies had to particularly focus on the search for water sources to supply the growing city (Peñafiel 1884) and to construct the infrastructure to drain the lakes (Junta Directiva del Desagüe 1902). Like other scientific fields, geosciences received a great push in the twentieth century, particularly in the 1920s and 1930s as a wave of new institutions received support of governments. Despite this push, the focus remained on mining and exploration for oil and gas, activities that are not important in the Basin. However, geological studies on the Basin focused on aquifers and geological hazards. The name that resonates in these studies, among others, is that of engineer Federico Mooser (1923–2021), whose contributions are of great importance for understanding the geological evolution of the lacustrine basins as a basis for future research (see Chap. 2). Unlike many other geological engineers, Federico Mooser took on several geological questions that created the first models that explain the origin and evolution of the Basin of Mexico and its lakes.
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1 Basin of Mexico and Its Lakes: Approaches and Research Questions
Along with concerns related to tectonic and volcanic hazards, researchers began to look more actively at the recent (i.e., Quaternary) geologic history (Santoyo-Villa et al. 2006; Mooser 2018). In this aspect, geophysics in geotechnical studies has contributed to the knowledge of the structure of sediments in the basins of the former lakes of the Basin (Auvinet et al. 2017). Particularly after the 1985 earthquake, the amount of research in geosciences produced significant information on the geological history and sedimentary structure of the lacustrine basins.
1.2.6 Quaternary Geology and Geoarchaeology Quaternary geology and geomorphology have contributed to the understanding of environmental changes that occurred since the last glacial stages of the Pleistocene, including the times early humans appeared in the Basin. Pioneer research in the first half of the twentieth century focused on finding relations between glacial advances and lake-level fluctuations (e.g., Jäger 1926). Subsequently in the 1940s and 1950s, the first attempts were taken to establish a Quaternary stratigraphic sequence in the Basin (e.g., Mooser 1956; De Terra 1949). This interest centered on localities with fossil megafauna and around sites with evidence of early human occupation, particularly the site of Tepexpan, located on the northeastern shore of Lake Texcoco. Luis Aveleyra Arroyo de Anda (1926–2001), who worked extensively in the Basin, published in 1950 his Prehistoria de México, the first treatise on prehistoric Mexico. Along with him, other scholars such as Manuel Maldonado Koerdell (1908–1972) contributed to the paleontology and paleoenvironmental reconstruction of the prehistoric lakes. Worth mentioning here are the contributions of foreigners such as the Kirk Bryan (1888–1950) and Helmut de Terra (1900–1981) who, along with their Mexican counterparts, contributed to the early studies of Quaternary deposits and landforms as means of understanding the landscape occupied by the first humans in the Basin. The finding of human and animal remains at Tepexpan and numerous other sites stirred the initiative of notable scholars such as Pablo Martínez del Río (1892–1963), Alfonso Caso (1896–1970), and Ignacio Marquina (1888–1981) to create the Department of Prehistory under the auspices of the National Institute for Anthropology and History (INAH) (Lorenzo 1967). In subsequent decades, Jose Luis Lorenzo (1920–1996), Francisco González Rul (1920–2005), and Federico Mooser (1923–2021) became the pioneers in the field of prehistory and geoarchaeology in Mexico. Notable in the reconstruction of prehistoric landscapes was the study of the Terminal Pleistocene deposits around the former island of Tlapacoya (Lorenzo and Mirambell 1986b), which provided the first example of interdisciplinary research in the study of Quaternary environments and early humans in the Basin. It is important to mention that nowadays, the field of geoarchaeology, or the application of earth science methods to archaeological problems (Butzer 1982), has created an important link between the natural and cultural aspects of the past. Since the publication of the works in Tlapacoya, which has a number of research in this
1.2 Scientific and Humanistic Approaches
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field, publications addressing archaeological questions from the geoscience view have increased. They involve aspects of geomorphology, soils, petrology, sedimentology, and dating, among others. Unlike those of the past, geoarchaeology sees the natural world also within a cultural perspective (Cordova 2018).
1.2.7 Paleoecology and Paleolimnology Within the field of paleoecology, or the study of past ecosystems, paleolimnology focuses particularly on past lacustrine ecosystems. In this endeavor, both fields reconstruct past environmental conditions using proxies such as microfossils (pollen, diatoms, spores, phytoliths, etc.), macrofossils (macroscopic plant and animals remains), and physical, chemical, and biological markers from sediments, soils, and organic materials. Additionally, as many of these proxies are controlled by climate, paleoecology and paleolimnology have strong ties to paleoclimatology, thus being also the basics for reconstructing regional climatic conditions. The number of Quaternary paleoecological and paleolimnological studies in the Basin rose steadily since during the 1960s and 1970s, accelerated in the 1980s and 1990s, and expanded exponentially in the past two decades, producing a sizeable amount of information to understand the lakes at least within the later parts of the Pleistocene and Holocene. Recently, deeper coring in Lake Chalco permits studying the evolution of the lacustrine environment and its surrounding climate for at least the past two glacial-interglacial cycles (Ortega-Guerrero et al. 2020; Lozano-García et al. 2017). Unfortunately, technical problems such as time resolution and preservation of proxies in the other lakes have not allowed building chronological resolution and paleocological details (see Chap. 6).
1.2.8 Cultural Ecology The processes of human adaptation to various environments cross the interests of scholars in many fields, particularly archaeology, anthropology, and geography. Of these, archaeology has produced the strongest conceptual basis and information for understanding such processes. The second half of the twentieth century saw the appearance of classical treatises on the human-environmental relations in the Basin of Mexico, including the collection compiled by Eric Wolf (1976) and the seminal work by Sanders et al. (1979). Also, the highly inspiring work by Christine Niederberger (1987), Paleopaysages pre-urbaines du Bassin de Mexico (Pre-urban paleolandscapes of the Basin of Mexico), provides an example of the integration of information to build a model of adaptation and resource exploitation in the process of the evolution of ancient societies. The study of an artificial island (tlatel) in Lake Xochimilco, Terremote Tlaltenco, (Serra-Puche 1988) provided ample information of the use of lake resources in pre-urban times.
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The appropriation of lacustrine spaces through the implementation of hydraulic technology is another aspect of cultural ecology that in many cases merges archaeology with ethnography and ethnohistory. The contributions by Pedro Armillas (1971), Angel Palerm (1973), and Teresa Rojas Rabiela (1974) produced information that has served as a guide to further research topics such as the human control of the lakes, which have served as the basis for subsequent research in lacustrine archaeology. These include the study of dikes, causeways, and canals that enabled the establishment of chinampas (aquatic farm beds) as well as habitation complexes in the lakes. Some of these studies confirm information from historical sources, but some also show the complexities of the processes of cultural and ecological change. Although there is substantial information on the use of the lakes by agricultural and urban societies, little information exists on the interactions of preceramic societies and the aquatic environments of the basin. Certainly, studies on Zohapilco site in the Lake Chalco Basin (Niederberger 1976, 1979) and the San Gregorio Atlapulco site in Lake Xochimilco (Acosta-Ochoa et al. 2021) show interesting aspects of early adaptation. Potential sites for studies of hunter-gatherers and proto-agricultural societies do exist in the Basin (Acosta-Ochoa
1.2.9 Environmental History The colorful landscapes revealed in nineteenth-century paintings show landscapes of the Basin of Mexico with its iconic lakes and snowcapped mountains in the back (Fig. 1.3) contrast to the densely urbanized and polluted environment of the Basin at present. Nonetheless, beyond the bittersweet feeling of collective guilt about the lost paradise, scholars in various fields have strived to answer questions about the processes of the environmental transformation that the lakes underwent. Because its basis lies in written documents and maps, environmental history is generally viewed as a branch of history (Hughes 2005). However, in a broader perspective, environmental history encompasses the study of the evolution of humans and the environment in both prehistoric and historic periods (Cordova 2018). In this sense, branches of other disciplines such as archaeology, geography, and geology participate also in reconstructing environmental histories. An even broader view of environmental history includes fields such as sociology and conservation biology, both of which are concerned with the well-being of society and the environment. Some of the issues tackled by environmental history concern the evolution of the interactions between humans and their natural surroundings, and in most cases the transformation of the environment by human societies. Contributions in this field to the study of the Basin of Mexico are numerous, some of which concern the lakes (e.g., Legorreta-Gutiérrez 2006; Tortolero-Villaseñor 2015; Ezcurra 1990), as well as numerous articles published by authors from different academic backgrounds. Unfortunately, there are many gaps in the environmental history of the Basin of Mexico and its integration with the results of research in other fields, namely archaeology, ethnohistory, and geosciences.
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Fig. 1.3 Paintings by José María Velasco. Above: The Valley of Mexico from Cerro Santa Isabel (1875), oil on canvas. Below: Lake Chalco (1882). Note the canal that enters Chalco and the Iztaccihuatl and Popocatepetl volcanoes in the background
1.2.10 Ecology and Conservation The disappearance of the former lakes is undoubtedly an environmental disaster that today affects the entire Basin of Mexico in the form of higher temperatures, flooding, sinking ground, and dust storms originating in the exposed lakebed, among others. As if the disappearance of the lakes and its consequences were not enough, the growth of Mexico City and other urban areas is threatening the ecosystems of the surviving bodies of water and wetlands of the former lake basins. This threat has sparked interest in understanding and saving such spaces through studies in fields related to ecology and biological conservation (De la Lanza-Espino and García- Calderón 2002; Alcocer and Williams 1996).
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1 Basin of Mexico and Its Lakes: Approaches and Research Questions
Endangered ecosystems and species are subjects of research by governmental institutions, academics based in universities, research institutes, and non- governmental organizations. The research projects in conservation ecology have documented the destruction of ecosystems and the status of the surviving ones with the goal of influencing decision-making to restore, manage, and protect the remaining aquatic environments in the Basin. At the center of this issue are the often- debated plans to reclaim the remains of the dry lakebed of Lake Texcoco (Fig. 1.2). The damage to flora and fauna in this environment has been documented for the support of a protected area, which now is about to materialize in the form of an ecological park. The issue of bodies of water for migratory birds is another aspect of great interest in conservation ecology and biology in the Basin, as well as the protection of aquatic fauna, facing extreme danger in all remaining lakes due to pollution and introduction of non-native species (Recuero et al. 2010; Alcocer-Durand and Escobar- Briones 1992). Although the remains of Lake Xochimilco are recognized as Ramsar protected wetland, numerous other similar wetlands in the former lake basins need protection. The chinampa area of Lake Xochimilco area, considered also a UNESCO World Heritage Site, is perhaps one of the centers of attention in conservation ecology. All the efforts produced in conservation biology and ecology have produced knowledge that finds common ground with the ethnohistoric and ethnographic studies of human use of natural resources in the ancient lakes.
1.3 Persistent Views Regarding the Former Lakes 1.3.1 Unfounded Paradigms Despite the recent advances in research, numerous misconceptions about the former lakes persist in the media, academic discourses, and even in the academic literature which unfortunately are cited in again and again. The origin of such misconceptions lies in the acceptance of scientifically unfounded proposals that over the years have been solidified into facts and paradigms. Such misconceptions include, among others, the poor understanding of the changing nature of the ancient lakes and the misinterpretation of historical and environmental events occurred in the lakes. Certainly, the lack of hard data and testing of hypothesis of certain features and events in the recent history of the lakes are among other causes for the acceptance and perpetuation of erroneous beliefs about the natural and cultural history of the lakes. Numerous authors (e.g., Niederberger 1987; Espinosa-Pineda 1996; Parsons and Morett 2004; Avila-Lopez 2006; Luna-Golya 2014) have recognized this problem of misconceptions, false assumptions, and unfounded paradigms about the lakes. Fortunately, new research in the fields of Quaternary geology, geoarchaeology, and geotechnical studies has begun to challenge some of the paradigm with substantial amount of data, some of which are presented and discussed in several chapters of
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this book. Unfortunately, the poor integration of information across the sciences and humanities has made certain hard data overlooked by those writing the histories of the lakes and their peoples. It is then one of the main objectives of this book to point to the main misconceptions and their origins and discuss the existing scientific evidence to refute them.
1.3.2 The Configuration of the Former Lakes on Maps Among the many geographic misconceptions of the ancient lakes are the simplistic cartographic representations of the lakes where the lakes appear much larger than they actuallty were. Figure 1.4 shows three different notions of the distribution of the former lakes of the Basin. The first configuration (Fig. 1.4a) often appears as the geographic representation of the lakes at the time of the Spanish conquest, though the same map appears in many publications as a background to show distribution of sites and figures of prehistoric periods (Fig. 1.4a). This map portrays the complex of lakes as a single large lake, which is geographically impossible as Lake Zumpango was actually six meters above Lake Texcoco. The origin of this artographic representation is unclear, though it is found in publications only since the middle twentieth century. The second configuration (Fig. 1.4b) distinguishes four lakes based on various geographic and archaeological criteria to represent the lake in pre-urban times (presumably pre-Teotihuacan). Therefore, this configuration represents the distribution of lakes without the control of the dikes and causeways of the Post-classic period (Niederberger 1987). However, as discussed in this book, the configuration of the northern lakes (Zumpango and Xaltocan) is only approximate, as we know very little about the extent and shape of these two lakes. The third configuration (Fig. 1.4c) represents the lakes in the mid-nineteenth century before the construction of the Grand Canal, which was published and commented by Orozco y Berra (1864). This version already considers the southern basin as two lakes, Chalco and Xochimilco, separated by the artificial island of Tlahuac and its dike-causeway. Such a division of this basin into two lakes did not exist in the literature and cartography until the beginning of the nineteenth century (cf. Chap. 7). Often times, the map also appears as a background for earlier periods, which would also be erroneous as the map portrays the lakes after numerous modifications and partial drainage. Maps drawn in the sixteenth century and early seventeenth century, when the lakes still existed in full, did not have the accuracy to represent objects at scale or in a coordinate system. However, some maps show settlements and certain features, which can be associated with localities known to have been insular settlements or located lakeshore (Gonzalez-Aparicio 1973). The 1524 Map of Nuremberg is the first European map that represents Tenochtitlan and its lakes (Fig. 1.5), the map that accompanied Hernan Cortes’s second letter to King Charles V (Mundy 1998). Despite its cultural distortions and geographic inaccuracies, the map provides the
1 Basin of Mexico and Its Lakes: Approaches and Research Questions
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c
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Fig. 1.4 Comparison of the maps of three lake configurations: (a) The single lake or connected basins, (b) the presumed pre-urban configuration (e.g., Niederberger (1987)), and (c) the configuration during the mid-eighteenth century before the desagüe (Díaz Covarrubias 1864)
European perception of the lacustrine city and its surroundings, at least providing some idea of features such as causeways and dikes. Another sixteenth-century map of the Basin of Mexico is the Uppsala Map (c. 1550), also known as the Santa Cruz Map after its author, royal cartographer Alonso de Santa Cruz (1505–1567) (León-Portilla and Aguilar 2016) (Fig. 1.6). The map has a strong detail of features in the city, which seem to be fairly accurate when compared with a description of streets, buildings, and canals as by a descriptive tour of its streets and immediate surrounding written in 1555 (Cervantes de Salazar 2007). Outside the city, town roads, rivers, canals, lakes, and dikes appear in detail, but with geographic inaccuracy, given the cartographic techniques of the time (Mundy 1996). It is noticeable that in the Uppsala Map, the connection between the two northern lakes (Zumpango and Xaltocan) and between them and Lake Texcoco is not evident (Fig. 1.6), which contrasts with some of the modern representations of the northern lakes in modern maps (e.g. Fig. 1.4). Also, noticeable on the map is the existence of Nezahualcoyotl’s dike, which apparently had ceased to exist before the map was made (see discussion in Chap. 13). The only early colonial map that shows the direct connection between lakes Zumpango and Texcoco is the seventeenth-century map by Jorge Enciso (Apenes 1943; Plate 14), which represents the effects of the flood of 1629, after which
1.3 Persistent Views Regarding the Former Lakes
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1. Tenochtitlan sacred precinct 2. Great Temple 3. Tlateloloco 4. Tepeyac causeway 5. Iztapalapa causeway 6. Tacuba causeway 7. Chapultepec aqueduct 8. Tacuba
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Fig. 1.5 Map of Nuremberg, dated c. 1524, with locations of important features
Mexico City remained flooded for four years (Candiani 2014; Ramírez 1976). The map shows that a single lake was created between Zumpango and Lake San Cristobal, suggesting perhaps that the extreme event and the existence of the San Cristobal Dam may have contributed to the merging of lakes Zumpango and Xaltocan into one large lake. Another problem for mapping the prehistoric lake configurations and shorelines is the rapidly changing nature of the lakes through the seasons, an aspect that Alexander von Humboldt (1811) and Manuel Orozco y Berra (1864) pointed out, but many contemporary scholars who write about the lakes ignore this. To these changes, one has to add the yearly, decadal, and centennial changes, all of which resulted from long-term precipitation fluctuations, an aspect discussed in this book.
1.3.3 A View from the City Versus a View from the Lakes The unsolved questions about the geographic extension of the lakes lie primarily in conceptual issues of perspective. The geography of the Basin’s lakes has been approached from the perspective of the city and not from the perspective of the lakes themselves. This perspective has persisted across scholarly fields and discourses, government policies, and public projects, and has strongly influenced our modern view of the former lakes.
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1 22
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Fig. 1.6 Uppsala Map or Santa Cruz map, dated c. 1550. Numbers indicate lacustrine bodies and other features on the historic and the inset map
One can see this urban-centric view of the lake in the historic cartography of the Basin, which represents the lakes from the city’s perspective. This view is evident, for example, in the Uppsala Map (Fig. 1.5) as well as in most maps produced in subsequent centuries (Apenes 1943; Lombardo de Ruiz 1996). However, this perspective has reduced our knowledge of the lakes, adding more misconceptions about the lakes to modern interpretations of the lacustrine geography of the Basin and its environmental historical discourses.
1.4 Thematic Research Questions The number of research questions regarding the evolution of the lakes and their societies could be immense and varied, as some concern the natural environment such as geology and climate change, while others to the social and economic changes related to archaeology and history. Therefore, their grouping into different themes could help addressing them in a more systematical way. In the thematic groups below, a selection of questions constitute the main guide to the arrangement of topics throughout the chapters of the book.
1.4 Thematic Research Questions
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1.4.1 The Evolution and Geographic Characteristics of the Prehistoric Lakes Despite stratigraphic and geomorphological information on ancient lakeshores, the representation of the prehistoric lakes usually portrays the idea of large and hydrologically stable lakes. However, many early colonial maps and descriptions describe shallow bodies of water with aquatic vegetation. The Uppsala map, for example, shows symbols of vegetation all through the existing lakes (Fig. 1.5), implying that the lakes were shallow, perhaps like large swamps. Additional archaeological and paleontological evidence show that life and cultural activities went on in the middle of Lake Texcoco (Parsons and Morett 2004; Carballal-Staedler 2007). Then the questions are: How did the lakes change through prehistoric times? How big were the lakes at different stages of their history? Were the water bodies of the Basin “lakes” or large wetlands?
The answer to these questions requires a review of the geological history of the lakes in the context of tectonics and volcanism in deep time, as well as changes in recent geologic time, namely the Pleistocene and Holocene epochs.
1.4.2 Long- and Short-Term Lacustrine Dynamics Most of what we know about the lacustrine geography of the Basin’s lakes draws on what we learned of the lakes in the past five centuries, when they were in the process of disappearance. Little is known, however, of the prehistoric past of the lakes in terms of short-term dynamics (e.g., seasonal and year-to-year changes) and long- term change (e.g., decadal, centennial, and millennial change). Then, the questions here are: How did the lakes behave throughout the year? How did the lakes change when climatic conditions were drier or wetter? How did the lakes change on decadal and centennial scales?
The most complicated part to provide an answer to these questions is the lack of environments to observe processes, as the lakes no longer exist. Therefore, the strategy to address these questions includes, on the one hand, the recent geologic record, and on the other the archaeological and historical record. Additionally, the use of modern analogues in lacustrine environments elsewhere outside the Basin helps understand and model some of the processes that occurred in the recent prehistoric and historic past.
22
1 Basin of Mexico and Its Lakes: Approaches and Research Questions
1.4.3 Lake Dynamics and Human Appropriation of Lacustrine Spaces The processes of human appropriation of lacustrine spaces, such as the rise and spread of chinampa agriculture and the construction of towns on lakes, are often discussed in the literature. Archaeology has provided large amounts of information on the human landscapes (or waterscapes), with several surveyed and excavated features (artificial islands, chinampas, dikes, canals, etc.). However, most of these features have been interpreted in terms of their functionality and not in terms of their dynamic environmental context. Then, the questions are: How did short-term and long-term lacustrine changes affect the processes of human appropriation in the lakes? How did the co-evolution lake and society occur in preagricultural and agricultural periods?
The archaeological and historical record is fundamental to answer these questions. Additionally, climate change and its effects on the hydrology are two relevant aspects to address these questions. However, although seemingly strange, aspects of geology and geomorphology are important here as settlements of the lake follow inherited geological patterns (e.g., springs and faults) as well as aspects of the lacustrine dynamics.
1.4.4 The Origin and Evolution of Tenochtitlan and Its Hydraulic System Most of what we know of Tenochtitlan and its lacustrine hinterland comes from historical events written in early colonial texts, maps, and some archaeological evidence. However, as noted in earlier sections of this chapter, the knowledge of the origin and development of the city are riddled with misrepresentations of the lakes and a static view of the landscape. Thus, this situation poses several questions: What was the lacustrine landscape of Tenochtitlan before its foundation? How did the city grow in a highly dynamic aquatic landscape? How did the city manage adverse condition such as saline waters, drying, and flooding? How did the city cope with drastic seasonal and decadal changes to maintain navigation and agriculture within its borders?
Addressing these questions is difficult in part because of the deeply rooted misconceptions about the evolution and dynamics of the former lakes, as well as the fragmentary and sometimes conflicting archaeological and historical record. However, here, all the other aspects of previous questions (geological, climatic, and hydrological) merge with the logical aspects of lacustrine dynamics to match a series of potential scenarios to explain the origin, evolution, and functioning of the hydraulic infrastructure of the Basin of Mexico.
1.4 Thematic Research Questions
23
1.4.5 The Lakes During the War of Conquest The quincentennial of the fall of Tenochtitlan, celebrated in 2021, put forward many questions about the events occurred during the almost two years encompassed between the arrival of the Spanish in the Basin of Mexico and the fall of the Aztec capital. Strictly speaking, the landscape of the war is rarely discussed, as studies of battlefield geography are practically inexistent. This goes not only for the construction and launching of the brigantines in Texcoco but also for their naval battles and siege of the city. Furthermore, histories rarely address the advantages and difficulties that the lakes posed on both warring sides, let alone of the dynamics of the lakes during this period. Therefore, the questions here are: What role did the lakes play in the developments that led to the fall of Tenochtitlan? Can the aquatic scene of the war be reconstructed? What can the chronicles tell us about the aquatic landscape and dynamics of the time?
Like the case of the origin and evolution of Tenochtitlan, conflicting views exist in the sources and in the multiple interpretations of the events. However, based on the cumulative information addressed by questions above, as well as a careful review and cross-examination of sources, some sort of scenery and scenario is proposed.
1.4.6 Spanish and Independent Mexican Attitudes Toward the Lakes The clash between a non-aquatic civilization and the lakes led to fundamental changes on the ecosystems that had supported civilization in the past few millennia. The changes led to the drastic measure of draining them out of the Basin. However, the consequences turned out to be disastrous from many points of view, a trend that in the twentieth century became reversed, thus now toward regenerating part of the aquatic system if not just protect the remaining ones. Thus, the question here are: What have been the attitudes toward the lakes through the Colonial and Independent periods? Could the lakes have been persisted with the social and economic development of the Basin of Mexico?
Honoring the “lacustrine systems and civilization” in the title of the book, it is imperative to look at the clash between the Spanish colonial society and the lakes, as well as the evolution of the views about the lakes through the Colonial and Independent periods. However, because too much has been written on this topic, here only general aspects of the conflict between society and the aquatic environment of the Basin in recent centuries are discussed.
Chapter 2
Resources for Reconstructing the Ancient Lakes
2.1 Diverse Sources of Information The information for reconstructing the environmental history of the former lakes of the Basin of Mexico is highly diverse including among other sources, maps, stratigraphic sections, numerical data, photographic resources, oral histories, and digital archives. This information can appear in different forms, named here “records,” each of which comprises different areas (natural environment, archaeology, and history), and different forms, and pertaining to different time scales (Table 2.1). Because of the diversity and nature of the records, this chapter focuses primarily on archaeological, historical (including ethnohistorical), and virtual records. Modern environmental records are discussed in Chap. 3 and geological and paleoenvironmental records in Chaps. 4, 5, and 6. Although vast in nature, the records discussed in this chapter focus primarily on the geography and history of the lakes and the cultures associated with them.
2.2 The Archaeological Record 2.2.1 The Preceramic Period Archaeologists have divided the pre-Conquest history of Mexico into the preceramic and ceramic periods. The preceramic period (etapa precerámica), often referred to as the Lithic period (etapa lítica), comprises the times dominated by hunter-gatherer societies or highly mobile groups. The ceramic period (etapa cerámica) in contrast encompasses agricultural societies or sedentary groups (García-Bárcena 2007). However, it is important to point out that the transitional period between the preceramic and ceramic involves the existence of societies who © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5_2
25
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2 Resources for Reconstructing the Ancient Lakes
Table 2.1 Types of records, their information, and time context Group of records Geological and paleoenvironmental records
Archaeological records
Ethnographic and ethnoarchaeological records
Modern environmental records
Virtual records
Types of records Cores, reports, publications, and photographs Records of sediments, soils, stratigraphy, structures, landforms and paleolandforms, and paleoenvironmental proxies (e.g., fossils, microfossils, chemical and biological traces) Survey and excavation records (published or in archived reports) Field notes, diaries, artifact collections, and photographs Excavated or visible sites
Information The prehistoric past, the geological past natural environments. Ancient landforms still visible in the landscape
The archaeological or prehistoric past Ancient/ paleo-geographies The modern distribution of ancient features Behavioral records traditional Traditional practices remaining among the activities such as population fishing, hunting, Linguistic records and collection of Oral tradition food Toponyms and words Oral history Media files, reports, The present and publications, maps, the contemporary photographs, digital archives, past landscape landmarks, oral Modern histories geographies Modern analogues and references Visual reconstructions The past, the Virtual realities of the past present, and the Simulation models future Geographical, historical, and archaeological simulations
Time scales Decades, centuries, millennia, and millions of years
Decades, centuries, and millennia
Multidimensional
Days, months, seasons, years, and decades
All scales
practiced some form of agriculture, but were not directly involved in the production of utilitarian ceramics (Niederberger 1979). Two existing chronological classifications for the preceramic exist: the more traditional and widely used classification by most Mexican archaeologists (Table 2.2) and the more Pan-North -American-oriented classification (Table 2.3). The first one (proposed by Lorenzo 1967) stresses the development of lithic technology in relation to hunting-gathering and the more permanent sedentarization period associated
27
2.2 The Archaeological Record
Table 2.2 Traditional preceramic chronological scheme for Mexico (Lorenzo 1967) with definitions and examples of localities in the lacustrine realm of the Basin of Mexico Period Archaeolithic (33,000-13,000 BP) Lower Cenolithic (13,000-9000 BP)
Upper Cenolitic (9000-7000 BP) Protoneolithic (7000-4500 BP)
Definition Hunting and collection of plants. Preference on large mammals, though small mammals are an important part of the diet Development of spear points, extinction of large mammals, extreme climatic changes
Sites in the lacustrine realm Tlapacoya
Tlapacoya, El Peñón woman III, Santa Isabel Iztapan, Atepehuacan, metro Balderas, Chimalhuacan man Collection of plants and hunt of small Tlapacoya, Tepexpan mammals, change in lithic technology to smaller points Appearance of grinding stones, Zohapilco-Tlapacoya, san Gregorio increase in plant consumption and Atlapulco, Chicoloapan processing
Table 2.3 Pan-North American preceramic chronological scheme for Mexico (Lorenzo 1967) with definitions and examples of localities in the lacustrine realm of the Basin of Mexico Period Paleoindian Arrival of humans to 10,000 BP (c. 8000 BC) Early Archaic 10,000-7500 BP (c. 8000-5500 BC) Middle Archaic 7500-5500 BP (c. 5500-3500 BC)
Definition Big game hunters, highly mobile, diet dominated by animal foods
Late archaic 5500-2000 (c. 3500-2000 BC)
Diet is increasingly based on some domesticated food plants
Highly mobile foragers and collectors camping in bands, diet depends mostly on animal protein Foragers and collectors spending longer time in camps, diet becomes increasingly more dependent on plant foods
Sites in the lacustrine realm Tlapacoya, Santa Isabel Iztapan, Atepehuacan, El Peñón Woman III, Metro Balderas Man, Chimalhuacan Man Tlapacoya, Texcoco man (?), Tepexpan
Tepexpan man, Texcoco man (?), Coatlinchan man (?), Tlapacoya- Zohapilco, San Gregorio Atlapulco, Playa I and Playa II phasesa, Atlapulco phaseb Tlapacoya-Zohapilco, San Gregorio Atlapulco, Zohapilco phasea
Niederberger (1976, 1979) Acosta-Ochoa et al. (2021)
a
b
with the development of agriculture, while the second one (proposed by Evans 2008) stresses more about the general changes not directly associated with lithics but with ways of life. Lorenzo’s (1967) periodization considers the Archaeolithic to begin around 33,000 years BP based on radiocarbon dates associated with lithic materials at El Cedral, San Luis Potosi (Lorenzo and Mirambell 1986a). Furthermore, recent findings in northern Zacatecas seem to support occupations corresponding to this period
28
2 Resources for Reconstructing the Ancient Lakes
(Ardelean et al. 2020), but such early dates are still debated among archaeologists. Instead, Evans’s (2008) leaves that date open to the still unknown time of the arrival of the first humans to the continent. It is important to mention that subsistence and behavioral aspects of the Archaic are based strongly on data from other parts of Mesoamerica, particularly the Tehuacan Valley and Guila Naquitz, both regions ecologically different from the Basin of Mexico. Thus, a different view of the development of sedentary life in the context of lacustrine and wetland environments should be distinguished. Thus, research of Archaic societies in the Basin of Mexico (Acosta-Ochoa et al. 2021; Niederberger 1976, 1979) produced a local chronology: the Playa I (6000-5550 BC), Playa II (5500-4500 BC), and Atlapulco (4200-3800 BC) and Zohapilco phase (3000-2200 BC) associated with the transitions in the Late Archaic (Table 2.3). Details on the cultural differences of these phases and their sites are discussed in light of the archaeological and paleoenvironmental data in Chap. 11.
2.2.2 The Ceramic Period The establishment of agricultural villages that produced utilitarian ceramics marks the beginning of the ceramic period, which is subdivided into numerous cultural periods and phases determined primarily by ceramic styles, architecture, funerary traditions, and settlement patterns, among other cultural attributes. Thus, the general ceramic cultural periods include the Formative (or Preclassic), Classic, and Postclassic, all of which contain subdivisions such as early, middle, or late (Fig. 2.1, first and fifth columns). However, given the issues of concordance across the Basin and other parts of the Mexican Highlands, Sanders et al. (1979) proposed a chronological scheme using the “horizons” (Fig. 2.1, right column), which is referred to in some of the archaeological literature. Other periodization schemes often divide the Classic into early and late and the Postclassic into early, middle, and late phases, and into cultural historical designation such as Toltec and Aztec (Fig. 2.1, fifth column). These subdivisions, although referring to cultural historical groups, rely heavily on the prevalence of ceramic styles, or ceramic complexes, also known as phases (Fig. 2.1, second and third columns). In reports and publications, the most frequently used chronology is that of the ceramic complexes or ceramic phases. Thus, one can read for example of events occurring in the Patlachique phase, which is part of the Terminal Formative, or the First Intermediate Phase 4 (Fig. 2.1). However, the frequent use of ceramic complexes as phases may be problematic, as many were established before radiocarbon dating, resulting in the shifting of their ages and overlaps with other styles. One such case is the complexes of the Aztec black-on-orange ceramics, which Vaillant (1941) subdivided into the sequential Aztec I, II, III, and IV. Now it is known that not only these phases overlap with each other in parts of the Basin, but also the earliest styles overlap with ceramic styles originally thought to have preceded them. For example, the earlier development of Aztec II overlaps with the late development of
29
2.2 The Archaeological Record
Years AD-BC
1500
1000
General Regional Chronology
Basin of Mexico
Teotihuacan
Tlatelolco
Teacalco
Tenochtitlan
Chimalpa
Middle Postclassic
Zocanco
Early Postclassic
Mazapan
Atlatongo Mazapan
Epiclassic
Coyotlatelco
Xometla Oxtotipac
Colonial Late Postclassic
500
Classic AD BC
500
Terminal Preclassic
Late Preclassic
Middle Preclassic 1000
Early Preclassic 1500
Ceramic complexes/ or archaeological phases
Initial Ceramic
Vaillant Aztec IV Aztec III Aztec II Aztec I Toltec
Regional Surveys Chronology*
Basin of Mexico Project**
Colonial Late Aztec Early Aztec Late Toltec
Late Horizon Second Intermediate
Early Toltec
Phase 3 Phase 2
Teotihuacan Late Classic Metepec Middle IV L.Xolalpan Horizon Teotihuacan E.Xolalpan III Tlamimilopa L. Tlamimilopa Teotihuacan Early Classic E. Tlamimilopa Miccaotli II Miccaotli Apetlac Tzacualli Teotihuacan I Oxtotla Terminal Cuicuilco V Late Formative Patlachique Ticoman Cuicuilco IV Tezoyuca Ticoman III L. Cuanalan First Late Intermediate Ticoman II Ticoman Intermediate Formative E. Cuanalan E. Ticoman Ticoman I Metepec
Phase 2 Phase 1
E. Pastora El Arbolillo Bomba Manantial Ayotla Coapexco NevadaTlalpan
Chiconautla Altica
Middle Zacatenco
Early Zacatenco E. El Arbolillo
Aztec IV Aztec III/IV Aztec III Aztec II Aztec I-II Aztec I
Phase 1
Xolalpan
CuautepecL. Pastora
Aztec B/O***
Middle Formative
Phase 5 Phase 4 Phase 3-B Phase 3-A Phase 2-B Phase 2-A Phase 1-B Phase 1-A
Early Formative
Early Horizon
Phase 2 Phase 1
Initial Ceramic
* Texcoco, Chalco, Xochimilco, Ixtapalapa, & Zumpango (Blanton 1972; Parsons 1971, 2008; Parsons et al. 1982) ** Sanders et al. 1979. *** The original Aztec ceramic phases have been adjusted based on recent dates (Gorenflo and Garraty 2016).
Fig. 2.1 Regional archaeological chronology of the ceramic period. Based on chronological schemes by Sanders et al. (1979) and Parsons et al. (1996)
Aztec I, and the earlier development of the latter with the Atlatongo Ceramic complex of the Late Toltec (Gorenflo and Garraty 2016; Parsons et al. 1996). Despite the time overlaps, the Aztec II ceramics defines the early Aztec period or the Middle Postclassic and Aztec III defines the Late Aztec or the Late Postclassic period (Fig. 2.3). The Aztec IV tradition, however, is problematic because it is a very late Aztec ceramic style that in many parts of the Basin continued to be produced into the Early Colonial period, at least through the sixteenth century (Charlton et al. 2007). It is only in the presence or absence of European styles and artifacts in the same context that the style can be classified as Aztec or post-Conquest. Fig. 2.1 shows an overview of the most used names and divisions in chronologies. Thus, for particular distribution and chronology of ceramic styles in the Basin of Mexico, the author suggests looking at the series of volumes edited by Merino- Carrión and García-Cook (2005–2007) as well as the works by De Lucia (2018), Gorenflo and Garraty (2016), Rattray (2001), Brumfiel (2005a, b), Nichols and Charlton (1996), Parsons et al. (1996), Niederberger (1987), Sanders et al. (1979), and Tolstoy et al. (1977).
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2 Resources for Reconstructing the Ancient Lakes
2.2.3 Recovery of the Archaeological Record Archaeological surveys involve the surface recording of sites and artifacts of a territory, resulting in geographic information of the distribution of sites of different periods across the modern landscape. Although small areas of the Basin of Mexico have been surveyed, large part of the geographic information of archaeological sites comes from the results of the multidecadal project known as the Basin of Mexico Survey, whose purpose was the study of settlement patterns with purposes of studying demographic and settlement pattern change (Parsons 2015; Sanders et al. 1979). The surveys comprised large territories within the Basin including parts of the former lakebeds. One important aspect of the Basin of Mexico Survey is that the recording of surface archaeology took place in the 1960s and 1970s, when many areas had not yet been overrun by the expansion of urban areas (Parsons 2015). Today, the data produced by the surveys have been used in projects focused on understanding the evolution of urban and rural settlements in the Basin. Multiple studies have also looked at demographic and environmental aspects of each period (Gorenflo 2015; Gorenflo and Sanders 2015). Other studies have used the information to reconstruct environmental change and landscape transformation by ancient settlers (e.g., Frederick and Cordova 2019; Cordova 2017; Millhauser and Morehart 2018; Luna-Golya 2014; Cordova and Parsons 1997). Unfortunately, the survey data have some limitations, especially because of many aspects not considered when they were carried out. One of them is that the recovery aimed only at archaeological material of the ceramic period, thus skipping potential preceramic sites. Another limitation is that the surveys focused only on surface archaeological material, thus missing sites buried under recent sediments in the alluvial plain (Parsons 2015). Another limitation is that vast areas of the lakebeds were not surveyed, particularly on Lake Texcoco, which, on the one hand, presented technical issues for the reconnaissance and, on the other hand, considered that the lake was too deep for settlement (Sanders et al. 1979). Nonetheless, many years later, a survey in the central part of Lake Texcoco, where the international airport was planned, found a large amount of in situ material representing a variety of activities including ceremonial and some associated with exploitation of lacustrine resources (Parsons and Morett 2004). Evidently, the findings support the idea that the lake was too shallow and underwent extreme changes in prehistoric times, an aspect that alludes to the particular long- and short-term dynamics of shallow lakes (Chap. 8). For similar reasons as the case of Lake Texcoco, the surveys covered only part of the lakebeds of the northern lakes (Fig. 2.2). Not until years later that a proper survey and excavation recorded the antiquities of the area south of the island of Xaltocan, namely its chinampa fields (Morehart 2012b). The bed of Lake Zumpango, which fell in the Zumpango Regional Survey, produced several sites, although some areas could not be surveyed because of standing water (Parsons 2008). Fortunately, the surveys covered substantial areas of lakes Chalco and Xochimilco, in part guided by the existence of archaeological chinampas reported earlier by Armillas (1971) (Parsons et al. 1982).
2.2 The Archaeological Record
31
Tula Valley N Temascalapa Region
Zumpango Region Zumpango Lake Zumpango
Teotihuacan Region
Xaltocan
Cuautitlan Region
Lake Xaltocan
Cuautitlan
Teotihuacan
Otumba
Tepexpan Tepetlaoztoc Tenayuca Azcapotzalco Tacuba Elevation in meters above sea level 2800 2600 2400
Survey regions
El Tepalcate
Texcoco Region
Lake Texcoco
Tacuba
Significant archaeological sites and Late Aztec towns
Texcoco Huexotla
Lake Texcoco Region Tlatelolco Tenochtitlan
Coyoacan Copilco
Mexicaltzingo Iztapalapa
Cuicuilco
Lake Xochimilco Xochimilco
Xochimilco Region
Iztapalapa Region Tlapacoya Xico
Tlahuac
Chalco Lake Chalco Temamatla
Chalco Region
Artificial insular complexes 16th century lakeshore in original map (Parsons 2015) 0 10 5 Prehistoric lakes according to kilometers Niederberger (1987)
15
Cuautla Valley
Fig. 2.2 Basin of Mexico surveys. (Adapted from Parsons (2015) with modifications by the author)
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2 Resources for Reconstructing the Ancient Lakes
Regrettably, many of the key lacustrine sites reported by the surveys were obliterated by the expansion of urban development. However, a few of them were excavated, thus providing some information on lacustrine sites. The cases of El Tepalcate and Tlatel de Tepexpan (Fig. 2.3), two artificial islands (tlateles), epitomize the fate of hundreds of sites on the lakebeds and lakeshores. Although both sites were excavated, resourceful though preliminary archaeological information was recovered information they are now out of reach for further research.
Auto
pista
Mexi
co-P
irami
des
Tlatel
N
Tepexpan Man locality and ,useum
0
100 200 meters
Tlatel de Tepexpan Lake Texcoco MexicoTenochtitlan core
Tlatel El Tepalcate Urban cover 0
5
10
Km
Tlatel
0
100
200
meters
Fig. 2.3 Location of pre-Hispanic lacustrine settlements (tlateles) at (a) Tepexpan and (b) El Tepalcate in 2017. (Google Earth Images)
2.2 The Archaeological Record
33
The rapid expansion of the urban area necessitated action to salvage some archaeological features and monuments under the city. Thus, the Dirección de Salvamento Archaeologico (DSA) and other divisions of the Instituto Nacional de Antropología e Historia (INAH) have taken on the study of sites in areas affected by the construction of new infrastructure. Likewise, there is the need to study the archaeology already below the city, especially in the city center, where the core of the Aztec lacustrine cities, Tlatelolco and Tenochtitlan, lays (Fig. 2.4). This area has had by far the highest density of work, including permanent projects of urban archaeology often linked to the Templo Mayor Museum have produced relevant information, particularly from the sacred precinct of the city (Rodríguez-Alegría 2017; Matos-Moctezuma 2003). The periphery of former Tenochtitlan includes former insular settlements, causeways, chinampa fields, and dikes (Fig. 2.4), some of which have been targeted in salvage archaeology projects led by INAH. One example is the salvage archaeological work at the Central de Abastos (a food distribution market) of Iztapalapa, where many ancient chinampas and tlateles were studied (Avila-Lopez 1991). Then, the
Tenayuca
N
Islands at the time of the Conquest
allej C. V
Causeways
Can
yac
Tlaltelolco-Tenochtitlan c. 1520
Gran
C. T epe
Tacuba
Sacred precincts
al Av e.
o Tepeyac
Azcapotzalco
Tlatelolco
P.
Nezahualcoyotl’s Dike
1
a or m Ref
Coyoacan
C.
Ign aci
oZ
Coyoacan 0
5 km
Colonial Mexico-City c. 1800 go za
Circuito In terior
C. de Tlalpa
n
Huitzilopochco
C. de La Viga
Pe ri f ér ico
Eje Ce ntral
Insur gent es Av e.
r
Mixcoac
Iztacalco
ara
2
according to: 1. Gonzalez-Aparicio (1968) 2. Lorenzo (1973)
Mexicaltzingo C. Ermita-Iztapa Iztapalapa lapa
Main modern streets EXCAVATED FEATURES Calzada Canal Embarcadero Chinampas Canoe Tlatel
Culhuacan
Salt production site
Fig. 2.4 Geographic summary of important excavated archaeological lacustrine cultural features in the metropolitan area of Mexico City indicating the first and second arbitrary zones of archaeological research. Compilation by the author, based on various sources. (Sánchez-Vázquez 1996; Sánchez-Vázquez et al. 2007; Ortuño-Cos and Moreno-Cabrera 1993; Ortuño-Cos et al. 1982)
34
2 Resources for Reconstructing the Ancient Lakes
rest of the lacustrine area of the Basin of Mexico has also seen important salvage work, especially with the construction of infrastructure such as freeways and subway lines. Notably this includes areas within former lakes Chalco and Xochimilco and other parts of Lake Texcoco. Many of these areas extend into the neighboring State of Mexico, where the regional INAH divisions have taken on several salvage projects.
2.2.4 Archaeology in the Urbanized Areas Perhaps the most notable amount of information on lacustrine sites comes from salvage archaeological projects carried out with the construction of the subway (metro) lines, which crisscross the bed of former lake Texcoco, including the territory of Tenochtitlan and the historic center of Mexico City (Fig. 2.5). Some lines cross ancient dikes, canals, and insular settlements (Sánchez-Vázquez et al. 2007). Some lines also cut through layers of sediments containing remains of Pleistocene fauna, whose recovery has added significant paleontological information (Carballal- Staedtler 2007). Despite the advantages of permitting a look into the past, the recovery of archaeological and paleontological information depends on many factors. One of them is the type of subway line under construction (Fig. 2.6). Another is the implementation of ways to record data, which have evolved since the construction of the first lines in the 1960s (Peralta-Flores 1996). In general, the surface and elevated lines represent limited excavation, thus encompassing mainly disturbed surfaces or modern fills. The deep tunnels often cut through old sedimentary deposits that predate human presence but provide a glimpse to Pleistocene alluvial and lacustrine stratigraphy. However, the access shafts have shown important aspects of Pleistocene stratigraphy, whether it is lacustrine, alluvial, or transitional. The trench tunnels are the ones that have produced most of the archaeological information as they reach mainly strata where most lacustrine settlements are to be found. Nonetheless, the type of subway construction is of less importance in recent projects as new measures of recovering information have been put in practice. These measures include the preemptive opening of test pits along the lines and in adjacent areas, particularly in areas where antiquities are expected to be found (Sánchez-Vázquez et al. 2007). This strategy permits the recovery of data even in the case of surface and elevated subway lines. Unfortunately, the construction of lines 1, 2, and 3, which were trench-tunnel lines crossing the heart of the Aztec city and the Spanish city, had no systematic recording of antiquities, except in places where monuments appeared accidentally (Gussinyer 1979). However, once the new measures to record findings were implemented along subsequent lines enormous amounts of information on dwellings, public buildings, canals, embarcaderos, chinampas, and causeways inside
2.2 The Archaeological Record
35 Late Aztec features
Line and station
Causeways
B
Islands at the time of the Conquest
N 76
Sacred precincts TlaltelolcoTenochtitlan
5 3
64
Dike
Tep
Colonial city Mexico City c. 1810
Tac
2
B
8 Tl
PB
Lake Texcoco
Ten Chp
1 1 9
4
Mix
59 A
12
Chapultepec Tlaltelolco Tenochtitlan Tacuba Iztapalapa Huitzilopoxco Tlahuac Mixhuca Mexicaltzingo Peñon de los Baños Peñon del Marqués
Chp Tl Ten Tac Izt Hui Tla Mix Mxc PB PM
PM Hui
7
Mxc
Coy
Izt
A
8 2
3 12 0
5 km
10
Lake Xochimilco Tla
Lake Chalco
Fig. 2.5 Mexico City subway lines against the background of Aztec Tenochtitlan and its causeways. The locations of dikes and causeways are based on Gonzalez Aparicio (1968) and Calnek (1972); the extent of the colonial city is based on Filsinger (2003)
Tenochtitlan or in its immediate surroundings (Sánchez-Vázquez et al. 2007; Sánchez-Vázquez 1996; Pulido-Mendez 1993; Ortuño-Cos et al. 1982). Likewise, large amount of information appeared in the periphery of the ancient city, thus augmenting our knowledge of archaeology and sediments in the area now under the metropolitan area of Mexico City.
36
2 Resources for Reconstructing the Ancient Lakes Surface B
Street level
Type of excavation 76
5
3
Elevated
Elevated Surface Trench tunnel Deep tunnel
64
± 1.2 m
Late Aztec features
2
Dike
8
1
Causeways
±2m
Tenochtitlan c. 1521
15 9 A
9
Street level
Colonial city
Street level
Trench tunnel
Mexico City c. 1810
4
± 12 m
12 7
8
2
A Street level
Deep tunnel
3
0
5 km
± 80 m
10
12
Fig. 2.6 Mexico City Subway lines classified by the type of excavation
2.2.5 The Artifactual Record of Past Aquatic Lifeways Surveys and excavation in the lacustrine realm of the Basin have produced artifacts that constitute the material culture of societies exploiting aquatic resources in their surroundings (e.g., De Lucia 2021; McClung de Tapia et al. 1987). Several other objects of use in the lacustrine realm include weight stones used in the nets (Parsons 2006; Parsons and Morett 2004) and ceramics associated with salt production (Parsons 2001) among others. In some cases, remains of wooden posts or their imprints indicate the locations of nets for trapping fish and birds (Parsons 2006) or posts for tying canoes in docking areas (McClung de Tapia et al. 1987). Unfortunately, many of the artifacts to catch or process aquatic products are made of perishable materials, and not easily preserved in archaeological deposits. Fishnets are made of fibers that do not preserve well, though under some conditions they preserve, as is the case of the highly organic and acid deposits of Terremote- Tlaltenco in Lake Xochimilco, where ropes and baskets appeared in excellent preservation (McClung et al. 1987). In some cases, the presence of certain objects of durable materials may suggest the manufacturing of objects of perishable materials, as is the case of scrapers used to process maguey fibers and bone needles to weave them (De Lucia 2021).
2.2 The Archaeological Record
37
Of great significance in terms of lacustrine material culture was the finding of a wooden canoe from a construction site in what used to be the Iztapalapa Causeway, now the Calzada de Tlalpan (Leshikar 1982; Angulo 1959). The recovered craft, now displayed at the National Museum of Anthropology, has relatively flat ends (Fig. 2.7) which, interestingly, represents a general prototype found in miniature canoes in ritual offerings, canoes depicted in codices, maps, and other pictorial documents of the early years of the Colonial period (Biar 2017; Favila-Vázquez 2011). A
50 cm
B
1m
50 cm
0 Scale
1m
50 cm
Length: 5.30 m
Length: 5.78 m
C
Fig. 2.7 Reconstruction of the canoe at the National Anthropology Museum in Mexico City. (a) Sketch from Leshikar (1982); (b) drawing from a photograph; (c) reconstruction of the same canoe with its occupant and cargo
38
2 Resources for Reconstructing the Ancient Lakes
2.3 The Historical and Ethnohistorical Record 2.3.1 Codices and Representations of Lacustrine Geography The generic term códice (codex) refers to a pictorial document representing historical events, mythological beliefs, taxation charts, and maps, among other things. Although fashioned in the tradition of pre-Hispanic art and writing, most codices were created in the early Colonial period by Hispanicized natives and in many cases by Spanish missionaries (Batalla-Rosado 2016). Many codices include side notes in Nahuatl written with Latin characters, and notes in Spanish, or Latin. Some notes include Gregorian calendar dates next to the glyphs representing Aztec calendar dates. Many codices provide information on historical events that occurred in and around the lakes (e.g., Codex Xolotl, Codex Aubin, Codex Ramirez), while others provide information on daily life in the lacustrine realm (e.g., Codex Mendoza and Florentine Codex). In particular, the Codex Xolotl consists of plates depicting historical events placed in the geographic background (Fig. 2.8). The depicted geography of the codex shows Lake Texcoco and its connection with the southern lakes through the Strait of Culhuacan, as well as the strait connecting with Lake Xaltocan, where the island of Xaltocan appears in the middle of it (Fig. 2.8). Interestingly, Lake Zumpango is missing, an aspect that reflects perhaps the nature of that lake in pre-Hispanic times (see discussion in Chap. 7). In addition to the lakes, the codex page shows the Sierra Nevada in the background and various and smaller mountain ranges. Cartographic representations of the Basin of Mexico in early colonial times are of great help for reconstructing the lakes and other geographic features. For example, the 1550 map by Alonso de Santa Cruz also known as the Map of Uppsala portrays natural features and towns around the lakes, even with the exaggerated size of Mexico City at the center of the lake (Fig. 1.5). Numerous other maps of the lakes made during the Colonial period provide information on the location of dikes, chinampa fields, islands, and the process of recession of the lakeshores (see collection of maps in Lombardo de Ruiz 1996; Departamento del Distrito Federal 1975; Carrera-Stampa 1949; Apenes 1943). Despite the inaccurate characteristic of the cartography of the time, these maps sometimes emphasize on particular aspects that are useful for reconstructing the configuration and dynamics of the lakes (see Chap. 7). Of notable significance is the Sigüenza Map, which depicts the arrival of the Mexica to the Basin of Mexico and their movements on the shores until they found the location where they would establish the city of Tenochtitlan. The map’s name derives from historian Carlos de Sigüenza y Góngora (1645–1700), but its authorship is unknown. The interesting aspect of the map is that it depicts the landscape where Tenochtitlan was founded as a marshy environment, which contrast with the idea that the city was founded on a preexisting island (see discussion on the primitive islands in Chap. 13).
39
2.3 The Historical and Ethnohistorical Record
6
5 2
4
1
3
Fig. 2.8 Page 1 of Codex Xolotl. Localities identified on the map: (1) Xaltocan, (2) Acalhuacan, (3) Lake Texcoco, (4) Culhuacan, (5) Lake Chalco-Xochimilco, and (6) Sierra Nevada
Other early colonial maps also help with details of the built environment in some areas. One of them is the 1524 Ordenanza de Tlatelolco which, despite some confusing features, helps reconstruct the hydraulic infrastructure (Carballal-Staedtler and Flores-Hernández 2004). The Plano en Papel de Maguey (Map on Maguey Leaf) is a map of an urban section of Tenochtitlan Moyotlan district of the city (see Calnek 1973). Despite the imprecise location, the map shows in detail the layout of chinampas, houses, canals, and causeways, and particularly the fact that houses were next to the chinampa fields.
2.3.2 Chronicles and Descriptions of Daily Life The chronicles of the Conquest War are of great use for reconstructing the landscapes of the lakes and towns in and around them, including features such as causeways and dikes, as well as shorelines and natural features such as swamps and inlets. The chronicles include those written by direct participants in the war of
40
2 Resources for Reconstructing the Ancient Lakes
conquest such as Hernán Cortés, Bernal Díaz del Castillo, and the Conquistador Anónimo, and those written on second-hand accounts such as those of Francisco López de Gómara, Fray Bernardino de Sahagún, Fray Toribio Motolinia, Fray Juan de Torquemada, and Francisco Cervantes de Salazar (see Chap. 14). In addition to the chronicles, there are numerous narratives of historical events obtained from the codices and oral accounts appearing in various works compiled and published by Spanish missionaries and Spanish and native Hispanicized scholars (see Sect. 1.2.2 in Chap. 1). Many of these works contain also accounts of daily life during the pre-Conquest time, including beliefs, traditions, economic activities, and the environment. Both as histories and daily life narratives, the works of Fray Bernardino de Sahagún (Historia General de las Cosas de Nueva España) and Fray Juan de Torquemada (Monarquia Indiana) are very important sources of information. The information recorded by these works, mostly from indigenous informants, constitute the basis of linking past aquatic activities, the archaeological record, and the modern ethnographic record.
2.3.3 Written Documents and Cartographic Sketches Documents dealing with various topics (geographic relations, litigations, land grants, public works, etc.) are of great help for reconstructing the colonial landscapes of the Basin of Mexico, as they mention landmarks and existing features. Among these written documents, those of greatest help are the Relaciones Geográficas (Geographic Relations), which are inventories of towns and regions ordered by the Spanish Crown in the late sixteenth century (Acuña 1985). Although focused on towns, the Relaciones Geográficas often mention landscape features, historical background, and in many cases aspects of climate and natural disasters. The need of the Spanish colonial authorities to manage the different aspects of economic and social life of the New Spain resulted in a wealth of documents on various aspects of administration, legal matters, trade, and the construction of infrastructure. The most prominent collection of documents is held at the Archivo General de la Nación (AGN) in Mexico City. Another important collection of colonial documents is at the Archivo General de Indias (AGI) in Seville, the Spanish city that served as the center for the administration of colonies in the Americas. Another important archive with information on matters related to the lakes and the city is the Archivo Histórico de la Ciudad de Mexico (AHCM). Although mostly comprising the Independent period, the documents in this archive include permits for construction, or the opening of certain businesses allude to aspects linked to water such as canals, bridges, or even former wetlands. Of all the document collections, the AGN has perhaps the most comprehensive, diverse, and useful documents, classified into grupos documentales (document groups). The groups with information related to the lakes of the Basin in the colonial period are desagüe (lake drainage works), Rios y Acequias (rivers and canals), Tierras (land litigations), and Mercedes (land grant requests). Often these
2.3 The Historical and Ethnohistorical Record
41
documents come with a sketch map depicting the landscape of the area in litigation or the spatial context of landscape features. Sketch maps of the in the Tierras branch of the AGN sometime show details of infrastructure, roads, shorelines, dikes, and canals provide information about landscapes that have been lost. For example, the1593 map accompanying a land dispute depicts sites easily corresponding to a dike on the western side of Lake Texcoco (Fig. 2.9a). The symbols of the original map show the lakeshore on the south side (right side on the map) bordered by aquatic vegetation until it reaches dryland covered with cultivated fields (sementeras). It also shows the canals that derived from the San Juan Teotihuacan River, the settlements, and the causeways, some of which can be seen in the modern landscape (Fig. 2.9b). Another sketch map that accompanies a Tierras document dated to 1579 refers to the boundaries of towns in Ayotzingo and Mixquic on the southern shores of Lake Chalco. The map uses native pictographic elements indicating features such as vegetation, hills, towns, roads, and lacustrine-raised fields (chinampas) (Fig. 2.10a). The map shows the lakebed completely occupied by chinampas, which today are concealed below one or two meters of sediments (Frederick and Cordova 2019). Other maps show more details in terms of natural and landscape features, which are of incredible help when reconstructing historical landscapes. An example is the map of the southeastern shore of Lake Chalco where the lobe of the Amecameca River delta and its main channel to the south appear (Fig. 2.10b). Although the channel migrated several times or bifurcated into two during colonial times (Frederick and Cordova 2019), this map shows it emptying near Ayotzingo. In subsequent centuries, improvements in cartographic techniques permitted better analysis of features, particularly those depicting parts of the Basin or the city. a
Oriente Reyes
S. Franco
5
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oco
c Tex oa
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a qu
e va
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petz 9 ingo
Nahut...
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ras
rrad
esta agua... aqui
Alba
Los Ahuehuetes
[Signature]
acequia y zanja de 6 agua
S. Xropbal Nexquipayac
1 Molino
es
te
ta
Atenco
Sur
min
Ca
Es
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LOCALITIES AND LANDSCAPE FEATURES
1 San Cristobal Nexquipayac 2. San Francisco Tepetzingo 3. La Transfiguracion (later Hacienda La Chica) 4. San Francisco Acuexcomac
5. Los Reyes (later Hacienda La Grande) 6. Canal 7. Cana leaving gristmill (Molino) 8. Road La Transfiguracion-Tepetzingo 9. Albarrada (causeway) 10. Laguna (lake)
2 0
Tepetzingo 500 m
Causeway-dike Huatepec
1 km
Fig. 2.9 (a) Land litigation map accompanying a document (Nexquipayac, Los Reyes y la Transfiguración, Tierras, AGN 1593). White spots on the sketch of the old map are parts that are missing or damaged. (b) Location of the same area represented in the litigation map with features on the map in the modern landscape. (Source Google Earth Pro)
42
2 Resources for Reconstructing the Ancient Lakes Sierra Nevada
b Lake Chalco
4500
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Pueblo de Santiago de Chalco Ayotzingo
a
4000
Chichinautzin volcanoes and Pueblo de lavas 2500 Mecameca
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Sierra Nevada
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Ca min Ca oq mi . va Tie no par rra de aO Ca zu lie m nte ba
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a Ayotzingo
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LANDSCAPE FEATURES OF INTEREST
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1. Amecameca River 2. Active deltaic channel 3. Delta
Pueblo de Tenango Tepopula
4. Lake Chalco 5. Lakeshore 6. Chichinautzin lava flows
uic a
Pueblo de Temamatla
Mojonera de entre Mesquic y Ayotzingo
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o Camin
Mesquic
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go
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Volcan
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Pueblo 6 de Ayotzingo 1 2 Pueblo de Huitziltzingo 3
4 5 nde se extie Laguna grande de Chalco que co tel Te Ayotzingo 4 y hasta
Fig. 2.10 Examples of colonial maps of the southeastern shores of Lake Chalco with approximate location on a modern map. (a) Map of Chinampas of Mixquic and Ayotzingo in the AGN document: Misquic, Xochimilco y Ayotzingo, Chalco, AGN 1579; and (b) map of the Amecameca- Chalco Region (possibly 1770), redrawn from a facsimile map by Apenes (1947)
However, not until the late eighteenth century did maps become more accurate and detailed. Maps of the city and its surroundings through the nineteenth century have long been a resource for mapping the extent of the lakes and changes in the hydrology (see Lombardo de Ruiz 1996; Departamento del Distrito Federal 1975; Apenes 1947). An important archive with a wealth of maps is the Mapoteca Manuel Orozco y Berra, located in the Meteorological Observatory of Tacubaya. It contains a collection of colonial and post-independence maps of the entire country, and in
2.3 The Historical and Ethnohistorical Record
43
particular several cartographic documents of the Basin of Mexico at different scales. One advantage of this map collection is that many of them are now accessible online.
2.3.4 Historical Landmarks and Historical Photography In addition to written documents and maps, historical landmarks are of great help for the mapping of ancient features now not visible in the landscaps. Examples of such places include canals and docking areas (embarcaderos), as for example the former Garita de San Lazaro, which served for a long time as the place where boats would depart from Mexico City to go to Texcoco. The Canal de la Viga and its features, now a street, are also important locations. Several of the existing thoroughfares such as the Calzada de Tlalpan, the Calzada Ermita-Iztapalapa, the Calzada de los Misterios, and the Calzada de Tacuba are former causeways that connected Tenochtitlan and early colonial Mexico City with the mainland (Fig. 2.4). Paintings are also sources of information on the extension and appearance of the lakes (e.g., Fig. 1.3), as is historical photography. Most of the photographs of the late 1800s and the 1900s show in detail the last times of the existence of a lacustrine life in the Basin. Likewise, aerial photographs taken through the twentieth century have been useful for archaeological surveys of the former lakebeds (Parsons et al. 1982; Armillas 1971; Parsons 1971). In some cases, photographs are a good resource in support of ethnographic studies, as shown in many examples across the Basin (e.g., Rojas-Rabiela 1998; Parsons 2001, 2006; Linné 1937). All such studies contain the 1930–1940 photographs by Ola Apenes (now in the Museum of Ethnography, Stockholm, Sweden), which are an invaluable ethnographic record of lacustrine activities. Historical aerial photography should also be mentioned as an important historical record of the lakes in the twentieth century, especially in areas where urban development has obliterated important features of the former lakes such as dikes, canals, and historical settlements. The example in Fig. 2.11 shows the area that is occupied today by the sprawl of recently built neighborhoods north of Chimalhuacan, the artificial Lake Nabor Carrillo, and the area destroyed by the construction of the failed airports and highways (Fig. 2.11a). Evident in the 1960 aerial photograph are the remains of the lake cut across by a road (now the El Peñón-Texcoco Highway) and the series of canals that two decades earlier people in Chimalhuacan used to navigate to open lake, now in the picture in retreat. On the dry lakebed, one can distinguish former artificial islands like the site of El Tepalcate, now completely overrun by the urban sprawl (see Fig. 2.3b), former beach ridges, and coppice dunes colonized by saltgrass. These examples show not only how much the landscape has changed in half a century, but also how useful aerial photographs are for reconstructing historic and prehistoric features.
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2 Resources for Reconstructing the Ancient Lakes
a 7
Abandoned installations NAICM
7
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Pumping station “Casa Colorada”
Rio de los Remedios canal 4 1
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1 Water regulation pools 2 Water processing plants 3 Drainage canals 4 Toll roads
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5 Outer perimeter of future L. Texcoco Ecological Park 6 Inner perimenter (fenced) of L. Texcoco Ecological Park 7 Urbanization c.1980s-present
Approx. 1 km
1 Tulares 2 Saltflat with coppice dunes 3 Paleobeach ridge 4 Former navigation canals
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Drainage canal “Dren del Valle”
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5 Saltworks 6 Drainage canal and protective levee 7 Canals to drain eastern rivers 8 Embarcaderos (mooring areas)
Fig. 2.11 (a) Lake Texcoco in 2017 from Google Earth Pro. (b) The same area in 1960, photo adapted from Compañia Mexicana de Aerofoto
2.4 The Modern Environment and the Ethnographic Record 2.4.1 Features in the Modern Landscape as Clues to the Past The features of the modern landscape in the areas of the former lakes are also a good reference to the past environments, as is the case of the remaining bodies of water and their features (e.g., canals and chinampas). Even those areas of the lakes deeply modified provide information on the lacustrine past, sometimes in the form of frequency of flooding, salt corrosion, soil cracking, deformation of streets, and subsidence. Interestingly, these adverse phenomena are good indicators of conditions of the lacustrine subsoil and features such as artificial islands and causeways built by its ancient lacustrine inhabitants in the past (Auvinet et al. 2017) (see Chap. 9). Features on the Lake Texcoco bed, some visible on Google Earth images or aerial photography, provide clues to former features such as canals or even former deltaic surfaces, beach berms, and even eolian features (see Chap. 5). Patterns of vegetation or land-use change in recent times also provide information on differences from former lacustrine grounds. In some cases, modern soils on the former lakebeds can also indicate aspects of former lacustrine environments and processes (Bautista-Guzmán 2018; Gutiérrez-Castorena and Ortiz-Solorio 1999). Therefore, the combination of both aerial and ground information complements the modern record for reconstructing the former lakes.
2.5 GIScience, Virtual Realities, and Modeling
45
2.4.2 The Ethnographic Record and Ethnoarchaeology Despite the efforts to drain the lakes, water remnants continue to thrive in parts of the Basin (Fig. 1.2). Thus, traditional ways of resource exploitation and wetland agriculture survived especially in Lake Xochimilco, where aquatic agriculture (chinampas) combines with extraction of resources from the canals (Rojas-Rabiela 1998). In Lake Texcoco, traditional activities such as fishing, waterfowl hunting, salt making, and collection of algae and insects continued through the twentieth century (Parsons 2001, 2006). While ethnographic studies aim at collecting information on modern traditional activities, ethnoarchaeology those modern traditional activities with those of the past, especially by comparing it with the archaeological record. Both ethnographic and ethnoarchaeological research has seen an immense amount of work in the lacustrine realm of the Basin of Mexico, particularly in the chinampa areas of the southern lakes and areas of ponds on the western side of former Lake Texcoco (e.g., Albor-Ruiz 2017; Parsons 2001, 2006; Rojas-Rabiela 1984). The activities studied in the lacustrine environment of the Basin of Mexico are diverse and include the hunting of birds and fishing; the collection and harvesting of plant foods, insects, and algae; and the management of chinampas and canals. Many of these activities were recorded in the Florentine and Mendoza codices and numerous other documents of the early years of Spanish colonial rule.
2.5 GIScience, Virtual Realities, and Modeling 2.5.1 GIS and Remotely Sensed Imagery It is not possible to view the modern environmental record without the support of maps and remotely sensed images, particularly those showing recent land-use changes and the relation with ancient landforms and settlements. Georeferenced archaeological sites and features, landforms, and stratigraphic data can be integrated into the modern landscape. Thus, using Geographic Information System (GIS) platforms, it is possible to provide a tool capable of storing information of the past and the present, which in turn can serve to locate features that disappeared over a large area. For example, the mapping of old chinampas, canals, and settlements in the context of modern chinampas and canals in Lake Xochimilco combines information recovered in archaeological survey with features in the modern landscape (Luna- Golya 2014). GIS can also help bring features on old maps to a modern geographic coordinate location (Martín-Gabaldón 2019). Digital geographic sources include digital elevation models (DEM), digital surface models (DSM), and point clouds structure for motion (SfM), and light detection and ranging (LiDAR) are useful for tools for detecting and reconstructing a number of features on the former lakebeds (Acosta-Ochoa et al. 2017a), including
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2 Resources for Reconstructing the Ancient Lakes
those not reported by the archaeological surveys. However, even accessible platforms such as Google Earth that provide images showing the recent changes in the modern environment also serve as a basis for the reconstruction of past environments with a certain degree of accuracy. Both the high-tech systems and the accessible platforms constitute the basis for virtual recreations of the landscape and modeling of processes.
2.5.2 Virtual Realities of the Past The advent of digital technology, and particularly the use of geographic information systems and remote sensing, has permitted the integration of data to reconstruct or reproduce phenomena in space and time. Many examples of the recreation of the lakes and their ancient built structures have appeared as sequential maps or visualizations in motion. Some are accessible online in the form of virtual reality or just as movies. One example of interactive reconstructions of the historic lakes is the work by Thomas Filsinger (2005). His reconstructive sequence of the lakes and settlements begins with 1325 and continues with 1500, 1580, 1660, 1780, 1810, 1850, 1910, 1950, and 2000. These attractive, colorful maps tied to locations on satellite imagery to which some cultural features were added are based principally on the historical data compiled on a previous map by Gonzalez-Aparicio (1968). However, the existence of the primitive islands in the pre-Tenochtitlan period, for example, is questionable, as discussed in Chap. 13.
2.5.3 Modeling Past Environments and Their Processes Models are abstractions of reality that provide information on the functioning of systems, for example environmental systems, in abstract form (Cordova 2018). Unlike virtual representations, which aim at representing phenomena visually, models permit changes based on quantitative and qualitative data inputs that create different simulations representing dynamic processes in past environments. Simulation models in many cases use algorithms, which makes them easier for computers to handle. However, not all models are mathematical and require computers, as some are theoretical and idealized, serving a heuristic purpose. For example, a theoretical model of lake variation in climatic and geologic terms is proposed in Chap. 8. Likewise, an idealized model, to some extent hypothetical, to explain the origin and evolution of Tenochtitlan in relation to lake dynamics is proposed in Chap. 13. Computer simulation models of lacustrine behavior in the past do not exist, though a number of studies have tried to model the subsoil of the Basin of Mexico through simulation models (see Auvinet et al. 2017). The purpose of these models,
2.5 GIScience, Virtual Realities, and Modeling
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often in civil engineering, is to influence decisions related to the control of geological hazards. In relation to reconstructing the past, some models aim at reconstructing past climate using certain inputs from sediments and geomorphic features as well as archaeological sites, similar to the reconstruction of Laguna Magdalena in the Late Holocene (García-Ayala 2018). Archaeological features also have attracted modelers, as is the case of a simulation model for the efficacy of Nezahualcoyotl’s dike (Torres-Alves and Morales-Nápoles 2020). Outside of landscapes there are also models that describe changes in one or two of the elements of the physical landscape, as in the series of changes in the lakes for which there are ample examples derived from Quaternary research (Chap. 6), or those for lake currents (Chap. 8). Simulation of temperature, atmospheric moisture, precipitation, and winds in the presence of the former lakes (López-Espinoza et al. 2019; Jazcilevich-Diamant et al. 2015; Ruiz-Angulo and López-Espinoza 2015) are also useful aspects of the virtual records that provide insights into past environmental reconstructions.
Chapter 3
Geographic Context and the Modern Environment
3.1 General Physiographic Background 3.1.1 Location and Major Landforms The Basin of Mexico is located in the south-central part of the Trans-Mexican Volcanic Belt at the south end of the Mexican Altiplano (Fig. 3.1). The Basin was originally endorheic (no natural drainage outlet), but in the course of the past five centuries, several artificial surface and subterranean outlets drained the Basin’s water into the Rio Tula, a tributary of the Moctezuma-Pánuco, which empties in the Gulf of Mexico. Similar endorheic basins with lakes exist elsewhere in the Trans-Mexican Volcanic Belt (TMBV), most notably the Oriental-Serdan Basin, the Patzcuaro and Zirahuen basins, and the San Marcos, Sayula, Atotonilco, and Zapotlan basins (Fig. 3.1). Exorheic basins with shallow lakes similar to those of the Basin of Mexico include the Upper Lerma, Cuitzeo, and Zacapu basins. Because of their morphological similarities, these lacustrine basins, along with others in the country, represent an important resource as modern analogues of the lacustrine dynamic systems that existed in the Basin of Mexico (see Chap. 8). The Basin of Mexico covers a surface of about 9560 km2, extending approximately between latitudes N 19° 02′ and N 20° 13′ and longitudes W 98° 14′ and W 99° 31′. The lowest elevation of the Basin, 2240 m, is located in the center of Mexico City on the lakebed of former Lake Texcoco. The highest elevation of the Basin is 5230 m on the summit of the Iztaccihuatl volcanic complex—more properly on the structure referred to as El Vientre (The Belly). Although the summit of nearby Popocatepetl volcano is higher (5426 m), this high point is not located within the divide of the Basin of Mexico (Fig. 3.2). However, the highest point of Popocatepetl within the limits of the Basin of Mexico is El Pico del Fraile (5013 m).
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5_3
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3 Geographic Context and the Modern Environment
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8 Atotonilco 9 San Marcos 10 Sayula 11 Zapotlan
Lakes in exorheic basins 12 Chignahuapan 13 Zacapu 14 Chapala 15 Magdalena
16 Meztitlan
Fig. 3.1 The Basin of Mexico in the geographic context of other lacustrine systems of the Trans- Mexican Volcanic Belt and other areas of Mexico
The mountain ranges bordering the Basin on its east, west, and south sides are the Sierra Nevada, Sierra de las Cruces, and Sierra del Chichinautzin, respectively (Fig. 3.2). To the northwest, the limits of the Basin are marked by volcanic and tectonic structures of low elevation and the Tlaxcala Block. The Sierra de Pachuca, the Sierra de Tezontlalpan, and other smaller elevations form the northern and northeastern border. The divide of the Basin reaches its lowest point in the northeast, in the area of Huehuetoca, which is the location of the first trench (Tajo de Nochistongo) dug to drain the Basin (Fig. 3.3). Although there are variations across the Basin, the geomorphic units from highest to lowest elevations are mountain summits, mountain slopes, piedmont, alluvial plain, and lacustrine plain. In some areas, as in the south, along the base of the Chichinautzin, lava flows conform the piedmont. In the Apan-Tochac basins (Fig. 3.2), the geomorphic units consist mainly of valleys and small elevations corresponding to tectonic blocks and small volcanic cones.
3.1 General Physiographic Background W 99° 45’ 00”
51
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de San Miguel V.
0
Tlaxc
L.Texcoco
Popocatepetl V.
Fig. 3.2 The Basin of Mexico, its original subbasins, and bordering mountain ranges
3.1.2 Topographic Characteristics of the Lacustrine Basins Although the general topographic characteristics of the lacustrine basins are evident in the digital elevation model (Fig. 3.3), topographic profiles emphasize some aspects of the terrain important to understanding their hydrological characteristics. Topographic profiles across the Lake Texcoco basin reveal the topographic gradients from mountain summits to lacustrine plain. On the eastern side of the Texcoco Basin, the mountains are taller and steeper, the piedmont is narrower, and alluvial plain is wider than its counterpart on the west side (Fig. 3.4, profile 1–1′). Such a difference is important in terms of the rivers that feed the lake from each side and the amount of sedimentation in the alluvial plains. A higher resolution topographic profile connecting the western and eastern piedmonts across reveals the deformation of the lacustrine plain, where the center of Mexico City now appears lower than bed of Lake Texcoco (Fig. 3.4, 2–2′). Originally, the west side of the lakebed was higher, but constant extraction of water and the weight of the buildings have caused continuous subsidence (Auvinet et al. 2017; Santoyo-Villa et al. 2006).
52
3 Geographic Context and the Modern Environment 4
1
eN od Taj
C. Citlaltepetl
1’ Topographic profiles
65
is och
Approximate location of former lakes
go ton
C. Gordo Teotihuacan C. Chiconautla Valley
4’ Sierra de Guadalupe 6’
S.
3’
Pa
tla
ch
iq
ue
2’
5’
Sie d rra as el
2
uc
Cr
5500 5000
Tlaloc V.
3 C. Chimalhuacan
1’
Telapon V.
ina
Catar
1
4000 3500
7’
Ajusco V.
3000
Sierr
2500 2240 2000 meters
5
8’ nta S. Sa
7
es
4500
0
C. de la Estrella
a del
10 km
Iztaccihuatl V.
Chich
8
inaut
zin
Popocatepetl V.
Fig. 3.3 Digital elevation model of the area of the main lakes with the location of topographic profiles (Figs. 3.4, 3.5, and 3.6)
The north-south profile across Lake Texcoco shows other important morphologies of the lakebed and its surroundings (Fig. 3.4, profile 3–3′). Noticeably, the transition between the smaller sierras and the lake is more abrupt and marked by bajadas instead of the broad piedmonts of the large western and eastern sides of the lacustrine basin. Bajadas occur at the foot of the smaller sierras (e.g., Santa Catarina, Sierra de Guadalupe) and smaller structures (e.g., the Cerros of Chiconautla and Chimalhuacan and the Cerro de La Estrella). They are fed by small intermittent and ephemeral streams that deposit their sediments at the foot of the mountains, thus creating steep and narrow alluvial plains. The basins of the northern lakes (Zumpango and Xaltocan) and their topographic relation with the Lake Texcoco basin to the south and the Tula basin to the north portray the topographic difficulties that made the artificial drainage of the lakes out of the Basin of Mexico (Fig. 3.5). The profiles from the Tula River Valley to Cerro Chiconautla (profile 4–4′) and from Citlaltepec to El Caracol (profile 5–5′) show the
3.1 General Physiographic Background W 1 Sierra de las Cruces La Palma Volcano Desierto de 3500 los Leones 3250 3750
53 Sierra Nevada 1’ E Tlaloc Volcano
Transect 1-1’ Sierra de las Cruces-Sierra Nevada
3000
Mexico City
2750
Tacubaya
2500 2250
Historic Center
Lake Airport Nabor Carrillo
1 km
Transect 2-2’ West-East, piedmont to piedmont across Lake Texcoco
W 2 2300
Anillo Periferico
2275 2250
Tlatelolco
Mexico City
Gran Canal
Lake Texcoco Ecological Park
2’ E
La Magdalena Panoaya 2240 m
2225
1 km
S
3
2300 2275 2250
Transect 3-3’ North-south, Cerro Chimalhuacan-Cerro Chiconautla Cerro Chimalhuacan
3’ Cerro Chiconautla
Chimalhuacan Atenco Lake Nabor Carrillo
2225
Lake Texcoco Ecological Park
El Caracol
N
2240 m
1 km
Fig. 3.4 Topographic profiles across the Lake Texcoco basin: (a) west-east, piedmont to piedmont; (b) west-east, Sierra de las Cruces to Sierra Nevada; and (c) north-south, Chiconautla-Chimalhuacan
notable differences in elevation between Lake Texcoco and the southern lakes, which meant the digging of a deep trench (Tajo de Nochistongo) to drain the lakes (Fig. 3.5). It is because it was impossible for the so-called Canal de Castera, built at the end of the eighteenth century, to overcome these topographic differences. Thus, it was not until the construction of a much deeper canal (Gran Canal del Desagüe) and tunnels (Tunel de Tequixquiac) that it was possible to drain the lakes (see Sect. 3.3.1). Profiles 5–5′ and 6–6′ show modern Lake Zumpango bordered by artificial levees, appearing to be higher than its surrounding plain (Fig. 3.5). This is a good example to the artificial nature of Lake Zumpango and the various changes that the lake underwent since early colonial times (Chap. 7). Profile 6–6′ shows that the abrupt transition from mountain to lake around the Sierra de Guadalupe consists mainly of bajadas. Evidently, this suggests that Lake Xaltocan had very little water input from stream flow, limited perhaps to the Cuautitlan River, before its diversion to the north, and flow from Lake Zumpango and local springs. The basins of the southern lakes (Chalco and Xochimilco), which hydrological are one single basin, present asymmetric topographies between their west and east ends (Fig. 3.6, profile 7–7′). On the east, the piedmont transitions to an ample alluvial plain of the Amecameca and Tlalmanalco rivers and then into Lake Chalco, where the rivers form deltaic systems. In contrast, on the west, El Pedregal lava field forms an abrupt transition with the bed of former Lake Xochimilco. Asymmetric topographies also characterize the north and south of the lacustrine basins (Fig. 3.6, profile 8–8′). Thus, the transition from mountain to lake on the south side (the lavas
54
3 Geographic Context and the Modern Environment Transect 4-4’ Tula River-Cerro Chiconautla 4
2400 2300
Tula-Pánuco Basin
Modern Former Lake Lake Zumpango Xaltocan Plain Gran Canal del Desagüe Xaltocan
Tajo de Nochistongo Divide Huehuetoca
2200
Cerro Chicoanutla Ozumbilla
4’
1 km
Modern 5 Lake Zumpango Citlaltepec
2300 2275 2250
Transect 5-5’ Cerro Citlaltepec-El Caracol-Lake Texcoco Gran Canal del Desagüe
5’
Former Lake Texcoco Plain El Caracol
1 km
6
Transect 6-6’ Citlaltepec-Sierra de Guadalupe-Lake Texcoco
Sierra de Guadalupe
6’
2700 2600 2500 2400
Modern Lake Zumpango
Cerro Tultepec
2300
Former Cuautitlan River channel
Former Lake Texcoco Plain Gran Canal del Desagüe
1 km
Fig. 3.5 Three topographic profiles across the basins of lakes Zumpango and Xaltocan: (a) Tula River valley to Cerro Chiconautla, (b) Citlaltepec-El Caracol across the strait of Ecatepec, and (c) Citlaltepec to El Caracol over the Sierra de Guadalupe
of the Sierra del Chichinautzin) is abrupt and almost devoid of alluvial plain. In contrast, the transition from the Sierra de Santa Catarina to the lake is less abrupt and formed by a combination of lava flows and bajadas descending from the volcanic peaks.
3.2 Climate 3.2.1 General Climatic Patterns Located roughly at latitudes 19–20° N, the Basin of Mexico receives high insolation throughout the year and is exposed to tropical and subtropical atmospheric systems. During the boreal summer, changes in insolation bring the ITCZ (intertropical convergence zone) north, creating a monsoon-type phenomenon that draws rain from the Gulf of Mexico and the tropical Pacific Ocean, resulting in the development of a rainy season roughly from May/June to September/October (Lozano et al. 2019; Metcalfe and Davis 2007). During the rest of the year, the retreat of the ITCZ south brings subtropical highs, resulting in dry conditions. However, occasional southward excursions of the Polar Jet Stream bring frontal rain during the winter months (Jáuregui-Ostos 2000). Climatic oscillations such as El Nino Southern Oscillation (ENSO) affect the yearly pattern of rainfall in this part of Mexico. Thus, under the influence of El Niño conditions, summers tend to be drier and warmer, while winters slightly cooler and
3.2 Climate
W
7
55
Transect 7-7’ - El Pedregal (Metro Universidad) - Tlalmanalco
7’ E
Metro Universidad
Xico
El Pedregal
2300
Tlamanlco
Lake Xochimilco
2250
Tlahuac
Lake Chalco
Chalco
1 km
Transect 8-8’ - Sierra del Chichinautzin-Tlahuac-Santa Catarina S
8
Sierra del Chichinautzin Teuhtli Volcano
Sierra de Santa Catarina
8’
N
2600 2500 2400
Lake Xochimilco
2300
Tlahuac 1 km
Fig. 3.6 Topographic profiles across the Lake Chalco-Xochimilco basin. (a) West-east profile (Universidad subway station-Tlalmanalco) and (b) south-north profile (Chichinautzin-Tlahuac- Santa Catarina)
Fig. 3.7 Climatic types (Köppen classification) for the Basin of Mexico (Adapted from Sanders et al. 1979) and climographs for selected localities. (Data from CONAGUA 2021)
56
3 Geographic Context and the Modern Environment
wetter, with the opposite occurring generally during La Niña events (Lozano-García et al. 2019; Metcalfe and Davis 2007; Pavia et al. 2006). Because of its location within the tropics and its elevation ranging above c. 2240 m above sea level, the Basin of Mexico has a tropical, highland climate transitioning from subhumid to semiarid. Two distinctive Köppen climatic types predominate in the Basin, one temperate (Cw) in the south and at higher elevation and another semiarid (BSkw) in the north (Jáuregui-Ostos 2000; Calderón de Rzedowski and Rzedowski 2001) (Fig. 3.7). Additionally, the highest points on the Sierra Nevada have pockets classified as Highland Tundra or Permanent Ice (EH) in the classification of Köppen (García 1988). Weather and climatic patterns at the time the lakes still existed have definitely changed, in part because of secular variations of climate (O’Hara and Metcalfe 1997) and global rise in temperatures (Jáuregui-Ostos 2000, 2002), land-use changes (Jáuregui-Ostos 2000; Berres 2000), and the reduction of moisture due to the disappearance of the lakes (López-Espinosa et al. 2019; Berres 2000). Simulation models based on the existence of the lakes in the sixteenth century indicate that the lakes regulated the temperature and wind (López-Espinosa et al. 2019; Ruiz-Angulo and López-Espinoza 2015), contrasting with the effects of the flat exposed beds and built-up areas that dominate the former lake areas today.
3.2.2 Temperatures Temperatures in the Basin of Mexico vary across the year depending on insolation, moisture, and cloudiness. The hottest season occurs in the spring, with April and May as the hottest months (Fig. 3.7, climographs). However, high temperatures can extend into June if rains fail to appear. Mean maximum temperatures in the hottest month (April) seem relatively low, usually between 22 and 27 °C (Fig. 3.8), in part because at night temperatures drop due to the relatively high elevation (over 2000 m) and low moisture. Nonetheless, during the day, temperatures may reach over 30 °C in the low areas, especially in the city. On the other hand, above 3000 m temperatures remain low (20 °C or less). Mean minimum temperatures of the coldest month (January), which occur in the early hours of the morning, fluctuate usually below 10 °C (Fig. 3.9). Minimum low temperatures vary also with elevation but in valleys tend to be low in wintertime due to thermal inversion in the early hours of the day (Jáuregui-Ostos 2000). Frosts are normal phenomena from November to February in some parts of the Basin, although they can extend into earlier or later periods, thus becoming a hazard for crops. Snowfall is common on the summits of the highest mountains (Popocatepetl, Iztaccihuatl and Ajusco) and rare below 3000 m. Although snowfall has been recorded in past centuries even in the low parts of the basin, lowest part of the Basin, there has not been such an event since 1967.
57
28
26
25
N
29
27
26
2 22 3
21
27
28
22
20
24
N 19° 24’ 10”
29
21
26
25
22
28
21
27
2 2 5 23 4
21 22
2 26 7
26
23 24 25
26
27
28
27
26
25
W 99° 45’ 00”
3.2 Climate
Mean maximum temperatures April
210 2
25 24 23
0 5 10 15 20 kilometers
Fig. 3.8 (a) Mean April temperatures. (Based on Jauregui-Ostos 2000)
3.2.3 Precipitation and Moisture Balance Precipitation in the Basin is concentrated between June and September, though normally the first rains begin in May and extend until October. Rain increases considerably in June, reaching its maximum usually in July or August and becoming considerably less in October (Fig. 3.7, climographs). From August to October, cyclones on both oceans can induce extraordinary amounts of rain in a short period (Jáuregui-Ostos and Vidal-Bello 1981). The dry season extends from late October to May in association with the influence of the subtropical highs, which inhibit rainfall (Jáuregui-Ostos and Vidal-Bello 1981). However, occasional rains occur in November, especially those associated with late tropical cyclones, or in January and February when cold fronts carried by southerly excursions of the polar jet stream descend to these latitudes (O’Hara and Metcalfe 1997; Jáuregui-Ostos and Vidal-Bello 1981). During such events, snow and sleet are common in the mountains of the Sierra Nevada, Sierra de las Cruces,
3 Geographic Context and the Modern Environment
W 99° 45’ 00”
58
2 1
1
5
5 4 3
4
2
0
0
1 2
2
2
1
0
2
1
2
0
3
N
3
1
2 4
2
3 4
7 6 5
2
3 2
3
4
2
4
Mean minimum temperatures January
2
3 4
4
1 N 19° 24’ 10”
1
5 3
2
5
0 5 10 15 20 kilometers
Fig. 3.9 (a) Mean January temperatures. (Data and isotherms based on Jauregui-Ostos 2000)
and parts of the Sierra del Chichinautzin. However, high insolation due to the low latitude leads to rapid melting. The largest amount of mean annual precipitation occurs in the higher elevations on the highest mountains in the south, where the orographic effect increases adiabatic rates. On the Sierra de las Cruces, the mean annual precipitation exceeds 1000 mm a year. The lowest precipitation levels are recorded in the lowest elevations on the western part of the former Lake Texcoco and in the northern and the northeastern parts of the Basin (Fig. 3.10). Precipitation is not the only factor in overall moisture, as water is taken back into the atmosphere through evaporation and evapotranspiration, two aspects of importance in understanding the hydrological balance that affects the lakes. Evaporation is the loss of molecules of water from the surface of liquid water. It is strongly related to insolation, which is affected by latitude, cloudiness, temperatures, and moisture. In general, however, areas with potential water loss to evaporation coincide with the areas of higher temperatures (Jáuregui-Ostos and Vidal-Bello 1981), which happen to be in the lower areas of the Basin, in the lacustrine basins. However, an increase in evaporation is also apparent from south to north, which means an
59
3.2 Climate S. Mateo Acuitlapilco W 99° 45’ 00”
60
0
mm 160 140 120 100
550
N
0
5
10
15 20
kilometers
600
80
0
60
800
40
J F M AM J J A S O N D
0
70
700
0
900 1000 1100 1200 1300
20
800 700
70
S. Mateo Acuitlapilco
0
80
0
60
Texcoco
55
0
Mean annual precipitation
90 0
Mean annual evaporation
mm 140
mm
Texcoco
200 180 160
Tlahuac
Tlahuac
140 120
120
100
100
80
80
60
90
0
90
00
20
10
00
40
0
12
1 13 100 00
60
0
N 19° 24’ 10”
40 20 0
J F M AM J J A S O N D
J F M AM J J A S O N D
Fig. 3.10 Map of mean annual precipitation (Based on data and isohyets from Jáuregui-Ostos 2000) and graphs showing monthly mean precipitation and evaporation from selected locations. (CONAGUA 2021)
increase in loss as precipitation declines. Evapotranspiration (ET) implies the loss of water from water surfaces and vegetation and soil cover. Unlike, evaporation, ET has an indirect effect on the basins, as it depends on how much is lost in the different land covers of each of the river basins feeding the lakes (Gómez-Reyes 2013).
3.2.4 Wind Patterns The current wind patterns in most of the Basin of Mexico have been directly affected by the “heat island” generated by the urban cover, resulting in the formation of a vortex that draws in winds to the core of the metropolitan area of Mexico City (Jáuregui-Ostos 2000). This implies modifications to the wind patterns of the past. Historical data point to at least three dominant wind directions, from the northwest, north, and northeast, with important components from the south and southwest (Comisión Ambiental Metropolitana 2011; Altamirano 1895). Historical data show that direction and velocity vary depending on the time of the day and the season, usually remaining from the north during the early hours before sunrise with
60
3 Geographic Context and the Modern Environment
modification throughout the day (Jauregui-Ostos 2002). Usually, winds tend to be stronger during the day, depending on the season and locality within the basin, though wind velocity and frequency vary with the season. By far, the strongest winds occur in the late winter and early spring months. It is during this time that dust storms (tolvaneras) afflict the inhabitants of the basin. The source of the dust is mainly the dry lakebeds and agricultural fields that at the time are being prepared for the incoming season. Certain topographic features modify wind velocity. Areas with strong winds include those in the narrow mountain passes where the flow of air undergoes a funnel effect. One of these areas is the Ecatepec strait, between the Sierra de Guadalupe and the Cerro Chiconautla (Fig. 3.3). Also, more open and flat areas tend to have stronger winds, as it happens in the center of the lacustrine basins. These topographic aspects are important in terms of reconstructing the effect of seasonal wind patterns over the lakes, especially for the generation of waves and currents, an aspect that is discussed in more detail in Chap. 8.
3.3 Hydrology 3.3.1 The Current Drainage System What is today the Basin of Mexico consisted of three main endorheic basins, namely, Tecocomulco, Tochac-Apan, and the Basin of Mexico proper (Fig. 3.2). However, during the past 400 years, the three basins were systematically integrated into a
a
Túneles de Tequixquiac Tajo de Nochistongo
b
Basin’s original divide Extent of former lakes
Major surface drainages Drainage tunnels
Streams and canals
Lakes and ponds
Deep trench drainage out of the Basin
Urban cover
Major surface drainages Drainage tunnels
Túnel Central
Lakes and ponds
Túnel Emisor Oriente (TEO)
Gran Canal del Desagüe
Canal CuautitlanTajo de Nochistongo
Túnel Emisor Poniente
5500 5000 4500 4000 3500 3000
0
5
10 km
2500 2240 2000 meters
0
5
10 km
Fig. 3.11 (a) Current hydrological surface network in the former lacustrine basins; (b) deep underground drainage
3.3 Hydrology
61
complex drainage system that now exits the Basin through various conduits through the northwest into the Tula Basin (Fig. 3.11). The oldest of these conduits is Tajo de Nochistongo, built in the seventeenth century, that first drains the basin of the Cuautitlan River (Fig. 3.11a), though today it taps water from other stream basins in the west (Fig. 3.11b). The Tuneles de Tequixquiac, completed in the early twentieth century, drains large parts of the former basins of Lake Texcoco and the southern lakes via the Gran Canal de, Desague (Fig. 3.11b). However, as these systems were not enough to reduce flooding in the growing city, two other deep tunnel systems were built in the late twentieth century the Tunel Emisor Poniente and the Tunel Central, with the latter being a deep tunnel (Fig. 3.11b). Then in the current century, Tunel Emisor Oriente (TEO) is an even deeper tunnel that collects water excesses (Fig. 3.11b). The irony of the current artificial drainage system is the loss of large amounts of surface water while the demand for water in the Basin falls short (Ezcurra 1990). Furthermore, the extensive urban cover has modified runoff, producing large amounts of water that not being able to infiltrate the ground that cause floods in some areas. In other instances, the drainage system collects the water, which is into the deep tunnels (Gomez-Reyes 2013), eventually leaving the Basin through the north (Fig. 3.10b). Plans for capturing more of the runoff and refilling part of Lake Texcoco have been proposed (Cruickshank-García 1998; Alcocer and Williams 1996), a matter that may materialize in part through the creation of the proposed Parque Ecológico Lago de Texcoco (Lake Texcoco Ecological Park). The idea of refilling the lakes has also materialized with the creation of the current Lake Zumpango, which is fed by the excess drainage of the Cuautitlan River that would normally flow into the Tula Basin via the Tajo de Nochistongo (see Chap. 7). As for the Apan-Tochac and Tecocomulco basins, they were in recent centuries integrated through a series of canals into the Avenidas de Pachuca River catchment, which today flows directly into the Tequixquiac tunnels (Fig. 3.11a). These two basins held lakes, of which Lake Tecocomulco is the only one that survives (Fig. 3.2), as the canal built in the 1950s to drain it failed because of the poor design of the canal, leaving it only for draining the excess water of the lake (Huizar-Álvarez and Ruiz-González 2005). At present, Lake Tecocomulco has a surface of approximately 27 km2, an average depth of 70 cm, and a maximum depth of 3 m (Huizar- Álvarez and Ruiz-González 2005). It is situated at an elevation of 2535 m, about 284 m above Lake Zumpango (elevation, 2251 m); as the highest of the five main lakes of the Basin, Lake Tecocomulco receives water from several streams, the two most important of which are the Tepozan and Cuatlaco, in addition to smaller intermittent streams.
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3 Geographic Context and the Modern Environment
3.3.2 The Modern Hydrological Record and the Former Lake Basins There is no data on how much water rivers contributed to the former lakes. Nonetheless, it is possible to use modern discharge (volume of water per year) of the rivers to create a rough estimate of the water flowing into the former lake basins. For this purpose, data from the old hydrological zones published by the Departamento del Distrito Federal (1975) permit differentiating the volume of incoming waters from the different sides of each lacustrine basin (Fig. 3.12, Table 3.1). The northern basins received their water input mainly from the Cuautitlan, Tepotzotlan, and Avenidas de Pachuca. Of these, the one that contributed more was the Cuautitlan, though today this includes the drainage from the Tepotzotlan River. The Avenidas de Pachuca, despite having a large catchment area, has a relatively low potential contribution to the northern lakes (Table 3.1, Fig. 3.11), as it drains the driest parts of the Basin (Figs. 3.7 and 3.9). It is possible that its contribution to the lakes in the past was larger, as the values in Table 3.1 contrast with those from other sources (e.g., Peña-Díaz 2019). In general, however, the northern basins seem to have been highly dependent on fluvial and pluvial input, which explains their sudden growth during rainy events in times before the completion of the Desagüe (see descriptions in Candiani 2014; Gurría-Lacroix 1978; Ramirez 1976). For Lake Texcoco, fluvial input to the former lake seems to have been asymmetric, with a large amount coming from the western catchments (Fig. 3.12b), where three rivers—the Magdalena, Tlalnepantla, and Mixcoac—had permanent flow. The eastern catchments, in contrast, where the San Juan Teotihuacan River had a permanent flow, contributed much less to the lake. Similarly, the potential influx of spring water was considerably higher on the western side of the lake (Table 3.1, Fig. 3.12b). This phenomenon may explain in part why the western part of the lake, the area of
V
a
IV
3000 2000 1000 500
b
Lake Zumpango Lake Xaltocan
VI
100000 80000 60000 40000 20000 Springwater 10000 discharge (l/sec) Stream mean annual discharge Zone V (x103 m3)
Zone IV
L. Zumpango L. Xaltocan
VII 5500 5000
III
Zones II & III
Lake Texcoco
4500
II
4000 3500
L. Xochimilco
3000 2500 2240 2000 meters
0
5
Zones VI & VII
Lake Texcoco
10 km
I
L. Chalco
Zone VI
VIII
Zone VIII
L. Xochimilco
L. Chalco
Fig. 3.12 (a) Hydrological network of larger streams and hydrographic zones; (b) annual volume of water contributed by streams and springs into each of the former lacustrine basins. (Map and data are based on information in the Departamento del Distrito Federal (1975; Vol. 1, 54–5, 59, Tables 3 and 7))
63
3.3 Hydrology Table 3.1 Hydrographic indicators for the catchment zones around the main lakes Catchment zones Area km2 Average mean annual precipitation (mm) Percent of precipitation volume infiltrated Number of springs Spring water discharge (liters/sec) Potential volume of water available in springs (×106 m3) Mean annual discharge (×103 m3)
I 522 891
II 234 1020
III 725 872
IV 972 789
V VI 1087 930 520 612
VII 1146 639
VIII 1124 855
29.1
15.41
10.2
19.27
17.9
14.4
14.7
16.3
91 489
51 809
17 19
8 382
16 190
42 586
10 28 2333 531
8.925 17.092 24.251 25.828
0.599 12.047 5.992
1212 21,009 79,593 116,215 514
4609
19.678
36,802 19,408
Estimates and data from the Departamento del Distrito Federal (1975), Vol. 1. See zones in Fig. 3.11
Tenochtitlan and its satellite islands, had a more substantial flow of freshwater, which permitted implementation of the chinampa agricultural system (see Chap. 13). The southern lake basins had only two large rivers, the Amecameca and Tlalmanalco, with catchments in the east. Smaller catchments with seasonal or torrential waters descended from the sierras north and south (Fig. 3.11a). Large amounts of porous basaltic rocks in these catchments reduced the amount of surface water but constituted the aquifer that fed most of the springs that kept the lake levels more stable and provided freshwater, an important aspect for irrigation and the maintenance of chinampas (Morehart and Frederick 2014; Rojas-Rabiela 1993). Thus, the amount of spring water is by far the largest contributor, especially for Lake Xochimilco (Fig. 3.11, Table 3.1). Unfortunately, most of the aquifers have been tapped to satisfy the city’s need for water, thus reducing the input into the lake leading to desiccation of wetlands and canals in recent years. Water and soil salinity has always been an issue, especially in Lake Texcoco. Historically, the southern lakes had predominantly freshwater, while Lake Texcoco had highly saline water. However, it is possible that salinity varied through the year and in different parts of the lake depending on influx of freshwater. The salinity situation in the northern lakes is ambiguous in the records. Lake Xaltocan was saline, but it may have had some fresh or brackish water, which in turn permitted also the implementation of chinampas (see Sect. 9.3.3). Lake Zumpango is often reported as reported as a saline lake, but in modern times, salinity reports have pointed to a brackish if not freshwater lake (Bradbury 1989: Table 3), and archaeological surveys provide very little evidence of salt production sites (Parsons 2008), which are relatively abundant in the Lake Xaltocan and Lake Texcoco basins.
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3 Geographic Context and the Modern Environment
3.4 Regional Ecosystems and Soils 3.4.1 Vegetation Communities and Floristic Composition Although rural land-use cover and anthropic vegetation communities have replaced large parts of the original vegetation communities, the potential natural vegetation is still a conceptual basis for understanding the ecological and climatic changes in the past. Thus, the classification of actual and potential natural vegetation communities (Calderón de Rzedowski and Rzedowski 2001) provides an important basis for understanding modern and past ecosystems and climates in the Basin of Mexico. Because of the temperature and precipitation gradients in the basin, many of these vegetation units constitute altitudinal belts (Fig. 3.13). However, horizontally, variations occur along a precipitation gradient from north to south (Fig. 3.10) and in relation to geological substrate and ground hydrological conditions. Additionally, human impact on vegetation, especially through fire and more recently by livestock, has also created vegetation communities that sometimes bear little relation to climatic or other natural conditions. Halophytic and aquatic vegetation communities occupy the former lacustrine basins and their remaining wetlands (Fig. 3.13). The type of vegetation surrounding these areas, roughly occupying the alluvial plains, is not clear, as over millennia it has been transformed by agricultural communities. It is possible that these areas were grasslands or covered by some sort of shrubby vegetation, as suggested by the existence of soils and paleosols of the mollisol and vertisol types (Cordova 1997). DOMINANT TREES AND SHRUBS Pinus hartwegii
Juniperus
Abies religiosa
Quercus frutex
Pinus montezumae
Xerophytic shrubs
Elevation in meters
Alpine grassland “zacatonal” tufted grasses
HERBACEOUS COMMUNITIES
Pinus
Festuca-Calamagrostis grass community
Quercus
Hilaria grass community
Alnus
4500
Aquatics graminoids
Liquidambar
Halophytes Crops and pasture
Juniper woodland
4000
Pine-dominated forests
Oak shrubland
3500
Xerophytic shrubland 3000
Grassland
2500
5000
Aquatic and sub-aquatic vegetation Halophilous vegetation
Oak-dominated forests
Crops, pastures and eroded land
Fir forest 3000
Mesophilous mountain forest 2500
Fig. 3.13 Altitudinal belts of vegetation communities in the Basin of Mexico based on descriptions and elevations in Calderón de Rzedowski and Rzedowski (2001) and rendered in the diagram by the author
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A complex mosaic of cropland, pastures, secondary shrub communities, and eroded areas dominate the piedmonts. However, islands of arboreal and shrubby oak suggest that they may have been occupied by oak forests (Rzedowski 1981). Moving upslope, around 2500–2800 m of elevation, forests usually begin on terrain not apt for agriculture, often with oak-dominated forests, pine-dominated forests, or forests co-dominated by both, usually referred to as mixed oak-pine forests (Fig. 3.13). The most species of oak are Quercus laeta, Q. deserticola, Q. crassipes, and Q. obtusata in the lower parts; Q. laurina, Q. Mexicana, and Q. rugosa at higher elevations; and Q. greggii and Q. microphylla at lower elevations in the north (Calderón de Rzedowski and Rzedowski 2001). Mixed with the highest belt of oak and higher, pines begin to appear, reaching dominance around 2800. The pine forests are dominated by Pinus montezumae until about 3000 m where Pinus hartwegii begins to appear (Calderón de Rzedowski and Rzedowski 2001). The pine, oak, and pine-oak forests are perhaps the most widespread communities in the Sierra de las Cruces, Sierra Nevada, Sierra del Chichinautzin, and Sierra de Pachuca. At the same elevation of oak-pine mixed and pine forests, other communities appear in areas where topography permits microclimatic conditions for moisture- loving tree species. One of such communities is the mesophilous forest, which thrives at elevations between 2500 and 2800 inside canyons dissecting the southern part of the Sierra de las Cruces, where the dominant species are Clethra mexicana, Cornus disciflora, Garrya laurifloria, and Ilex tolucana (Calderón de Rzedowski and Rzedowski 2001). Another arboreal community thriving in habitats with moister microclimates is the Abies religiosa co-dominating with Alnus spp. at elevations between 2700 and 3500 m, in narrow valleys and north-facing slopes (Calderón de Rzedowski and Rzedowski 2001). Forests of Pinus hartwegii dominate the uppermost arboreal belt, until it becomes and interspersed in the zacatonal around 3500 m. The latter community is composed of tussock grasses of species such as Calamagrostis tolucensis and Festuca amplissima, with important representations of Stipa ichu and Muhlenbergia spp. This grass-dominated community forms the highest vegetation belt, extending from the upper tree line to areas below the snow line. Xerophytic shrub communities dominate the slopes of small hills, parts of the piedmont, and the surface stony soils commonly below 2700 m. The composition of the shrub communities varies across the Basin, though Opuntia streptacantha, Zaluzania augusta, Mimosa biuncifera, and the non-native Schinus molle tend to be present in all of them. Other common shrub species in these communities include Eupatorium spinosum, Eysenhardtia polystachya, Jatropha dioica, and Gymnosperma glutinosum. The juniper woodland is a community dominated by Juniperus deppeana thriving on the slopes of the Sierra Nevada, the Sierra de Pachuca, and the northwestern part of the Basin at elevations between 2400 and 2800 m. Its existence seems to be the result of the destruction of the oak and pine forests, rendering it as one of the anthropogenic vegetation communities (Calderón de Rzedowski and Rezedowski 2001). Likewise, the oak shrubland (Quercus frutex) community, found between
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2350 and 2100 m, on shallow soils in the northern part of the Basin, is another anthropogenic community produced by frequent fires (Calderón de Rzedowski and Rzedowski 2001). Other forms of grassland, different from the zacatonal, are the halophytic grasses (mainly Distichlis spicata), which are common in the saline lakebeds, and the semiarid grassland dominated by Hilaria cenchroides, found mainly in the northern and northwestern parts of the Basin at elevations between 2300 and 2700 m and occasionally in small patches on the piedmonts interspersed with the shrub communities.
3.4.2 Fauna The faunal species in the Basin of Mexico used to be high according to historic accounts, but encroachment on habitats and deliberate overhunting have reduced the populations and in some cases led to total extirpation, resulting in a sharp decline in biodiversity (CONABIO 2016, Vols. 2 and 3). The lower parts of the forests and wetlands have been the habitats most affected by the elimination of fauna, while remote areas of the forested mountains still have populations of animals that once inhabited other parts of the Basin. Because the focus here is on fauna associated with the aquatic environments of the former and modern lakes and wetlands, this chapter does not present and discuss the variety of terrestrial fauna outside the lake basins. However, it is important to mention that each of the vegetation communities described above has its distinctive fauna, despite many species (Departamento del Distrito Federal 1975). A good reference for the lists of species representative of the Basin of Mexico is La Biodiversidad en la Ciudad de Mexico (CONABIO 2016).
3.4.3 Soils and Landscapes The altitudinal ecological gradients extending from the lakebed to high mountains show the influence of climate, geological substrate, vegetation, and slope on the diversity of soils (Fig. 3.13). Notably, at high elevations, soils are thin because of high slopes and poor vegetation cover and thus dominated by patches of alpine grasses (zacatonal). Under the forest cover, a series of soils develops, usually beginning with different types of Inceptisols (andepts) and Lithosols, which transition into the Mollisols and Vertisols of the piedmont. The alluvial plains usually have recent sedimentation, resulting in poor soil development, thus making the orders of Entisols (fluvents) and Inceptisols (udepts) common soils, except in areas of Vertisols developed on older alluvium. Toward the lakebed, alluvial soils become thin and prone to salinization, thus giving way to the highly saline Solonchaks (Fig. 3.14). Although the Solonchaks dominate most of the lacustrine beds, soil
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Former Lake Texcoco bed (2239 m)
N Tlaloc Volcano (4115 m) Chicoloapan
Coatepec
Telapon Volcano (4050 m) 5
0 Km LACUSTRINE PLAIN
ALLUVIAL PLAIN
Elevation in m
4000
2500
Halophytic vegetation and barren ground
S.Vicente Chicoloapan
MOUNTAIN Oak-pine forest
Cultivated under irrigation
3500 3500
UPPER PIEDMONT
LOWER PIEDMONT
Zacatonal and pine Pine Forest
Pastures, shrubland, and eroded lands Rain-fed cultivated
Coatepec
SOILS
GEOLOGICAL SUBSTRATE
2240 Lacustrine clay and silts
FAO
Recent alluvium
Solonchak Vertisol-FeozemFluvisol
USDA Solonchak
Vertisol Mollisol (udolls) Entisol (fluvents)
Alluvial fans and lahars
Feozem-Cambisol
Mollisol (udolls) Inceptisol (ustepts)
Pyroclastic flows, indurated tuff, lahars, and ancient alluvial fans
Cambisol-Regosol-Feozem Inceptisol (ustepts) Entisol (urthents) Mollisol (udolls)
Lavas, mass wasting periglacial debris and tephras
Leptosol-Cambisol-Andosol
Lithosol Inceptisol (udents, andepts)
Fig. 3.14 Example of geomorphic units, vegetation, and soil on the western side of Lake Texcoco from the lacustrine plain to the summit of Telapón Volcano
types in other parts of the lacustrine beds vary depending on the hydrological conditions of the ground being in some cases Gleysols and in others Histosols. It is important to mention also the existence of anthropogenic soils in many parts of the basin, especially in terraced slopes and parts of the lacustrine plain. In the latter case, desiccation of the lakes (less than 400 years) resulted in the deliberate alteration of salinity, pH, and texture to make soils productive for agriculture (Bautista-Guzmán 2018; Reséndiz-Paz et al. 2013; Gutiérrez-Castorena and OrtizSolorio 1999). In parts of the southern lakes, the chinampas are the typical anthropogenic soils of the lakebed in wet areas or in areas of former chinampas now habilitated for modern agriculture.
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3.5 Lacustrine Flora and Fauna 3.5.1 Aquatic, Subaquatic, and Halophytic Vegetation The original vegetation communities have practically disappeared from the former lakebeds, except in certain protected areas in Lake Xochimilco. In other aquatic habitats, even in areas where lakes have been reclaimed, vegetation has little resemblance to what it once was, in part because introduced and invasive alien species have displaced the native species. In other cases, the drying of springs and drainage of wetlands and canals have led to replacement of aquatic vegetation by halophytic and other forms of secondary vegetation. One problem throughout the surviving bodies of water in the former lake basin is eutrophication or the enrichment of nutrients that provokes microscopic floral overgrowth that kills aquatic fauna (Alcocer and Williams 1996). Vegetation on the dry lakebed of Lake Texcoco consists mainly of halophytic species. One of the most notable is seepweed (Suaeda nigra), locally known as romerito, whose green leaves are edible. Very widespread are patches salt grass (Distichlis spicata) (Rzedowski 1957), which form on dunes on the former lakebed (Fig. 3.15a). The aquatic vegetation formed by monocotyledoneae is general referred to as juncales or tulares and includes cattail (Typha latifolia) and sedges (Schoenoplectus tabernaemontani and Cyperus spp.) (Lot and Novelo 2004; Rzedowski 1957). Today, many non-native species thrive on the former lakebeds, including halophyte shrubs such as Kochia scoparia, and small trees such as Tamarix plumosa, T. chinensis, and Casuarina equisetifolia, all introduced as windbreakers and to protect soil from wind erosion. However, despite these revegetation efforts, extensive areas of the former lakebed are barren (e.g., Fig. 3.15b). Surrounding the salinized lakebed, vegetation is predominantly ruderal, particularly on abandoned agricultural fields and areas of high disturbance, with various shrubs and trees, particularly exotic species such as Eucalyptus spp. and Schinus molle (pirul) along canals and roads. Disappearing, but once important in this area, is Taxodium mucronatum (ahuehuete), some of which still survive in a few areas of the eastern part of Lake Texcoco. Halophytic vegetation similar to that described for Lake Texcoco characterizes most of the beds of former Lake Xaltocan, except in areas where irrigation habilitated soils for agriculture. The modern Lake Zumpango, an artificial body of water, has substantial aquatic vegetation on its shores, though the main problem in that area is the invasive water hyacinth (Eichornia crassipes), a plant that proliferates as an excess of nutrients from agriculture and wastewater. Aquatic flora is more abundant in Lake Xochimilco, growing along the canals (Fig. 3.15c). In the canals are tulares with Schoenoplectus tabernaemontani, Cyperus spp., Typha latifolia, and T. domingensis; submerged species such as Polygonum pusillum and Stuckenia pectinata; and floating species in the families Lemnaceae and Nymphaeaceae. Despite the diversity of native aquatics, a number
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Fig. 3.15 Modern lacustrine bed vegetation. (a) Tular of Typha latifolia in one of the remnants of Lake Texcoco, the Cienega de San Juan (Google Earth Pro); (b) salt flat with coppice dunes colonized by Dactylis spicata in the former Lake Texcoco bed (Photograph by the author); (c) canals of former Lake Xochimilco, with Nymphaea gracilis growing in the water of the canal and Salix bonplandiana trees on the edges. (Google Earth Pro)
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of introduced and invasive species characterize the area due to the strong human presence and agriculture (Lot and Novelo 2004). As the case of Lake Zumpango, water hyacinth is a notorious invasive species in Lake Xochimilco, where campaigns for their removal have had limited success. Within the floral kingdom, it is important to recognize the role of microscopic plants such as algae and diatoms, both very common and important in the lakes from various points of view, ecological and human subsistence, and even for reconstructing the past of the lakes. One of the notable species of algae in the saline lakes of the basin is spirulina (Spirulina geitleri), which was, and is, collected by ancient and modern populations near Lake Texcoco (Parsons 2006). Its economic importance is such that it has been collected at industrial scale in the former circular evaporator known as El Caracol (Fig. 1.2). Diatoms are microscopic plants whose shells are made of silica, which survives after the organism is dead, forming conspicuous accumulations in lacustrine sediment (i.e., diatomite), and are mined for multiple uses, including beds in chinampas (Ávila-López 1991; Rojas-Rabiela 1988). Furthermore, diatom shells are an important resource for the reconstruction of past lake conditions, and climate adds relevance to this group of organisms (see Chap. 6).
3.5.2 Fish Bernardino de Sahagun’s Historia General reported several species that have been identified with modern species (Rojas-Rabiela 1988). However, very common in the Nahuatl tradition was the use of different names for the same fish at their different stages of life, to refer to species of the same genus with the same name (Alcocer- Durand and Escobar-Briones 1992). At present, the identified fish in the aquatic environments of the Basin belong to three families (Table 3.2), all of which are consistently distributed in all other lacustrine environments of the Trans-Mexican Volcanic Belt (Fig. 3.1).
Table 3.2 Main families and species of native fish in the lakes of the Basin of Mexico Family Atherinidae
Goodeidae Cyprinidae
Species Chirostoma humboldtianum (Cur. and Valenc.) Chirostoma jordani jordani (Woolman) Chirostoma regani (Jordan and Hubs) Girardinichthys viviparus (Bustamante) Algansea tincella (Cur. and Valenc.) Notropis aztecus (Woolman) Evarra eigenmanni (Woolman) Evarra tlahuacensis (Meek) Evarra bustamantei (Navarro)
After Acocer-Durand and Escobar-Briones (1992)
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Fig. 3.16 (a) Chirostoma humboldtianum and (b) Algansea tincella; sketches have no details and are meant to convey the idea of size; (c) Girardinichthys viviparus standard length for female, 30 mm (Source: Sedeño-Díaz and López-López 2009); and (d) Ambystoma mexicanum. (Courtesy of Juan Cruzado)
The Atherinidae family includes a group of species of the genus Chirostoma, which in modern Mexico are generally known as charales (singular, charal). The Nahuatl name iztacmichin (white fish) seems to be the most used for the group, although yacapitzahuac (small or narrow nose) is used for some varieties (Rojas- Rabiela 1998). During certain stages according to their size, the name could also be amilotl and xalmichi (Alcocer-Durand and Escobar-Briones 1992). Generally, the Atherinidae are small fish inhabiting most freshwater lakes and commonly caught for food. Of all the species, Chirostoma humboldtianum (Fig. 3.16a) is the species endemic to the Basin of Mexico and consequently an endangered fish (Huidobro- Campos et al. 2016; Alcocer-Durand and Escobar-Briones 1992). The Cyprinidae, generally known as xohuillin in Nahuatl or juiles in its Hispanicized form, include several species (Table 3.2), of which Algansea tincella (Fig. 3.16b) is the most common. The Goodeidae seems to have included several species, but the most common in recent times is Girardinichthys viviparus (Fig. 3.16c), which receives the name mextlapique, or the widely known Chapultepec splitfin (Sedeño-Díaz and López-López 2009). Currently, introduced fish species plague the remaining bodies of water, particularly in the Lake Xochimilco area, where the carp (Cyprinus carpio) and the tilapia (Oreochromis niloticus) have been detrimental to the populations of native fish and other aquatic species (Huidbro Campos et al. 2016). Adding to this problem are the pollution, heavy traffic, and drying of some canals, which represents a problem for fish and all other native aquatic fauna.
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3.5.3 Amphibians and Reptiles Like the fish, amphibian fauna in the Basin of Mexico may have been more abundant in the past and may have disappeared as habitats were destroyed. The known species belong to four families: Ambystomatidae (salamanders), Ranidae (frogs), and Hylinae and Bufonidae (toads). The most iconic of all the amphibians in the lakes of the Basin is the ajolote, or axolotl (Ambystoma mexicanum Shaw and Nodder 1798) (Fig. 3.16d), whose meat was highly appreciated in ancient times. The ajolote is still present in the aquatic environments of the Lake Xochimilco basin (Rojas-Rabiela 1998) and existed in some of the ponds in Lake Texcoco (Albor- Ruiz 2017). Clinging to life in the canals in the Xochimilco area, the ajolote species are seriously threatened, but recent efforts to protect them and breed them in captivity may save the species (Recuero et al. 2010). In Lake Texcoco, the ajolote disappeared with the drainage of the last few ponds in the northwestern part and pollution when waters of El Caracol leaked into these areas after their abandonment by the closing of the Sosa Texcoco (Albor-Ruiz 2017). Identified frogs in the lacustrine realm of the Basin of Mexico include four known species (Rana montezumae, R. esculenta, R. temporaria, and R. pipiens) and are widely present in the Lake Xochimilco area. Toads include Hyla eximia and Bufo compactilis. Like the ajolote, frogs and toads represented an important part of the diet of former inhabitants (Niederberger 1987). Like the ajolote, frogs are threatened by pollution and habitat encroachment. Among the reptiles, two species of turtles (Kinosternon hirtipes Wagler, Kinosternon integrum Gmel, and Onichotria mexicana Gray) were widely distributed in the aquatic habitats, especially in Lake Xochimilco. In addition to several species of lizards, the most notable reptiles are the water snakes (Thamnophis collaris Jan, T. pulchrilatus Cope, T. insignarum Cope, and T. scalaris Cope, among others) and snakes that were not essentially aquatic but lived near water (e.g., Pituophis deppei Oan and Gerrhonotus imbricatus Wieg). The water snakes are generally harmless, can remain underwater for relatively long periods, and feed mainly on amphibians (Departamento del Distrito Federal 1975, Vol. 1, 160).
3.5.4 Aquatic Avifauna According to many references, resident and migratory aquatic birds were abundant and diverse in the Basin of Mexico when large water bodies existed, as recorded in the Florentine Codex (Parsons 2006) and the fossil record (see Corona 2020). Species such as pelicans, ibises, and herons were reported in the nineteenth century, when the lakes were larger (see Corona 2020; Departamento del Distrito Federal 1975). The creation of certain bodies of water such as Lake Nabor Carrillo and the modern Lake Zumpango have contributed to attracting species that had not been seen in the area in a long time (Alcocer and Williams 1996).
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The orders that comprise most of the waterfowl recorded in the Basin in the twentieth century include the Anseriformes (ducks and geese), Gruiformes (cranes and rails), and Charadriiformes (avocets, sandpipers, and allies) (Departamento del Distrito Federal 1975). In addition to these groups, birds of prey (hawks and eagles) appear often in the wetlands of the Basin, as well as a number of other bird species that are not necessarily typically seen only in aquatic environments. The Anatidae family dominates the Anseriformes, including resident and migratory species. Some of the resident species include the coot (Fulica Americana Gmelin, 1789), the white-fronted goose (Anser albifrons Scopolli, 1769), the pato triguero (Anas diazi Ridgway), and the pato tepalcate (Oxyura jamaicensis rubida Wilson). The highly diverse migratory Anatidae include species that normally reside in the Basin between November and March. They include the Canadian goose (Branta canadensis L.), greater white-fronted goose (Anser albifrons (Scopolli)), and gadwall (Anas strepera L.). Closely related to the Anatidae are the Dendrocygnidae, with Dendrocygna autumnalis lucida (Friedman), as the most common reported species in the Basin’s wetlands. Among the Gruiformes, herons were important, though practically vanished from the region. The Charadriiformes include avocets, sandpipers, and sanderlings, collectively known as chalchicuilotes (chalchicuilotl in Nahuatl). Among the existing or historically reported groups are the sanderling (Crocethia alba), plovers (e.g., Charadrius wilsonia (Ord.)), gulls (Larus atricilla, Linn), and Wilson’s phalarope (Phalaropus tricolor Vielliot, 1819). The high diversity of extirpated and existing taxa includes abundant lists of birds. The author suggests consulting the sources cited above and their references therein for more information on aquatic and nonaquatic fauna.
3.5.5 Other Living Forms in the Aquatic Environments The waters of the former lakes also have several invertebrate species that played an important role in the ecological cycles of the lake and certainly in the diets of its human inhabitants. This is evident not only in the historical sources, notably the Florentine Codex (Sahagun 2002), but in recent studies of aquatic biotic resources collected by traditional human communities living around surviving bodies of water (Parsons 2006; Rojas-Rabiela 1998; Ramos-Elorduy and Pino 1989): insects, crustaceans, gastropods, mollusks, and sponges, among others. Aquatic insects constitute an important part in the trophic chains, as they are the source of food for amphibians and reptiles. In the lakes, wetlands, and canals of the Basin, most of the insects belong to three orders: Coleoptera (beetles), Diptera (winged), and Hemiptera (half-winged). The Coleoptera, known generically in Nahuatl as axayacatl and as mosco in Spanish, include several edible species in the genera Krizoscourixa, Corisella, Notonecta, and Abedus, all of which have very high protein content (Ramos-Elorduy and Pino 1989). The Diptera, though abundant, has only one edible species, the Cybister explanatus L. (Parsons 2006). The
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Hemiptera have Elyris hians S., as the most nutritious and the one that produces highly nutritious eggs, referred to as ahuauhtli, harvested in the lakes using grass leaves planted in shallow waters (see Parsons 2006). In its worm larvae stage, Elyris hians S. and probably other species as well constitute the requezón, which fisherfolk caught in nets, dried under the sun, and used as food and fertilizer (Parsons 2006: 128). The name requezón or requesón (ricotta cheese) is due to its smell and taste of cheese (queso). Interestingly, the first recording of requezón harvesting for food was by Bernal Diaz del Castillo (1982), who reported that during the siege of Tenochtitlan, the starving inhabitants of the city collected it. He relates that “despues de seco tenia un sabor como de queso” [when dry it had taste like cheese] (Diaz del Castillo 1982: 398). The Crustacea are a diverse taxonomic group that includes shrimps, crabs, ostracods, and crayfish. Among the most common crustaceans in the Basin to this day is the acocil (Cambarellus montezumae), which is harvested and edible. Although more common in freshwater, acociles were available in some brackish ponds in Lake Texcoco, where it was still harvested in the twentieth century (Parsons 2006). Mollusks in the Basin of Mexico constitute two classes, the Gastropoda (snails) and Bivalvia (bivalves). There are 11 species of aquatic snails in the existing bodies of freshwater and four species of bivalves registered in Xochimilco (Cano-Santana et al. 2016: 209). The latter are highly endangered from the heavy traffic and pollution in the canals (Cano-Santana et al. 2016). In the past, however, the bivalves (almejas) along with insects were important source of protein (Parsons 2006).
Chapter 4
Geological Evolution of the Lacustrine Basins
4.1 The Geological Record 4.1.1 Stratigraphic Sequences The vast majority of the geological information about the Basin of Mexico comes from data obtained from studies aimed at prevention and mitigation of natural hazards, groundwater prospecting, and the construction of major works of drainage and city services. Thus, in addition to their immediate purpose, the results generated are the basic information for reconstructing the geologic evolution of the Basin of Mexico and its lacustrine basins. Alternatively, studies focused directly on the evolution of the lacustrine basins provide information on the most recent geological past, that is to say, the Quaternary period. Of all the geological information, stratigraphic sequences obtained from cores drilled through sediments and rocks are the basis for understanding the processes that created the Basin of Mexico and its lacustrine basins. Such cores vary in depth, thus providing different resolutions of time in the geological history of the Basin. For this reason, the cores are here arbitrarily divided according to their depth. The deep cores provide information for the formation of the Basin of Mexico during the Cenozoic, while the medium-depth and shallow-depth cores provide information for the evolution of the individual lacustrine basins during the Pleistocene. Furthermore, the subsurface cores and open stratigraphic exposures provide information for the upper and terminal Pleistocene and Holocene, particularly during the time when humans were present in the Basin. The distribution of these categories of cores appears in the map in Fig. 4.1, and their details and significance for the study of the lacustrine basins are reviewed in the subsections below.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5_4
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24 23 22 21
N Core categories and approximate depth range Deep (> 1000 m) Medium depth (100-1000 m) Low depth (25,080) Marqués (27,190) Till-like deposits
Iztaccihuatlc (36Cl year) Ayoloco (Little Ice Age, 5750)
MI (36,000–32,000)
Nexcoalango (190,000 36 Cl)
Pre-Wisconsin
The chronology of Iztaccihuatl is based on 36Cl dating; other chronologies are based on 14C, unless otherwise indicated Modified from Vázquez-Selem and Heine (2011) a Modified from Heine (1994) b Modified from White and Valastro (1984) and White (1986) c Modified from Vázquez-Selem (2000) d Modified from Heine (1988, 1994)
due to the location of the Iztaccihuatl far from the source of moisture in the oceans; in contrast, the Tancitaro and Cofre de Perote, closer to the Pacific Ocean and Gulf of Mexico, respectively, have experienced glacial during the coldest LGM proper (Vázquez-Selem and Lachniet 2017). Despite the mismatch with the timing of the LGM, most of the younger moraines coincide with less prominent cold events such as Heinrich event 1 (Hueyatlaco-2, Iztaccihuatl), the late Younger Dryas (Milpulco-1, Iztaccihuatl), and the 8.2 ka event (Milpulco-2, Iztaccihuatl; MIV, Nevado de Toluca; and possibly MIII, La Malinche) (Table 6.2). Two minor glacial events in the form of rock glaciers and gelifluction appeared during cooler events in the late Holocene, more precisely during the Neoglacial, c. 3500–2000 year BP, and the Little Ice Age, c. 700–200 year BP (Table 6.2). Interestingly, advances occurred in the deglacial and Holocene, supporting the idea that moisture is as important as temperature when glaciers form in the mountains of Central Mexico (Lachniet et al. 2013). The timing of glacier advances and the fluctuations of lake levels are complex (Fig. 6.8). While the coldest part of the LGM coincides with the driest period in the Basin, the lake levels do not appear necessarily low. This is likely because of the low temperatures and low spring-summer insolation and low insolation seasonality, which reduced evaporation of lakes despite the relatively low precipitation (Fig. 6.7).
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139
However, during other global colder events such as the Younger Dryas and the 8.5 ka event, which created glacial landforms on the Iztaccihuatl (Table 6.2), coincide with relatively low lake levels (Fig. 6.8). In these two cases, despite low global temperatures, spring and summer insolation levels and insolation seasonality were higher, which increased evaporation rates in the lakes.
6.3.3 Vegetation Changes Around the Lakes Most of the reconstruction of Late Quaternary vegetation in the Basin of Mexico is based on pollen data from lakes Texcoco and Chalco and a few smaller lakes in the mountains (Fig. 6.2). The sequences from Texcoco and Chalco encompass longer time spans, including parts of the upper Pleistocene and the Holocene, but their resolution, particularly for the Holocene, is low. The mountain pollen sequences, on the other hand, cover only the Holocene but they have more resolution. The first published pollen record from the sediments of Lake Texcoco comprises a 70-m deep sequence published by Sears and Clisby (1955), which was later redrawn and reinterpreted by Bradbury (1971). The core (named Madero) was obtained downtown Mexico City as part of a study of the mechanical properties of the subsoil below the city (Zeevaert 1953). However, the exact changes indicated by the core have no chronological control; they have no absolute dates and no correlation with tephra markers. The first dated core from Lake Texcoco came from the center of the basin from a location northwest of the Benito Juarez International Airport (Fig. 6.4). The original core (Quintero and Flores-Mata 1980) was later redrawn and reinterpreted with two radiocarbon dates (Brown 1985). According to the latest interpretation, the sequence encompasses the past 30,000 years, during which pine pollen dominates, except for the upper zone of the core, presumably in the late Holocene (Brown 1985). The original interpretation of the core (Quintero and Flores Mata 1980) relied heavily on the distinction between pollen grains of different pine species in the region, which is problematic because measurements and characteristics between pollens of different species overlap (Brown 1985). The interpretation of pollen spectra in central Mexico tended to focus on the most abundant pollen taxa, e.g., Pinus, Quercus, Alnus, and Abies (Lozano-García and Ortega-Guerrero 1994; Lozano-García and Xelhuantzi 1997). However, it is now becoming clear that these four taxa indicate only general trends, while those with lower spectra, which are more sensitive to subtle changes, are important in refining climatic interpretation (Lozano-García and Xelhuantzi 1997; Lozano- García et al. 2014). For example, Liquidambar and Podocarpus indicate humid mesic conditions; in contrast, Mimosa and Bursera indicate environments much more arid than today, and aquatics such as Isoëtes indicate deeper clear lakes (Lozano-García 1994). This change in the interpretations of pollen is based mainly on the use of pollen grain in the different vegetation communities, which is supported by multivariate statistical analyses (Lozano-García and Ortega-Guerrero
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6 Lacustrine Change in the Late Quaternary
1994; Lozano-García et al. 2014). Additionally, the inclusion of microscopic charcoal in pollen analysis provides an important proxy for regional paleofires, which may be related to climatic conditions and volcanic events (Martínez-Abarca et al. 2021a). Although the most comprehensive pollen data in the Basin covers only the past 40 ka (end of MIS 3), the new Mexidrill project now has obtained cores dating back earlier in the Pleistocene (Lozano-García et al. 2017), which will complement the information on vegetation responses to climate change during glacials, terminations, and interglacials, in the absence of humans, and during periods of long volcanic inactivity.
6.3.4 Paleosols and Paleoclimatic Change The importance of buried paleosols in paleoeclimatic and paleoecological research lies first in that they contain datable organics if they are within the range of radiocarbon. From another point of view, paleosols indicate stable conditions in the paleolandscape and thus serve as paleoclimatic indicators. Finally, given the possibility of their direct dating and association with stable periods, they can serve as stratigraphic markers within certain areas (Cordova 2018). In the Basin of Mexico, soil development has direct and indirect relation to lacustrine fluctuations. The direct relation appears in soils developed in lakeshore environments which often exhibit hydromorphic features indicative of high and low lake levels, as studies in Tlapacoya (Flores Diaz 1986; Limbrey 1986) and Tepexpan (Sedov et al. 2010) demonstrate. The indirect relation appears in soil development environments outside the lacustrine realm, whose feature indicates climatic trends as the cases studied in Cuicuilco and Teotihuacan Valley (Ibarra-Arzave et al. 2019; Sánchez-Pérez et al. 2013; Sedov et al. 2010; Solleiro-Rebolledo et al. 2003). The indirect relation with lacustrine development lies in those soils developed inland bear stronger climatic influences that can be correlated with long-term lacustrine changes. Furthermore, soils and paleosols can indicate human disturbances through land use, which are processes that affect the catchments and sedimentation in the lakes (Frederick and Cordova 2019). The indirect aspects of paleosol and soil formation in relation to climatic changes and human agency are discussed in more detail considering the evolution of society around the lakes in Chap. 12.
6.3.5 High-Resolution Records Tree-rings of certain species present in the Basin of Mexico and neighboring areas provide a high-resolution paleoclimatic record useful for correlating with lacustrine changes at decadal and centennial scales. Among the species studied are Taxodium mucronatum (Montezuma bald cypress) in low areas and Pinus hartwegii (Hartweg’s pine) in the high mountains (Astudillo-Sánchez et al. 2017; Villanueva-Díaz et al.
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2014, 2015). Additionally, regional records comprising a broader geographical sample of T. mucronatum rings provide information about droughts and moist periods (Stahle et al. 2000, 2011). Despite their use for reconstructing short-term climatic changes, tree-ring climate records barely surpass the past twelve centuries. Yet it has been useful for studying the latest climatic trends that affected the lakes before they disappeared. Isotopic data from speleothems are another source of high-resolution paleoclimatic data, but because of the predominantly volcanic make-up of the Basin of Mexico, karstic environments are absent. Nonetheless, data from surrounding areas normally provide information on regional climatic fluctuations that in somehow correlate with hydrological changes in the lakes of the Basin of Mexico (Lachniet et al. 2012, 2013, 2017). Likewise, isotopic, mineralogical, and magnetic data from high-resolution sediments in phreatomagmatic craters (i.e., maar lakes) in the Oriental Basin (Ohngemach and Straka 1983; Park et al. 2010; Bhattacharya et al. 2015) and the Bajio region in the state of Guanajuato (Wogau et al. 2019) provide information on regional trends that affected large areas of the Mexican Highlands. Despite some inconsistencies, proxies from dendrochronological, speleothem, and high-resolution sedimentation systems outside the Basin correlate with many developments in the Basin of Mexico, including droughts recorded in certain documents and drastic changes in the archaeological record. These records are the basis for correlating geoarchaeological evidence of transgressions and regressions that occurred in recent millennia (Chaps. 12 and 13).
Part II
The Lakes: Geography and Environmental Dynamics
Chapter 7
A Geographic Sketch of the Historic Lakes
7.1 Cartographic Representations of the Lakes 7.1.1 The Former Lakes in Modern Maps The reconstruction of the lacustrine geography of the Basin of Mexico in historic and prehistoric times faces multiple challenges due in large part to the scarcity of data on lacustrine changes at various times in the past. This has led to geographic representations of the lacustrine former lakes of the Basin based on assumptions and generalization of information in the records. One of the most common trends in representing the lacustrine paleogeography of the Basin is to use the configuration of the lakes reconstructed for the time of the Spanish Conquest (1519–1521). Although the model seems to be correct for the sixteenth century and perhaps for the end of the fifteenth century, many scholars use it to represent the lake geography of earlier times. It is important to mention that at the time of the Conquest, the configuration of the lakes responded first to the climatic conditions of the time and second to the control of their flows by dikes and a number of human-made structures. In recent decades, the most cited model of Conquest-time lacustrine geography is Luis González-Aparicio’s 1968 Plano de la Reconstruction de Tenochtitlan al Comienzo de la Conquista (Reconstructive map of Tenochtitlan at the beginning of the Conquest), which accompanies his geographic description of the cultural landscape around Tenochtitlan (González-Aparicio 1973). This map, however, portrays only the lacustrine landscape of Lakes Mexico-Texcoco, Xochimilco, and Chalco. The northern lakes, Zumpango and Xaltocan, do not appear in it. The location of towns and landscape features in González-Aparicio’s map is the result of ethnohistorical research based on matching locations with existing landmarks and recent maps. Its author demarcated the lakeshore using, in some cases, historic references to certain places mentioned in the chronicles of the Conquest, © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5_7
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and in others, using the meaning of place names in Nahuatl. One example for the latter is the recurrent name Atenco (place next to water), which indicates a place on the shore. Another case is a settlement called Atoyac, which refers to a river, but it is on what seems to be the lake, suggesting that this was the mouth of one of the rivers, probably a deltaic plain. Gonzalez-Aparicio’s map shows the shoreline with a line in blue. The problem is that it is not clear whether this line means the average maximum or minimum level of the year or the average level of both. In any case, the best practice is to consider that the line marks the average lake level, keeping in mind that the dikes across the lake would make the elevation of the shoreline different in some parts of the lakes. Among other problems in the cartography of the lakes is use of particular contours to mark former shorelines. For example, the common and repetitive use of the 2240 m contour to mark the shorelines of the former lakes results in several problems. One is that it leaves numerous archaeological sites underwater. Another is that the constant sinking of the ground changes the ground leads to changes in the topography of the lake. To point out the cartographic, historic, and geographic issues mentioned above, this chapter discusses the past and present geography of the lacustrine complex of the Basin of Mexico. However, to achieve this goal, this chapter discusses first historical changes in the designations and nomenclature of the lakes, which in part influence our current perceptions of the former lakes.
7.1.2 Cartographic References for Reconstructing the Ancient Lakes The discussion in this chapter uses as a cartographic reference of the map by Christine Niederberger (1987) (Fig. 7.1). The map presents the lakes without the biases created by features of the Aztec and early Colonial periods and pre-determined elevations as lakeshores, though it shows islands that should have not been there in Pre-Aztec times, as they were artificial (see discussion about the “primitive islands” in Chap. 13). Nonetheless, the map is a good basis for discussing the prehistoric lakes, at least during the middle and late Holocene. Additionally, some aspects of the discussion refer to a redrawn version of the Carta Hidrográfica del Valle de Mexico by Francisco Díaz Covarrubias (1863) (Fig. 7.2), which represents the extent of the lakes before the final phase of the desagüe that at the turn of the twentieth century drained the lakes. The map is also the basis for some of the influential historic writings of the nineteenth century (e.g., González-Obregon 1902; Garay 1888; Orozco y Berra 1864), which were influential in shaping our understanding of the historical lakes about modern times. The discussion also refers to some historical maps of the sixteenth and seventeenth centuries, which, despite the inaccuracies and inconsistencies with other maps, show features that could be historical references for historic-geographic changes of significance. The most important cartographic reference is to the Uppsala Map (1555) (Fig. 1.5), which shows in detail the lacustrine geography before the
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N
onte
Bajo
Lake Zumpango
Lake Xaltocan
de M
C. Tultepec
Teotihuacan Valley
Sierra
Cerro Chiconauhtla
te Alto
Sierra de Guadalupe
Sierra de Mon
Tepetzingo Huatepec
Lake Texcoco
Sierra de las
Peñon del C. de la Marqués Estrella
Sierra
Lake Xochimilco
C. de Chimalhuacan
rina
ta Cata
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Sierra Nevada
Cruces
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Tlapacoya
Lake Chalco
Xico
Main streams Artificial channels of main streams Existing or historical springs Areas above 2500 m
Sierra del Ch
ichinauhtzin
Mean extension of Holocene lakes
Areas between 2300 and 2500 m Areas between 2250 and 2300 m
0
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10
Km
Areas between 2250 and 2300 m 2240m countour (CETENAL 1970-1975), possibly changed by ground subsidence
Fig. 7.1 The lacustrine systems of the Basin of Mexico. (Based on Niederberger-Betton (1987) with modifications by the author)
first works of the desagüe. The 1609 map of Enrico Martínez (Fig. 7.3) and the 1774 map of Joaquín Velázquez de León and José Burgaleta (Fig. 7.4) provide the geographic distribution of infrastructures built for the desagüe and flood protection during the seventeenth and eighteenth centuries.
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7 A Geographic Sketch of the Historic Lakes Zumpango L. DE ZUMPANGO
Canal de Castera (abandonned)
3
Lakes LAGO DE XALTOCAN
Towns
Mudflats/ saltflats
Roads Dam
Alluvial plains
Cuautitlán L. DE S. CRISTOBAL
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Inactive canals
Texcoco
LAGO DE
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TEXCOCO 2
Mexico City 6 Tacubaya
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Iztapalapa L. DE SANTA MARTA
1. La Viga 2. San Lazaro
Artificial river courses 3. Cuautitlán 4. Guadalupe 5. Consulado 6. La Piedad 7. Churubusco
To Pu e
bla
Tlalpan L. DE XOCHIMILCO
L. DE CHALCO
Chalco
Fig. 7.2 The lacustrine systems of the Basin of Mexico in the mid-nineteenth century based on the Carta Hidrográfica del Valle de Mexico (1862) by Francisco Díaz Covarrubias. (Sources: Apenes 1943; Niederberger-Betton 1987)
7.1 Cartographic Representations of the Lakes
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1 Avenidas de Pachuca R. 2 Presa del Rey 3 San Juan Teotihuacan R. 4 Presa de Acolman 5 L. Xaltocan 6 San Cristobal Dam a nd L. San Cristobal 7 L. Zumpango 8 Old Cuatitlan R. 9 New Cuautitlan R. 10 Canal de Huehuetoca 11 Mexico City
9
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Fig. 7.3 Map of the Basin of Mexico in the early seventeenth century by Enrico Martínez (1609) with references to important works destined to the desagüe. Original at the Archivo General de Indias. (Source: Departamento del Distrito Federal 1975)
5
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6 12 10
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Fig. 7.4 Northern lakes, map of Joaquín Velázquez de León and José Burgaleta 1774. Original in the Archivo General de la Nación. (Source: Departamento del Distrito Federal 1975). Note the area seasonally flooded around the main water bodies. Existing lakes and features: (1) Lake Texcoco, (2) Presa de Acolman, (3) L. San Cristobal, (4) L. Xaltocan, (5) Avenidas de Pachuca River, (6) L. Zumpango, (7) L. Coyotepec, (8) Cuautitlán River, (9) old Cuautitlán River course and Derrame del Molino, and (10) Huehuetoca-Nochistongo canal (a.k.a Tajo de Nochistongo). Planned structures: (11) Túnel de Tequixquiac and (12) Canal de Castera
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Worth mentioning as references in this discussion are Francisco Javier de Clavijero’s 1780 map (Apenes 1943, Plate 29) and Alexander Humboldt von Humboldt’s 1804 map (Apenes 1943, Plate 29). They were among the first attempts to map the lacustrine landscape of the Basin at the time of the conquest, essentially the same objective Luis González-Aparicio (1968, 1973) had with the map mentioned above.
7.2 An Ever-Changing Lacustrine Geography 7.2.1 The Lakes and Their Changing Shorelines One recurrent problem in the interpretation of archaeological remains with respect to the ancient lakes is the assumption that lakeshores through all the archaeological periods were the same or similar to those reconstructed for the time of the conquest. For example, many works referring to prehistoric periods refer to Gonzalez- Aparicio’s map, which is meant to represent only the geographic representation of the lakes in the early sixteenth century, at the time of the War of Conquest. At that time, the hydrography of the lakes responded to the climatic conditions of the time and the series of dikes and hydraulic management. Therefore, it seems that the Gonzalez-Aparicio model is a static view of the lakes projected to all prehistoric periods. The question as to where the lake shorelines were at a given time is difficult to answer because of the dynamics of the lakes themselves, that is, the seasonal changes between the end of the dry season and the end of the rainy season. These changes would represent the lowest and highest medium annual extent of the shoreline, respectively. Some maps even show areas around the lakes that portray the idea of high and low levels (e.g. Fig. 7.3). However, in addition to seasonal lake-level changes, one has to consider the year-to-year and decade-to-decade changes, which depend on cycles of wet and dry years. Seasonal and year-to-year changes are apparent in some descriptions of the landscape (e.g., Sahagún 2002; Motolinia 1990) as well as numerous descriptions linked to the desagüe (e.g., Mora 1823; Cueva-Ramírez y Espinosa 1748). Decadal and centennial changes were rarely observed, but evidenced when descriptions are compared over time (e.g., Orozco y Berra 1864; Rojas-Rabiela 1974; Ramírez 1976; García-Quintana and Romero-Galván, 1978; Motolinia 1990; Candiani 2014). This high variability in lake levels modifies the configuration of lake shorelines, which becomes a problem when cartographers define lakeshores at a particular time using maps or documental references. At centennial scales, lacustrine changes depend on regional and global climatic changes, leading to long periods of high and low lake-level stands. Paleoclimatic and geoarchaeological studies show that the a high lake level prevailed in the Classic and low lake level during stand Epiclassic and Early Postclassic (Lachniet et al.
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2017; Cordova et al. 2022). However, those high or low levels meant that the range of seasonal and decadal fluctuation moved up or down in elevation.
7.2.2 Connected or Disconnected Lakes? In some maps, the lakes appear as separate connected lakes; in others, as unconnected; and in others, as lake basins connected to form one large lake. The latter, as discussed above, is a cartographic misconception not supported by historical data, topography, and hydrology. The lakes are often perceived as connected basins, but whether that connection is permanent, i.e., year-round, or seasonal is a matter that needs discussion. Some of the maps drawn in colonial maps (e.g., Figs. 1.5, 2.11, 2.9, 2.10, 7.3, and 7.4) and descriptions in chronicles and documents of the time provide some clues to the connectivity between the lake basins, when the lakes still existed. The historic connection between the southern lakes (Chalco and Xochimilco) and Lake Mexico-Texcoco was through the strait west of the Cerro de la Estrella (Fig. 7.1), thereafter referred to as the strait of Culhuacan. This connection seems to have been permanent and supported by documents of the conquest, maps of the sixteenth century, and most maps of the seventeenth century (e.g. Figure 7.3). Many of the historic maps suggest that the most permanent flow of water was along the east side of the strait, i.e., closer to Culhuacan. Perhaps this was the deeper part, with the west part perhaps being flooded only during high lake stands. North of this strait, the Mexicaltzingo dike controlled the flow across the strait and at the same time served as a causeway, with an underpass for canoe traffic (Ramírez 1976; Rojas-Rabiela 1974; Palerm 1973). Maps of the sixteenth and seventeenth centuries show the strait connecting the two lakes permanently, but as the waters of Lake Mexico-Texcoco receded, maps in the eighteenth and nineteenth centuries begin to show the two basins connected only by means of canals. The flow of the southern lakes went through the Canal de la Viga and Canal de San Lázaro into Lake Texcoco (see Fig. 7.2). Both canals served as drainage and navigation waterways. A permanent water connection and navigability along the strait connecting the northern lakes (Zumpango and Xaltocan) and Lake Mexico-Texcoco, as some modern maps of the former lakes show, is questionable based on the few historical maps that exist before the San Cristobal Dam was built across it. For example, the 1550 Uppsala Map (Fig. 1.5) and the 1609 map of Enrico Martínez (Fig. 7.3) show only a stream channel connecting Lake Zumpango directly with Lake Texcoco, bypassing Lake Xaltocan. The Uppsala Map shows the mouth of the strait into Lake Texcoco crossed by a road and a canoe, suggesting that its crossing could be by land or by water. Interestingly, a canoe appears at the same place in the Codex Xolotl (Fig. 2.8), and the name of the locality is Acalhuacan (Nahuatl: a place of those who have canoes) (Garcia-Chávez 2018). Thus, it is possible that water flow into Lake Texcoco was seasonal, with relatively low amounts of water passing in the dry season and more
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water in the rainy season. However, large outbursts sometimes occurred during extreme events, which led the colonial authorities to build the San Cristobal Dam to protect the city from sudden flooding (Ramírez 1976; Candiani 2014; Garcia- Chávez 2018). Often neglected question about the connectivity between lake basins is the possible existence of a strait between Lake Xochimilco and Lake Texcoco through the low area east of Iztapalapa that forms a pass between the Sierra de Santa Catarina and the Cerro de la Estrella (Fig. 7.1). Angel Palerm (1973) was a proponent of the existence of a flow of water through this area as a means to explain the existence of the dike east of Iztapalapa mentioned in the Conquest chronicles during a battle between the Spanish army and the natives of Izapalapa in February 1521. Furthermore, he alludes to the idea that a substantial amount of fresh water would have been necessary to maintain chinampas in the Iztapalapa area. Ironically, however, in November 1519, Cortes’s army on their way to Tenochtitlan walked through this area along a road connecting Tlahuac and Iztapalapa and yet none of the chroniclers mentions any water flow through this area. In the salvage archaeological project linked to the construction of the subway Line 12 (see Fig. 2.5), Medina-Jaén (2008) used late 1930s aerial photography to identify possible sites and extension of the lake into this possible strait. He concluded that the modern lacustrine plain does not intrude into the Iztapalapa strait. Nonetheless, the Secretaría de la Defensa Nacional map at scale 1:25,000 (Sheet Xochimilco 14-Q-h-88) shows a small swampy area in the middle of the strait. This map contrasts with the 1:50,000 INEGI soil map, which does not show evidence of soil types formed in lacustrine or palustrine environments. Based on modern elevations, the highest point in this supposed strait is about 2247 meters, while the average of the lakebeds north and south is 2237 and 2244 meters, respectively. The low elevation of this strait led the desagüe engineers in the nineteenth century to design a canal, later known as Canal de Garay, to drain excesses of water in Lake Chalco into the section of Lake Texcoco known as Laguna de Santa Marta (see Fig. 7.2). The functioning of the canal, however, never materialized. Even though the waters of former Lake Xochimilco could hypothetically reach the elevation of the alleged strait during a given extreme lake-level rise, it is unlikely that water would flow through it, as water would rather flow through the strait of Culhuacan, which is at a lower elevation (2243 m). As for historical cases of extreme events, none of the most catastrophic floods registered have reached this point. Furthermore, although the proposed seasonal high levels in pre-Conquest times, such as the transgression proposed during the early Classic period (second to fourth centuries AD) (Lachniet et al. 2012, 2017), could have reached the floor of the suspected strait, no archaeological or geomorphological evidence exists to support such a scenario. Richard Blanton’s (1972) archaeological survey does not report sites in the lowlands of the presumed strait, except for a few late postclassic salt- procurement stations, which are evidently on the seasonally flooded bed of Lake Texcoco. Certainly, surface evidence of sites could be buried under recent sediments as occurs in other parts of the Basin (Frederick and Cordova 2019; Cordova 1997).
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Unfortunately, the area today is completely urbanized, making any research to find this possible inter-basin water connection practically impossible. Although no archaeological evidence exists of a recent connection between lakes Xochimilco and Texcoco through the strait of Iztapalapa, geotechnical data provides existence of lacustrine clays below the strait. The area between the Cerro de la Estrella and Sierra de Santa Catarina is marked by an abrupt transition between marked as Zone III “lake,” and fractures indicate that there is a steep transition between zone 1 (hills) and zone 3 (lacustrine) (Fig. 4.8). Although no stratigraphic data from cores are available from the area, it is possible that the lacustrine clays correspond to the sets of clays that appear in cores elsewhere (e.g., Figs. 4.4 and 4.5).
7.2.3 Lagos or Lagunas? Interestingly, in historical maps and writings from the sixteenth to early nineteenth centuries, the lakes of the Basin of Mexico are referred to as lagunas, as opposed to more recent maps and literature, which refer to them as lagos. This chance can be seen in the map collections in Ola Apenes (1943) and Lombardo de Ruiz (1996). The full transition from using laguna to using lago occurred around the mid- nineteenth century, and the latter term remains in use today, even to refer to remnants of the former lakes. The distinction between lago and laguna in the Spanish language has no parallel in the English language, for both terms translate as lake. However, in the Spanish language, these two terms designate different types of lacustrine systems, based mainly on size and hydrological dynamics. It is therefore important to analyze the evolution of the word usage, as the change in terms has changed over time the perception of the ancient bodies of water. Although Spanish language dictionaries provide variable definitions of lago and laguna, the geographic literature distinguishes between the two. According to Ortiz- Pérez (1975), a lago is a “deep body of water with depths larger than 8 meters and more stable shores” (Ortiz-Pérez 1975: 134–135). A laguna is “a body of water of any origin with stagnated water, and unstable with large variations of water levels, being ephemeral or perennial depending on the pluvial or hydrological regime; and characterized by shallow deposits and bottom” (Ortiz-Pérez 1975: 134–135). Other characteristics provided by the same author for a laguna are that “its bed has continuous and smooth bathymetric profiles… [and] its shores are poorly defined” (Ortiz-Pérez 1975: 135). Although this is the modern definition, Sebastián de Covarrubia’s (1611) dictionary (Tesoro de la Lengua Castellana o Española) also provides the distinction between the two: Lago: deep locality (place), in which there is water permanently that originates from springs in it, and from the arroyos and sometimes rivers. The difference between lago and laguna, is, that the latter contains water that descends from the surrounding slopes, and sometimes dries out in the summer. However, the lago has always water. There are many lagos that are navigable, like the Lago de Garda (Covarrubias 1611, 512) [translated by the author].
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Evidently, this description of laguna above better fits the nature of the former lakes of the Basin of Mexico, which were shallow and highly variable in size through the year. Not surprisingly, the accounts of the conquest wars (1519–1521) by Bernal Díaz del Castillo (1982), Hernan Cortés (1994), Francisco López de Gómara (2006), and El Conquistador Anónimo (1941) refer to the lakes of the Basin as “lagunas.” Later documents, including the Florentine Codex (Sahagún 2002), the Relaciones Geográficas of the sixteenth century, and documents of the desagüe, refer only to the term “laguna.” The word lago is totally absent in any of these documents. Therefore, the authors of the accounts and maps referred to the lacustrine bodies of the Basin as lagunas, as they were shallow and rapidly changing bodies of water. The transition from using laguna to using lago in official documents, maps, and literature occurs in the first half of the nineteenth century, when the two words interchangeably. This indistinctive use of the two words is evident in the Memoria que para informar sobre el origen y estado actual de las obras emprendidas para el desagüe de las lagunas del Valle de México (Mora 1823), which is the first document pertaining to the desagüe. This continues through the 1820s and 1830s, notably in documents by the ideologue and politician of the new republic Lucas Alamán (Aguayo-Spencer 1945). The term lago completely replaces the word laguna in maps and literature in the second half of the nineteenth century (e.g., Orozco y Berra 1864; Díaz Covarrubias 1876; Peñafiel 1884; Garay 1888) and remains the only term until the present. During this period, laguna is used to designate smaller remains of lakes cut off from the main lakes by dikes or structures (e.g., Laguna de Santa Marta and Laguna de San Cristobal) (see Fig. 7.2). There is also an interesting point regarding the use of the terms in other languages that may have influenced the change in usage in maps and literature about the Basin’s lakes. From the sixteenth through the eighteenth centuries, several maps of Mexico City and its surroundings in Italian and French use the cognate lago and lac, respectively (see collection of maps Apenes 1943). Although these words directly translate to Spanish as lago, they refer to both lago and laguna – just like the English word lake. In Italian, the distinction between lago and laguna exists, but the latter refers to the same feature designated by the English word lagoon, which is a coastal body of water separated from the sea by a sand bar (NOAA 2018). This is the same meaning that the cognate French words lagon and lagune have. Only Spanish uses laguna to mean small or shallow and ephemeral lakes, a situation similar to the Portuguese word lagoa. Interestingly, the Spanish term laguna can be used to designate a lagoon, except that in that case it appears as laguna costera. The reason why the change in usage from lago to laguna occurs in documents and maps is not clear. It could have been French influence, which at the time, in the 1800s, had become a prominent second language of the high and educated classes in Mexico. It could be just that lago became more fashionable. It is important also to point out that Francisco Javier Clavijero’s 1780 map in Italian (Apenes 1943: Plate 29), which accompanied his Historia Antigua de Mexico (Clavijero 1974), was widely cited by scholars thereafter. Clavijero was a Jesuit who lived in exile in
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Italy after the expulsion of the Company of Jesus from New Spain in 1767. However, there might be other reasons for the change in designation usage, a matter that perhaps needs more research.
7.2.4 Shifting Names and Shifting Lakes
1500
1700
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2000 Lago
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Smaller lake bodies
Zumpango Citlaltepetl
Zumpango
L. deCoyotepec
Xaltocan
Xaltocan
L. de San Cristobal
Texcoco
San Lázaro
México
Lago Nabor Carrillo
Xochimilco Chalco
Historic events
Chalco
1500
Texcoco
L. de Santa Marta L. de Mexicaltzingo
Enrico Martínez begins the Desagüe works at Huehuetoca Map of Uppsala
Adriaan Boot arrives in Mexico
First major flood War of Conquest
Great Flood of 1629
Building of San Cristobal Dam
1600
1700
Lacustrine basins
Main lakes nomenclature
Terms in use
The literature of the twentieth century to present generally recognizes five original lakes in the Basin of Mexico: Zumpango, Xaltocan, Texcoco, Xochimilco, and Chalco. However, the number of lake units, or lake basins, and their names have changed in cartographic and written representations during the previous four centuries (Fig. 7.5). In his letter to Emperor Charles V, Hernan Cortés describes the valley where Tenochtitlan is located, referring to only two lakes: “laguna de agua dulce” (fresh- water lake) and “laguna de agua salada” (saline-water lake) to the east and west of the dike, respectively (Cortés 1994). Plainly, the description considers the freshwater lake as the combined basins of Chalco-Xochimilco and the part of Lake Texcoco west of Nezahualcoyotl’s dike (see Fig. 1.5). Interestingly, Cortes never mentions the existence of lakes Zumpango and Xaltocan in his letters. In his description of his attack on Xaltocan in early 1520, Cortes mentions esteros (wetlands and ancient channels filled in with water) and acequias (canals) around the town landscape, a description that is consistent with
Xochimilco Nuevo Lago de Chalco (New Lake Chalco)
Chalco
Humboldt visits Gran Canal de Desagüe and the Basin of Mexico Tajo de Tequixquiac Jesuit expulsion Independence Sistema del War of Independence Drenaje Profundo Mexican American War Founding of Porfirio Díaz’s rule Colegio de Minería
1800
1900
2000
Fig. 7.5 Chronological changes in designation and nomenclature of the lacustrine bodies of the Basin of Mexico
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7 A Geographic Sketch of the Historic Lakes
the accounts by Bernal Díaz del Castillo (1982) and Francisco López de Gómara (2006), whose accounts have no mention of the two northern lakes. Furthermore, after the Noche Triste (Sad Night) event (June 1520), the Aztec army chased the Spanish and their allies across the northern part of the Basin in their flight toward their friendly territory in Tlaxcala. In the description of this event, Cortés and the other chroniclers mention several towns in the area but no lakes. It is hard to say why there is no mention of the lakes. However, they do appear in documents and maps in later decades. Lake Zumpango appears in various documents with the name Citlaltepec (also Citlaltepetl, Zitlaltepetl, or Zitlaltepec), which is also the name of the town on the northern shore of the lake, just west of the town of Zumpango. It is not clear, however, whether these two names refer to the same lake or whether the name Citlaltepec refers to a section of the lake. In some maps, an elongated island by the name of Zatlatelco appears in the center of the lake (Fig. 7.3). Perhaps extended periods of low lake levels extended this island to create a land bridge between the northern and southern shores, thus dividing the lake into two basins. However, the name Citlaltepec fades out from the documents by the end of the eighteenth century, leaving Zumpango as the sole name for the lake. The names of the other lakes have also changed because of desiccation processes linked to the desagüe or to structures built in their basins. Thus, what we know today as Lake Texcoco was known originally as Lake Mexico (i.e., Laguna de Mexico), named after Mexico City. The less common name “Laguna de San Lazaro” appears in some maps and documents in the sixteenth century, most likely referring to the port by the same name located on the eastern outskirts of the city. This suggests that the shifting of the lakeshore eastward meant that the place to reach the lake was through San Lazaro. Interestingly, the rapidly shrinking lake necessitated the construction of a canal to connect San Lazaro with the lake. Thus, by the mid-eighteenth century, the name of the lake had shifted to Lake Texcoco, most likely because by that time the eastern lakeshore had receded so much that the lake became geographically closer to Texcoco than to Mexico City. In some cases, the name would appear as “Laguna de Mexico y Texcoco” (Fig. 7.4), but by then all documents and maps practically refer to it as “Laguna de Texcoco.” During the Colonial period, the two southern lakes (Chalco and Xochimilco) were considered one lake, whose name was Lake Chalco (e.g., Fig. 7.3), even though they had been separated by the Tlahuac dike since pre-Conquest times. The western part of the lake referred to as Lake Xochimilco only in the early nineteenth century is the. Later, however, with Lake Chalco drained in the early twentieth century, only Lake Xochimilco has survived. The construction of dams during the desagüe also created smaller lakes. Thus, in the early seventeenth century, the construction of the San Cristobal Dam (or Acalhuacan) created Lake San Cristobal (known as Laguna de San Cristobal) (Figs. 7.2 and 7.4). The lake disappeared by the end of the nineteenth century with the construction of the main drainage canal known as Gran Canal del Desagüe (Junta Directiva del Desagüe 1902).
7.3 A Geography of the Historic Lakes
157
The Laguna de Coyotepec was an artificial small lake created to the west of Lake Zumpango. Named after the town just west of it, this body of water formed when, in the early seventeenth century, the dike known as Albarradón del Rey (also known as Albarradón de Coyotepec) was constructed. The idea was that this dike would create a small lake where the Cuautitlan River would deposit its sediment load before entering the tunnel that would take it out of the Basin, i.e., the Túnel of Huehuetoca (Gurría-Lacroix 1978; Candiani 2014). This small lake appears in many of the maps concerning the desagüe projects (e.g., Fig. 7.4), but disappeared by the end of the eighteenth century as its basin silted up. The construction of new causeways across the basins dammed existing lakes, creating new bodies of water. For example, the construction of the new road to Puebla, which later became the railway line, dammed the part of lake Texcoco south of El Peñón del Marqués, thus creating the Laguna de Santa Marta (cf Fig. 7.2), but by the end of the nineteenth century, this lake had dried up. In summary, the number and names of the historic lakes, along with changes in their designations (i.e., lago and laguna), seem to be merely geographic facts. However, they are important aspects that contributed to the perceptions that the inhabitants of the Basin, and particularly the authorities and scholars, had about the lakes, and those perceptions are important in the creation of misconceptions about the lakes and the cartographic errors discussed above.
7.3 A Geography of the Historic Lakes 7.3.1 The Lacustrine Complex Despite changes in nomenclature and the number of lake units, the general consensus in the literature is the existence of five lacustrine basins: from north to south they are Lake Zumpango, Lake Xaltocan, Lake Texcoco, Lake Chalco, and Lake Xochimilco (Fig. 7.1). Lakes Texcoco and Xaltocan were saline lakes with occasional inputs of freshwater from streams and springs; Lake Zumpango was a brackish- water lake perhaps with periods with mostly freshwater; and lakes Xochimilco and Chalco were freshwater lakes. Before the beginning of the desagüe projects, water flowed from the northern and southern lakes into Lake Texcoco, which occupied the lowest elevation. Thus, Lake Zumpango, the highest of the lakes, poured its waters into Lake Xaltocan, and then into Lake Texcoco. In the south, water flowed from the slightly higher Lake Chalco into Lake Xochimilco, and from there into Lake Texcoco. Although the general dynamics of water flows between basins were evident to witnesses, there are no historical records of lake depths, even in the chronicles of war during the conquest of Tenochtitlan in the early sixteenth century, or through the Colonial period. Estimates calculated by Alexander von Humboldt (1811) proposed a mean depth of two meters for Lake Texcoco during the time of the conquest.
7 A Geographic Sketch of the Historic Lakes
158
However, Manuel Orozco y Berra (1864), among others, considered Humboldt’s estimates unreal on grounds of seasonal lake-level changes and the fragmentation of the lake created by dikes and causeways. In the mid-nineteenth century, more advanced triangulation methods provided relatively accurate elevations of lake bottoms and average water levels. Manuel Orozco y Berra (1864) published the elevation of average standing water between February and May of 1862 in the existing lakes at the time in relation to a location in Mexico’s central square (in the Zócalo) (Table 7.1). In 1878, the surface of each lake was measured again (Espinosa 1902), with results very similar to the ones in 1862. This time, however, the floor of each lake was also measured (Espinosa 1902), from which the depth of each lake was estimated (Table 7.1). The elevations of mean lake water surfaces and basin floors (Table 7.1) show some interesting facts about the lake basins. One is that Lake San Cristobal’s average level appears slightly higher than that of Lake Xaltocan, while the bed of the latter is lower. This may be due to the existence of a dam between the two (Fig. 7.4). It is also noticeable that the bed of Lake Xochimilco is slightly higher than that of Lake Chalco, a fact that Alexander Humboldt had postulated without measurements. This fact may also suggest that the purpose of the Tlahuac dam may have been twofold: to protect Lake Xochimilco from flooding from Lake Chalco when stream input became high, as usually presumed, and to prevent the waters of Lake Xochimilco from flowing into Chalco when the levels of the latter were low. Although an interesting reference, one has to be careful with extrapolating these measurements to modern times. With the sinking of the city, today the Zócalo is several meters below the elevation of the current bed of Lake Texcoco (Auvinet et al. 2017). Likewise, one should use these measurements carefully when assessing lake levels in the sixteenth century or earlier, as siltation and changes caused by the desagüe projects changed the lakebeds and the water supply from streams.
Table 7.1 Elevations of the Basin of Mexico lakes in relation to Lake Texcoco Metersa above mean level of Lake Texcoco
Zumpango Xaltocan San Cristobal Texcoco Xochimilco Chalco
Metersa above Zocalob Mean water surface Floor 4.15 3.35 1.57 1.17 1.69 1.09
Mean water surface 6.06 3.47 3.60
Floor 5.26 3.07 3.00
0 3.19 3.08
−0.50 −1.91 2.74 1.17 2.40 1.20
Orozco y Berra 1864; Espinosa 1902 See Fig. 7.2 for the location of bodies of water a Rounded to two decimals b Street curb on the north corner of the National Palace
2.41 0.77 0.52
Average depth meters
0.80 m 0.40 0.60 0.50 0.40 0.68
7.3 A Geography of the Historic Lakes
159
7.3.2 The Northern Lakes: Zumpango and Xaltocan 7.3.2.1 Lake Zumpango The basin of Lake Zumpango occupies the highest point of the lacustrine complex. In its original form, the lake received the waters of the Avenidas de Pachuca River, the Tepozotlán River, and a series of small, intermittent streams from the surrounding hills (Fig. 7.6). In historic times, the Cuautitlán River also emptied into Lake Zumpango after its diversion from its original course east into the strait connecting Lake Xaltocan and Lake Texcoco (Fig. 7.6). The first diversion of the Cuautitlán River, attested to by the Anales de Cuautitlán (Codex Chimalpopoca), occurred in the year 1435 (Anonymous 2011: 175). The document briefly mentions that the construction of a dam redirected the waters of the Cuautitlán into Citlatltepetl (i.e., Lake Zumpango). However, in 1535, fearing that the drying up of Lake Texcoco caused by a protracted drought would affect the traffic of canoes into and through the city, the colonial authorities diverted the Cuautitlan back to its former southern course. Then, later in the same century, as floods began to afflict the city, the first attempts of the desagüe diverted the Cuautitlán back to the north, first into a water of body separated by a dam from the
1
5
7
6 8
Lake Zumpango
Prehistoric lakes* Areas of fluviolacustrine/deltaic sedimentation Former marshy areas
2
Gran Canal del Desagüe
1. Tajo de Nochistongo, (former Tunel de Huehuetoca) 2. Former Albarradón del Rey 3. New Cuautitlan River Canal 4. Old Cuautitlan course 5. Entrance to the Tunel de Tequixquiac 6. Avenidas de Pachuca River 7. Citlaltepec 8. Zumpango 9. Xaltocan 10. Tonanitla 11. Ozumbilla 12. San Cristobal Dam
3 9
Former Lake Coyotepec
Lake Xaltocan
Current Canals
10
Canal de Castera (abandonned) Sod dams, bordos Manonry dam
11
N
4
Prehispanic tlatel towns Prehispanic chinampas *According to Neiderberger (1987)
0
12
1
2 km
500 m
Fig. 7.6 The northern lakes, Zumpango and Xaltocan. Geomorphic and historic features against the contemporary landscape
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7 A Geographic Sketch of the Historic Lakes
rest of Lake Zumpango and then into the Túnel of Huehuetoca out of the Basin (Candiani 2014). During copious rains, the Avenidas de Pachuca River (avenida is one of the words in Spanish that refers to “flood) brought in considerable amounts of water in the basin of Lake Zumpango and from there it would flow down into Lake Texcoco, raising its waters and causing floods in the city. In view of this problem, the colonial authorities built the Presa del Rey to control the Avenidas de Pachuca River in its course to Lake Zumpango (Fig. 7.4). Additionally, they built a sod dam to prevent the lake’s overflow down into Lake Texcoco (Candiani 2014). This dam, which has been reinforced multiple times and was also used as a main road to Zumpango, has survived to this day. Its v-shape provides the southernmost limit to the current lake (Fig. 7.6). The construction of dams and canals such as the Canal de Castera and Canal de Guadalupe in the late eighteenth century further modified the hydrology of Lake Zumpango (Fig. 7.6). Additional canals and dams built in the nineteenth and early twentieth centuries modified the size and shape of the original lake. Eventually, the lake was drained and desiccated and its exposed bottom cultivated until the 1980s, when land disputes, unscrupulous land schemes, and problems with flooding resulted in the authorities’ decision to restore the lake (Maldonado-Aranda 2005). The new lake began to fill up in the 1990s, thus becoming an artificial lake occupying the bed of the former Lake Zumpango, similar to the role Lake Nabor Carrillo plays in the Lake Texcoco bed (see section on Lake Texcoco below). As Lake Zumpango is fed by the excess waters from rivers and drainage canals, its waters are highly eutrophic. This condition has led to an invasion of water hyacinths (Eichornia crassipes), and its water produces unpleasant odors. However, efforts to improve the conditions by treating the incoming water have recently paid off, and the lake is becoming a local tourist attraction. The Lake Zumpango is often believed to have been saline or brackish (Sanders et al. 1979). However, the archaeological surveys of the basin found no evidence of pre-Hispanic salt-production sites on its bed (see Parsons 2008) in contrast to the abundant salt-production sites in western and northern parts of Lake Xaltocan (Parsons 2008; Sanders and Gorenflo 2007). In fact, the level of salinity of the prehistoric and historic Lake Xaltocan is not known and information on it is conflicting, as characteristics of freshwater and alkaline-saline lake exist. On the one hand, wetland agriculture existed on the lakebed near Tezoyuca in early colonial times as suggested by historic documents (see Rojas-Rabiela 1974; Strauss 1974). This area, however, seems to have been a swampy area near the incoming waters of Tepotzotlan-Cuautitlan Rivers (Fig. 7.6). However, issues with salinity in modern soils suggest minor, though still manageable, levels of salinization (Reséndiz-Paz et al. 2013). Furthermore, the historic collection of tequesquite, a mineral powder precipitated by evaporation on the exposed beds of alkaline lakes, suggests an environment similar to the highly saline lakes Xaltocan and Texcoco. Analyses of conductivity (e.g., proxy for salinity) from existing ponds and marshes in the area show lower salinities at the end of the rainy season in September and higher salinities peaking at the end of the dry season in March (Bradbury 1989, Table 2). However, in both cases, the production of tequesquite and farming on the
7.3 A Geography of the Historic Lakes
161
bed would have occurred during the dry season. Perhaps then, these activities occurred in different locations of the basin; the collection of tequequite in the center of the basin and farming on the deltaic areas (Fig. 7.6), where the influx of fresh water would have reduced salinity and, most important, provide water for irrigation. The contrasting information on the salinity of Lake Zumpango is linked to another issue, the lack of information on the nature or even existence of the lake in prehistoric times. Absent in the Codex Xolotl (Fig. 2.8) and not mentioned in the chronicles of the war of Conquest. Some of the towns mentioned during some episodes are name of the towns where the Spanish army passed, which suggests that to march around the north they passed through Citlaltepetl (Chap. 14). If this was the case, maybe the routes tried to avoid either a lake or an area of wetlands. Moreover, the Map of Uppsala shows it more as a wetland than a lake, although Lake Xaltocan appears similarly in the same map. However, it is mentioned in the Anales de Cuautitlan, although it is not clear if the diversion of the waters of the Cuautitlan created Lake Citlatepetl in the Zumpango basin. Unfortunately, the construction of the v-shaped dam at the beginning of the seventeenth century retained the flow of water in the basin, giving the appearance that a large natural lake existed there. In this case, it is difficult to know what was the shape and size of the lake in pre- Hispanic times, and if so, whether it was a permanent lake or seasonal wetland. However, this is only a supposition that needs to be supported with further research. 7.3.2.2 Lake Xaltocan Lake Xaltocan takes its name from the town of Xaltocan, located on a former artificial island. The original lake was fed by the overflow of Lake Zumpango by the Cuautitlan River before its diversion to the north, by small ephemeral streams from the east, and by several springs. However, despite the influx of freshwater from Zumpango and the springs, the lake had mostly saline waters. Archaeological surveys show several pre-Hispanic salt-production sites (Parsons 2008), which are also evidence of the presence of highly salinized soils (Bautista-Guzmán 2018). Despite its saline waters, a chinampa agricultural system developed on its bed fed with fresh water from Ozumbilla Spring in the Cerro de Chiconautla to the southwest of the lake (Fig. 7.6). Although knowledge of the chinampa system existed, recent excavations showed the real size of the area originally thought to have been cultivated on chinampas, and it is perhaps the oldest chinampas in the Basin of Mexico (Morehart and Frederick 2014). The chinampa system, however, collapsed as the desagüe projects reduced the flow of water into the Xaltocan basin and the water from the Ozumbilla spring was diverted to Mexico City. Like its neighbor to the north, there is little in terms of paleoenvironmental research, except for some work done in areas of the former Pleistocene faunal sites (Carballal-Staedtler 2007; Lorenzo and Mirambell 1986a) and some recent studies on geomorphology and soils (Frederick et al. 2005). It is possible that during the Pleistocene Lake, Xaltocan was much larger than the historic lake, which is attested to by the extent of its flat bed and the presence of lacustrine clays in an even larger area.
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7 A Geographic Sketch of the Historic Lakes
The lakebed is at present completely dry, making it the only lake of the five in the Basin without any water remnants (Fig. 1.2). Parts of its dry bed are under agricultural or pastoral land use, but many areas remain unused because of strong soil salinization. Its western side has experienced rapid urban development (Fig. 7.6). The Santa Lucia Airbase, on its former northern shores, is one of the proposed locations for the construction of a new International Airport, an action that may attract more urbanization to the area.
7.3.3 Lake Texcoco Lake Texcoco, also known as Lake Mexico-Texcoco, was the largest of the four lakes of the Basin of Mexico (Fig. 7.1). It was also the lowest in elevation, which made it the recipient of all the excess water from the other lakes (Table 7.1) and numerous streams flowing directly into its basin. Thus Lake Texcoco was the endpoint for all waters in the Basin, except those in the northwest (e.g., L. Tecocomulco and Apan), which at the time did not flow into the major lacustrine system until recent. Because of soluble salts from rocks, high evaporation rates, and saline waters flowing from the north, the waters of Lake Texcoco had high salinity. Nonetheless, its southwestern part received considerable amounts of freshwater from permanent streams, springs, and the overflow from the southern lakes. It is because of this that later in history the construction of dikes allowed the establishment of chinampa agriculture on its western side (see Chaps. 8 and 9). At the arrival of Hernan Cortés’s army (1519), the western part of the lake was divided into several sections by a series of dikes that prevented the mixing of saline water from the east and protected the city of Tenochtitlan from floods in general (Ramírez 1976; Palerm 1973). The war of Conquest, however, brought destruction to many of the dikes and the hydraulic infrastructure, which the Spanish authorities were slow to repair as water levels remained low due to a prolonged drought in the decades following the conquest (Candiani 2014). The return of wet conditions in the late sixteenth century brought frequent floods to the city, which forced the Spanish authorities to repair some of the old hydraulic infrastructure, but that was not enough to contain the floods (Gurría-Lacroix 1978). Unable to cope with the problem, the authorities began directing efforts to the desagüe projects, which over the next centuries reduced the amount of water flowing from the northern lakes into the basin of Lake Texcoco (Candiani 2014), which led to the gradual desiccation of the lake (Fig. 7.7). The western parts of the lake began to dry out faster, as it was shallower than the rest of the lake and circumscribed by causeways that formed smaller basins. The causeways acted as dams that helped fill up the basins with silt. By the end of the seventeenth century, the connection between Lake Xochimilco and Lake Texcoco was only through a canal as the receding lake had retreated too far from the strait connecting the two basins. By the second half of the eighteenth century, the western
7.3 A Geography of the Historic Lakes
163
c.1550
c.1500
c.1650
Texcoco
Azcapotzalco Tacuba Mexico (Tenochtitlan) Coyoacan
Iztapalapa
2 km
c.1750
2 km
2 km
c.1950
c.1850
Texcoco Azcapotzalco Tacuba Mexico 2 km Coyoacan
2 km
2 km
Iztapalapa
N
N
10 km
Lake Texcoco
Texcoco
1950 Azcapotzalco
1850 1750
1750
Tacuba
1650 1550 1650
Coyoacan
Mexico (Tenochtitlan)
1850
1550
0
Ixtapalapa
1
2 km
500 m
Fig. 7.7 The gradual diminution of Lake Texcoco since the 1500s. Shoreline changes based on Filsinger (2005) and the author’s research. The shorelines from 1550 to 1950 are placed against the modern landscape
shore of the lake already lay west of El Peñón de los Baños, by which time its name had long since shifted to Lake Texcoco (Fig. 7.7). In addition to the construction of the San Cristobal Dam (1604), which reduced the flow from the northern lakes, modifications to the rivers emptying into the lake
164
7 A Geographic Sketch of the Historic Lakes
reduced the volume of water in Lake Texcoco. The construction of dams, notably the Acolman Dam (Fig. 7.3), which attempted to reduce the flow of water into the lake as a measure to reduce the flooding of the city (Ramírez 1976), was also an important factor in the reduction of the lake. In addition to this reduction in water volume, the reinforcing of dikes in the area of Mexicaltzingo and Culhuacan reduced the flow of water from the southern lakes (Candiani 2014; Rojas-Rabiela 1974). The flow of water from the western rivers declined considerably through the seventeenth and eighteenth centuries, as farms and towns tapped their water for irrigation and gristmills, leading to the faster desiccation of the areas south, west, and north of the city (Fig. 7.7). Furthermore, the deliberate diversion of streams into fields to fertilize lands in the dry beds contributed to the siltation of these basins and their faster desiccation (Candiani 2014). The main blow to the dying lake occurred at the turn of the twentieth century with the completion of the Gran Canal del Desagüe under President Porfirio Díaz. This project cut the lake off from the streams feeding the lake from the west and the flow of water from the southern lakes. Fed only by the mostly intermittent eastern streams, the lake was reduced to a salt flat with small shallow ponds during the rainy season (Fig. 3.10). Attempts to use the exposed lakebed for agriculture in the 1920s failed due to the high concentration of salts in the soils (Espinosa-Castillo 2008). The procurement of salts and other minerals deposited by evaporation became the only way of commercial use of the area. In the mid-twentieth century, the existing ponds on the eastern side (Fig. 7.7) were still used by traditional communities on the east shore for traditional activities such as fishing, waterfowl hunting, collection of insects, and production of salt (Parsons 2001, 2006). Although Lake Texcoco no longer exists, people still refer to the vast area of salt flats and seasonal ponds as “Lago de Texcoco.” In official documents, the designation of this area appears as “antiguo vaso del lago de Texcoco” (former basin of Lake Texcoco) or simply “Ex-lago de Texcoco,” an area which is demarcated as a federal zone (Fig. 1.2). Inside this zone, the largest body of water in the former lakebed is Lake Nabor Carrillo, an experimental project of the 1970s and early 1980s that focused on recreating the lacustrine landscape on areas covered mainly by salt flats and ephemeral lakes. Projects for the development of lakes and wetlands have since been proposed and failed (see Chap. 15).
7.3.4 The Southern Lakes: Chalco and Xochimilco Lakes Chalco and Xochimilco are the two freshwater lakes in the Basin. The two lakes constitute one lacustrine system, originally known as Lake Chalco, but divided into two basins by the Tlahuac dike in Aztec times (Fig. 7.8). However, despite their artificial separation, the two sub-basins have noticeable natural differences. The eastern part (i.e., Lake Chalco) has a stronger influence from the sedimentation of two large permanent streams, the Tlalmanalco and Amecameca Rivers, both
7.3 A Geography of the Historic Lakes
Huitzilopochco Coyoacan
6
165
7
Mexicaltzingo 5
Iztapalapa
a
Culhuacan
Xitli Lava Field (El Pedregal)
8
Cuicuilco
5
Parque Ecologico Lago de Xochimilco
Proposed pre-eruptve shoreline Prehistoric lakes*
3
La Caldera
Cerro de La Estrella
Sierra
de
Sant
Tlapacoya
4 Laguna de San Gregorio Laguna de Tlahuac
Xochimilco
Tlahuac
Former river channels Former or failed canals Modern drainage canals *According to Neiderberger(1987) Current Chinampa areas Former seasonally flooded plains
Selected prehispanic features Inland settlement Insular settlement (tlatel-type) Prehispanic dikes and causeways
3 2
Valle de Chalco settlement New Lake Chalco
Xico
Ponds in Lake Chalco Areas of deltaic sedimentation
a
arin
Cat
Canals 1. Amecameca 2. Tlalmanalco 3. La Compañía 4. Canal de Chalco 5. Canal Nacional 6. Río Churubusco 7. Former Canal de la Viga 8. Failed Canal de Garay
Chalco
N
4 1
Mixquic
0
1 2 km
500 m
Fig. 7.8 The southern lakes, Xochimilco and Chalco, with selected natural and cultural features against the modern landscape
originating in the Sierra Nevada, as well as several small ephemeral streams descending from the Sierra del Chichinautzin. Lake Xochimilco, on the other hand, has only minor influences from small perennial streams, but a strong inflow of water from springs at the base of the Chichinautzin and in the lakebed. The physical differences described above have implications in the patterns of human use of the two lakes in the past. The most obvious of these differences is that ancient and modern chinampa fields are more abundant in Lake Xochimilco than in Lake Chalco. With a more stable flow of water from springs and a lack of mineral sedimentation from large rivers, Lake Xochimilco constitutes an environment more suitable to chinampas. Still, chinampa systems in Lake Chalco existed on the southern end and around Xico. The southern lakes were practically unmodified through the Colonial period, in part because they represented an apparent smaller threat of flooding to Mexico City and because the productivity of its chinampas was essential for food supply to Mexico City (Candiani 2014; Rojas-Rabiela 1974). However, major modifications to the southern lakes occurred at the turn of the twentieth century when, under President Porfirio Díaz, a project to supply Mexico City with water began to tap water from the springs that fed Lake Xochimilco (Legorreta-Gutiérrez 2006). The last blow to the lakes came with the drainage of Lake Chalco into the Gran Canal del Desagüe system, which practically turned the lakebed into agricultural land for the local large haciendas (Tortolero-Villaseñor 2015). Today what remains of these two lakes are small bodies of water and a reduced, but still extensive, area of chinampas in Lake Xochimilco (Fig. 7.8). Water extraction has created some problems to Lake Xochimilco as some canals are drying and cracks are appearing in the ground. In contrast, in the Lake Chalco basin, water pumping is causing the ground to subside, leading to the formation of ponds that
166
7 A Geographic Sketch of the Historic Lakes
gradually grow in size thereby flooding adjacent fields and settlements (Ortiz Zamora and Ortega Guerrero 2007). The largest of these new ponds has grown to become the so-called Nuevo Lago de Chalco (New Lake Chalco) (Fig. 7.8).
7.3.5 Recapping on the Geographic Nature of the Former Lakes Cartographic representations, geographic nomenclature, and toponyms provide an idea of what the lakes of the Basin of Mexico look like. With some of the evidence in the patterns of sedimentation and distribution of archaeological sites, the picture seems to be clear on the nature of the lacustrine systems that in recent centuries scholars writing in Spanish call lagos. The material reviewed in this chapter suggests that the very broad picture of the former lacustrine systems is that of shallow lakes (Chalco-Xochimilco and Texcoco), and some of them as wetlands (Xaltocan and Zumpango). Except for lakes Chalco and Xochimilco, the former lakes did not have permanent connections as depicted in some recent cartographic models, although the flow of water between basins occurred when water exceeded the capacities of the higher basins. If at all, as suggested by some of the chronicles of the conquest, swampy channels (esteros) existed in the straits connecting the basins (discussed amply in Chaps. 8 and 14). Lake Texcoco, the largest of them, was an extensive shallow lake with considerable fluctuations throughout the year and through cycles of dry and wet years. Freshwater lakes such as Chalco and Xochimilco constituted a single lacustrine basin dominated in large part by aquatic vegetation, which are prone to considerable changes over time but less drastic than those of Lake Texcoco. Lake Xaltocan seems to have been a saline wetland as it fails to appear in some early maps and descriptions as a lago or laguna. It is likely that damming in colonial times may have created a body of water that gave the idea that in pre-Hispanic times was a lake. Lake Zumpango appears even an enigmatic lake, whose existence may likely have been that of a large alluvial wetland formed by the impoundment of waters of the Tepozotlan and Avenidas de Pachuca. Anthropogenic changes such as the deviation of the Cuautitlan in the 1400 s may have changed its size. However, its existence as a lake may have materialized only with the construction of dams.
Chapter 8
Models of Lacustrine Dynamics and Environments
8.1 Conceptual Framework and Methodological Approaches 8.1.1 Characterization of the Basin of Mexico’s Lacustrine Systems The geological evolution of the Basin of Mexico is the primary factor in shaping the nature of the physical characteristics of its lacustrine basins, because its tectonic and volcanic origin caused the formation of endorheic drainage amid steep slopes. In this endorheic hydrological context, the influx of volcanic materials and alluvium filled in the basins and interbedded with lacustrine sediments forming a relatively flat bottom, thus creating an ample area for water to accumulate. The surrounding high-gradient topography resulted in small fluvial catchments dominated by torrential flow that would bring even more sediments to further flatten the basin bottom. Secondary to the tectonic and volcanic origin that created the contrasted topography of the basins is the strong seasonal precipitation regime, characterized by a marked rainy season and a relatively long dry season. Concurrently, the high-altitude and very continental location of the Basin, and its exposure to solar radiation under mostly open skies, results in high evaporation rates of the waters in the basins, especially during the dry season. The amount of water coming from springs compensates for the relatively low and seasonal precipitation and high evaporation, but it is not enough to maintain lake levels constant throughout the year. Furthermore, the influx of water from deep faults and the minerals dissolved in it gave the lakes’ water high alkalinity and salinity, which are only enhanced by the high evaporation rates. In summary, the high-gradient small catchments with torrential flow that feed the low-gradient lacustrine basins under strong seasonal precipitation and high evaporation rates result in shallow lakes with high variability in size throughout the year and relatively highly alkaline and saline waters. However, despite these characteristics, © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5_8
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the former lakes of the Basin of Mexico were not quite like the playa lakes of arid environments, as they were in a sub-humid temperate area with enough precipitation, enough cloudiness during the summer, and abundant underground water flowing out from springs to maintain at least some standing water in the basins throughout the year in the basins. In view of the characteristics summarized above, the dynamics, landforms, and depositional environments of the lakes of the Basin of Mexico are examined here in the context of shallow lake limnology. Therefore, this chapter attempts to reconstruct the possible ways the lakes behaved in recent prehistoric times until their disappearance, based on geological, limnological, geomorphological, archaeological, and historical evidence.
8.1.2 Approaches to Reconstructing the Dynamics of Vanished Lakes Paleolimnological and paleoecological data provide information for reconstructing millennial environmental changes in the lacustrine realm of the Basin (Chap. 6), but not for reconstructing the lakes during the last few millennia of the Holocene, especially the scale of centuries and decades. Therefore, the reconstruction of the dynamics of the original lakes of the Basin of Mexico relies on three approaches: (1) historic descriptions of the lakes when they still existed, (2) the geomorphological and stratigraphic record (i.e., geoarchaeological record), and (3) references to other lakes with similarities to the ancient lakes of the Basin. Descriptions of the lacustrine dynamics of the Basin’s lakes exist in pictorial and written historical documents. In particular, the chronicles of the conquest provide some interesting information on lacustrine features and dynamics (see Chap. 14). Additionally, descriptions of floods in early colonial times as well as documents concerning the desagüe projects are of great help in understanding lacustrine dynamics in the Basin (Candiani 2014; Gurría-Lacroix 1978; Ramirez 1976; Everett-Boyer 1975). To this information, one can add the early Colonial maps, which, though largely inaccurate, in some cases represent the general distribution of the lakes and associated features (e.g., Figs. 1.6, 7.3, and 7.4). Furthermore, information recorded during the nineteenth century (e.g., Garay 1811; Orozco y Berra 1864; Mora 1823; Humboldt 1811) provide glimpses of how the lakes behaved throughout the year and from year to year and, in many cases, numerical data on depths and relatively accurate maps (e.g., Fig. 7.8). The geomorphological and stratigraphic records provide evidence of a number of lake environments, especially features such as beach deposits, deltaic deposits, marshes, and a series of other natural and cultural features that help in reconstructing the dynamics of the lakes (Cordova et al. 2022; Frederick and Cordova 2019). Although these features are difficult to corroborate with the historical record, they sometimes correlate with particular archaeological features or artifacts that permit their placement in space and time.
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Fig. 8.1 Sequence of high and low stands on the northern shore of Lake Atotonilco, Jalisco. (a) End of the rainy season (October 2007); (b, c and d) end of the rainy season in May 2005, April 2011, and April 2019, respectively. Source: Google Earth Pro. D deltas, P pools created by streams coming into dry lakebed; WS wetlands fed by springs; and S saltflat
References to modern analogs of lacustrine systems elsewhere help us understand the lacustrine environments that have disappeared. Modern analogs of shallow lakes in tectonic basins in subhumid and semiarid environments exist elsewhere in the Transmexican Volcanic Belt, other parts of the Mexican Altiplano (Fig. 3.1), and parts of the western United States. Whether or not they pertain to the characteristics of the Basin’s lakes, they provide information useful in the interpretation of lacustrine dynamics in shallow lakes. Although this information exists mainly in observations published in the geomorphological literature, direct observations of shallow lakes can be obtained from sequential aerial imagery (Figs. 8.1, 8.2, 8.3 and 8.4).
8.2 Shallow Lacustrine Systems 8.2.1 General Characteristics of Shallow Lakes Water depth has an important influence on temperature stratification and hence on other processes such as circulation and sedimentation. In deep lakes, water stratification comprises a warmer top layer (epilimnion) separated from a deeper colder layer (hypolimnion) by a thin transitional layer (metalimnion) where temperature changes quickly (Cohen 2003). The waters of the stratified layers in a deep lake generally do not mix except in specific circumstances, when certain external processes combine with the morphology of the basin (Sly 1978; Dent et al. 2002).
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a
E
D E E FD
D 1 km
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Fig. 8.2 Provo Bay, east shore of Utah Lake, Utah, USA. (a) Low lake stand (June 2005) and (b) high lake stand (June 2013). (Source: Google Earth Pro. D active deltas, FD former deltas; and E inlets (i.e., esteros))
Under conditions of water stratification, surface currents rarely have any effect on the bottom sediments, except in areas near shore where turbulence from the wind can reach the bottom (Fig. 8.5a). In contrast, in shallow lakes, where there is no water stratification, wind force creates waves and currents that reach the bottom of the lake (Fig. 8.5b), producing sediment translocation in a process called sediment resuspension (Evans 1994; Hamilton and Mitchell 1996) (Fig. 8.5c). The removal, transport, and deposition of sediments involved in the resuspension process depend on winds, currents, the morphology of the basin, the presence of
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a
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FD
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D FD 1 km
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Fig. 8.3 Deltaic system on the northern shore of Lake Santiaguillo, Durango. (a) High lake stand and (b) low lake stand. D active deltas, FD former or inactive deltas, probably active during high lake stands
emergent vegetation, and sediment (James and Barko 1994). Usually, areas of dense aquatic vegetation trap sediments and fix them to the ground (Fig. 8.5c). Thus, sediments trapped by aquatic vegetation may survive as organic layers or peat, and in general appear as dark or brown layers in the stratigraphy. In Lake Texcoco, they seem to be preserved only in a few places, as shown in stratigraphic models (Figs. 5.3). In the more vegetated southern lakes, however, layers of peat and organic sediment are more substantial and extensive. Nonetheless, in general, constant sediment removal by resuspension results in low sedimentation rates apparent in thin sediment deposits and stratigraphic hiatuses, as in the Holocene sediments in the cores and exposures of the lakebed in the Basin’s lakes, particularly in Lake Texcoco. Depth and lake-level fluctuations are important for differentiating lacustrine from palustrine environments (Ismail-Meyer and Rentzel 2016; Verrecchia 2007).
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L DL DL D D
D 500 m
N
Fig. 8.4 Northern shore of the Salt Plains Lake, Oklahoma, where two types of deltaic systems converge in the lake. D deltas, DL deltaic channel levees, L lagoon dammed by delta channels
Palustrine environments generally are characterized by a dense agglomeration of plants and other forms of microscopic life (e.g., ostracods, diatoms, and algae), authigenic minerals, and oxidation-reduction processes (Verrechia 2007, Fig. 9.10). Interestingly, the most common sediments reported in Holocene layers in all the lakes of the Basin include peat, organic mud, snails, silicified roots, carbonated deposits, and sediments with gleyzation, all of which fit more clearly the characteristics of palustrine sediments. This is the case in sections near the historic shores (Cordova et al. 2022; Frederick and Cordova 2019; Sedov et al. 2010; Frederick et al. 2005; Limbrey 1986; Bradbury 1989), as well as deep inside the lake basins (Ortega-Guerrero et al. 2017; Frederick et al. 2005; Lozano-García and Ortega Guerrero 1998; Bradbury 1989; Carballal-Staedler and Flores-Hernández 1989a). In addition to sedimentation, the depth and shape of a lake basin influence the ways in which lakeshores fluctuate during low and high lake stands. Accordingly, a drop in the water level in a shallow lake exposes more of its bottom surface. The diagrams in Fig. 8.6 illustrate the hypothetical responses of a deep lake with a high- gradient basin and a shallow lake with a low-gradient basin to a 15% reduction in their water volume. The water level drop exposes more surface in the shallow lake than the deep lake example. To illustrate this case with a real example, the sequences of the images of Laguna de Atotonilco (Fig. 8.1a–c) show how much of the lakebed is exposed in times of drought within a period of 6 years. The continual seasonal and occasional lake-level drops in shallow lakes expose the lakebed to subaerial erosive processes by wind and water, which remove sediments, thus creating stratigraphic hiatuses. At present, the permanent exposure of
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most of Lake Texcoco’s bed has created removal of top sediments by deflation (Fig. 3.13b). Water erosion removes exposed lacustrine sediments through overland flow and rill erosion, or even channel scouring of the lakebed. Examples of the latter have been reported in eastern part of Lake Texcoco where during prehistoric lake-level drops, streams eroded the exposed lacustrine bed creating channels as is the case of localities such as the Tocuila mammoth site (Morett-Alatorre 2021), the Tlatel of Tequexquinahuac (Cordova et al. 2022) (Fig. 9.6), and the Texcoco Man locality (Fig. 5.5). These aspects of lacustrine sediment erosion account for many of the hiatuses found in Lake Texcoco, especially in the Pleistocene-Holocene transition and during parts of the Holocene. This explains also the fact that many Aztec-period occupation deposits lie directly on Pleistocene clay, an aspect that is significant when discussing the settlement of Tenochtitlan (Chap. 13).
8.2.2 Wind, Currents, and Waves: A Model The importance of currents in the lakes is an important aspect not only for the removal of sediments but also for the distribution of natural and cultural features within the lake basins. Winds are the main factor that powers currents, though this depends on the topography of the basins and direction and strength of dominant winds throughout the year. Although wind data is available from the various meteorological stations, they should be interpreted with care when extrapolating it to the past, especially because the large urban cover of Mexico City and its metro area influence wind modalities (Jáuregui-Ostos 2000). Unfortunately, however, most meteorological stations in the Basin of Mexico were established after the lakes had disappeared and the city had already attained a large size. The Tacubaya Observatory (established in 1873) has the oldest records, but its location is not representative of the various areas of the lakes, except perhaps for the western shore of Lake Texcoco. Despite the lack of historical wind measurement records, it is possible to reconstruct wind direction patterns and their possible influence on currents and waves in the lakes, using historical references and the few early measurements. Some of the sixteenth-century Relaciones Geográficas report seasonal wind directions for some localities around Lake Texcoco: Culhuacan, Iztapalapa, Chicoloapan Texcoco, Tepexpan, and Tequisistlan (Acuña 1985). Additionally, references to general and seasonal wind direction appear in historical reports of weather conditions during the years before the lakes were drained (e.g., Altamirano 1895; Garay 1888; Humboldt 1811; Orozco y Berra 1864). One may add the location of beach deposits as well, which may indicate wave direction and lakeshore currents. Although beach formation depends on other factors such as the supply of sand and the topography, some of the identified beach deposits of the Late Holocene (see Sect. 5.3.1) may suggest frequent currents in the past. Additionally, inferences from the emplacement of the main dikes built to protect Tenochtitlan provide clues to the movements of water in the Basin, which in turn indicates the flows produced by wind-powered currents.
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The combination of historical proxy data and the location of beach deposits results in a map of possible wind-powered currents, which could serve at least as the hypothetical currents of Lake Texcoco (Fig. 8.7a). It is also important to mention that in addition to winds, the elliptical shape of the lake basin with its main axis from north to south was important in the movement of wind-propelled waves. Although the Coriolis Effect would have been almost negligible because of the size and depth of the lake, it would still have been important as the preferred, clockwise, direction for water circulation. Another factor to consider is the influx of water from the northern and southern lakes should have been important, particularly important in those times of the year when the excess of water in those basins created a stronger flow into Lake Texcoco (Fig. 8.7b). The movements that these incoming currents would have generated would be from the north through the Ecatepec strait and from the south through the strait of Culhuacan. They should be important, especially when large amount of waters, presumably in the rainy season, would flow into Lake Texcoco. Historical and modern wind data suggest that an important component from the N and NW, and NE was the passes that formed between the sierras in the north (Monte Bajo, Sierra de Guadalupe, Cerro Chiconautla, Sierra de Patlachique, and the Sierra Nevada) and between the Sierra de Guadalupe and Cerro Chiconautla. The N and NW winds would power currents moving toward the south and southeast toward Chimalhuacan (Fig. 8.7b). The terrain and morphology of the coast would direct the currents westward toward the area between Iztapalapa and El Peñón de los Baños. Here perhaps currents would dissipate in the shallows or return north, depending on the force if the northwest wind coming from the port west of the Sierra de Guadalupe counter its force (Fig. 8.7b). Winds from the NE, on the other hand, would directly power currents to the center of the lake toward the southwestern part of the basin (Fig. 8.7c). In both cases, the wind-powered currents would have exerted pressure on the part of the lake where most population settled in the Aztec period, which is an aspect to consider when explaining the construction of dikes in that part of the lake. A less common but also important wind direction in certain times of the year is the S and SE wind, which perhaps increased through the gaps that formed between the western piedmont, Cerro de la Estrella, the different volcanic structures of the Sierra de Santa Catarina, the Cerro de Chimalhuacan, and the eastern piedmont. The resulting circulation of lake currents would have shifted slightly, pushing water toward the northwest side of the basin (Fig. 8.7d). This pattern would have been more common during the certain times of the rainy season, when apparently southern and southwestern winds can be common. Empirical evidence of current directions comes from the beach bar deposit at El Tepalcate where one ridge formed in NW-SE direction and another in N-S direction (Fig. 5.8). The main ridge (NW-SE) may have been formed by the action of waves coming from the north, as shore currents carry sand from the mouths of rivers, while the smaller ridge (N-S) seems to have been formed by waves powered by the southwestern wind (Fig. 8.7). Other beach deposits show waves from the southeast at Tlatel Tequexquinahuac (Cordova et al. 2022) and at Huatepec, the youngest paleobeach (see Fig. 5.8) (Morett-Alatorre 2001). The waves associated with this current
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may have been moving along the east shore, although in some cases, the SE direction may also have created waves. In any case, currents along the shore would have been important for transporting sediments from the river mouths that would provide sand for beach building. Finally, the north-south emplacement of Late Aztec period dikes and the largest causeway dikes (Fig. 13.2) suggest that the city was mainly protected from currents coming from the east, essentially those created by winds blowing from the north, northeast, and northwest directions (Fig. 8.7b, c). Nevertheless, it is possible that the dikes were also placed in that particular direction because they served as dams to retain water (see discussion in Chap. 13) or to protect the city of surges created by storms (next section).
8.2.3 Effects of Storms and Seiches Observation during times when the lakes still existed report that strong wind- generated waves were catastrophic for navigation and in some cases inundated flat areas east of Mexico City (e.g., Orozco y Berra 1864; Tylor 1861). Hernan Cortes, in his description of the lakes (1985: 85), referred to these phenomena as mareas (tides), suggesting also that they formed in the saline lake (Lake Texcoco) and threatened the freshwater part of the lake (see full citation in Chap. 14). Most likely what these references suggest is that strong winds created surges that would press against areas of the shore in the form of lake seiches. These could be created by strong winds, especially during the windy season (late winter and early spring) or by winds generated during storms. If the model of currents (Fig. 8.5b) represents the real movements of water in the lake, the surges created by seiches would have been a threat to Tenochtitlan and other settlements on the western and southwestern sides of the lakes, which would explain the north-south direction of the dikes. Current patterns in the basins of the southern lakes of the Basin may have varied, given the shapes and sizes of the lakes and the relative closeness to the surrounding mountains. However, given the dominant winds, they may have been similar to those of Lake Texcoco, perhaps with a stronger dominance of the SE winds. Furthermore, like in the case of Lake Texcoco, storms generated strong currents and surges; Humboldt (1811) reports that strong winds dislodged vegetation on the banks creating the famous floating mats (bandoleros). The northern lakes may have had stronger winds from the NW, N, and NE, but the fact that the lakes were smaller, or perhaps were only wetlands (see discussion in Chap. 7), makes it difficult to predict what the currents would have been like. Most likely, the flow of water from Zumpango toward Texcoco created some sort of seasonal currents in Lake Xaltocan (Fig. 8.5). The fact that dikes also existed in the area suggests perhaps also some sort of control of water flows, but this is also a conjecture.
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a
Epilimnion
Terrigenous sediments
Hypolimnion
Wind
Lake-bottom sediments
b Wind
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Fig. 8.5 (a) General scheme showing lake stratification, current circulation, and sedimentation differences between deep and shallow lakes (loosely based on Cohen 2003); (b) surge caused by wind in a shallow lake; and (c) sediment resuspension and aquatic vegetation
8.2.4 Fluvio-Lacustrine Environments: Deltaic Systems The interaction between fluvial and lacustrine environments generated a series of deposits and landforms such as deltas, inlets, sand bars, and sediment shoals, many of which have clear expression in the stratigraphic records in lacustrine and perilacustrine areas (Cordova et al. 2022; Frederick and Cordova 2019). Of all the landforms, deltaic systems deserve attention as they seem to have been widespread in the lacustrine basins of the Basin of Mexico (Fig. 5.11). Thus, the natural dynamics of deltas is important in terms of understanding these areas, which at some point became attractive to resource exploitation and habitation by ancient societies. Although the mechanisms are similar in principle, substantial differences exist between marine and lacustrine deltaic systems. Morphological classifications of marine deltas are based on the dominance of three influences: rivers, waves, and tides (Galloway 1975). However, with tides absent in lakes, rivers and waves remain the most important influences (Nabetani et al. 1992). Additionally, factors such as slope gradient and type of fluvial sediment become important in lacustrine delta classification (Yu et al. 2018; Postma 1990). In this sense, lacustrine deltas vary from the so-called fan deltas, where the typical Gilbert-type delta is common due to
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Exposed surface
Low
SHALLOW, LOW-GRADIENT BASIN High
Exposed surface
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Exposed surface
Exposed surface
Fig. 8.6 Diagrammatic model showing the effects of lake-level drops in a deep, high-gradient lake basin, and a shallow, low-gradient lake basin when approximately 15% of the water is removed. Notice the difference in the surface of their exposed lakebeds
high-energy sediment deposition, to the Hjulstrom-type deltas formed under low- energy deposition (Postma 1990). The morphology of the latter is closer to the case of the shallow lakes of the Basin of Mexico. Typical deltaic deposition consists of three types of sedimentary packages, namely topsets, foresets, and turbidite deposits that are imbricated from the shore to the deepest part of the lake (Postma 1990). However, in a shallow lake, topsets are not overlying foresets, as both systems tend to be interstratified or separated along a horizontal plane (Feng et al. 2015). This layout responds to the fact that the shoreline fluctuations in shallow lakes vary considerably (e.g., Fig. 8.6). In other words, deltaic deposition would migrate lakeward during low lake-level stands, leaving dead channels behind, and during high lake-level stands, the active deltaic deposition would migrate landward. The example of Santiaguillo Lake shows that the
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Localities mentioned in text: 1 Huatepec beach deposits 2 Tlatel de Tequexquinahuac beach deposits
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Fig. 8.7 Hypothesized currents in prehistoric Lake Texcoco without dikes and artificial islands
present delta channels and landforms indicate deltaic deposits at times when the lake levels were higher (Fig. 8.3). Likewise, in the image sequences of Provo Bay, the delta on the east side of the bay is under water during high stands (Fig. 8.2). The different types of lacustrine deltas are the birdfoot, lobated, braided, and subaqueous fan types (Yu et al. 2018). Modern analogs in most shallow lakes (e.g., Fig. 8.1) suggest that the most common type of delta in shallow lakes is the birdfoot type, whose arms penetrate shallow lake environments and are usually composed of fine-grained deposits (Yu et al. 2018). This type of deltaic channels is bordered by levees, which act as barriers that form small lagoons between them as in the northern deltaic channel in the Salt Plains Lake (Fig. 8.4), which forms a lagoon almost completely separated from the rest of the lake. However, modern analogs and geomorphological evidence from the west side of Lake Texcoco (Cordova et al. 2022) suggest that the birdfoot delta was the most common in the shallow environments of the Basin of Mexico.
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Based on the characteristics of shallow lake delta shape and dynamics, an illustrative diagram of the evolution of the birdfoot-type delta explains the deltaic sedimentary structures and responses to high and low lake-level stands (Fig. 8.8). The examples of Provo Bay and Lake Santiaguillo (Figs. 8.3 and 8.4) show that the parts of a delta may include older delta deposits and the submerged parts of the system (Fig. 8.8a, b). During a high stand, delta arms are submerged, and during a low stand, they re-emerge, although not necessarily as active channels. In the end, the network of the abandoned levees of the channel arms form islands and shoals (Fig. 8.8c, f). These islands and the former channels may be colonized by aquatic vegetation, or in some cases upgraded with building material to become tlatel-type settlements (see Sects. 9.2.4 and 10.2.1), or sand may accumulate in areas where currents and wind form beach deposits. Furthermore, during times when the delta is active or after the abandonment of the islands, small swamps can form between the arms and in the inactive channels, creating a diversity of habitats. Although very few stratigraphic and geomorphic records attest to the existence of deltas in Lake Texcoco and Lake Chalco (Cordova et al. 2022; Frederick and Cordova 2019), it is possible to locate other deltaic systems in the Basin using modern topography and soils and historic evidence from maps. Deltaic systems existed in all the lakes, mainly at the mouths of the largest river systems (Fig. 8.9), some of which correspond to areas of settlement at certain times in the human history of the Basin (more discussion in Chaps. 12 and 13). Among the most prominent deltaic features in the Lake Zumpango Basin is the former Avenidas de Pachuca River delta of the south of the town of Zumpango, where it is still visible on some maps and in the topography of the area, but the delta itself has disappeared below the waters of the artificial lake. Not clear, but possible, is the existence of another small delta in the area of Teoloyucan at the mouth of the Tepoztlan River in the southern part of the Lake. Farther south on the west side of Lake Xaltocan, there is evidence of a substantial deltaic system formed by the former Cuautitlan River (Fig. 8.9). On the eastern side of Lake Texcoco, the San Juan Teotihuacan formed a delta, as suggested by sediments and the distribution of settlements. However, it is possible that this area also formed part of the Papalotla River delta. Farther south, the most prominent deltaic systems are the Chapingo-San Bernardino system, documented in Cordova et al. (2022), and the Santa Monica-Coatepec system, clear in the surface sediments of the area (Fig. 5.12). On the western side of Lake Texcoco, deltaic systems existed over an extended area between the shores and the western edges of El Peñon de los Baños, as sandy sediments and loams extend in that direction (Carballal-Staedler and Flores-Hernández 1989a). Certainly, the Magdalena- Mixcoac system formed a delta, which may have changed over time. However, confirming sediments and features in this area, now completely urbanized, makes difficult any confirmation of the exact locations of the deltas. On the western side of Lake Chalco, the two confirmed deltas include the Amecameca and Tlalmanalco-La Compania (Frederick and Cordova 2019). The Amecameca delta was active until the disappearance of Lake Chalco, when the river channels was diverted into the Canal Nacional at the end of the 1800s. On the
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Lake level ascent, deltaic surfaces are i mpounded while higher subaerial detlaic arms remain above surface
Lake level ascent to a level slightly lower than initial stage (c). Former subaserial high deltaic arms become islands while waves rework sand into beaches
Fig. 8.8 Model representing evolution of a lacustrine delta in relation to lake-level changes. (a) Plan view; (b) longitudinal profile; and (c–f) delta progradation and responses to lake-level ascent and descent
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Main streams
N
Areas above 2500 m
Artificial channels of main streams Inferred mean extension of Holocene lakes.
Areas between 2300-2500 m 1
Areas below 2250 m
?
L. Zumpango
Map based on Niederberger-Betton (1987)
2
? L. Xaltocan
3
?
?
Deltaic systems of Lakes Zumpango and Xaltocan 9
1 Recent-Modern Avenidas de Pachuca 2 Tepotzotlan and diverted Cuautitlan 3 Original Cuatitlan
10
Tx-A-3 11
4
Tx-LF-14 (Tlatel de Tequexquinahuac) 12
Lake Texcoco Tx-TF-46 (El Tepalcate)
5
6
13 14
6
8
Lake Xochimilco
Late Holocene fluvio-lacustrine systems of theBasin of Mexico Historic deltaic and alluvil sediments (Colonial-Independent) Approximate extent of prehistoric deltaic systems (subsurface sediments) Inferred deltaic systems under Xitli lava field Pro-deltaic sedimentation. Sediment-bank areas (shoals) Inferred former stream courses Inter-basin flows
15
Lake Chalco 16 17
0
5 Km
10
Deltaic systems of Lake Texcoco and Chalco-Xochimilco 4 Tlalnepantla-Guadalupe 5 San Joaquin-Los Morales 6 Tacubaya-La Piedad 7 Mixcoac-Magdalena 8 Cuicuilco pre-eruptive rivers 9 San Juan-Teotihuacan 10 Papalotla
11 Xalapango-Texcoco 12 Chapingo-S. Bernardino 13 Santa Monica 14 Coxtitlan-Coatepec 15 Tlalmanalco-San Francisco 16 Amecameca 17 Tlaixtlahuanca
Fig. 8.9 Late Holocene deltaic systems in the lakes of the Basin of Mexico
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8 Models of Lacustrine Dynamics and Environments
eastern end of Lake Xochimilco, deltaic systems existed prior to the Xitle eruption, fed by several rivers that after the lava blockage were diverted into the Magdalena River basin (Cordova et al. 1994) (see Sect. 12.2.3).
8.3 Natural Features in the Lacustrine Realm 8.3.1 Islands, Shoals, and Tulares Rocky promontories in the middle of the lake beds are the only stable natural islands in the lacustrine system of the Basin of Mexico. These promontories include El Peñón de los Baños and El Peñon del Marqués, Huatepec and Tepetzingo on Lake Texcoco, and Tlapacoya and Xico on Lake Chalco (Fig. 7.1). It is also possible that at some point the Cerro de la Estrella was an island, if communication between the Lake Xochimilco and Texcoco occurred simultaneously through the Culhuacan-Pedregal and the Cerro de la Estrella-Sierra de Santa Catarina straits. All these promontories had steep slopes, transitioning to the lake in ramps formed by colluvial sediments intermingling with lacustrine deposits. In contrast to these permanent islands, temporary islands formed by abandoned deltaic arms, sand bars, beach ridges, or emerged shoals existed across the lacustrine basins. Other types of islands were artificial, often associated with structures built for certain activities and habitation (see Chap. 9). Shoals were shallow elevations in the lakebed created by sedimentation, especially through the process of sediment trapping by aquatic vegetation (Fig. 8.5c) or by sediments at the mouth of deltaic channels (Fig. 8.8a). Although many of these shoals were close to the shores, they also formed in the central parts of the lakes, as in the area of the bed of Lake Texcoco surveyed by Parsons and Morett (2004) (Fig. 2.2), where evidence of human activity suggests an area exposed during certain times. At the same location, test pits provide evidence of what seems to be low- energy alluvial sedimentation (see Ortuño-Cos 2015). Sedimentation for the formation of shoals in this part of the lake may have been favored by water incursions from the northern lakes through the strait of Ecatepec (Figs. 8.7 and 8.9). Evidence of strong flow from the north exists documents in the desagüe that justify the construction of San Cristobal Dam (see García-Chávez 2018; Candiani 2014). Presumably, such water incursions from the northern would bring sediments that, if not carried by the currents, would settle out once reaching the calm water, thus forming the shoals reported in the surveys of that part of the lake. A modern analog of sediment carried along a strait appears in the strait connecting Provo Bay with the open lake (Fig. 8.2a). Another feature common in all the former lakes was tulares (singular, tular) or groves of cattails and bulrushes in shallow areas (Fig. 3.13a). Tulares were abundant in freshwater lakes or the less saline parts of the brackish and saline lakes. Some may have been associated with the shoals, especially where resuspended sediment occurred (Fig. 8.5c). These communities of aquatic plants were very important, not only as materials for basketry and mats (petates) but also as habitats for many animal species, including as locations for bird nesting (Parsons 2006).
8.3 Natural Features in the Lacustrine Realm
183
8.3.2 Mudflats, Saltflats, Marshes, and Swamps During the dry season or during extreme and protracted drought periods, extensive areas of the lakes were exposed creating areas of seasonal flooding or mudflats. In saline lakes, however, these would have consisted of saltflats, the surface where soluble minerals precipitated. These were particularly the areas where salt and tequesquite were collected. Marshes occurred in areas of the former lake basins where aquatic vegetation was abundant, and in some cases would have been interspersed with mudflats during periods of low water levels. Swamps would have occurred in those parts of the lakes that were vegetated, but water would have been more permanent. The most typical areas of swamps and marshes were in Lakes Xochimilco and Chalco, though they seem to have been common in some parts of the other lakes. In Lake Texcoco and Xaltocan, on the other hand, marshes and swamps existed in association with deltaic systems in places of abandoned channels and enclosures created by the deltaic arms but also in areas of freshwater springs. It is in the swampy and marshy areas of the Basin’s lakes, particularly in brackish or freshwater, that raised-field agriculture (i.e., chinampa agriculture) developed (Chap. 12).
8.3.3 Inlets (Esteros) Inlets are narrow, swampy passages connecting two open-lake bodies, two swamps, or connecting open lake and an embayment. Although absent in most of the maps of the Basin, they appear in some cartographic sketches and are mentioned in some chronicles under the name estero. Such references appear in some chronicles of the war of the conquest (1519–1521), especially in Bernal Díaz del Castillo’s (1982) Historia Verdadera de la Conquista de la Nueva España. In some cases, however, the reference seems to designate swampy channels in the straits connecting the lakes, in others, swampy channels or bodies of water along the lakeshore, and in others, an embayment on the shore (Díaz del Castillo 1982: 315, 332, 357, and 358). The embayment could also have been a small lagoon formed by the encirclement of a deltaic arm, as in some cases the descriptions were of areas of former deltas (Fig. 8.8). Thus, judging by these possible geographic settings in the descriptions, estero inlets in the former lakes of the Basin can be classified into three categories: inundated stream channels, enclosed lagoons (Fig. 8.10a), and channels formed along the straits connecting two lakes (Fig. 8.10b). Inlets are common in shallow lakes as shown in modern analogs. An inundated abandoned channel appears in the eastern end of Provo Bay (Fig. 8.2) and perhaps if a high stand inundates some of the channels in the delta of Lake Santiaguillo (Fig. 8.4), as well as in the “f” to “g sequence in the delta model of Fig. 8.5. Embayment by the encirclement of a deltaic arm appears in the north end of the deltaic system of Salt Plains Lake (Fig. 8.3). A channel across a strait connecting two bodies of water appears in the strait connecting Provo Bay and the open lake at low lake levels (Fig. 8.2b).
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8 Models of Lacustrine Dynamics and Environments
a
Low stand
High stand
b
Low stand
High stand
High ground, rocky hill
Low ground not flooded, but with high water table
High ground, bajada
Low ground prone to seasonal or extreme-event flooding
Wet area
Seasonal pond or muddy area
Fig. 8.10 Inlet (esteros) types in the former lakes of the Basin of Mexico. (a) Abandoned fluvial channel inundated by the lake and (b) swampy channel connecting two bodies of water
8.4 Ecological Expression of Depositional Environments
185
8.3.4 Springs Based on the toponyms, historical mentions, and hydrological surveys, many springs existed around and in the lacustrine plain, some of which were of significance because they were sources of water that maintained the water in the lakes or parts thereof during the dry season. Additionally, in saline lakes, many springs would have produced freshwater that attracted animal and human populations. Springs in the lacustrine plain were associated with faults and fractures that tapped deep aquifers or were water that had percolated through lavas of porous rock and flowed out at the lakeshore. Springs associated with deep faults were abundant in and around the lacustrine basins. Some springs were associated with rock promontories, notably El Peñón de los Baños in Lake Texcoco and Tlapacoya in Lake Chalco. This fact is important as these two islands had occupations dating back to the earliest humans in the Basin of Mexico. El Peñon de los Baños had thermal waters, which contributed to the deposition of travertine, where bones of animals and humans were preserved (González et al. 2014; Mooser 1956). Possibly, also the rocky promontories at Huatepec and Tepetzingo in Lake Texcoco had springs, as some forms of canals or conduits have been found adjoining the dike connecting them. Other fault-associated springs also existed near the shores, most likely where water flowed into the lakes, as at Chapultepec and Tepexpan and the Ozumbilla Spring (Bradbury 1989; Niederberger 1987). Springs associated with porous lava flows were abundant along the southern shores of lakes Chalco and Xochimilco, where apparently were the main sources of water into the lake (Fig. 3.12 and Table 3.1). There were probably some associated with the lava flows from the Sierra de Santa Catarina, where historically many springs existed (Peñafiel 1884). In all cases, the abundant and permanent flow of these springs was the main reason of the southern lakes’ predominantly freshwater.
8.4 Ecological Expression of Depositional Environments 8.4.1 Geomorphological and Ecological Diversity Across the Former Lake Basins Based on the conceptual framework of lacustrine dynamics and the features discussed above and sedimentary environments in Chap. 5, it is possible to define eleven discrete environments within the aquatic ecosystems of the ancient lakes of the Basin of Mexico (Fig. 8.11). These environments can be divided into littoral and mid-lake, based on their location with respect to the shore. At the same time, littoral environments can in turn be subdivided into those with high or low gradient depending on the slope dipping into the lake. It is important to note that the eleven types of environments are only illustrative models that represent, on the one hand, geomorphic environments, and on the other
186
8 Models of Lacustrine Dynamics and Environments
LOW-GRADIENT LITTORAL ENVIRONMENTS 1
Seasonal drainage channels Silt dunes
Seasonal evaporation pond
Silt dunes
2 Stream-fed channel Seasonal evaporation pond Lakeshore Stream and lake-fed Haophytic Vegetated abandoned meadow channel lakeshore meadow channel
Estero
Spring-fed pond
Inlet of water
Estero
Estero
High evaporation compensated by streamwater input
3
Open lake
Saline lake
Open lake vv
Water fed by saline lake High evaporation
4
Fresh/brackish water
Saline water and salt crusts
Freshwater input 5
Salix bonplandiana
Lakeshore meadow
Natural canal
Tular Springs
Floating vegetation
Tular
Springs
HIGH-GRADIENT LITTORAL ENVIRONMENTS 6
7 Shrubs
Shrubs Halophytes
Lakeshore meadow
Taxodium mucronatum
Shrubs Halophytes
Tulares
xxxxxxx
xxxxxxxx
8
xxxxxxx
vvvvv
MID-LAKE ENVIRONMENTS 9 Spring water trapped in a natural pool
Tular fed by springwater
11
10
Wind, waves,and currents Beach bar
Springs
Tular Sediment bank
vvv
Exceptional high level Seasonal mean low level
SYMBOLS Fresh
Backish
Saline
Clastic sedimentation
Erosive processes Slopewash
xxxxxx
Deflation Wave erosion Resuspension
Siltation Silts trapped by vegetation
vvvvvvv
Beach deposition
Eolian accumulation
Seasonal mean high level Exceptional low level
Chemical sedimentation Salt and other precipitates
Alluvial sedimentation Colluvial deposition
Fig. 8.11 Model types of the littoral and mid-lake environments in the Basin of Mexico in relation to topographic gradients
hand, ecological zones within the former lacustrine environments of the Basin. Such environmental models are references used in subsequent chapters for discussing aspects of human adaptation, appropriation, and transformation of the lacustrine environments in the Holocene. Furthermore, they serve as a guide for reconstructing environments using data from recent sedimentary records.
8.4 Ecological Expression of Depositional Environments
187
8.4.2 Low-Gradient Littoral Environments Environment 1 represents littoral saltflats with silt dunes and paleobeach ridges. The typical environment represented is from the southwestern part of the Lake Texcoco bed in the area around El Tepalcate (Figs. 5.5 and 5.7). Crusts of salt and minerals were collected where water had recently evaporated. During extended periods of exposure, the water table may have dropped, creating cracks on the surface, where winds would remove small clods of clay. Such clods would be deposited in coppice dunes fixed by salt grasses (Distichlis spicata) (Fig. 3.13c). Alluvial influence would have been only occasional, and streams deepening into it may have caused erosion in the lakebed, thus forming paleochannels cut in lacustrine clay. However, during extreme and protracted low lake levels, streams would have eroded the ground creating channels, as the stratigraphy of the Texcoco Man locality shows (Fig. 5.5). Although perhaps widespread in Lake Texcoco, similar environments may have existed in some parts of the northern lakes’ basins. Environment 2 comprises a mosaic of microenvironments formed by the combination of perennial stream influence, springs, and open saline lakes, including transitions from fresh to brackish to saline water. Natural features such as deltaic channels and former beach ridges added to the diversity of depositional microenvironments. Dense patches of aquatic vegetation (tulares) occurred in the more permanently inundated areas, with lakeshore meadows in areas that were only occasionally wet but had a relatively high water table underneath. The best example in the stratigraphy exists in the Tlatel de Tequexquinahuac, located in an area with multiple deltaic islands and paleobeaches (Cordova et al. 2022). Stratigraphic layers in some excavations below the city (Fig. 5.3, models 4, 9, 13 and 16) suggest that this type of sedimentary and lacustrine mosaic existed in the area where Tenochtitlan was founded (see Chap. 13). Possibly, this environment existed in Lake Zumpango, especially near the mouths of rivers. Likewise, a similar aquatic mosaic in a freshwater environment may have existed along the eastern shore of Lake Chalco, as suggested by the varied stratigraphy there (Frederick and Cordova 2019). Environments 3 and 4 represent small lakeshore lagoonal environments associated with a birdfoot type of delta, similar to the one represented in the analog in Fig. 8.4, or with the one illustrated in the deltaic model in Fig. 8.7. Hypothetically, in saline lakes, these lagoons may have varied in salinity, consisting of brackish water for those with stream feeding (environment 3) and those with saline water (environment 4). The upper layers of the stratigraphy at Tepexpan (see Sedov et al. 2010) suggest a slow accumulating environment with gleyic soils that may have constituted a lagoon of this type that formed on the north side of San Juan Teotihuacan delta. Environment 5 is a typical mosaic of tulares and open lake areas, or marshes and swamps. The source of water into these areas was largely from springs, which kept some level of fresh water throughout the year. The most important characteristic in terms of sedimentation is the predominance of peat and organic fine sediments, except in areas closer to the streams. This type of environment dominated in Lake Xochimilco and in large parts of Lake Chalco before the widespread construction of chinampa fields.
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8 Models of Lacustrine Dynamics and Environments
8.4.3 High-Gradient Littoral Environments Environments 6, 7 and 8 appear in the lower part of the bajadas of the small Sierras that are flooded seasonally during extreme wet events or long-term high lake-level stands (Fig. 8.11). Environment 6 is a featureless gradient from bajada to lake, usually showing interbedding of fine and coarse sediment layers, and in many cases crusts of carbonate. A typical environment is the area of tlateles between west of Tepexpan (see De Terra 1949; Litvak 1964) and those at the base of the Sierra de Guadalupe like El Risco (Mayer-Oakes 1959). It is evident that many of the localities along the shores of the Iztapalapa Peninsula (Cerro de la Estrella and Sierra de Santa Catarina) presented this type of environment according to the descriptions of the archaeological survey (Blanton 1972) and stratigraphic profiles along the southeastern segment of subway line 8 (Sánchez-Vázquez 1996). Environment 7 also forms in areas of transition between bajadas and environment 5 and consequently is typical of areas along some shores of the southern lakes. The stratigraphy at Tlapacoya, in particular, shows the transition from bajada to lake, with interbedded layers of lacustrine and palustrine sediments, colluvial coarse materials, and volcanic ash (see Gonzalez et al. 2015; Lorenzo and Mirambell 1986a, b; Niederberger 1976, 1979). Environment 8 represents possible variations of environments 9 and 10, but with beach deposits. A more substantial example of a beach depositional environment at the foot of a bajada has been reported on the eastern side of Huatepec Hill (Fig. 4.5). By analogy, it is possible that other areas exposed to open fetch such as El Peñón del Marqués (Tepeaopolco) and El Peñón de los Baños may have also had similar beach deposits laid against bajada and colluvial deposits.
8.4.4 Mid-Lake Environments Environments 9, 10, and 11 represent areas offshore. Environment 9 may be associated with mid-lake springs feeding this shallow part with fresh water, representing a better environment for the proliferation of aquatic vegetation. Environment 10 may be an inactive beach ridge or sand bar inundated by high lake levels similar to the one at El Tepalcate (Fig. 5.8), which suggests that this environment may be in transition with Environment 1. Environment 11 represent shoals of sediment formed by sediment carried by currents (i.e., resuspension) and trapped by vegetation (Fig. 8.5b). This environment seems to have been pervasive, as the dark late Holocene sediments lie directly on the Pleistocene green bentonitic clay as shown in some sections in the interior of Lake Texcoco (e.g., Fig. 5.2), including areas below Mexico City (Fig. 5.3, models 9 and 15).
8.5 Dynamics of the Basin’s Lacustrine Complex
189
8.5 Dynamics of the Basin’s Lacustrine Complex 8.5.1 Physico-Geographical Factors To understand the functioning of the lacustrine system of the Basin of Mexico as a whole, it is important to comprehend first the geologic, geomorphologic, and climatic characteristics of the lacustrine basins (Fig. 8.12). The geologic aspects of the basin are very influential in the geomorphologic characteristics of the catchments feeding the basin, and in the nature of the underlying rocks and faults that water into the ground, and the water that feeds the basin through springs. One can also think of geologic and geomorphic processes as part of the addition of sediment into the basins, through both erosion and pyroclastic deposits (Fig. 8.12). Independent from the geological and geomorphological factors, climatic factors act as variables directly influencing the amount of water entering and exiting the basin via the atmosphere, for example, via precipitation and evaporation/evapotranspiration. Precipitation is the source of meteoric water coming into the basin directly or via streams and shallow aquifers. Temperatures influence evaporation and evapotranspiration, which is an important factor in maintaining hydrological balance (Fig. 8.12). In turn, vegetation cover in the catchment areas modifies the amount of water from precipitation through infiltration and evaporation, thus modifying runoff into the lakes and determining the amounts of water and sediment delivered to their basins.
Hydroclimatic P
E
Ri
Ri
ET
ET P
Lo
Li
Zumpango
GWo
E
Lo
Ri
E
ET
Li
P
P
Ri
Xaltocan GWo
GWi
E
Ri
GWo
Gain:
Precipitation (P)
Loss:
Evaporation (E) Evapotranspiration (ET)
Ri
Li Lo
Ri
Texcoco
E P ET
ET
ET
P E
Lo
Ri
Ri
XochimilcoGWiChalco
GWi
Ri
GWi
GWi
Runoff inflow (Ri) Lake inflow (Li)
Groundwater inflow (GWi) Groundwater outflow (GWo)
Lake outlfow (Lo)
Geomorphic and geologic Zumpango
Ef
Er
Sediments
Positive/ upgrading/ constructive: Negative/ downgrading/ destructive:
Va
Va
Ed
Er Ee
Xaltocan Ef
Ed
Er Ee
Va
Ef Ed
Va
Va Va
Texcoco Er
Ef
Ed
Ef
Xochimilco Ee
Vl Ef
Chalco Va
Vf
Va Ef
Rock basement
Endogenous Volcanic
Endogenous Tectonic Uplift
Ash fall Va
Pyroclastic flows, lahars Vf
Exogenous-physical
Exogenous-chemical
and biologial Sediment input from rivers and lake overflow Lavas Chemical Organic Lake sediment Ef Vl sedimentation sedimentation redeposition Ee
Other
Ed
Subsidence
Lakebed sediment erosion Er
Net sediment compaction
Fig. 8.12 Conceptual models of the hydroclimatic and geological-geomorphic dynamics of the lacustrine basins of the Basin of Mexico
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8 Models of Lacustrine Dynamics and Environments
The geomorphic aspect in particular is also important in terms of the connection between basins. This means that the elevation of each of the basins and the connection with one another also determine the amount of water in each basin. Clearly in the case of the Basin of Mexico this means that excesses of water in the Zumpango- Xaltocan and Chalco-Xochimilco basins flow into the Texcoco Basin (Fig. 8.12). The latter, with no exoreic drainage, would tend to bear all these excesses. In the opposite situation, deficit of water in the higher basins would mean less delivery to the Texcoco basin. It is then possible to think that Lake Texcoco would bear the effects of extreme wet and dry events.
8.5.2 Seasonal, Interannual, Decadal, and Centennial Lacustrine Dynamics Based on the conceptual model in Fig. 8.12, it is possible to deduce the hydrological functioning of the lakes throughout the year and for longer periods depending on changes in precipitation, evaporation, and the flow of water between lacustrine basins. Thus, throughout the seasons of the year, the lacustrine complex would have responded to the fluctuations from the rainy and dry seasons and the effects of solar radiation and cloudiness. Accordingly, lake levels would have been highest at the end of the wet season and at the end of the dry season (Fig. 8.13).
5
0
10 Km
Rapid replenishment Large amounts of water input Considerable interbasin flow Flood danger with extreme rain events
+ _
_
N
10 Km
5
Rapid descent and lowest levels Minimum input from streams Basins may become disconnected Critical situation for navigation +
+
+
_
_ J FM A M J J A SO N D
Fig. 8.13 Idealized seasonal changes in the lacustrine complex by quarter
_
Precipitation
Temperature
+ +
_ J FM A M J J A SO N D
0
10 Km
Steady descent of lake levels Stream inflow decreases Flow from higher to lower areas continues Navigation may be affected in dry years
Precipitation
_
_ J FM A M J J A SO N D
_
5
d
_ J FM A M J J A SO N D
Solar radiation
+
N
Solar radiation
_
+ +
Precipitation
Precipitation
_
0
Highest lake levels Water input decreases Interbasinal flow continues Flood danger if rains persist Solar radiation
+
Solar radiation
+ +
10 Km
5
c
Temperature
0
N
b
Temperature
N
Temperature
a
8.5 Dynamics of the Basin’s Lacustrine Complex
191
During rainy season, substantial amounts of water would have entered the system, directly from precipitation and through the catchments via the incoming streams. Concurrently, reduced irradiance due to high cloudiness and higher relative humidity resulted in diminishing evaporation rates (Fig. 8.3a). The volume of water in the basins would have a maximum in late summer (August and September) (Fig. 8.13b) if rains and cloudiness remained steady or increased due to the influence of tropical storms and hurricanes, typical of that time of the year. During this time, if the volume of water exceeded the capacity of the northern and southern basins, the water would have flowed into Lake Texcoco. During the early months of the dry season, streams may have still delivered water into the lake basins, but not enough to offset water loss by evaporation. The relatively dry atmosphere and cloudless days would have contributed to evaporation, leading to a sustained decline in lake levels (Fig. 8.13c). This evaporation loss would have slowed down temporarily during the occasional rain and cloudiness from cold fronts, but not significantly. The continued dry conditions, low cloudiness, and high temperatures during the spring would have led to excessive loses, at a time when the only input to the lakes was from springs and a few of the perennial rivers, which did not provide enough water to offset the loss by evaporation. Thus, the lowest lake levels would have been reached in the month of May (Fig. 8.13d). At this time, the inflow from the northern lakes might have been reduced considerably, if not completely stopped, during extremely dry years. Reduced flow from the southern lakes would have occurred at this time, though perhaps not completely disappeared as springs may have still contributed to partial water flow into Lake Texcoco. Year-to-year and decade-to-decade changes would depend on factors such as ENSO and other phenomena of climatic variability that could have affected the amounts of water in the seasonal cycle. Thus, during extremely wet years, flooding would occur during the west season, while during extremely dry years, extensive drying and dislocation of water bodied could have occurred. On the other hand, at longer time scales, multi-decadal and centennial climatic changes resulting from longer cycles of variability in ocean and atmosphere circulation, and solar irradiance (e.g., the Medieval Warm Anomaly and the Little Ice Age), could have brought long-term regression or transgression of the lakes. In both extreme situations, seasonal variations as explained above would still have occurred, but at different levels than normal. Long, extremely dry periods would have led to lake regressions and exposure of large areas of lakebed (Fig. 8.14). Under this scenario, Lake Zumpango could have disappeared or become a fluvial wetland that barely reached Lake Xaltocan or was completely disconnected from it. Under these conditions, Lake Xaltocan would have retreated to its lowest part, fed only by a reduced flow of the Cuautitlan River and springs. It is possible that given the nature of the basin (see Chap. 7), Lake Xaltocan would have not only reduced in size but partitioned into two or more bodies of water. Concurrently, lakes Chalco and Xochimilco may have split into two basins, which would explain in part the proliferation of settlements in some periods at the strait connecting the two lakes in Tlahuac (Chap. 12). With less water flowing from streams and the other lakes, Lake Texcoco would have shrunk considerably (Fig. 8.14) if not perhaps broken into smaller bodies of water.
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8 Models of Lacustrine Dynamics and Environments
N
L. Zumpango
Lake Zumpango probably fragmented into two small, seasonal lakes fed by two larte incoming streams The northern part of Lake Xaltocan became isolated; small streams and springs maintained a brackish swamp
L. Xaltocan
The southern part of Lake Xaltocan was fed by the Cuautitlan River and easonal water excess from the Lake Zumpango basin.
Swamps and marshes Brackish or freshwater
Seasonal flow across Ecatepec Strait Cuautitlan River may have flowed directly into Lake Texcoco
Freshwater
L. Texcoco
Extensive areas of saltflats exposed around Lake Texcoco. Areas that receive waters from rivers and springs may have had brackish or seasonally freshwater wetlands. These were more extensive in the southwestern part of the lake Reduced flow, probably seasonal, through the Culhuacan strait into Lake Texcoco.
L. Xochimilco
0
5
10 km
L. Chalco
Shrinking of lakes surrounded by extensive areas of swamps fed mostly by springs. Reduced water flow between the two sub-basins, but the two bodies of water may have been connected during the rainy season.
Fig. 8.14 Idealized state of the lakes at the end of long-term drought period
In contrast, extremely humid periods would have resulted in lacustrine transgressions and growth of the lake areas (Fig. 8.15). Lake Texcoco would have grown considerably during wet periods, as its basin would have received the excess from the other lake basins in addition to more abundant fluvial input from its own catchments. Such a situation seems to have occurred during the Terminal Formative and Classic periods, when settlements were practically absent in the lakebed and salt producing sites were farther inland, or during the Late Postclassic (i.e., Late Aztec), as geoarchaeological and paleoclimatic evidence shows (see Chaps. 12 and 13). Finally, it is important to clarify that the lacustrine dynamic model proposed here is open to modifications as well as testing through computer simulation models as more research develops. The objective at this point is to create a hydrological framework for the environmental reconstruction of the lake with the purpose of establishing hypotheses regarding the processes of human adaptation and control of the aquatic ecosystems in the Basin of Mexico.
8.5 Dynamics of the Basin’s Lacustrine Complex
N
L. Zumpango
193
Lake Zumpango probably formed a single lake with constant flow into Lake Xaltocan The northern swamp of Lake Xaltocan grew in size and depth. The southern lake was larger and often may have threatened the northern swamp with saline water.
L. Xaltocan
The flow of water through the Ecatepec Strait was more permanent, but the volume of water would vary through the year.
Swamps and marshes Brackish or freshwater Freshwater
With more permanent water flowing from the other lakes and incoming rivers, the levels of Lake Texcoco grew considerably high. Deltaic areas would be inundated and of saline water flooding and soil salinization may have been a problem for areas around the lake
L. Texcoco
Water flow through the Culhuacan Strait was permanent and abundant.
L. Xochimilco
0
5
L. Chalco
Extensive areas were impounded, though many swamps became narrow areas along the shores and around islands
10 km
Fig. 8.15 Idealized state of the lakes at the end of long-term wet period
Chapter 9
Cultural Features in the Lacustrine Realm
9.1 Cultural Features: Environmental Context and Basic Structures 9.1.1 The Lacustrine Context of Human-Made Features Artificial islands, raised fields (chinampas), dikes, causeways, and canals were common cultural features built for the purpose of habilitating the lacustrine realm of the Basin of Mexico for habitation, agriculture, and the exploitation of aquatic resources. Often the features are referred to in the archaeological and ethnohistorical literature of the Basin of Mexico as hydraulic infrastructure or hydraulic works (obras hidraulicas). They have received considerable attention from archaeologists, historians, and architects, though often their interpretations remain within the confines of their fields. However, there are still so many questions regarding their functionality and environmental contexts. Attempts to place the Basin’s hydraulic infrastructure environmental and social contexts appear in numerous works (e.g., Armillas 1971; Calnek 1972; Palerm 1973). Notably among them is Angel Palerm’s (1973) ethnohistorical review, which provided certain guidelines for investigating some of the environmental factors in the construction of hydraulic works. Evidently, Palerm’s work remains at a theoretical stage, but in that capacity, it serves as a hypothetical model to place hydraulic features in their environmental and historical contexts considering recent information generated through archaeological and geoarchaeological research. Therefore, this chapter focuses mainly on reviewing the archaeological and historical record of all types of cultural lacustrine features as a prelude to review some of Palerm’s idea and propose a classification of cultural lacustrine features and models of environmental-social dynamics in the ancient lakes of the Basin of Mexico.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5_9
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9.1.2 The Palisaded Enclosure as a Basic Construction Feature There is a general confusion in the popular media and even in some scholarly papers regarding the construction and function of platforms, tlateles, and chinampas. Very often it is said that Tenochtitlan was built on chinampas or that people lived on chinampas, which is an error as the original settlements were not chinampas, and most chinampas were primarily agricultural fields (Chap. 13). Likewise, platforms, built to sustain houses and buildings, are often confused with chinampas. Therefore, before reviewing the archaeological and historical record of the different cultural features, it is important to clarify the similarities and differences of their construction. The confusion or misinterpretation of the features may in part originate in some of the similarities of construction used in all of them. Tlateles, platforms, chinampas, and dikes relied primarily on the construction of enclosures or rows of wooden stakes that were later filled with a variety of materials depending on the structure (Fig. 9.1). The sides of the palisade are normally filled in with branches to retain the material, and the overall idea is to raise the ground above the lake level. The differences among them are the materials used in the fill as well as their final purpose. The palisaded enclosure is known as chinamitl, from where the name chinampa derives, consists of stakes planted in the ground and later filled in with mud from the lake, aquatic vegetation, and other materials with the purpose of creating porous soil for subsurface irrigation. Palisades for platforms and dikes, on the other hand, were filled in with stronger materials, mostly earth, gravel, and larger stones, especially a
c
b Stratigraphy
Stratigraphy
Fill
Lake sediment, peat, organic sediment, leaves, sod, ash, and diatomite
Palisade
Fill
Sand, stones, sediment from lake and mainland, trash tezontle, tepetate, and materials from older constructions
Palisade
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Boulders, cobbles, pebbles, sand, tezonte, clay, and sediment from the mainland
Fill
Palisade
Fig. 9.1 Basic phases of construction from palisade to fill and to final structure for (a) a chinampa, (b) a platform, and (c) a dike. The sequence goes from bottom to top
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if they were to sustain buildings. The variety of materials used in the construction of structures are discussed in more detail in Sect. 9.6 and variations of the individual features in Chap. 10.
9.2 Tlateles, Platforms, and Complex Insular Settlements 9.2.1 The Concept of Tlatel in the Lacustrine Context of the Basin of Mexico The word tlatel derives from the Nahuatl, tlaltelli (tlalli, earth; tetl, stone), which generally designates an earthen mound (Molina 1571), and in some instances an island (López de Gómara 2006). The alternative Spanish names for an earthen mound are terremote, terremoto, and montículo, all of which refer to a heap of earth or rocks on water or dry land. On the other hand, islote (islet) may be synonymous with tlatel when built in an aquatic environment. However, in its broad meaning, islote means small whether settled or not. However, despite its origins and synonyms, the term “tlatel” evolved in the archaeological lexicon of the Basin of Mexico to refer to an insular small settlement in a lake or wetland (Cordova et al. 2021). The word tlatel appears as part of other words in several toponyms as in Tlaltenco (meaning next to the tlatel) and purportedly also in Tlaltelolco (now Tlatelolco). Tlaltelolco is associated with tlatelli (or tlatel), which according to the Anales de Tlatelolco and the Codex Ramírez refers to a terraplén (Böehm de Lameiras and Pereira 1979: 23). Terraplén is translated as something like an embankment, mound, or earth piled up and flattened, or an earthen platform. An alternative name to Tlatelolco is possibly Xaltelolco (Torquemada, book 3, chapter 23, p. 399), translated as a mound of sand. Interestingly, the glyph that prevailed in documents is exactly a mound of sand. Tlatel also appears with frequency on nineteenth-century maps of Lake Texcoco, especially to designate places like Tlatel de los Barcos and Tlatel de Chapingo. The inhabitants of the towns around the eastern side of Lake Texcoco often use the term to designate a promontory in the plain that is often isolated during flooding. It is perhaps from these usages that the term was adopted into the archaeological jargon of the Basin of Mexico in the early twentieth century as archaeologists began to look at such small insular settlements, often associated with salt making (e.g., Apenes 1943; Noguera 1943). Subsequently, the use of the term became common in the regional archaeological literature to designate this type of settlements in lake beds of the basin (Acosta-Ochoa et al. 2021; Parsons 1971, 2008; Parsons et al. 1982; Litvak-King 1962, 1964; Mayer-Oakes 1959). Despite their original association with salt procurement stations, archaeological excavations in several localities of the former lakes show that tlateles had various purposes, from seasonal camps to permanent habitation (Cordova et al. 2021; Luna-Golya 2014; Parsons et al. 1982).
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Instances exist in which tlateles formed complexes often called plataformas (platforms) and terraplenes (embankments) in archaeological jargon. With respect to these two closely related terms, it is important to clarify that a platform is akin to a tlatel in the sense that both are made of artificial materials. However, platforms, at least in the archaeological sense, seem to be flat islands and what in Spanish is known as terraplén. Normally, the term appears in reports of excavations within Tenochtitlan and Tlatelolco, as well as other areas, where a surface has been built to accommodate a building or buildings (see for example the usage in Sánchez- Vázquez et al. 2007 and Gonzalez-Rul 1998). Second, the construction of several tlateles, as for example at Terremote-Tlaltenco, seems to be in the form of creating a platform, which sometimes makes the distinction between tlatel and platform difficult, especially outside the large urban areas of the Postclassic. This distinction is made clearer in the proposed classification of lacustrine cultural features in this chapter.
9.2.2 From Tlatel and Platform to Insular Complexes Some tlateles and platforms and artificial island complexes of the Postclassic period in the Basin of Mexico seem to have occupied preexisting landforms or natural elevations in the lakebed while others appear to have been built entirely with accumulations of materials (Cordova et al. 2021). The examples discussed in subsequent sections suggest locations in different lacustrine environments and various strategies and materials used for their construction. In essence, the role of tlateles and platforms was to permit a certain activity or habitation on a terrain permanently, seasonally, or occasionally impounded. This seems to be the case with similar wetland settlements in other parts of the globe. For example, the Dutch terpen (singular: terp) is a mound for permanent habitation in the frequently flooded lowlands. However, unlike this case, it seems that not all the tlateles in the Basin of Mexico were occupied permanently. Some may have been seasonal settlements focused on certain activities. Cases of seasonal settlements in lacustrine deltas have been reported in East African lakes; in the Omo Delta, for example, some seasonal settlements were built on groves of cattails (Butzer 1971). Ample zones of the former lakes may have been occupied by groves of sedges, bulrushes, and cattails (i.e., tulares) and ephemeral islands (Fig. 8.11). Similar cases exist in Lake Titicaca, where islands are made completely of plant material (Parsons 2006). Although cases like this one are absent in the lakes of the Basin of Mexico, or any of the other lakes in Mexico, aquatic vegetation may have served as ground for building a tlatel or as a source of material for building tlateles (see examples in subsequent sections). Survey of some areas of the southern lakes show that tlateles form constellations of settlements, usually forming hamlets and villages (Luna-Golya 2014). Elsewhere in the world, there are examples of such settlements, as is the case of villages of Ganvie established on a deltaic system in Lake Nkoue, Benin, by refugees fleeing
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capture for the slave trade (Soumonni 2003). Seen on Google Earth images, the constellation of aquatic settlements looks like a city on water. This sounds reminiscent of what Tenochtitlan may have looked like as in reality the city was a constellation of tlateles, platforms, causeways, and raised fields (chinampas) and not an island as often believed (see Chap. 13). In other cases, other insular towns of the Postclassic period in the lakes of the Basin of Mexico seem to be artificial islands formed by the coalescence of platforms and tlateles, as is the case of Xochimilco, Tlahuac, Mixquic, and Xaltocan. These examples are suggestive of the fact that tlateles and plaforms can grow and coalesce to form single large settlements or large artificial urban islands.
9.2.3 Tlateles and Salt-Production Even though lacustrine settlements were constituted of tlateles with many purposes, it is important to analyze the aspect of salt production, which in the first place brought the word tlatel to the archaeological jargon in the Basin of Mexico. The frequent appearance of certain types of ceramics associated with salt production since the Formative period has often been connected to mounds on the lakeshores (Parsons 2001; Charlton 1969; Meyer-Oakes 1959; Noguera 1943). In particular, the Texcoco-fabric pottery (i.e., cerámica de impresión textil) of Middle and Late Postclassic (i.e., Aztec) is linked to salt production sites (Millhauser 2016; Parsons 2001; Charlton 1969). Although these ceramics appear in areas outside the lakebeds, they appear in many small sites in the saline lakes (Fig. 9.2). Nonetheless, a clear look at some of the descriptions of such sites in the surveys of the saline lakes (e.g., Cordova et al. 2021; Parsons 1971, 2008; Sanders and Gorenflo 2007; Sanders et al. 1979; Blanton 1972) reveals that not all tlatel settlements yielded salt- production pottery, which suggests that their existence is linked to other activities or simply to habitation. From a different perspective, even if pottery associated with salt production characterizes several tlateles in the saline lakes of the Basin, there is no certainty that these were used exclusively for salt production. Thus, tlateles may have also served as stations resources such as algae, insects, and fish may also be possible (Parsons 2001, 2006). The possibility that in some cases some may have used for ceremonial purposes is also open in the context of some findings in the survey of the central part of Lake Texcoco (see Parsons and Morett 2004).
9.2.4 Archaeological Examples of Tlateles The Middle-to-Late Formative lacustrine site of Terremote-Tlaltenco on the bed of Lake Xochimilco is a clear example of a complex settlement of tlateles (Fig. 9.3a). Its formation involved the use of aquatic plants and wood with the addition of stone
200 Fig. 9.2 Salt production sites in Lake Texcoco during the Late Postclassic (i.e., Aztec Period). Based on Millhauser (2016), Sanders and Gorenflo (2007), and Parsons (1971), with additional information compiled by the author
9 Cultural Features in the Lacustrine Realm N
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for the construction of platforms sustaining houses (Serra-Puche 1988). Excavation showed that the accumulation of materials to build the tlateles bore some similarities to the construction of chinampas, especially with the use of plants and muck as part of the construction material (Serra-Puche 1988). However, the recovery of numerous cultivated and ruderal plants (McClung de Tapia et al. 1987) shows that the site was a residential site, not an agricultural site, probably for exploiting lake resources (Serra-Puche 1988). Well-preserved materials such as ropes baskets provide more information regarding the use of local vegetation, and wooden stakes show that each unit had a place for docking canoes (Fig. 9.3b). Excavation of El Tepalcate (Site Tx-TF-46) in Lake Texcoco provides information on tlatel construction in a saline lake (Fig. 9.4). The tlatel was built and occupied mainly during the Patlachique phase of the Terminal Formative presumably for
9.2 Tlateles, Platforms, and Complex Insular Settlements
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Fig. 9.3 Terremote-Tlaltenco. (a) Map of the complex of tlateles and (b) partial profile of mound 1 showing an embarcadero (docking place). (Adapted from McClung de Tapia et al. 1987) NW
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Wave-cut bench
Max. elev. approx. 2242 m
Lacustrine clay beds and volcanic ash layers
Typha sp.(cattail) layer 2090±35 14C yr B.P. (cal B.C. 82-37) (1σ)
Mostly eolian sand and clay pellets Mostly beach sand
Undif ferentiated cultural deposits
Lacustrine clay (jaboncillo)
Lacustrine clay and sand
Fig. 9.4 Map of El Tepalcate on the Lake Texcoco Bed and general stratigraphy. (Adapted and summarized from Cordova et al. 2021)
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9 Cultural Features in the Lacustrine Realm
salt production, though structures seem to indicate that it had a habitational use (Gámez-Eternod 2005). Its location in the southeastern part of Lake Texcoco (for location and context, see Figs. 2.11 and 5.12) is relatively far from the former shore, but most likely it was built in a shallow part of the lake, possibly with aquatic vegetation (Cordova et al. 2021). Although founded on what seems to have been a tular of Typha sp. (Fig. 9.4), most of the structure was made of a combination of terrestrial materials. Only the top of the site constitutes a series of beach deposits, a landform that served as the ground for the ephemeral Late Aztec occupation. Its function as a salt production site has been proposed based on the ceramics, but it could have been used as a station for fishing and collecting aquatic resources. Multiple occupations in tlateles are not uncommon, as is the case of the Tlatel de Tepexpan, located on the northeastern shore of Lake Texcoco (Fig. 2.3). The stratigraphy shows three occupational layers with material of the Classic period, with the top layer indicating only minor occupations in the Toltec and Aztec periods (Litvak- King 1964). Excavation of the sterile layers also shows that the initial occupation was founded on a firm layer of caliche (layer 4), as opposed to the less stable lacustrine clay. The setting of the tlatel is suggestive of many environmental aspects as it is relatively higher in elevation than other tlateles in Lake Texcoco, suggesting that its creation occurred during the relatively high lake stand of the Classic period (Cordova et al. 2021) (Fig. 9.5). The environmental context and the setting of tlateles are interesting aspects to study as part of understanding lacustrine dynamics and human occupation. Settings in deltaic areas seem to be recurrent in the lakes of the Basin, particularly in association with levees of deltaic channels as is clearly the case of the Tlatel de Tequexquinahuac (Fig. 9.6). The occupations occur in the highest parts of the levees of deltaic channels where natural and artificial sediment accumulations elevate the terrain. The natural accumulations are created by fluvial accumulation that entails levee formation in combination with beach sand accumulation. Excavations in the area of the former lobes of the Amecameca River delta on the southeastern shore of Lake Chalco have revealed buried remains of Early and Late Postclassic tlateles built on the levees of a channel (Fig. 9.7). Although not a deltaic Meters from datum 1.98
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Meters a.s.l 33 32
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Fig. 9.5 Stratigraphy of a section of the Tlatel de Tepexpan. (After Litvak-King 1964)
2240.97
9.2 Tlateles, Platforms, and Complex Insular Settlements
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Highest point approx. 2240 m
0
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Pre-ocuppation deposits
Syn-ocuppation deposits
Occupation features and deposits
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Tlahuac/GCB Tephra
Puddle mud deposits
Beach sand
Peat fill in river channel
10 m
Post-ocuppation deposits
1
2m
Occupation surfaces
Alluvial silts
Cultural features (mainly pits, hearths, and burials)
Irrigation canals (recent)
Beach sand with ash lenses
Fig. 9.6 Cross-section of Tlatel de Tequexquinahuac. (Adapted in a simplified form from Cordova et al. 2021) 17
18
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0 Modern A.D. 1419-1619
1 A.D. 1182-1296 2 3
A.D. 1513-1667
A.D. 863- 994
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A.D. 382- 645 3647-3382 B.C.
A.D. 1426-1624 A.D. 1467-1636
4 meters
5770-5635 B.C. Horizontal not to scale
Indurated sand
Post-conquest alluvium Anthropogenic deposit (Tlatel) Lacustrine/palustrine deposits
Calibrated radiocarbon date
Tephra (Pomez Marcadora Superior?)
Jardines de Chalco
Xico
Chalco de Covarrubias
Lakebed Lakebed
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Deltaic complex
Lakebed 500 m
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nne
17 San Martin Xico Nuevo
St
ab
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rfa ce
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cam
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Fluvial d
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Fig. 9.7 Tlateles buried under historic alluvium on the side of a channel of the Amecameca River (From Frederick and Cordova 2019 with modifications). and their location in their modern landscape
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channel proper, the areas to the west and the south of these localities have numerous other settlements associated with channel levees, which on the surface form linear settlements Frederick and Cordova 2019). Linear patterns of tlatel-type settlements are also common in other deltaic areas, as is the case of the shores between Tepexpan and Atenco as revealed by surface surveys (Parsons 1971). In this area, the original Texcoco archaeological survey maps (originals in the archives of the Bentley Historical Library, University of Michigan) provide evidence of several tlateles barely above the historic alluvium. Farther inland, strips of Postclassic surface material connect tlateles and modern towns, suggesting that many of the modern towns such as Santa Isabel Iztapan, San Cristobal Nexquipayac, Atenco, and Tocuila, among others, occupy former tlateles. In areas covered by alluvium around the modern town of Tocuila, several tlateles built directly on the lakebed have been identified (see Arciniega-Ceballos et al. 2009). Other areas with tlateles associated with deltaic systems may exist in the former delta of the Cuautitlan River, where settlements and towns also seem aligned (see maps in Gorenflo and Sanders 2015). However, the most important area of deltaic systems may be in the stretch of former fluvio-lacustrine systems of the western part of Lake Texcoco (see Fig. 8.9), which suggests that some of the settlements of Tenochtitlan-Tlatelolco and their satellites may have also been associated with deltaic features (see Chap. 13). Tlateles abound in the former beds of southern lakes, some of which are associated with chinampa fields (Luna-Golya 2014; Parsons et al. 1982). Detailed excavation of one of a tlatel structure is the one at El Japón, San Gregorio Atlapulco, in Lake Xochimilco (Acosta-Ochoa et al. 2021; McClung de Tapia and Acosta-Ochoa 2015) show a complex construction of and platforms and mounds surrounded by archaeological chinampas (Fig. 9.8a). Beyond their Aztec architecture and landscape context, these platforms lie on a preexisting tlatel constructed in the pre- ceramic period (Fig. 9.8b). This suggests that the building of tlateles may have been a strategy developed by the inhabitants of the lacustrine realm even before the development of agriculture (Chap. 11). Another important case to cite is Tlatel Tx-A-4 in the northwestern part of Lake Texcoco next to the modern channel of the San Juan Teotihuacan River (Fig. 9.9). Dominated by Late Aztec ceramics, the site lacks salt-production pottery, suggesting that unlike many other tlateles in the area, it had other purposes, possibly linked to the management of water. The immediate geographic and archaeological context reveals that the site was part of a structure linked to a Late Aztec causeway connecting Nexquipayac with Tepetzingo, depicted in the 1593 map of Tepezingo and La Transfiguración (see Fig. 2.9). The modern town of Xaltocan is on an artificial mound, probably composed of various tlateles forming an insular settlement and connected to the mainland by a causeway (Morehart 2012a; Frederick et al. 2005). Excavations reaching the base of the tlateles show that their construction consisted of accumulations of sand and
9.2 Tlateles, Platforms, and Complex Insular Settlements
a Azec
Excavation unit A
as
mp hina
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as
amp
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Fig. 9.8 Tlatel complex at El Japón, Ejido de San Gregorio Atlapulco, Xochimilco. (a) Aerial view (Google Earth Pro) and (b) cross-section
gravel sourced from the Pleistocene beach and strand plain of Xaltenco just north of it (Fig. 5.10) (Frederick et al. 2005). The town of Tonanitla, south of Xaltocan, seems to also have been a settlement on an artificial accumulation probably similar to Xaltocan. Additionally, to the west of it, various tlateles built for salt production extend on the lakebed (Fig. 9.2). Tlateles and artificial islands created by agglomerations of tlateles were ubiquitous in all the lakes, particularly in the area of Tenochtitlan and its immediate hinterland, where recent geotechnical studies have identified anomalies suggestive of accumulations of materials on lacustrine sediments (Auvinet et al. 2017; Barba- Pingarrón 2008) Many of such anomalies have been confirmed by excavation and historical surveys as is the case of Mexicaltzingo, Churubusco (Huitzilopochco), Iztacalco, and Tlahuac, among others (Fig. 9.10). In addition to evidence from the anomalies and soundings of the terrain, many of these ancient tlateles have become evident through the phenomenon known as apparent terrain emersion (Fig. 9.11). Although the general area of Mexico City is sinking in this process, the rate of sinking is usually lower in areas where former structures such as tlateles, causeways, and dikes existed, giving the appearance of rising from the surrounding surface.
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9 Cultural Features in the Lacustrine Realm
a Tlatel
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r cau
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Fig. 9.9 Tlatel site Tx-A-4. (a) Picture from the south, (b) view from above, and (c) cross-section
9.3 Chinampas 9.3.1 Definition and Description In a broad sense, chinampas are artificial soil beds in a swamp or shallow lacustrine plain destined for the cultivation of crops. Archaeological, historical, and modern documentation of suggests that chnampas consisted of layered accumulations of organic mud and muck from the lake bottom often in a rectangular shape delimited by stakes and aquatic trees (Salix bonplandiana, locally known as ahuehuete or huehuete) (Coe 1964; Armillas 1971; Ávila-López 1991, 2006). The layout of chinampa fields consisted of alternating sequences of elevated beds and canals (Fig. 9.12). The crops planted in the chinampa obtain moisture through capillary absorption of water that seeped through the chinampa from the canal, that is to say a form of sub-irrigation (Crossley 2004). In essence, the chinampa is a system of capillary irrigation, though irrigation by hand is often present (Rojas-Rabiela 1993).
9.3 Chinampas
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Geotectechnical zones Zone 1 (Hills) Zone 2 (Transition)
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7 11 0
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Fig. 9.10 Tlateles and tlatel complexes identified in the city through stratigraphic anomalies and apparent emergence. Numbers 1 through 8 have been confirmed with geophysical methods. (Source: Auvinet et al. 2017)
The accumulation of organic sediment and muck from the adjacent canals serve a soil proper and as renewable nutrients for crops. The term chinampa derives from the Nahuatl word chinamitl, which translates to “seto o cerca de cañas” in Spanish (fence of reeds or stakes) (Molina 1571). The suffix –pa is a locative that means on or in, so literally the term means “inside a fence of stakes” or loosely and simply “fenced around by stakes.” However, the use of the word in early historical documents suggests that chinamitl and chinampa may have originally been applied only to the seedling bed (almácigo), where crops were first sown before their transplanting to a larger field (Böehm de Lameiras and Pereira 1979), though at present the seedling bed is known as chapin (Crossley 2004; Rojas- Rabiela 1998).
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9 Cultural Features in the Lacustrine Realm Aparent emergence
Aparent emergence
Aparent emergence
Raised fire hydrant
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Dry and compacted clays
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Saturated clays
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2230 2220 2210
Fig. 9.11 Idealized sequence that explains the concept of the apparent emergence of terrain in relation to preexisting tlateles and causeways in urban areas of the Basin of Mexico
The key point in the building of a chinampa bed is the accumulation of nutrient- rich muck from the adjacent canals. Nonetheless, historical sources and archaeological contexts suggest that variations to this process existed especially in the sequence and layout of materials to build the chinampa bed (Parsons et al. 1982; Ávila-López 1991, 2006; Frederick 2007). Thus, in some cases, layers of other materials such as ash, diatomite, and mats of aquatic vegetation (cinta) and sod (céspedes) were used in the process of building up the layers along with muck from the canals. The origin, purpose, structure, and evolution of chinampas have been the matter of discussion in various studies, some of which draw information from historical sources, modern chinampas, and archaeological examples (Armillas 1971; Böehm de Lameiras and Pereira 1979; Coe 1964; Crossley 2004; Parsons et al. 1982; Rojas- Rabiela 1991, 1998; Sanders 1995; Luna-Golya 2014). There is a consensus that the idea that the chinampas were “floating gardens” is a misconception that unfortunately has been repeated in the literature (Crossley 2004). However, it is possible that the floating-chinampa idea came from carrying the seedlings in some sort of raft, as suggested by some sources (Böehm de Lameiras and Pereira 1979). The structure and purpose of chinampas in the Basin of Mexico are not much different from those of similar elevated fields in other aquatic environments in Mexico, such as the raised fields of the lowlands of eastern Mexico and the Mayan region and other parts of lakes and wetlands in central Mexico (Williams 2014;
9.3 Chinampas
209
Fig. 9.12 Types of chinampas by construction. (Source: Ávila-López 2006)
XOCHIMILCO
Chinampa top soil Organic matter layer Sediment from canals Lacustrine deposit
IZTAPALAPA
Chinampa top soil Lacustrine deposit
MEXICALTZINGO
Chinampa top soil Layer of volcanic ash Lacustrine deposit
SAN LUIS TLAXIALTEMACO
Chinampa top soil Diatom bank
Siemens 1983). In all cases, the purpose was to make a permanent or semi-permanent flooded area available for farming by using the moisture and nutrients of the ground (Crossley 2004), and in the broader context to maximize food production (Sanders 1995). In the Basin of Mexico, chinampas adapted to the specific conditions in the lacustrine/wetland environment of its lakes. Those conditions included obstacles such as water salinity, torrential rivers coming into the basins, rapid seasonal and annual lake-level fluctuation, and climatic issues such as frosts and occasional prolonged droughts (Böehm de Lameiras and Pereira 1979; Crossley 2004; Sanders 1995). For this reason, aspects such as the methods of chinampa construction and emplacement in the context of the lakes are important to understand the essence of
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the system in the context of lacustrine dynamics and the social and economic changes that played as factors the appropriation of the lacustrine spaces of the agricultural history of the Basin of Mexico through time.
9.3.2 Types of Chinampas Despite the general characteristics of a chinampa, several types have been proposed based on mode of construction, geometric characteristics, and emplacement in the context of the broader landscape. The mode of construction varies depending on the characteristics of the lacustrine environment and available materials, resulting in the most basic types proposed by Ávila-López (2006) based on excavated fields (Fig. 9.12). However, historical sources and modern chinampa construction portray different layering of chinampa beds. Frederick (2007) compared historical descriptions of chinampa construction with the stratigraphy of archaeological chinampas in the southern lakes: the Iztapalapa field excavated by Ávila López (1990), the Xaltocan Chinampas, and modern chinampas in Mixquic and Xochimilco. The comparison led to the definition of at least three main types of chinampa construction extending from massive to stratified accumulations of organic materials. On the massive accumulation end is type 1 and on the well-defined stratification end is type 3. Type 2 is an intermediate type with characteristics of both. Interestingly, type 3 is the one described in most of the sources and modern chinampas, with types 1 and 2 corresponding mostly to archaeological chinampas (Frederick 2007). Nonetheless, some archaeological chinampas that evolved into modern chinampas it is possible to see the original, possibly pre-Hispanic single layer, overlaid with modern layers (Frederick 2007; Ávila López 1990). Figure 9.13a shows an example of this relation, where stratum I is the original pre-Hispanic layer and strata I and II the modern or recent layers. Noted in the same figure is the width change between the archaeological and the modern/recent chinampa, an aspect that refers to the radio between chinampa size and canals (Fig. 9.13b). The geometric characteristics of chinampas proposed by Ávila-López (1991) refer to the ratio between the areas of beds and canals, which refers to the land-to- water ratio. The ratio has been applied to spatial and temporal variations of chinampas, especially in describing their evolution from pre-Hispanic to modern times. This evolution is apparent in the stratigraphy, where canals in older chinampas have been filled in to enlarge the chinampas (Fig. 9.13b), as well as in comparisons of abandoned (archaeological) and modern chinampas in aerial photographs (Parsons et al. 1982; Armillas 1971). This process seems to have occurred slowly and have accelerated in recent decades. In Lake Xochimilco the average land-to-water ratio went from 1.07:1 in Aztec chinampas to 2.75:1 in 1941 to 10.11:1 in 2012 (Luna- Golya 2014). The classification of chinampas by their emplacement in relation to the aquatic environment has its source in Palerm (1973:22), who recognized two types, the
9.3 Chinampas
a
211 Modern canal
Modern chinampa bed
0
Strata I and II Stratum III
1 meters
Archaeological chinampa beds 5
0
10
meters
b Prof ile view
Plan view
2.75:1
2.75:1
Archaeological chinampa beds Archaeological canals Late Postclassic cultural material 10.1:1
10.1:1
Fig. 9.13 (a) Modern/historic and Postclassic chinampas in the stratigraphy of Cala 1 (Trench 1) of the Iztapalapa chinampa field (after representation by Frederick 2005 and original by Ávila- López 1991). (b) Idealized representation of areal change in terms of land-to-water ratios as calculated for the period 1936–2012 in Lake Xochimilco. (Based on data from Luna Golya 2014)
chinampas de laguna adentro (in-lake chinampas) and chinampas de tierra adentro (inland chinampas). From the descriptions of these two types, the chinampas de laguna adentro were within the lakes. However, the descriptions of the chinampas de tierra adentro are vague, suggesting that they may have been in areas of high- water tables or seasonally flooded areas on the shores of lakes or riverine flood plains. Following the same idea of emplacement in relation to the aquatic environment, Angel Garcia-Cook (1985) proposed a similar classification where the raised fields outside the lake could have been in stream valleys (chinampas de rio) and on the shore of a lake (chinampas de la orilla de la laguna) (Garcia Cook 1985:37–38). Those on the lakeshore, however, could be considered as in transition between the laguna adentro and tierra adentro when land was exposed during the dry season. Therefore, combining the observations by Palerm (1973) and Garcia-Cook (1985), it is evident that a modified version of the two-type classification should include the transitional third type “lakeshore chinampas.” In-lake chinampas (chinampas de laguna adentro) constitute the most common type of archaeological, historical, and modern chinampas in the Basin of Mexico. These include those in Lake Xaltocan, Lakes Chalco and Xochimilco, and the western part of Lake Texcoco, including those of Tenochtitlan, Iztapalapa, and those formed between these two cities around tlatel islands.
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Inland chinampas (chinampas de tierra adentro or chinampas secas) were camellones built in drained fields in fluvial wetlands, more similar in setting and functioning to those in the lowlands of the Gulf coast and Yucatan Peninsula, which are generally referred to as raised fields. This type of raised fields includes the chinampas de rio (river chinampas) based on reports of features in fluvial context in the valleys of Tlaxcala and Puebla (Garcia-Cook 1985; Fowler 1987). In the Basin of Mexico, the existence of historic raised fields in floodplains in the Teotihuacan Valley (Evans and Nichols 2015) and the area of Teoloyucan, south of former Lake Zumpango (Strauss 1974). Interestingly, in the same area today, a type of raised fields of tierra Negra (black earth) exists to this day (Reséndiz-Paz et al. 2013) (see Sect. 5.4). Lakeshore chinampas (chinampas de orilla) occupied lacustrine areas where the seasonal fluctuations of lakes exposed rich soils. Although Garcia-Cook (1985) did not provide concrete examples of this type of chinampa, they appear in other parts of Mexico. For example, remains of raised fields along the shores of the former Laguna de Magdalena, Jalisco (Weigand 1994) seem to constitute an example of lakeshore chinampas. In the Basin of Mexico, this type of raised fields may have existed on the shores of Zumpango and the eastern side of saline Lake Texcoco (Palerm 1973), although at this point, no archaeological or historical evidence is strong enough to support it. The author and colleagues carry out research in the area of Atenco where there are signs that the area sustained lakeshore chinampa agriculture. Lakeshore chinampas may have also existed in the southern lakes. The proposal that pre-Aztec raised fields existed in settlements around Cerro Xico in Lake Chalco (Parsons et al. 1982) or areas adjacent to Tlapacoya (Niederberger 1987), or around Cuicuilco (Pastrana 2018), implies that this type of chinampas may have existed, but like the above cases, no detailed archaeological evidence exists.
9.3.3 Chinampa Fields in the Context of Other Features The surface archaeological record shows that chinampa fields formed a network of canals of different orders, from those used for navigation to smaller canals separating the chinampas (Luna-Golya 2014; Ávila-López 1991; Armillas 1971). Additionally, tlateles and platforms would interlock with the chinampa fields, presumably for habitation and ceremonial purposes. A fragment of a reconstructed prehistoric field in Lake Xochimilco (Fig. 9.15a) provides a sense of the fabric formed by chinampas, canals, docking areas (embarcaderos), and tlateles. The exact distribution of chinampas and other features in the urban area of Tenochtitlan is not known, though evidence from the Map on Maguey Leaf and pieces of evidence from documents suggest a more organized pattern (Calnek 1973). A sample from a researched area shows how rows of houses and chinampas align with the canals and the main causeways (Fig. 9.14b). Such a distribution has support in some descriptions of the city’s canals and streets in the early chronicles of the War of Conquest (e.g., Diaz del Castillo 1982; Cortés 1985; Conquistador Anónimo 1941).
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213
a SC
0
Av. Juárez
50
meters
E
T
E
b
T
E
MC SC
MC
C. Azuela
SC
Av. Balderas
T
MC
1:5K
Chinampas
Residential platforms
Modern streets as reference
Fig. 9.14 (a) The fabric of archaeological lacustrine cultural features (chinampas, canals, and tlateles) in Lake Xochimilco. (Redrawn from Luna Golya 2014); T tlateles, E embarcaderos, MC main canal, and SC secondary canal. (b) Chinampas in the context settlement patterns in the ward of Moyotlan in Tenochtitlan. (Redrawn from Calnek 1972, 1973) N
0
Xaltocan
0.5
1 Kilometers
2
Tertiary canals
Archaeological features Main spring canal Primary canals Secondary canals
Chinampa beds
Mapped chinampa parcels and tertiary canals Insular settlement
N
Lake Zumpango
Zumpango
Xolox 224
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Acauitlapilco Jaltenco
Tonanitla
l
na
0 1 2 km
Lake Xaltocan
Xaltocan
Ca
40
22
Nextlalpan
Spring Ozumbilla
Cerro Chiconautla
Tonanitla
Fig. 9.15 Archaeological chinampa field in Lake Xaltocan. (Redrawn from Morehart and Frederick 2014; Morehart 2012a)
In the Iztapalapa region, the emplacement of chinampas seems to have been reminiscent of those in Lake Xochimilco, given the descriptions in the chronicles. In an excavation of a chinampa field north of Iztapalapa chinampa, Ávila-López (1991)
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showed that the fields were smaller than those in Lake Xochimilco. However, the fact that this location was in a saline lake, dikes were an important part of the system. In fact, existence of a dike mentioned in one of the campaigns of the War of Conquest suggests that a dike used to divide freshwater from saline water (see Chap. 14). Survey and excavation of the pre-Hispanic chinampa field in Lake Xaltocan provides a better view of their spatial and environmental context of chinampas in a saline lake (Morehart and Frederick 2014; Morehart 2012a). The field, located in a saline lake, depended on water carried via a canal from the Ozumbilla Spring at the base of the Cerro de Chiconautla (Fig. 9.15). One aspect still to be investigated is how the flows of saline water were kept from invading the chinampas. Though the answer may lie in a series of dams or dikes, perhaps along the Xaltenco-Tonanitla- Chiconahuac axis, meant to protect the field from water incursions from the western part of the lake, a hypothesis for future research in the region.
9.4 Canals and Embarcaderos 9.4.1 Canals and Their Purposes Canals were an important feature in the lacustrine realm of the Basin even after the conquest, remaining so until today in Lake Xochimilco. The words canal and acequia in Spanish, as well as apantli in Nahuatl, remain in the nomenclature of many cities and localities in the modern landscape (Jiménez-Vaca 2017). In pre-Hispanic times, canals were important communication arteries for transporting goods and accessing chinampa fields for their maintenance. Furthermore, the organic silt in canals served as material to elevate and fertilize the chinampa beds (Frederick 2007; Rojas-Rabiela 1991, 1993; Ávila-López 1991). In fact, not only were the canals between chinampas dredged for this purpose, but the main navigation canals were also dredged, a practice common through the Colonial and Independence periods along La Viga canal (Jiménez-Vaca 2017; Ávila-López 1991; Alzate y Ramírez 1831). Networks of canals consisted of several hierarchies: from those for navigation and trade to those to access settlements and chinampa fields to those between chinampas (e.g., Fig. 9.14a). Navigation canals linked inland localities with open lake areas. Alva Ixtilxochitl (1975:150) cites canals connecting the town of Texcoco with the deeper part of the lake. Whether one such canal was refurbished for the Spanish brigantines in 1521 is not clear but possible (Chap. 14). Canals connecting ChimalhuacanAtenco with the open lake existed until the early twentieth century, with marks of them visible in aerial photographs in times before urbanization (e.g., Fig. 2.11). Some canals in the lakebed probably had to be dug into the lakebed as the lake levels dropped in the dry season or during prolonged drought periods. Eventually, as the lakes receded, such canals remained as routes through dry land, as did the Canal de la Viga (formerly known as Acequia Real), connecting the city with Texcoco via the Canal de San Lazaro, both remaining the only route between lakes Xochimilco and Texcoco until the end of the nineteenth century (Jiménez- Vaca 2017).
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215
9.4.2 Embarcaderos (Dockings) With no beasts of burden, the canoe was an alternative means for transporting goods around the lake and the only way of transport to many insular towns. Using canoes meant the need for areas for loading and unloading, if not also areas where a community could keep canoes protected from strong winds, waves, and currents. Thus, coves or dead-end canals were built to serve for that purpose, creating the docking features known in the modern aquatic environments of the Basin and in the archaeological literature as embarcaderos. Embarcaderos were artificial coves in the chinampas and tlateles or along the lakeshore, as the ones that are represented in association with the archaeological chinampas (Fig. 9.14). Embarcadero features have been reported in the archaeological record in the Lake Xochimilco-Chalco (Luna-Golya 2014; Serra-Puche and Lazcano 2009; Serra-Puche 1988; McClung de Tapia et al. 1987) and Lake Texcoco (Jiménez-Vaca 2017; Sánchez-Nava et al. 2007). They are evident in paleotopography and in the stakes presumably used for tying up canoes as shown in the stratigraphic sections of Terremote-Tlaltenco (Fig. 9.3) and Tlatel de Tequexquinahuac (Fig. 9.6). However, salvage archaeological work has uncovered embarcaderos with masonry and steps in the Tenochtitlan-Tlatelolco urban complex, notably an example along subway line 4 (Sánchez-Vázquez et al. 2007; Ortuño-Cos et al. 1982) and in the southwestern part of the sacred precinct of Tlatelolco (Carballal-Staedtler et al. 2008). Complexes of embarcaderos existed not only in Tenochtitlan but also in port towns along lacustrine trade routes. A well-known lacustrine port in Lake Chalco is the town of Ayotzingo, where goods from Tierra Caliente (now Morelos) and the Gulf of Mexico arrived to be shipped by canoe to Tenochtitlan (Jalpa-Flores 2016). It was such an important port that at some point the Spanish considered it as a possible alternative to Texcoco for launching the brigantines for the final naval assault on Tenochtitlan (Díaz del Castillo 1982: 315).
9.5 Dikes, Dams, and Causeways 9.5.1 Features and Functions Dikes in the lakes of the Basin were structures for the control of the flow of water inside lacustrine basins and between lacustrine basins. However, dikes in some cases served as causeways connecting islands with the mainland. Most of the information about their layout, construction, and function comes from historical written and pictorial documents, archaeology, and geophysical data. Dikes, also known albarradas and albarradones in historical sources, were structures of different dimensions and made using different techniques. The description provided by Fray Juan de Torquemada indicates that poles would be planted tightly in rows and the spaces in between would be filled in with sediment from the
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a WEST
b
Modern fill and pavement
20 m 59m
Alluvial sand f ill
Tephra layer
Aztec causeway
Colonial f ill
EAST
Silted up channel Archaeological deposit Bentonite (Pleistocene lacustrine clay deposit) NORTH
SOUTH
0.0
Floor 1
Floor2
Floor 3
Floor 4
Floor 5
1.0 2.0
OFFERING
3.0 meters
c
Clay
Sand and gravel
Lacustrine clay deposit Modern street pavement Fill
Fill
Fill Fill East wall Fill
West wall Intrusion Not excavated Wooden stakes and posts
Lacustrine clay deposit
Modern sewer
Red scoria (tezontle) 0
0.5
1
2
meters
Fig. 9.16 Archaeological examples of causeways in Greater Tenochtitlan: (a) Calzada de Iztapalapa. (Redrawn and modified from González-Rul and Mooser 1961), (b) Calzada Nonoalco- Tacuba, and (c) Calzada de Tepeyac. (Redrawn and modified from Carballal-Staedtler and Flores- Hernández 1989b)
lake, aquatic vegetation, stone, and gravel (Torquemada 1975: 1975: Book 2, XLVII, 219). However, archaeological research shows that other techniques several other materials were uses especially for dikes that also served as causeways (Carballal Staedtler and Hernandez-Flores 1989b; Rojas-Rabiela 1984). Causeways (calzadas) were similar to dikes, but with the main purpose of connecting islands and the mainland, though some causeways also played the role of dikes (Carballal-Staedtler and Flores-Hernandez 1989b; Rojas-Rabiela 1974; Palerm 1973). According to the descriptions in the Conquest chronicles, causeways connecting islands with the mainland had openings that allowed the flow of water and the passage of canoes with the two sides of the opening connected by wooden bridges that could be removed in case of the threat of invasion (Cortés 1975; Diaz del Castillo 1982). In addition to the descriptions in the chronicles, several of the former causeways lying below the city have been excavated, showing some of the materials used and the additions and repairs made (Fig. 9.16). Earth, wood, and stone were often used, as well as the mixture of volcanic scoria (tezontle) and plaster, as in the causeway-dike between the former islands Huatepec and Tepetzingo (Figs. 9.17 and 9.18).
9.5 Dikes, Dams, and Causeways
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Fig. 9.17 Surviving Aztec causeway connecting two former islands, Huatepec and Tepetzingo, near the eastern shore of Lake Texcoco. (a) View toward Huatepec and close-up to an exposed side. See the location in Fig. 2.10b
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9 Cultural Features in the Lacustrine Realm N
1960
El Caracol
Bordo
2020
Bordos
N
Stone
Sluice
1 2
Saltflat
Bordos 3
1 S.J. Teotihuacan River Channel 2 Tepetzingo 3 Ancient causeway 4 Huatepec
4
Fig. 9.18 (a) Bordos delimiting ponds on the northwestern shore of Lake Texcoco between El Caracol and the former delta of the San Juan Teotihuacan River in 1960, photo by Compañia Mexicana Aerofoto; (b) the area in the rectangle as see on Google Earth Pro in 2018; (c) view of one of the ponds with a stone used to close the bordo
In addition to the more elaborate dikes and causeways, lesser features are apparent in the ancient and modern aquatic environments of the basin, one of which is small dams or bordos. The term does not pertain uniquely to the lakes and wetlands and also to fluvial environments where artificial levees or dams to divert streams are referred to by that name. Their construction is less elaborate than that of the dikes as they are often made of accumulations of earth and plants. The bordos in the modern lacustrine landscape as well as the descriptions in some historical documents suggest that their construction involved mainly earthen materials and plants and that their sides were usually asymmetric, with the external forming a talus. Examples in the modern lacustrine realm still existed in recent times in Lake Texcoco in the Ciénega de San Juan (Fig. 9.18). The dams are made of bordos laid in square and rectangular shapes as to form basins. Their function was to retain the fresh water coming from the artificial canals of the San Juan Teotihuacan River, instead of letting them flow into the saltflats. In some of the basins formed by the bordos, the catching of charales (Atherinidae) and ajolote was practiced until recently (Albor-Ruiz 2017). Following this example, it seems that bordos may have been used for the management of water through the compartimentos (water compartments) in Palerm’s (1973) interpretation of structures in the area of Greater Tenochtitlan and other areas of Lake Texcoco where chinampa systems were developed (see Chaps. 10 and 13). Examples of bordos in old maps and descriptions are rare, and normally they are referred to by the term albarrada. For example, in the description of the battles
9.6 Tools, Human Power, and Construction Materials
219
inside the city of Tenochtitlan, Díaz del Castillo (1982) and Cortés (1985) mention the crossing and the destruction of some albarradas in and around the city. They are probably referring to levees to manage or separate fresh water from brackish water (see the models in Chaps. 10 and 13). Similar references to water diverted to repel Spanish assailants occurred during the battles of Iztapalapa, Xochimilco, and Xaltocan (Cervantes de Salazar 2007; Corteés 1985; Díaz del Castillo 1982) (Chap. 14).
9.5.2 Features Associated with Dikes and Causeways Aqueducts were built to convey fresh water from its source (often springs) to islands. The very well-known aqueduct that conveyed water from the Chapultepec springs to Tenochtitlan is an example of a causeway that was also used as an aqueduct. Possibly, the Iztapalapa causeway conducted water from the spring of Huitzilopochco before the ill-fated events toward the end of Ahuizotl’s reign, as described in the sources (e.g., Torquemada 1975; Duran 1897). As noted above, causeway-dikes also served as important connections with tlateles and chinampas, as they were part of the matrix of rural and urban hydraulic infrastructure for the control of the flow of water in the lacustrine realm. Certainly, the urban matrix may have been more complex than that represented in maps recreating Tenochtitlan and its surroundings (e.g., Gonzalez-Aparicio 1968), and small structures such as bordos may be left out.
9.6 Tools, Human Power, and Construction Materials 9.6.1 Tools and Human Power The materials used in the construction of tlateles, platforms, dikes, chinampas, and other features included those obtained internally (i.e., lacustrine sediment and aquatic vegetation) and those that had to be brought in externally (i.e., sand, gravel, rock, coria, pumice, loose earth, lime, and wood), all of which are documented archaeologically and in historical sources. The implements used in the collection of internal of lacustrine materials would not have been different from those used in the agricultural activities (Rojas Rabiela 1993). Thus, the pre-Hispanic hoe (huictli) and the wooden spade (huizoctli) may have been readily used for scooping mud from the lake or for cutting meadow sod blocks (céspedes) (Fig. 9.19). Perhaps hand-axes and knives with obsidian blades were also used for cutting vegetation. Regarding implements for building chinampas and other lacustrine features, one must consider the canoe as the only means of transportation of materials in the lakes, except when causeways allowed transportation of materials carried on back.
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Collecting céspedes Tular
Reeds Blocks of céspedes Wet meadow
Sediment Diatoms Sediment Cinta Sediment Cinta Sediments / volcanic ash
Chinampa
Floating velgetation (cinta) Excavated sediment
Fig. 9.19 Cutting of céspedes (above) and cinta (below) for construction of terraces. The diagram below shows a staked fence (chinamitl) and the stratigraphy of different plant and non-plant materials
The hydraulic infrastructure had to be constantly maintained, which implied the organization of labor to procure and transport materials and do the mending work at the sites where it was needed. Aspects of the organization to carry out these tasks appear in the sources; some were communal, but in many cases such as in Tenochtitlan, carrying out these tasks implied tribute (taxation) in the form of work (Rojas-Rabiela 1984). Interestingly, this system of taxation by work remained in place through the colonial period for the repair of structures as well as the construction of desagüe works (Candiani 2014; Gibson 1964).
9.6.2 Lacustrine Raw Materials The most used construction materials collected in the lakes were vegetation and mud. Reeds and sedges were used directly for laying beds, as appears in the archaeological example of Terremote-Tlaltenco (McClung de Tapia et al. 1987), or as bedding in some layers in the chinampas (Ávila-López 2006). They would also been used in the construction of huts and as fences. Aquatic vegetation was also used in construction in the form that the sources call céspedes and cinta (Fig. 9.19). Although the term césped in modern Spanish means lawn, turf, or sod, in Colonial Mexico it referred to mats of aquatic vegetation used in the construction of chinampa
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beds and other structures (Boehm de Lamerias and Pereyra 1979). The Nahuatl terms that Molina (1571) provides for céspedes are cueptli and tlachcuitl; the first comes from the verb cuepa (return or turn over) and the second from the verb tlachqua (cave in or remove a clod of soil). Thus, it seems that céspedes were not aquatic vegetation in the broad sense, but blocks of aquatic sediment that retained fibrous roots in the soil and were used in the same way as bricks (see the illustration in Fig. 9.19). In the mosaic of environments in the lakes, the céspedes would be available in lakeshore meadows (see Fig. 8.10, environments 2, 5, and 7). Another form of aquatic vegetation was the floating vegetation, which in the nineteenth-century literature is called cinta, but its Nahuatl term could have been atlapalacatl (Rojas Rabiela et al. 2009), which comes from atlapalli (leaves) and acatl (reeds or aquatic monocots). Mats of cinta are still used as bedding in the chinampas (Rojas Rabiela 1993, 1998). References to floating vegetation come predominantly from the southern lakes, which perhaps were the most vegetated of all. The use of the wood of subaquatic trees such as ahuejote (Salix bonplandiana) is also known in modern contexts. Not only the trees themselves provide stability to the sides of chinampas and platforms, but they are also used as stakes with intertwined branches to form a fence (Fig. 9.10). Wooden stakes in the ground also served as mooring bollards for canoes, as found in Terremote-Tlatlenco (Fig. 9.3) and Tlatel de Tequexquinahuac (Fig. 9.6), or as posts for larger structures such as causeways (Fig. 9.15c). Wooded structures could also be made from trees growing on shore or along rivers (e.g., Taxodium mucronatum), from shrubs, or from other inland trees. Organic mud from the bottom of the lake, particularly what accumulated in canals, was known to be used as a soil builder for the chinampas, a technique used to this day in the areas where canals exist (Rojas-Rabiela 1991, 1993). Lake sediment was also used to fill in fences to build platforms, tlateles, causeways, and other structures (see Chap. 10). Hardened layers sediment and soil (tepetates or caliches) that formed in desiccated parts of the lake were used as materials for construction, as well as sediment from the incoming streams, particularly in deltaic environments.
9.6.3 Non-lacustrine Materials The external materials had to be transported from the shore or farther inland, which implied a great deal of human labor and the use of canoes. Although quantities of stones from the shores were used for construction in the lakes, one of the most common materials was basaltic scoria (tezontle), which was common in volcanic cones around the lakes. Being a puffy material, tezontle is light, which makes it easy to carry in large quantities. Tezontle had multiple uses in construction, as fill or as mixed with lime to make plaster. Lime was widely used for making plaster for floors and walls in buildings, but its appearance in structures such as aqueducts and causeways is very common. Sources of lime in the basin are rare, given the predominance
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of volcanic rocks. However, pre-Hispanic sources seem to have been in areas in the northern part of the Basin or the neighboring Tula Basin (Sanders et al. 1979). These are the few areas where older calcareous rocks, below the Tertiary and Quaternary, are available on the surface. Very common in construction were the tepetates, a generic term that refers to hard surfaces, which could be calcretes, silcretes, or endurated ignimbrites. Many of these substances existed in all parts of the Basin, especially in the piedmonts, though many also formed in areas where processes of desiccation and precipitation of certain minerals created hard crusts in the lakebed (Gutiérrez-Castorena et al. 2006). Likewise, sand of different grain sizes (fine, medium, coarse, and very coarse) appears to have been used in many structures, most commonly as fill for the construction of tlateles. Sand may have been mixed with earth and rocks as at El Tepalcate (Cordova et al. 2021) or molded into mudbricks to reduce breakage when dry. Given the use of substantial amounts of earth and stone materials brought from the shores or mainland to build tlateles and causeways, it was also possible that discarded ceramics and trash were among the materials. Such use implies the possibility of adding ceramic styles of periods older than the construction, which may lead to confusion about the dating of the actual structures. Similarly, organic trash, including fragments of charcoal, could have been brought in, adding older dates to the construction. Therefore, this aspect should not be ignored when using ceramic styles or radiocarbon for dating cultural features.
Chapter 10
Models of Lacustrine Features and Settlement Development
10.1 A Classification of Cultural Lacustrine Features 10.1.1 Theoretical and Conceptual Framework The literature on cultural features in the lacustrine realm of the Basin of Mexico is extensive and founded on a variety of studies in various fields. Some information has its foundation on ethnohistoric and ethnographic data (e.g., Rojas-Rabiela 1974, 1984; González-Aparicio 1973; Palerm 1973; Calnek 1972). Others rely on data obtained from surface archaeology and landscape archaeology (e.g., Luna-Golya 2014; Morehart 2012a; Parsons et al. 1982; Armillas 1971), and others on archaeological excavations (e.g., Morehart and Frederick 2014; McClung de Tapia and Acosta-Ochoa 2015; Morehart and Frederick 2014; Frederick 2007; Ávila-López 1991, 2004; Carballal-Staedtler and Flores- Hernández 1989a, b; Serra-Puche 1988). The interpretation of the archaeological examples of cultural features, whether obtained through survey, excavation, or both, is often based on attributes such as shape, orientation, and function. In particular, after Pedro Armillas (1971) introduced the concept of landscape archaeology while interpreting the layout of archaeological chinampas in the Chalco-Xochimilco basin, the concept gains an important value in subsequent studies, especially those dealing with surveys using aerial photographs (e.g., Luna-Golya 2014; Morehart and Frederick 2014; Morehart 2012b; Parsons et al. 1982). Concepts of site-formation processes introduced by Michael Schiffer in various papers and in his opus magnum (Schiffer 1987) brought a framework to archaeological research in the 1980s and later regarding the uniqueness of processes that form sites. This approach seems fundamental in the interpretation of the tlateles at Terremote Tlaltenco (e.g., McClung de Tapia et al. 1987), or even those of chinampas in Xochimilco and Iztapalapa (Ávila-López 1991, 2006), and, in general, of chinampas in the Basin of Mexico (Frederick 2007). In a way, this approach © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5_10
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Table 10.1 Attributes of cultural features as anthropogenic landforms with a utilitarian purpose Features Tlateles and platforms Chinampas Canals Embarcaderos Dikes, calzadas, and bordo dams Platform-dike
Construction Positive Positive Negative Negative Positive Positive
Purpose Habitation, manufacturing Agriculture Navigation, drainage Navigation Flood protection, water storage, water diversion, transportation, territorial division Habitation, protection, water diversion
addresses the technological aspects of construction of certain features (e.g., chinampas) and not complex or interconnected features (e.g., Luna-Golya (2014). The assessment of aspects such as shape, orientation, formation processes, and technology in the cultural features of the lakes of the Basin can be approached from different points of view. The view that may include all of these factors into one broad concept is to see cultural features as anthropogenic landforms. The term landform in geomorphology connects form (or shape), origin (formation processes), and function in the environment (purpose). The technological aspect, which is excluded from the natural concept of landform, is what constitutes the cultural part of the anthropogenic landform concept. Thus, like their natural counterparts, anthropogenic landforms act as catalyzers for geomorphic processes. A dike can perhaps have the same role as a sand bar or a natural levee, with the difference that the former was put in place artificially. Anthropogenic landforms can be classified according to two main attributes: their mode of construction and their purpose (Table 10.1). Like natural landforms, cultural features are positive if they are formed by the accumulation of materials or negative if their creation implies the removal of material. Some anthropogenic landforms have a specific purpose while others are multipurpose. A dike, for example, can serve to protect an area of the lake from flooding and at the time it serves as a causeway. Another important aspect of cultural features is their location in the lacustrine system (i.e., setting), which explains their construction and purpose. Cultural features also have shape and size, which adds to the list of attributes that relate to their construction, purpose, and location. Thus, all these attributes permit a classification of features, useful for understanding the geography and evolution of lacustrine landscapes in the Basin of Mexico.
10.1.2 Feature Typology by Setting and Type of Construction The basic classification of cultural features proposed here includes tlateles, chinampas, canals, embarcaderos, dikes, and causeways. Tlateles are of at least eight types, designated by letters A-H (Table 10.2) based on their setting with respect to
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Table 10.2 Types of tlateles in the lacustrine setting Types Type A: Morphotectonic anomaly Type B: Morphotectonic anomaly with spring deposits Type C: Deltaic Island Type D: Sediment shoal Type E: Beach landform Type F: Bajada landform Type G: Hardened ground layer Type H: Vegetated ground
Original geomorphic features Faulted terrain with uplifting Faulted terrain with water Levees of deltaic arms Shallow area produced by accumulation of sediments Abandoned beach ridge Created by colluvial, volcanic, or alluvial-fan deposits transitional to the lakebed A hardened surface layer, probably calcrete or silcrete, on a dry lakebed No apparent lakebed form; flat surface with groves of aquatic vegetation
Table 10.3 Types of chinampas according to their lacustrine setting Types In-lake chinampas (chinampas de laguna adentro) Lakeshore chinampas (chinampas de orilla de laguna, chinampas secas) Inland chinampas (chinampas tierra adentro, chinampas de río)
Association with the lacustrine environment Built inside the permanently impounded area of a shallow lake or marsh Built on a fluctuating lakeshore, often close to the mouth of a stream, possibly associated with deltaic environments, and built by digging drainage canals and elevating fields with fertile soil No association with the lake. Built in fluvial swamps or permanently flooded areas inland by digging drainage canals
lacustrine geomorphic features. Likewise, chinampas are distinguished into three types according to their setting with respect to the lake (Table 10.3). On the other hand, for canals, embarcaderos, dikes, and causeways, no locational emplacement is apparent, unless these features are associated with another type. Additionally, the classification of all cultural features based on the form of construction encompasses multiple types (Tables 10.4, 10.5, 10.6, 10.7 and 10.8). Each type has support from one or more sources, namely archaeological, historical, or ethnographic, or simply inferred by their lacustrine setting. The latter refers to two types of inferences, those deduced from the archaeological, historical, or ethnographic context, and conjectures based on the natural (geomorphic, geological, cultural) context of the feature in question. The level of complexity in the last column in Tables 10.4, 10.5, 10.6, 10.7 and 10.8 has three numerical categories referring to a sequential level of technological and social organization involved in their construction (Chap. 15). Thus, number 1, the lowest category, designates simple features, whose construction generally implies the involvement of smaller populations and elemental technology. These types of features appear throughout the ceramic period or even earlier. In some
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Table 10.4 Artificial islands (tlateles and platforms) Types Type 1 Natural accretion of sediments forming occupation surfaces. Habitational or temporary activities Type 2 Natural accretion of sediments behind artificial features. Habitational or temporary activities Type 3 Deliberate piling of organic (plants) and inorganic material Type 4 Platform created by filling in a staked perimeter with mud and plants, as well as other materials Type 5 Platform similar to type 4 but elongated Type 6 Platform constructed with rock and masonry
Corroboration Archaeological
Complexity level 1
Inferred
1
Archaeological
1
Archaeological, historical
1–2
Archaeological, historical Archaeological, historical
2 2–3
Table 10.5 Canals Types Corroboration Type 1: Created by removing aquatic vegetation Inferred, ethnohistorical Type 2: Dug-out navigation route Historical, archaeological, anomalies Type 3: Dug-out navigation canal with side Historical, archaeological chinampas Type 4: Chinampa canal Archaeological, historical, ethnographic Type 5: Canal along a causeway Archaeological, inferred Type 6: Canal bordo or water conduit across a Inferred and hypothetical lakebed or floodable plain Type 7: Canal in an habilitated deltaic channel Historical, inferred (estero) Type 8: Canal built for inland accessibility Inferred
Complexity level 1 2 3 3 3 3 2–3 3
cases, they involve a simple natural feature as opposed to a built new feature. Number 2 designates features that show a more advanced degree of construction and complexity but still involve moderately simple technology and require more complex organization than those at level 1. Number 3, the highest category, designates structures whose construction involves complex organization and technological support, often corresponding to large structures. Most of these structures appear to have been developed in the Late Postclassic period and are often associated with urban complexes on the lakes. The three categories in the level of complexity serve as the basis for a proposed model discussed in Chaps. 12, 13, and 15.
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10.1 A Classification of Cultural Lacustrine Features Table 10.6 Embarcaderos Types Type 1: Docking in an enclosure made in spaces between tlateles and chinampas Type 2: Docking place in abandoned channel or estero Type 2: Docking place at the end of an inland canal Type 4: Docking in a built enclosure with steps
Complexity level 2
Corroboration Archaeological, historical, ethnographic Archaeological
1
Inferred from historical accounts Archaeological
3 3
Table 10.7 Chinampas Types Type 1: Raised field with dug-out canals Type 2: Canal-side chinampa Type 3: Field drained by canals
Complexity level 2
Corroboration Archaeological, historical, ethnographic Historical, archaeological Hypothetical, historical, archaeological outside the Basin of Mexico
2 2
Table 10.8 Dikes or causeways, and bordo dams Types Type 1: Dike, or causeway, made with stakes and earth Type 2: Dike-causeway of clay and sand Type 3: Dike-causeway of stone and masonry Type 4: Dam or bordo
Corroboration Archaeological, historical Archaeological Archaeological Historical, inferred
Complexity level 3 3 3 2
The terminology for the cultural forms here may have variations, particularly in their usage in the archaeological, historical, and architectural literature. In this case, the proposed categories of cultural features constitute generic names. Thus, tlatel may encompass mounds, platforms (plataformas or terraplenes), and other architectural forms built in the lacustrine or palustrine environment. Likewise, chinampa, the common name used in the Basin of Mexico, is a term interchangeably used with raised fields (campos elevados). For the case of dikes (diques) and causeways (calzadas), names albarrada and albarradón are used, while the name bordo is a generic form used here with the idea of a dam built in the lacustrine realm.
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10.2 Types of Features: Models and Examples 10.2.1 Tlateles Based on Geomorphic Setting The classification of tlateles by geomorphic settings in the lacustrine realm encompasses eight types (Table 10.1). The construction of a tlatel in type A setting occurs on a preexisting elevation of the lacustrine floor caused by a tectonic deformation, usually faulting (Fig. 10.1). This the case of the tlatel excavated San Gregorio site in Lake Xochimilco (Acosta-Ochoa et al. 2021), which encompasses an Aztec settlement on swamp deposits formed directly on a surface bearing a pre-ceramic site on an apparently old terrestrial deposit in the middle of the lake’s basin (Fig. 9.8). Another possible example of this type of setting is El Tepalcate (Fig. 9.3), which seems to be aligned along possible fractures or faults (Cordova et al. 2021). The latter, however, may also be associated with springs created by water seepage through faults, thus giving a variant to this setting (type B). It is assumed that the spring inside could be contained by building a protective dam around it (Fig. 10.1). This type of tlatel seems to have been widespread in the area later occupied by the
Tlatel setting A
Tlatel setting B Spring
Fault
Fault
Fault
Spring
Cultural deposits (tlatel building material) Aquatic vegetation (tulares) Peat or sediments trapped by aquatic vegetation Spring deposits High Low
Average seasonal lake levels
Fig. 10.1 Idealized formation stages of tlateles in geomorphic setting types A and B. Sequence of development from top to bottom
10.2 Types of Features: Models and Examples
Tlatel setting C
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Section view
A
Plan view
B A
A’
A’
A’
B’
B’
Tlatel setting D A
A’
Section view
Shoals (sediment bank)
A’’
B’
B’’
Aquatic vegetation (tulares) Cultural deposits (tlatel building material) High Low
Plan view B
Average seasonal lake levels
A
B
A’
A’’
B’
B’’
Peat/organic deposit Beach deposits Fluvial deposits Emerged sediment bank/ Sand ridge
Fig. 10.2 Idealized formation stages of a tlatel in geomorphic setting types C and D. Sequence of stages from top to bottom, and cross sections of some stages on right
former Tenochtitlan, as springs associated with fault systems may have created sources of water (see Chap. 13). The type C setting occurs on levees of stream channels impounded by the lake during high stands (Fig. 10.2). Typical cases appear in the formation of the Tlatel de Tequexquinahuac (Fig. 9.6) and the levees of the channels of the Amecameca River delta (Fig. 9.7). The type D setting may also occur in fluvio-lacustrine environments
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especially on banks of sediments or shoals in pro-deltaic areas (Fig. 10.2). This type may also occur in the presence of vegetation that could fix some of the loose fine sediments in shoals, as is the case of environment 11 (Fig. 8.11). Specific cases of this setting have not been confirmed archaeologically, but they could have been important on the western side of Lake Texcoco, where sediments from incoming rivers may have created these shoal areas, later occupied by settlements such as many of the islands around Tenochtitlan. Evidence of such banks are sometimes apparent in the stratigraphy city (Fig. 5.3) and in soundings in areas of known tlateles (Auvinet et al. 2017) (Fig. 9.10). Possible topographic anomalies of the lakebed may be caused by other types of sedimentation beach ridges (type E), sediments accumulated at the end of a bajada in contact (type F), or by hard surfaces formed by crusts of calcrete or silcrete on the bed (type G) (Fig. 10.4). Additionally, it is conceivable that a tlatel on a type H setting could be built on a vegetated surface without a particular geological or geomorphological feature (Fig. 10.3). The type E setting seems to be present in the Late Aztec occupation at El Tepalcate (Fig. 9.2) or some of the occupations on the beaches accreted against the levees at Tlatel de Tequexquinahuac (Fig. 9.5). The type F tlatel setting occurs in areas of short transition between hills and lakebed, either around the large sierras or at the base of rocky islands, such as El Risco (Mayer-Oakes 1959) and many other salt stations around the Sierra de Guadalupe (Fig. 9.10). Similar sites occur along the southern shore of Lake Texcoco along the base of the Sierra de Santa Catarina, as evident in the Iztapalapa Region Survey (Blanton 1972) and along the construction of subway Line 8 (Sánchez-Vázquez 1996). The type G setting occurs when a tlatel is built on a preexisting crust provided more stable and slightly higher ground for building an artificial island. The only archaeological example of this type is the Tlatel de Tepexpan (Fig. 9.5), where yhe base of the oldest cultural layer (Layer III) rests on a caliche (calcrete) crust. Interestingly, according to the map of the area by De Terra (1949), other tlateles are built on the same calcrete surface. Finally, the type H setting, though with no Tlatel setting E Beach landform Beach ridge/sand bar
Tlatel setting G Hardened surface Aquifer Hardened layer (tepetate)
Tlatel type H Vegetated ground Tlatel setting F Bajada-lakeshore
Tular
Fig. 10.3 Idealized formation of tlatel types E, F, G, and H. Sequence of stages from top to bottom
10.2 Types of Features: Models and Examples
Tlatel type 1
231
Pre-existing natural feature
Combined natural and cultural accretion of sediment
Tlatel type 2
Tlatel type 3
Tlatel-platforms type 4
Single-dwelling
Multi-dwelling
Tlatel-platforms type 5
Lengthwise
Wooden bridges Chinampa
Chinampa
Sidewise
Tlatel-platform type 6
Masonry buildings
Fig. 10.4 Tlateles and platforms based on the type of construction. Sequence of stages are indicated by arrows
preexisting geological or geomorphological feature occurs when groves of aquatic vegetation (tulares) constitute the base of a settlement, if earth and rocks are brought in from the shore. In many cases, however, the layer can serve as the base of a temporary settlement or a palafite for offerings, as suggested by several cultural features reported in the center of Lake Texcoco (Parsons and Morett 2004).
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10.2.2 Tlateles and Platforms Based on Construction Type Regardless of the geomorphic setting or lacustrine environment where they are built, artificial insular habitational features (i.e., tlateles and platflorms) vary based on the type of construction (Table 10.4 and Fig. 10.4). Types 1 to 3 are considered tlateles, and their setting could be any of those depicted in Figs. 10.1 and 10.2. Types 4–6 are considered platforms, for which more elaborated and planned forms exist. Although platforms may have been built in any of the settings above, they usually appear on lakebeds or in marshes. Type 1 tlateles are usually habitational features established on preexisting cumulative natural feature, which could be a beach ridge, shoal, and deltaic channel levees, among others. One example is the Tlatel de Tequexquinahuac (Fig. 9.3), whose occupation occurred in tandem with accumulation of sediment on a levee and the formation and retreat of a beach deposit. This type of tlatel could also form on a cumulative feature that would be high enough for habitation during a seasonal high lake-level stand. This could be a surface of hard material (e.g., caliche or tepetate), as is the case of the Tlatel de Tepexpan (Fig. 9.5), or elevated former lacustrine and volcanic deposits, as is the case of the tlateles shown in Fig. 9.8. A type 2 tlatel would be formed by the accumulation of materials carried by rivers or currents behind an artificial structure, which could be a dike, causeway, or bordo. Although no archaeological remains of such type are reported, it seems that the original settlement of Tlatelolco began in a structure where a preexisting albarrada (dike) existed (see discussion and sources in Chap. 9). The possibility of such occurrence in areas near rivers made perhaps this type of tlatel a common occurrence. A type 3 tlatel consists of an accumulation of anthropogenic material (earth, sand, plants, or stones). Its shape is round or irregular, for example, El Tepalcate, Figs. 2.3 and 9.3) and the Tlatel de Tepexpan and Tocuila (Fig. 9.6) and built several materials. This could be also the case of the tlatel (or tlatel complex) of Xaltocan, which was constructed mainly from sand carried in from the shore (Frederick et al. 2005). A type 4 tlatel is a basic platform bordered by a palisade and filled in by sediment, stone, and organic materials as detailed in Fig. 9.1b, which often served as the base for a small building or a dwelling or a group of small dwellings (Fig. 10.4). The materials filling in the palisaded area were earth, lake sediment, or plant material much in the way some sources describe them: Tezozomoc 1998: 73; Códice Ramírez 1975: 27; and Durán 1897: vol. 1: 42, who described the first platform built for the first temple shrine and the ball court during the founding of Tenochtitlan. Nonetheless, organic materials were also used in the southern lakes where plants were abundant, as is the case reported from Terremote-Tlatlenco (Serra-Puche 1988; McClung et al. 1987). Type 5 platforms differ from those of type 4 in that they are elongated and likely had several dwellings and even served as dikes (Fig. 10.5). An example of such construction appears in the row of houses along a canal on one of the maps of Tenochtitlan by Calnek (1972), represented in Fig. 9.14b. This type is assumed to
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10.2 Types of Features: Models and Examples Fig. 10.5 Canal types 1, 2, and 3
Canal type 1
Canal type 2
Canal type 3
Chinampas
Chinampas
have been constructed using the same techniques as those for type 4 with the only characteristic of being long and serving as sides for canals. Type 6 platforms are made of rocks and masonry (lime and tezontle). Wooden stakes or posts were used as piles to transfer the weight to the ground with the purpose of giving the building more stability in the saturated clay ground (Mendoza 1990). These platforms were common in the sacred precincts of Tlaltelolco and Tenochtitlan, where they supported large buildings and temples (cf. Gonzalez-Rul 1988; Mazari et al. 1989; Mendoza 1990; Matos-Moctezuma 2006). The use of wooden piles, however, was not exclusive to these platforms as they may appear in other forms of tlateles or causeway dikes (see Fig. 9.16c).
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10.2.3 Canals The eight types of canals are based on their purpose and the part of the lacustrine environment where they are built. Type 1, 2, and 3 canals constitute the main navigation thoroughfares in shallow parts of the lakes (Fig. 10.5). The making of a type 1 canal simply requires removal of dense aquatic vegetation (tulares) or mud, which involves dredging, to accommodate the canoe traffic (Fig. 10.5). Type 2 involves the deepening of a canal by scooping up mud, which is necessary in shallow areas where lake levels may be too low for navigation during a seasonal or prolonged dry period. Type 3 is a variation of type 2, in which sediments dredged from the bottom were used for building chinampas on the side of the canal, a practice with ample ethnographic, historic, and archaeological references (Luna Golya 2014; Rojas- Rabiela 1993). One historic sample of type 2 is the Canal de la Viga, which was at some point an open lake route but, because of sedimentation and eventual lake-level drop, needed deepening to remain a throughway for the canoes traveling from the southern lakes to the city (Jiménez-Vaca 2017). Interestingly, as described by Jose A. Alzate y Ramírez in 1791 (published in Alzate 1831), the sediment extracted from the dredging of the Acequia Real (i.e., Canal de la Viga) as well as from other navigation canals in Xochimilco served as material for constructing chinampas along the channel in places like Nextipac, Iztacalco, and Mexicaltzingo (Alzate 1831: 390). In the same text, Alzate alludes to the fact that sediment from the bottom of this canal would not be salinized, as opposed to that where the chinampas were being built. Even before the lake levels dropped through the process of desiccation, navigation canals in pre-Hispanic times had to be dredged so that they are still navigable during low lake-level stands (Fig. 10.5). This practice would have applied to the routes between Mexicaltzingo and Tenochtitlan-Tlatelolco, but also along the navigation routes connecting Mexicalztingo with Ayotzingo (the main port for incoming products from the south and east) across lakes Xochimilco and Chalco (Jiménez- Vaca 2017). Other types of canals are built with purpose other than navigation, but more on accessibility or used to convey water in the lacustrine realm. Thus, type 4 canals (i.e., chinampa canals) are built in the process of chinampa formation, as material was dredged from the bottom and piled on the chinampa beds (Fig. 10.6). Subsequently, the canals served as means of accessing the chinampas by canoe, which in turn gave accessibility to the fields. These canals would have been narrow and not as deep as navigation canals, and thus in many cases are considered secondary (Luna-Golya 2014; Morehart and Frederick 2014) (Figs. 9.14 and 9.15). The type 5 canal (canal along a causeway) may have been created as sediment from the bottom was dredged to upgrade a causeway (Fig. 10.6). A typical case appears along the sides of the former Iztapalapa causeway (Fig. 9.16a). In addition, a kind of deposit next to the borders of the Tepeyac causeway suggests, perhaps, the existence of a deeper part running along the dike (Fig. 9.16c). The logic of this type
10.2 Types of Features: Models and Examples
235
Section view
Canal Type 4
Canal Type 5
Chinampa bed Canal
Section view B
A
Causeway B
A
A
B
Canals
Plan view A
B
B
A
A
Causeway
Canal Type 6
B Causeway
Section view
A
B
A
B
Plan view A
B
A
B
Fig. 10.6 Canal types 4, 5, and 6
of canal would be, first, the source of material to fill in the palisades and build up the dike, and, second, the possibility of having a navigation canal when lake levels are low as shown in the far-right diagram of type 5 (Fig. 10.6). The type 6 canal is built to convey water from an inland area to a water compartment on the lakebed, usually from a spring or river to a location in a saline lake. For this purpose, the construction of the canal requires levees (bordos) to protect it from incursions of saline water. The canal that fed the Xaltocan chinampas from the Ozumbilla spring represents this type (Fig. 9.15), although it is possible that similar cases existed in Lake Texcoco, where in fact in the area of Iztapalapa chinampas were fed by canals bringing water from springs or from the southern lakes (Palerm 1973). It is also important to consider that this type of canal could also convey water from a stream to a compartment, as is the modern case of the San Juan Teotihuacan River channelized to the ponds in the Ciénega de San Juan (Fig. 9.18). The type 7 canal occupies a former deltaic channel or estero (Fig. 10.7). An apparent case fitting this type is the channel in the Tlatel de Tequexquinahuac (Fig. 9.6), which was perhaps also used as an embarcadero (see type 3 embarcaderos). This type of canal existed in other deltaic areas, as is the case in several towns along the channels of the Amecameca River delta including during colonial times (Jalpa- Flores 2016: 116) (see the map in Fig. 2.10b). In fact, the description of Ayotzingo as an important harbor (Díaz del Castillo 1982; López de Gómara 2006) suggests the use of deltaic arms for connecting inland settlements with open lakes.
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Canal type 7
Abandoned deltaic channel habilitated as navigation canal
Active deltaic channel Active deltaic channel
Canal type 8
Plan view Section view Bordos made of dug-out sediment A
B
A B
Stakes for reinforcing canal sides
Seasonal lake levels
Fig. 10.7 Canal types 7 and 8
The type 8 canal (inland accessibility canal) corresponds to a canal built perpendicular to the lakeshore to connect an inland point with the deeper part of a lake (Fig. 10.7). Only one historical account of a type 8 canal exists, referring specifically to a canal connecting Nezahualcoyotl’s palace with Lake Texcoco (cf. Alva- Ixtilxochitl 1977: 150), as well the canal that was habilitated during the conquest war to convey the brigantines from the shipyard to Lake Texcoco (see Chap. 14). This type of canal existed in the southeastern part of Lake Texcoco, where the canals connected the embarcaderos of Chimalhuacan Atenco with the open lake still through part of the early twentieth century. On the aerial photograph of this area in 1960, the network of the already dry canals is still visible (Fig. 2.11).
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10.2.4 Embarcaderos Docking areas for the loading and uploading of goods to and from canoes appear in the archaeological record of the Basin of Mexico. In general, docking areas are coves with stakes used for tying canoes, but according to their context in the matrix of lacustrine cultural features, they can be of four types (Table 10.5 and Fig. 10.8). Type 1 embarcaderos occupy the space left between chinampas and tlateles or small coves indented in tlateles (e.g., Fig. 9.14a), or large coves formed by connected tlateles (e.g., Fig. 9.2b). Type 2 embarcaderos can be inferred from the possibility that some abandoned river channels (esteros) could be used as protected spaces for docking. The finding of stakes inside the channel at the Tlatel de Tequexquinahuac (Fig. 9.3) suggests that it was used for tying up canoes. Likewise, abandoned channels of large rivers or natural bays formed by deltaic arms could serve that purpose. Type 3 embarcadero occupies cove inland connected to the lake by a canal (Fig. 10.8). Accordingly, this would be an embarcadero associated with type 8 canals (Fig. 10.7). The only evidence of an embarcadero of this type is probably inside Nezahualcoyot’s palace in Texcoco, whose description was given by Ixtilxochitl (1988: 150)when referring to a passage from the palace to the lake. However, similar canals may have existed elsewhere, though perhaps not documented. Type 4 embarcaderos involve a more elaborate structure, as they have steps that facilitate access to the canoes from higher structures such as platforms (Fig. 10.8). Often these structures were made of a combination of not only stone and wood but also stonework. Archaeological examples have been uncovered on the southwest side of the central precinct in Tlatelolco (Carballal-Staedtler et al. 2008) and at one locality along subway line 4 (Ortuño-Cos et al. 1982). Therefore, it seems that this type of docking structure existed at important ports in Tenochtitlan and Tlatelolco and possibly in other large lacustrine towns along the main trade routes.
10.2.5 Types of Chinampas by Setting In principle, chinampas are considered artificial islands, but their use for farming and the unique techniques for their construction make them a category that is different from tlateles and platforms. However, like tlateles and platforms, chinampas also occur in specific settings in the lacustrine realm, based on which they are classified into three types of settings: the in-lake, inland, and lakeshore types (Table 10.2 and Fig. 10.9). The in-lake chinampas (i.e., chinampas de laguna adentro), occupied areas of open lake, probably areas permanently inundated (Fig. 10.9a). This setting seems to be the most common in the lakes of the Basin, as suggested by archaeological and historical examples in the southern lakes, in Tenochtitlan, and in Lake Xaltocan.
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Plan view Tlatel
Embarcadero Type 1 Section view
B’
A’
A
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Fig. 10.8 Types of embarcaderos
They seem to be associated with stable lake levels that would permit construction and accessibility by canoe.
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c Inland chinampas
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Fig. 10.9 Schematic representation of chinampa settings proposed by Palerm’s (1973) and modified by the author: (a) open-lake, (b) inland, and (c) lakeshore
The inland chinampas (i.e., chinampas de tierra adentro), formerly proposed by Palerm (1973), are of two subtypes, the inland chinampas proper and the lakeshore chinampas (i.e., chinampas de orilla). To distinguish the latter from the former, the diagrams in Fig. 10.10b, c show the possible stages in their formation. The inland chinampa usually occupied floodplain wetlands along large rivers and were often made possible by drainage canals. The lakeshore chinampas were built on the seasonally flooded parts of the lake, often those areas where fresh water was available for the removal of salts from the soils and irrigation of crops.
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Chinampa Type 1 Sediment dredged from canals
Chinampa bed Canal
Chinampa Type 2
Dredging navigation canal
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Water table Water table Floodplain or Digging drainage canals lakeshore wetland
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Fig. 10.10 Basic types of chinampas based on construction techniques
10.2.6 Types of Chinampas by Construction Based on the numerous archaeological, historical, and ethnographic references, the methods of construction of chinampas were diverse (Frederick 2007; Ávila-López 1991, 2006; Rojas-Rabiela 1991, 1993) (see Sect. 9.3.1). However, for the sake of simplification, chinampas can be divided into three basic types based on the method of construction (Fig. 10.10). This classification is independent of the shape of the chinampas, which in any case the length-to-width ratio was high for pre-Hispanic chinampas (see the discussion in Sect. 9.3.2), but only applicable to the in-lake chinampas, as there is no archaeological or ethnographic information on the other types of chinampa settings. Type 1 chinampas are the most common form reported in archaeological surveys and excavations. They consist mainly of long beds separated by canals and usually occupy the interior of a lake, suggestive of Angel Palerm’s laguna adentro (i.e., in- lake chinampas) (Fig. 10.9). Type 2 chinampas are presumably associated with the sides of type 1 canals, thus constructed not only with muck from the sides of canals but also from the dredging of the main navigation canals (Fig. 10.5). They include historical examples along Canal de la Viga and the main routes along lakes Chalco and Xochimilco. The environment for their formation also fits the general classification of in-lake chinampas. Type 3 chinampas are those in drained swamps, where the drainage canals were the divisions between the beds. Although muck from the canals could be used for
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upgrading the bed, the system implies that the bed is at the level of the original plain. The setting of this type of chinampa corresponds primarily to the inland type, or the one that would be built on a floodplain marsh or swamp and not really associated with a lake (see Fig. 10.9b). Citations of historical inland chinampas include those in the floodplains of the Teotihuacan Valley (Sanders et al. 1979), in the Teoloyucan area south of Lake Zumpango (Strauss 1974), and in other parts of the Altiplano (see Sect. 9.3.2). This type of chinampa, however, was not necessarily like the others in the lacustrine realm, but perhaps in areas that were in transition from inland to lakeshore chinampas. Although the three types above may only be applicable to the in-lake settings, as there are no archaeological examples for the inland and lakeshore chinampa settings, it is possible that the construction of chinampas in inland and lakeshore settings was similar. These types, however, may correspond to digging drainage canals and using the materials to build the beds, or as in the case of the tierra negra soils of Teoloyucan (Reséndiz-Paz et al. 2013), it may imply bringing organic materials from a nearby swamp or lake (see Sect. 5.3).
10.2.7 Dikes, Causeways, and Bordos As discussed in Chap. 9, causeways often served as dikes; thus, both structures constitute one category in terms of construction technology. Furthermore, dams (bordos) and artificial levees usually had a purpose of containing water in a way that a dike does, though on a smaller scale and often using different construction materials. Therefore, based on their construction materials, techniques, and function, these structures are categorized into four basic types (Table 10.8 and Fig. 10.11). Type 1 dikes or causeways are constructed with two parallel rows of wooden stakes or posts interwoven with horizontal twigs and branches and filled in with sediment and rocks, much in the way Torquemada (1975: Book 2, XLVII, 219) describes the construction of Nezahualcoyotl’s dike. Type 2 dikes or causeways involve accumulations of clay, sand, and sometimes gravel layered along the structure, as represented by the archaeological example of the Nonoalco-Tacuba Causeway (Fig. 9.16b). Whether they had retaining wooden structures on the side is not clear. However, it seems that the layers of material are upgrades made to increase the height of the structure. Type 3 dikes and causeways are stronger structures with borders of stone or built entirely of stones, as seen in the archaeological example of the Tepeyac causeway (Fig. 9.16c). The use of lime and tezontle masonry seems to have been common in the construction, as shown by the example of the Tepetzingo-Huatepec causeway- dike (Fig. 9.17) referred to here as causeway-dikes. Type 4 structures (dams or bordos) had the function of managing water levels and floods on a smaller scale than dikes. As discussed in Chap. 9, their function may have been for protection of fields, for containing fresh water, or as levees. Their construction involved the use of earth, stakes, and céspedes, and perhaps they had
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10 Models of Lacustrine Features and Settlement Development
Section view
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Fig. 10.11 Types of dikes, causeways, and bordo dams
sluices as the modern bordos in the Ciénega de San Juan shows (Fig. 9.18). The concept can be extended to other functions for retaining water, especially water from springs, an occurrence mentioned by Tezozomoc (1998: 32) when describing how, during the early days of the founding of Tenochtitlan, the Mexica constructed a protective enclosure around a spring. It is obvious that the spring was the only source of fresh water in an otherwise saline swamp. Similarly, bordos also protected canals conveying freshwater from springs as is the case of type 6 canal (Fig. 10.6).
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10.3 Processes of Lacustrine Appropriation and Control 10.3.1 Complexes of Cultural Features in the Lakes of the Basin of Mexico Although in most cases they are seen as separate entities, cultural features described in this chapter function as an integrated system in tandem with the seasonal and year-to-year lacustrine dynamics. However, when it comes to long-term dynamic changes, it is difficult to comprehend changes, though it is possible to hypothesize how the systems of cultural features in the lake, or the so-called hydraulic works changed through the centuries in view of the archaeological survey data and historical sources. Thus, two hypothetical models of lacustrine landscape evolution are proposed here for freshwater and saline/brackish lakes (Figs. 10.12 and 10.13). The former would correspond to lakes Chalco and Xochimilco and the latter to lakes Texcoco and Xaltocan. The sparse archaeological and geoarchaeological information from Lake Zumpango, however, does not permit placing it in any of the models, though most probably it would fit in the saline-brackish lacustrine one. In essence, the proposed hypothetical models exemplify centennial, decadal, and seasonal lacustrine changes, with the addition cultural features (i.e., tlateles, chinampas, canals, dikes, etc.). Like the individual models of lacustrine cultural features, these are heuristic models, meaning to show a hypothetical development of the pre-Hispanic lacustrine landscape, subject to testing with archaeological, historical, ethnographic, and possibly experimental data.
10.3.2 Processes of Cultural Development and Control of Freshwater Lakes The logical development from a marshy or highly vegetated shallow lake to the widespread settlement and development of agriculture in the lake is shown in Fig. 10.12. The model here represents changes in a sequence of four different time snapshots but is not linked to a particular period of the archaeological chronology. The sequential representation serves only to portray the development of cultural features in the freshwater lakes of the Basin of Mexico. Likewise, spaces do not represent exact locations or configurations of the lakes in question, but they intend to be an illustrative model of changes in lakes Xochimilco and Chalco. As suggested by the pattern and type of pre-Aztec sites, including those in preceramic and early ceramic sites, Chalco and Xochimilco may have been shallow freshwater lakes with vast vegetated areas. The earliest aquatic settlements occupied key areas for seasonal settlement including preexisting promontories or areas of dense aquatic vegetation (Fig. 10.13a), which later may have served sites where tlateles were built. The idea proposed by Niederberger (1979) that some form of wetland agriculture existed should be applied to some areas given that these lakes
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Fig. 10.12 Hypothetical sequential model of freshwater lake reclamation
had much less seasonal fluctuation than the other lakes of the Basin. If so, many such localities could have existed along certain shores near the settlements or springs (Fig. 10.13b). At some point, occupation of the lake by building settlements
10.3 Processes of Lacustrine Appropriation and Control
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5 6 7 Salt procuremenet station 1 2 3 4 Seasonal settlement 1 Stable land, not f looded by lake Permanent small 2 Flooded by lake in extreme events settlement 3 Seasonally f looded lakebed Large settlement or 4 Streams regional center 5 Freshwater or low salinity waters 6 Permanently wet lakebed Urban center 7 Open lake area
Fig. 10.13 Hypothetical sequence of reclamation and management of brackish and saline lakes
and early chinampas and the need for navigation for trade may have contributed to reducing the vegetated surfaces, thus making room for open lake areas (Fig. 10.13c). Subsequently, the connection of islands through causeway dikes may have
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facilitated the growth of towns and the control of water flows, thus providing more stable conditions for the expansion of chinampa agriculture (Fig. 10.3d). Along with this development, the deepening and integration of navigation canals or type 1 canals (Fig. 10.5) would have resulted in the complex system found by the Spanish in the early 1500s.
10.3.3 Processes of Cultural Development and Control of Saline Lakes Given the condition of high salinity and alkalinity, saline lakes likely had different phases of development as represented in the illustrative model of Fig. 10.13. Although the model aims to represent processes of change in Lake Texcoco, it may apply at least to some parts of Lake Xaltocan. The idea is the use of freshwater sources mainly from springs and rivers for the development of the lake, which implies control of the flows of water. The archaeological record attests to occupations in the saline lakes by hunters, fisherfolk, and salt-makers, in many cases on tlateles (Fig. 10.13a). Whether by population pressure or other environmental changes, these lakes had many attractions despite their salinity. Low water levels would change this colonization as sources of freshwater and vegetation would vary (Fig. 10.13b). As proposed by Palerm (1973), water compartments were essential for the use of fresh water inside the lake (see Sect. 10.3.3), including compartments on the shore (C1) and inside the lake (C2 and C3) (Fig. 10.13b, c). It is likely that bordos were used to redirect water from streams and springs to compartments, which would have been the first step in establishing chinampas on the lakeshore or around springs (Fig. 10.3c). At an advanced state, construction of dikes and aqueducts permitted the system to evolve rapidly into the complex network the Spanish found in the early 1500s (Fig. 10.3d). The management of fresh water in saline and brackish lakes is an important key to their use and resulted in lacustrine communities dedicated to both aquatic agriculture and salt extraction and processing at the same time. The only documented case of the management of fresh water in saline lakes for agriculture in the Basin of Mexico is associated with the chinampa fields in Lake Xaltocan (Fig. 9.15), purportedly connected to the Ozumbilla spring and canal (Morehart and Frederick 2014). The supply of fresh water for the chinampas of Iztapalapa and Tenochtitlan remains in question that Palerm (1973) tried to answer by proposing the water compartments (compartimentos) explanation (see Sect. 10.3.4). However, as the model shows, the sources of water varied, including incoming streams, springs, and flow of freshwater from the southern lakes (Fig. 10.13). Certainly, the notable difference between the developments of freshwater and saline/brackish lacustrine systems lies in the availability of fresh water and vegetation. Interestingly, fresh water in the southern lakes would have been available in the lake and springs, whereas in Texcoco and the northern lakes, it would have been
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from streams and, to a lesser extent, from springs. The combination of agriculture with other activities (fishing, hunting, and harvesting flora, salt, and minerals) would have been different in the two models and influential in their development.
10.3.4 Water Compartments in the Agricultural Development of Saline and Brackish Lakes The idea of having chinampas in saline lakes or swamps has already been discussed by Palerm (1973), particularly in reference to Tenochtitlan and Iztapalapa. In the case of the latter, he envisioned the possibility of chinampas in the lakebed area north of the Cerro de la Estrella with the use of a protective dike and a source of fresh water. According to him, the dike that protected the chinampas was the same one reported in the chronicles of the conquest as being broken to deter the attack of the Spanish on the Iztapalapa lacustrine settlements (see Chap. 14). As for the source of fresh water, Palerm (1973) thought of canal bringing fresh water from the southern lakes or from springs. Regardless of the origin of the freshwater, Palerm (1973) referred to the possibility of compartimientos estanco (water compartments) that permitted draining an area of its saline water and replacing it with fresh water. For that, however, some form of bordos or dikes with sluices would have been necessary. Modern versions of such compartments without chinampas were still seen in the twentieth century in the area of Lake Texcoco near the mouth of the San Juan Teotihuacan River (Fig. 3.16). Based on the three types of chinampa settings described in this chapter and using the schematic representation of the cultural features on a saline lake, three types of watertight compartments can be hypothesized (Fig. 10.13c, d). The C1-type compartment, perhaps the best explanation for the inland and lakeshore chinampas, certainly would have involved the construction of bordos to either retain water or protect crops from flooding by saline water. This type of management exists in some way in the area south of Lake Zumpango today, where raised fields are flooded with fresh water to remove salts (see Reséndiz-Paz et al. 2013). In essence, this scheme of agriculture and irrigation would correspond to the inland or lakeshore chinampas (see Fig. 10.9b, c). The C2-type water compartment may be associated with the more complex flooding of compartments when the incoming fresh water swelled the lake. These compartments would be more appropriate for in-lake chinampas, but under a complex set of canals and dikes (see Fig. 10.4d). In contrast, the more localized compartments in the middle of a lake may also be associated with local sources such as springs (Fig. 10.3d). Water compartments may have been only part of the process, as other aspects for building and maintaining chinampas were necessary. Hypothetically, chinampas could have been built using salt-free organic silt and plants (céspedes) brought from
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elsewhere and built at a certain elevation above the possible capillary migration of salts. Thus, the water would have to have been replaced before contamination from salts from the ground. Although no descriptions exist on watertight compartments proposed by Angel Palerm, it is evident that no other solution would have been viable to maintain chinampas in saline lakes. The Iztapalapa and Xaltocan chinampas depended on an influx of freshwater brought in through canals; however, the case of Tenochtitlan is more complicated and should be understood in the context of the development of the city from its foundation, a matter of further discussion in Chap. 13.
Part III
Lacustrine Systems in the Evolution of Civilization
Chapter 11
From the Upper Pleistocene to the Agricultural Beginnings
11.1 The Lakes Through the Upper Pleistocene and Holocene 11.1.1 The Lakes Before the Appearance of Humans in the Basin Although this chapter focuses on the interaction between early human groups and the lakes, it is important to go farther back into the Upper Pleistocene (starting c. 130,000 years BP). Thus, although the evolution of the lacustrine landscapes during this early period may not be of interest to most archaeologists, it provides an environmental background for understanding the changes that the Basin’s lakes underwent to become attractive to humans. In other words, the geological background of earlier periods helps understand the landscape that the earliest human groups found and used for survival. Thus far, only Lake Chalco has paleolimnological records covering the entire Upper Pleistocene and Holocene (Figs. 6.6 and 6.7). Records from lakes Xochimilco and Texcoco provide shorter, more fragmented records, at least for the Terminal Pleistocene and Holocene (Fig. 6.3). Furthermore, associated with these records or not, pollen data cover at least the past 40 ka, which adds some information on environmental change around the lakes. Although these records were introduced in Chap. 6, their interpretation is summarized in the next section based on marine isotopic stages.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5_11
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11.1.2 From MIS 6 to MIS 2 The period between the end of the MIS 6 and the beginning of MIS 2 spans about 100 years, during which the world experienced an interglacial (MIS 5) and glacial (MIS 4) and an interstadial (MIS 3) period. As discussed in Chap. 6, high summer and/or spring insolation in combination with high seasonality influenced alkalinity, salinity, and evaporation from the basins. Thus, during glacials and stadials (MIS 6, MIS 5.4, 5.2, and MIS), Lake Chalco experienced conditions of fresh water and low evaporation, resulting most likely in relatively high lake levels. In contrast, during interglacials and interstadials (MIS 5.5, 5.3, 5.1, and MIS 3) the lake’s water experienced high salinity and alkalinity. As seen in more recent records, high evaporation (i.e., high Ca/Ti ratio) meant low lake levels, as seen through the terminal Pleistocene and Holocene (i.e., MIS 1). Unfortunately, there are no pollen records yet for periods previous to 40 ka, though charred particles in sediments going back to MIS 6 show that periods of higher fire incidence coincide with warm periods, during which there were more vegetation and fuel, higher temperatures, and more seasonal climates (Ortega- Guerrero et al. 2020). Volcanic eruptions, however, were probably conducive to disruptions of vegetation and changes in sedimentation in the lakes, though this is visible only at shorter time scales (Ortega-Guerrero et al. 2020). During the last part of MIS 3, roughly 40 to 26 ka, Lake Chalco experienced high variability in salinity and alkalinity, and a sudden change to freshwater conditions lasting from 26 to 15 ka, coinciding with a drop in temperature and occasional, but short increases in precipitation (Fig. 6.6). Coinciding with this trend and despite the lower time resolution in the record, Lake Texcoco shows conditions of deeper waters between c. 27 and 17 ka (Bradbury 1989) (Fig. 6.2). These deeper conditions appear to coincide with the accumulation of clay after the deposition of the Tlahuac Tephra in some of the sequences (Figs. 5.1 and 5.2). In the pollen record of Lake Texcoco, the MIS 3-MIS 2 transition appears as a decline in arboreal taxa, suggesting cooling and drying, while local aquatic pollen and spores point to high lake levels (Lozano-García and Ortega-Guerrero 1998), which is consistent with the diatom record (see Bradbury 1989). This seems to parallel the reconstructed mean annual precipitation anomalies in Lake Chalco (Fig. 6.6).
11.1.3 The Last Glacial Maximum The last glacial maximum (LGM) is the period established by the lowest global sea level stand and the maximum extent of the glaciers, coinciding with the period 26.5–19 ka and caused by a minimum of summer insolation in the Northern Hemisphere (Clark et al. 2009). At the latitude of the Basin of Mexico, summer insolation and seasonality were at their lowest, while spring insolation was slowly
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rising (Fig. 6.6). The low temperatures associated with the low insolation meant low evaporation rates, which preserved the lakes despite the low precipitation. In turn, salinity, alkalinity, and dissolved solids were maintained at a low level through most of the LGM in Lake Chalco (Caballero et al. 2019) (Fig. 6.6). Despite the global cooling, low precipitation meant that glaciers did not develop in the mountains surrounding the Basin of Mexico except at the end of the LGM, c. 20–19 ka, when the Hueyatlaco-1 glacial advance formed on the slopes of Iztaccihuatl (Vázquez-Selem and Heine 2011). This advance coincided with an increase in precipitation while temperatures were still low (see Fig. 6.6). In stratigraphic profiles from Lake Texcoco, green clay accumulation seems to be substantial and uninterrupted above the Tlahuac Tephra until perhaps 20 ka (see Lozano-García and Ortega Guerrero 1998; Bradbury 1989) (Fig. 5.1a). At the Patos section, magnetic susceptibility through the package of lacustrine clays, which encompasses 1.80 m, hardly changes, suggesting a very stable and steady deposition (Fig. 5.2). Concurrently, diatom records from various cores indicate that for the most part, Lake Texcoco had moderate and stable levels (Bradbury 1989). Although dating has low resolution in the pollen record from Lake Texcoco, taxa identified through the LGM suggest cold and dry conditions (Lozano-García and Ortega-Guerrero 1998). Pollen zones C1 and C2 roughly correspond to the LGM, during which Pinus was relatively abundant, but not other arboreal species (e.g., Alnus, Quercus, and Cuppressaceae); the incidence of local aquatic vegetation was low, suggesting that lakes were larger and probably deeper (Fig. 6.8). Information on human presence in the Basin during this period is scarce, except for evidence from Tlapacoya with dates between 22,000 and 20,000 year BP (Lorenzo and Mirambell 1986b). Despite the cold and dry conditions, the relatively enhanced and stable lakes may have provided resources that attracted fauna and subsequently human hunters. Unfortunately, the poor dating of paleontological remains does not permit assessing the relative of megafauna through the phases of the LGM.
11.1.4 The Deglaciation and the Younger Dryas The global warming trend that followed the LGM, beginning around 19 ka, was driven by an increase in summer insolation in the northern hemisphere (Clark et al. 2012). This trend occurred with high variability in successions of warming and cooling periods that triggered the melting of the world’s ice caps and that continued until the onset of the Holocene with cold spells, such as the Heinrich event 1 and the Younger Dryas (YD), and warm periods, of which the most prominent was the Bølling-Allerød (BA). During these periods, the lakes of the Basin underwent changes inflicted by the variations in temperature and precipitation at a time when volcanic activity also intensified (Ortega-Guerrero et al. 2017, 2018a). Indirectly, the climatic changes associated with these periods altered vegetation and the stability of slopes around the lakes, thus influencing patterns of sedimentation
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(Ortega-Guerrero et al. 2015, 2018a). Likewise, salinity and temperatures were highly variable during this period (Caballero et al. 2019) (Fig. 6.6). Through the deglaciation period, lake levels seem to have been low for the most part, with some extreme low periods particularly toward the transition to the Holocene (Figs. 6.6 and 6.8). The eruptive activity seems to have been concentrated between the major events that created the Tutti-Frutti and Upper Toluca Pumice, with several tephras originating from eruptions in Chichnautzin volcanic field (Fig. 6.1b). The Tutti-Frutti eruption, which originated in Popocatepetl, devastated the slopes draining from the east into the lakes (Siebe and Macias 2004) and left its tephra distributed over large portions of the lacustrine basins. The Upper Toluca Pumice, though originating in the Nevado de Toluca outside the Basin, also had a widespread impact across the Basin of Mexico (Siebe et al. 1999). Despite the high climatic variability and recurrent volcanic activity, megafauna became very prominent in the Basin, according to dated remains as well as those that by their stratigraphic position can be assigned to this period (see Sect. 11.2.1). However, their numbers decline to finally disappear during Younger Dryas, not only in the Basin of Mexico but also in all North America. Humans seem to have adapted well to the highly variable landscape and resource availability. Although archaeological evidence of their presence is scarce, it seems that the highest numbers of remains are relatively more abundant during the Pleistocene-Holocene transition (Sect. 11.2.2). Ironically, this is the time when records show the lowest lake levels and high salinity (Figs. 6.3, 6.4, and 6.6). Perhaps, then, certain strategies permitted bands of hunters to exploit a broad range of resources, using lake resources only during certain season.
11.1.5 Early and Middle Holocene Environments Paleolimnological data from early Holocene lacustrine deposits points to increasing alkalinity and salinity and low levels in Lake Texcoco and the southern lakes (Caballero et al. 2019; Bradbury 1989). Despite relatively higher amounts of annual precipitation compared to the previous millennia, high temperatures and high seasonality led to higher evaporation (Caballero et al. 2019; Ortega-Guerrero et al. 2018a) (Figs. 6.5 and 6.6). Consequently, the hydrological balance of the lakes was negative, leading to extreme low water levels and high concentrations of salt and minerals in sediments. Despite the dry hydrological conditions, springs in the southern lakes may have compensated for most of the loss by evaporation, but the situation was different in Lake Texcoco, where diatom data indicate that large parts of the lake may have disappeared (Bradbury 1989) (Fig. 6.4). At Tepexpan, the lacustrine and palustrine deposits accumulated during the deglaciation were succeeded in the Holocene by gleyic soil horizons (Sedov et al. 2010), which provide evidence that the permanent cover of water had retreated. Elsewhere in the basin of Lake Texoco, there seems to
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have been no deposition during this period, which explains the hiatuses in many stratigraphic sections during the early Holocene (e.g., Figs. 5.1a, 5.2, and 5.3). The explanation for the hiatuses corresponds with no deposition in the absence of a lake and the removal of exposed sediments by erosion (see Sect. 5.2.2). Pedo-sedimentary sequences from Tlapacoya also suggest that during this period, a considerable lowering of the levels of Lake Chalco occurred, with palustrine environments being replaced by colluvial deposits (Limbrey 1986; Niederberger 1976). During this period of relative dryness in the lake, pollen data show contrasting results regarding moisture (Fig. 6.8). Some pollen records show a rather dry trend (Bradbury 1989; González-Quintero 1986) in the basins, while others point to an increase in trees in the mountains, where diverse forests and moisture-requiring species thrived on the highest slopes of the mountains (see Lozano-García et al. 2019). This improvement of moisture in the mountains may have been the result of higher precipitation due to orographic effects and relatively lower temperatures at high elevations. Lake levels did not recover until the middle Holocene, at which time most data, palynological and paleolimnological, suggest an improvement in the lacustrine realm that also coincided with an increasing human presence on the lakeshores (Acosta-Ochoa et al. 2021; González-Quintero 1986). (See the discussion and concrete examples in Sect. 11.3.) Thus, conditions began to improve around 7000 years BP according to most of the records, resulting in more freshwater conditions in the southern lakes (Caballero et al. 2019; Ortega-Guerrero et al. 2018a) and a larger Lake Texcoco (Bradbury 1989). Therefore, environmental conditions became more attractive for habitation and early practicing of plant harvesting and cultivation and the procuring of aquatic and terrestrial resources (see Sect. 11.3).
11.2 Lakes, Megafauna, and Early Humans in the Basin 11.2.1 Megafaunal Sites Although the Pleistocene megafaunal record in the Basin is vast and rich, many findings lack absolute dates, and those found before the second half of the twentieth century lack proper stratigraphic provenience (Lorenzo and Mirambell 1986b). In recent decades, findings have been systematically recorded under the aegis of salvage archaeology (Carballal-Staedtler 2007), thus providing stratigraphic and paleoenvironmental context where animals lived and died. Interestingly, most Pleistocene megafaunal findings tend to be largely concentrated in the lacustrine realm, particularly in the basins of lakes Texcoco and Xaltocan (Fig. 11.1). The Columbia mammoths are the most common among the species of mammals in numbers in findings, though other mammal species such as horse, bison, camel, and large felines appear occasionally (Corona et al. 2020; Carballal-Staedtler 2007; Arroyo-Cabrales et al. 2006; Morett-Alatorre et al. 2003;
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Lake Texcoco
1 Santa Isabel Iztapan I 2 Santa Isabel Iztapan II 3 S. Bartolo Atepehuacan 4 Talisman metro station 5 Chiconcuac 6 Lago de Texcoco 7 Tocuila 8 Chimalhuacan Atenco 9 Huatepec 10 Los Reyes La Paz 1 11 Los Reyes La Paz 2 12 Santa Marta Acatitla 13 Iztapalapa 14 Coyoacan 15 Colonia del Valle 16 Tacubaya metro station 17 San Joaquín metro sta. 18 Tezoyuca metro sta. 19 El Rosario 20 Ticomán 21 Potrero 22 Gertrudis Gutiérrez 23 Aviación 24 Amplicación Linea 1
25
-(various)-FL-S-N
Northern Lakes
-(?)-BV-N -(1.0-2.40)-B-S-N
31
1 -(2.0)-B-N-
-(1.75-2.5)-B-N-
2
+
9
22
-(18.0)-F-N
16
5
15 14
23 24
-(0.9-1.15)-M-N
-(1.66-2.32)-BS-N -(18.0-19.0)-F-N
13
-(0.4-1.25)-B-N
+ -(0.75-1.25)-B-O-
8
-(3.6)-B-N
-(13.2-21.2)-F-N -(15)-F-N
-(2.5)-BV-N
12
-(1.25)-BS-N
Association with humans Lithics
10 11
Worked bone
-(1.75-3.0)-S-N
33 Tlapacoya 34 Xico 35 Xico East
-(1.0-2.5)-M-S-V-
Fauna
-(7-7.5)-D-N -(1.5-3.0)-DV-P
7
-(15.0)-F-N
-(3.35)-FFLLake Texcoco 19 -(0.9)-B-N 18 21 -(1.4-2)-B/O-N 4 6 -(3.5-6.0)-B-N -(2.75-3.25)-M-N
17
-(2.0-3.0)-S-N
3
Southern Lakes
1
-(various)-BFLS-N
-(1.5-3.0)-B-FL-O-I
B - Lacustrine bentonitic clay O - Other lacustrine facies M - Marsh S - Shoreline deposits FL - Fluvio-lacustrine F - Fluvial D- Mudflows and debris flows V - Lahar and volcanic ash deposits C- Colluvial deposits 20
Other fauna: Bison Camel Horse Feline Ground sloth Glyptodon + Avian fauna Crane eggs Fish
+
L. Xaltocan
Depositional environment in which remains were found 30
-(5.4-7.0)-F-B-N
-(1.2-2.6)-B-
32
28
29
-(1.4-2.3)-B-N -(2.10-2.6)-B-
27 26
L. Zumpango
25 Los Reyes Acozac 26 Santa Lucia I 27 Santa Lucia II 28 Nextlalpan various 29 Tultepec San Pablo 30 Coacalco 31 Ecatepec various 32 Santa Lucia AIFA
Site number
Mammoths: Multiple individuals Isolated individuals Sparse remains
N
KEY Depositional environment
-(1.8-2.5)-B-
Depth range in meters Association with humans
Lake Xochimilco
34
35
Lake Chalco
33
P Post-mortem utilization I Inferred N None
-(?)-? -(>1.5)-V-C-N 0
5
10
kilometers
Fig. 11.1 Pleistocene megafauna localities in the lacustrine realm of the Basin of Mexico. Compiled by the author from sources cited in the text
Morett-Alatorre 2001; Carballal-Staedtler et al. 1997; Lorenzo and Mirambell 1986a) (Fig. 11.1). Remains of birds, fish, and fragments of eggs appear preserved in certain sedimentary contexts (Carballal-Staedtler 2007; Morett-Alatorre 2001). Additionally, although not included in the map of Fig. 11.1, mollusks, bivalves, and other invertebrates can be added to the list of faunal remains of the Pleistocene lakes (Cano-Santana et al. 2016). Megafaunal concentrations appear to be close to springs and river mouths, probably former deltaic complexes. The area of Santa Lucia in the northwestern part of Lake Xaltocan seems to be close to the former mouth and delta of the Avenidas de Pachuca River (Fig. 11.1). The sandy ground of the Xaltenco area (Fig. 5.10) may have acted as a sponge and aquifer that would have sustained the flow of water in
11.2 Lakes, Megafauna, and Early Humans in the Basin
257
springs around the lake, thus creating spots of fresh water and vegetation. A similar environment may have existed on the western shore of the lake at the localities of Tultepec I and Tultepec II, where the Cuautitlan River may have created a deltaic system with swamps. On the northeastern shore of Lake Texcoco, the area of Tepexpan and Santa Isabel Iztapan may also be associated with the deltaic system formed by the San Juan Teotihuacan River, with similar sites along the shore, including the Tocuila mammoth site (Fig. 11.1). Springs may also have been important places for megafauna to congregate, which explains findings along the southern shore of Lake Texcoco, at the base of the Sierra de Santa Catarina and the Cerro de Chimalhuacan. Evidence of human association with megafauna is limited to a few findings, some of which are still not convincing to many archaeologists. The strongest case for human hunting of mammoths comes from the Santa Isabel Iztapan site where series of tools was found in direct association with the killing and butchering of mammoths (Aveleyra-Arroyo de Anda and Maldonado-Koerdell 1953; Aveleyra- Arroyo de Anda 1956). More recently, mammoth findings in what appear to be hunting traps have been reported from Tultepec west of Lake Xaltocan (Corona et al. 2020), though the association still casts doubt among many archaoelogists. In other cases, remains are associated with cultural deposits as is the case of bone fragments found in Tlapacoya (Lorenzo and Mirambell 1986b), suggesting possible hunting or scavenging of bones. Postmortem utilization of bones appears to have been the case in other localities, particularly at Tocuila (Morett-Alatorre 2021; Arroyo-Cabrales et al. 2006) (Fig. 11.1, number 7). The association between mammoth findings and sedimentary depositional environments shows interesting patterns. The first one is of mammoths stranded in the highly plastic bentonitic clay, a pattern that is persistent in all the findings in Santa Lucia, Santa Isabel Iztapan, Chimalhuacan, and the center of Lake Texcoco, among other localities (Fig. 11.1). The stranding of the mammoths at Santa Isabel Iztapan, has been seen as an opportunity for hunters, as shown in the display at the National Museum of Anthropology. Another recurrent pattern appears when mammoth remains are found embedded in alluvial deposits, which is highly common along the western shore of Lake Texcoco, especially in the area of Azcapotzalco and Tacuba (Fig. 11.1). The Chiconcuac mammoth also represents association with an alluvial environment (Fig. 5.14). The third and less common pattern is the trapping of mammoths in deposits of sudden catastrophic events such as mudflows and lahars, as in the case of the Tocuila mammoth (González et al. 2014; Morett-Alatorre 2004; Siebe et al. 1999) or in pyroclastic deposits like the Milpa Alta mammoth (Guilbaud et al. 2015). Incidentally, Pleistocene large megafauna findings are virtually absent in and around the southern lakes, despite fragments found in Tlapacoya and remains reported from Xico (Fig. 11.1). The Santa Ana Tlacotenco mammoth that died trapped in volcanic ash (see Guilbaud et al. 2015) is the only significant finding in the southern part of the Basin, but its location is far from the lakeshore (not on the map in Fig. 11.1).
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11 From the Upper Pleistocene to the Agricultural Beginnings
There is no clear explanation for this virtual absence of faunal remains in the basins of the southern lakes. While water and sediment chemistry such as low pH could have been detrimental to preservation of bone, though paleolimnological records do not indicate an acid environment (see Ortega-Guerrero et al. 2018a; Caballero and Ortega-Guerrero 1998; Bradbury 1989). One possible clue to the lack of remains in this area lies in the fact that large numbers of animals, especially mammoths, in the other lakes seem to have died while stranded in the bentonitic clay (jaboncillo), which is practically absent in the southern lakes. But beyond these taphonomic reasons, it is possible that paleoenvironmental conditions in the southern lakes may not have been attractive to mammoths and other fauna, though this is more difficult to believe as abundant aquatic flora and freshwater environments seem more than ideal for large grazers. However, beyond possible original causes for the lack or scarcity of megafaunal remains in the southern lakes, one must consider that many findings in the Basin are associated with construction projects. Notably the area of Mexico City, and particularly the areas of the subway lines, and the construction of airport installations in Santa Lucia have produced the largest number of findings (Fig. 11.1). In contrast, the southern lakes have remained more of a rural area, outside the reach of megaprojects and subway lines. Nevertheless, in the Texcoco area, for the most part a rural realm, many remains have appeared in small local constructions of wells and other small diggings. Therefore, an explanation for the scarcity or lack of findings in the southern basins deserves a focused study.
11.2.2 Pleistocene Human Occupations in the Basin of Mexico The prime question regarding Pleistocene human-environmental interactions in the American continent is “When did the first humans arrive?” For a very long time, the Clovis-First paradigm, which dated human presence in the continent as early as c. 13,000 years BP, was accepted; however, this paradigm collapsed when numerous sites across the continent provided earlier dates (Gruhn 2020; Acosta-Ochoa 2016; Sánchez 2016). In Mexico, human tools and activity areas in sites such as Tlapacoya in Lake Chalco (Lorenzo and Mirambell 1986b) and El Cedral in San Luis Potosi (Lorenzo and Mirambell 1999) have produced dates older than 20,000 years before the present. More recently, a study in Chalchihuite Cave in northern Mexico provided a set of dates suggesting human presence c. 26,500 year BP (Ardelean et al. 2020), an early date but not unique among the findings in South America (Gruhn 2020). In the Basin of Mexico, outside the Tlapacoya site, evidence of Pleistocene human occupation is scarce and fragmentary. In many cases, human presence appears in the form of artifacts associated with megafauna (Fig. 11.1). For a long time, out-of-context stone tools have been recovered from many localities (see Lorenzo 1967; Aveleyra Arroyo de Anda 1950). Nonetheless, a focused research program to search for Pleistocene occupations has not been implemented; thus,
11.2 Lakes, Megafauna, and Early Humans in the Basin
259
these findings are mainly fortuitous. Most archaeological surveys have focused only on ceramic sites, an aspect that reduced the possibility of recovering sites of the lithic period (Parsons 2015). Still the multidisciplinary study of Tlapacoya (Lorenzo and Mirambell 1986b) and the numerous findings associated with mammoths, notably Santa Isabel Ixtapan, Tepexpan, San Pablo Atepehuacan, Santa Maria Aztahuacan, and Tultepec (Fig. 11.1), provide a testimony of human presence at least during the terminal Pleistocene. These findings as well as the human remains dating to the Pleistocene- Holocene transition are not only the basis for our understanding of the human relations with the environments of the Basin of Mexico but also a clue that should permit us a systematic search for sites in the non-urbanized parts of the Basin.
11.2.3 Preceramic Human Remains and Sites Concurrent with the location of megafaunal remains, most sites with tools, activity areas, and human remains of the preceramic period (Pleistocene and Holocene) are in the lacustrine realm of the Basin (Fig. 11.2). The apparent concentration of sites and human remains in Lake Texcoco (Fig. 11.2) may suggest particular focus on the lake, although this may be also the case of fortuitous findings due to urban development, as it may occur with megafaunal remain findings, as discussed in the one above. In addition to being close to the historic lakeshores, the distribution of findings shows that recurrent pattern in their location occurs near or within areas of springs. Alternatively, findings have been also preserved embedded in travertine, as the case of those from El Peñon, or buried under alluvium, as the case of Chicoloapan and Texcoco. Others appear associated under calcretes as is the case of Tepexpan, Tocuila and Balderas; tephras, as is the case of San Gregorio and some findings in Tlapacoya; palustrine deposits with influx of alluvium, as is the case of Santa Isabel Iztapan, or in some cases colluvial deposits as some findings in Tlapacoya. Unfortunately, for some findings there is no detailed provenience, as for many of the megafaunal remains cited in the previous section. Although of the several humans remains findings have no proper stratigraphic provenience, some have been directly dated, resulting in their being some of the oldest human remains in Mexico (González et al. 2003). By far the oldest dated human remains in the Basin of Mexico are El Peñón Woman III (10,755 + 30 14C year BP, OxA-10,112), the Metro Balderas Man (10,500 year BP, by tephra), the Chimalhuacan Man (10,500 14C year BP, by tephra), and the Tlapacoya I Man (10,200 + 65 14C year BP, OxA-10,225) (González et al. 2003, 2015; Jiménez-Lopez et al. 2006). Much younger, but still during the Pleistocene-Holocene transition, are the remains of Astahuacan “10,300 + 600 BP” (cited as Berger and Potsch, 1989, by Hernández-Flores and Serrano-Sánchez 2017: 124). The Metro Balderas and Chimalhuacan human remains seem to be contemporaneous, as both are associated with the UTP tephra, which provides their relative ages (González et al. 2015).
260
11 From the Upper Pleistocene to the Agricultural Beginnings
Preceramic localities
N L. Zumpango
Tultepec
Terminal Pleistocene sites Human remains + Megafaunal sites with signs of human presence
Los Reyes Acozac +
Early-middle Holocene sites With human remains With no human remains
L. Xaltocan
+
Main streams
No stratigraphic context, no provenience, and/or no clear evidence
(?)
Tepexpan
Artificial channels of main streams Inferred old channels Inferred mean extension of Holocene lakes.
+
Santa Isabel Iztapan
+
+ Tocuila + San Bartolo Atepehuacan
Lake Mexico-Texcoco Texcoco Metro Balderas
Peñon III Peñon I, II, IV (?) Chimalhuacan
Peñon del Marqués & Santa Marta Acatitla (?)
Chicoloapan
+
Los Reyes-La Paz El Arenal, Nezahualcoyotl (?)
Santa Maria Aztahuacan (?)
San Gregorio Atlapulco Tlahuac
Zohapilco Tlapacoya I and XVIII
Lake Xochimilco-Chalco 0
5
10
Km
Fig. 11.2 Pleistocene and preceramic localities with human remains and dates. Compiled from Acosta-Ochoa et al. (2021), Hernández-Flores and Serrano-Sánchez (2017), McClung and Acosta- Ochoa (2015), and González et al. (2003, 2014)
11.2 Lakes, Megafauna, and Early Humans in the Basin
261
The rest of the preceramic human remains are associated with the early and middle Holocene. The early Holocene findings include the Tlapacoya II skull (9920 ± 250 14C year BP, I-6897) (Lorenzo and Mirambell 1986b) and the Tlahuac Man (8330 ± 100 14C year BP). The middle Holocene remains include the Tepexpan Man (4700 ± 200 year BP by U-Th dating) (Lamb et al. 2009) and the Chicoloapan Man (4410 + 50 14C year BP, OxA-10,111) (González et al. 2003). Dated human remains without proper provenience include those from El Peñón I (3852 + 34 14C year BP), El Peñón V (4965 + 30 14C year BP), and El Peñón del Marqués (4247 + 29 14 C year BP) (Jiménez-López et al. 2006).
11.2.4 Rock Promontories and Early Humans in the Lacustrine Realm In the southern basins, most of the findings of Pleistocene human life come from the multiple excavations around the andesitic rock promontory of Tlapacoya (Fig. 11.3). At times an island, at times a peninsula, Tlapacoya represents environment model 7 of the natural settings in the lacustrine realm (Fig. 8.11). It represented dryland surrounded by water and areas of dense aquatic vegetation, while close to other inland resources. Furthermore, the existence of a spring provided water security for temporary or permanent settlers. Excavations in the area have produced substantial information, extending from earliest humans (Pleistocene) of mobile foragers to sedentary groups practicing some form of plant cultivation to those settled in villages and using ceramics. Most of the excavations of preceramic levels at Tlapacoya took place between 1965 and 1973 (excavations I to XVIII) with results appearing in various publications, notably in the volumes by Lorenzo and Mirambell (1986b) and Niederberger (1976, 1979). Unfortunately, the rapid growth of modern urbanization in the area reduced the possibility of more research. However, in a small plot, González et al. (2015) obtained significant stratigraphic and chronological information that adds to the understanding of paleoenvironments at the site. Evidence of occupation during the last glacial maximum (LGM) is substantial in the form of hearths, burnt rocks, lithic artifacts, and several faunal remains associated with them. Interestingly, most excavations, notably trenches I, II, and IV, are cut perpendicular to the lakeshore, which permits associating lake-level changes with occupations through time. Some excavations in rock shelters (e.g., Tlapacoya IV, V, and IV, top of II) produced little evidence for the early occupations but produced relevant information for later periods. Worthy of mention is the recovery of two human skulls, the Tlapacoya I in the stratigraphic context near Tlapacoya I Beta trench and a second in trench XVIII (see the dates in Sect. 11.2.3). Both dolicocephalic skulls present morphological characteristics similar to El Peñón Woman III, suggesting the presence of humans with characteristics different from those of modern Amerindian populations (González et al. 2003).
262
11 From the Upper Pleistocene to the Agricultural Beginnings 2250
TL-III
N
2275
2300
Tlapacoya main pyramid
23 25 23 50 75
Tlapacoya Late & Terminal Formative habitational area
23
TL-XVII TL-II
2275 2300 232 5
Ayotla Early & Middle Formative site
2350
TL-IV
Zohapilco
242
24
5
00
2445.25
00
24
TL-V TL-VI TL-XIII TL-VII
Canal
0 240 5 237 0 235 5 232 300 2 75 22 0 5 22
TL-VIII TL-I
β
α
TL-XIV TL-XV
TL-X TL-XVIII TL-XI Skull TL-XII TL-IX
Mexico-Puebla toll highway GEOMORPHIC UNITS
SYMBOLS
Andesitic hill
Modern roads
Bajada, terrestrial-lacustrine transition
Modern buildings
Lacustrine plain (Lake Chalco)
Former springs
Skull
A-B-C
0
100
200
300
400
meters ARCHAEOLOGY
TL-I-XIV
INAH excavations (1965-1973) Formative sites after Blanton (1972)
A-B-C
Area studied by Gonzalez et al. (2015)
Fig. 11.3 Tlapacoya promontory with location of excavated preceramic and ceramic sites. Based on Niederberger (1976), Lorenzo and Mirambell (1986b), and González et al. (2015)
The spring deposits at el Peñón de los Baños in Lake Texcoco has produced human remains of several ages (Fig. 11.2). Unfortunately, this locality, though apparently rich in prehistoric occupations, never saw a widespread excavation project like that at Tlapacoya, as it was taken over by urban development very quickly. Another promontory, El Peñón del Marqués (Tepeapulco), produced human remains and megafauna nearby (Figs. 11.1 and 11.2), but unfortunately was also overrun by urban sprawl. Finally, the promontories Tepetzingo and Huatepec on the northeastern part of Lake Texcoco likely presented opportunities for preceramic occupations.
11.3 Preceramic Societies Around the Lakes
263
Although the locality has been important for its Postclassic occupations (Parsons 1971), exploratory work in the surrounding sediments has shown evidence of faunal remains and lakeshore deposits suggesting an attractive environment for prehistoric peoples (Morett-Alatorre 2001) (Fig. 5.9). Likewise, Cerro Tultepec in the northern lakes area may also have potential for Pleistocene occupation sites, as it is surrounded by numerous findings of megafauna and lacustrine and palustrine environments.
11.3 Preceramic Societies Around the Lakes 11.3.1 Archaeological Findings and Their Chronology Early-to-middle Holocene preceramic sites offer a picture of the transition from mobile to sedentary communities as well as the beginning of agricultural production (McClung de Tapia and Acosta-Ochoa 2015; Niederberger 1987), which occurs through the millennia comparing the so-called Protoneolithic or Middle-Late Archaic periods (Tables 2.1 and 2.2). Archaeologists in the Basin of Mexico often distinguish three phases for the middle and late Archaic of the Basin of Mexico based on a seriation from Zohapilco-Tlapacoya (Niederberger 1976, 1979). The Playa-1 phase (6000–5500 BC) and Playa-2 phase (5500–4500 BC) mark the transitional period to agriculture, and the Zohapilco phase (3000–2220 BC) denotes the establishment of cultivated plants (Niederberger 1976). Recently, however, Acosta- Ochoa et al. (2021) at San Gregorio Atlapulco found and named the Atlapulco phase (4200–3800 BC), which seems to fill in the temporal gap of no occupation in Zohapilco between the Playa II and Zohapilco phases. Other sites in the Basin, outside the excavated sites of Zohapilco and San Gregorio Atlapulco, are deemed potentially important for understanding these transitional phases. 11.3.1.1 Zohapilco The Zohapilco site is located at the eastern base of Tlapacoya where trench IV (Fig. 11.3) provided the first sequence of transition from foraging to agriculture in the Basin. The stratigraphy exposed in the trench consists of a sequence of lakeshore, lacustrine, palustrine, and colluvial sediments with some tephra layers (Fig. 5.7). Although many of the layers are sterile, conspicuous human presence in the form of artifacts and activity areas appear in some layers, classified into three occupational phases. The Playa-1 phase comprises lakeshore and peat deposits (layers 25-23) (Fig. 5.7), with numerous lithic materials and the presence of Zea mexicana, Physalis, and Amaranthus, which were probably cultivated (Niederberger 1976, 1979). The Playa-2 phase corresponds to lakeshore deposits (layers 22-21) with abundant lithic material and the remains of cultivated plants similar to those found
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11 From the Upper Pleistocene to the Agricultural Beginnings
in the previous phase. Then, a transgression represented by layer 20 and a volcanic event represented by pumitic ash in layer 19 (Fig. 5.7) mark an end to this occupation (Niederberger 1976, 1979). It is possible that this pumitic layer corresponds to the PMS (Pómez Marcadora Superior) or part of the UPCPES (Upper Preceramic Plinian Explosive Sequence) (see Table 6.1). After the volcanic event, the next occupation corresponds to the Zohapilco phase, whose remains appear layers of interbedded sand, silt, and peat (layers 17-13) (Fig. 5.7). Artifacts and biological remains of this occupation are remarkably different from those in the previous phases. Baked figurines and grinding stones as well as a series of edible plants indicate a more sedentary way of life strongly dedicated to farming (Niederberger 1979, 2000). The timing and cultural assemblage coincides with the appearance of early sedentary agricultural sites in other parts of Mesoamerica (McClung de Tapia and Acosta-Ochoa 2015). 11.3.1.2 San Gregorio Atlapulco The preceramic site of San Gregorio Atlapulco (SGA) is situated in the ejido by the same name at the locality known as El Japón and beneath an Aztec platform (Fig. 9.8). The sequence of deposits prior to the preceramic occupation includes several tephras, lacustrine lakeshore deposits, and paleosols (Fig. 11.4). The preceramic occupations proper constitute a series of artificial accumulations of earth, which are interpreted as an early form of a tlatel (Acosta-Ochoa et al. 2021). The earliest preceramic occupation corresponds to the Playa-1 and Playa-2 phases, with sparse artifacts and biological remains indicating a seasonal camp
Radiocarbon ages BP
Depth 0 cm
Cultural deposits and phases Deposits of Aztec platform
Pumice ash 5210±40 -50 cm 5435±90 6030±30 7290±30
-100 cm
Deposits with bone fragments, charcoal, and obsidian and basalt artifacts. Lower layer is more compacted Charcoal, bones, and artifacts - Atlapulco Phase
Accumulations of bones, obsidian and basalt artifacts, and organic sediments - Playa Phase
NATURAL DEPOSITS Ash with pumice and or other rock fragments -150 cm
Paleosol and/or deposit with pedogenic development Krotovina Sand with volcanic ash compacted at the bottom
-200 cm
Paleosol 8010±40 Upper Toluca Pumice Paleosol Tutti-Frutti Pumice
Sandy loam with canals and roots filled in with opaline Clay loam deposit
Fig. 11.4 Stratigraphy of the San Gregorio Atlapulco Site. (Adapted from Acosta et al. 2021)
11.3 Preceramic Societies Around the Lakes
265
(Acosta-Ochoa et al. 2021). The levels associated with the Playa-1-Playa-2 transition are characterized by a decline in artifacts and biological remains (Acosta-Ochoa et al. 2021). Micromorphological analyses of these levels suggest relative drying conditions (Rivera-González 2019), though this short trend does not appear in the paleolimnological record of Lake Xochimilco (Ortega-Guerrero et al. 2018a). Nonetheless, macroscopic and microscopic evidence of plants and artifacts indicates increased human presence again in the Playa-2 phase. The deposits in the Playa-2 phase level transition to an anthrosol, suggesting the addition of sediment to elevate the ground and a relatively higher lake level (Acosta- Ochoa et al. 2021). The cultural change seen in this higher level corresponds to the Atlapulco phase, whose deposits produce artifacts and biological remains indicating an increase in the consumption of cultivated plants. Grinding stones and materials used for constructing fishing and bird nets appear also in association with this level. The existence of floors indicating permanent occupation suggests that the community inhabiting this site during the Atlapulco phase was more sedentary and complex than that in the previous Playa phases (Acosta-Ochoa et al. 2021). This occupation coincided with increasing moisture and high lake levels and the productivity recorded in the paleolimnological record between 5100 and 4200 BC (c.7050–6150 year BP) (Ortega-Guerrero et al. 2018a). The end of the Atlapulco phase occurred with the deposition of volcanic ash (Fig. 11.4) with characteristics similar to the ash reported in layer 20 at Zohapilco (Fig. 5.7). However, research at SGA did not find the Zohapilco phase, which according to data from Tlapacoya IV occurred c. 800 years later. It seems then that the gap between the Playa-2 and Zohapilco phases may not be directly related to a lacustrine transgression, as proposed by Niederberger (1976, 1979). Therefore, the causes for the gap between the Playa and Zohapilco occupations need to be reconsidered (Acosta-Ochoa et al. 2021). 11.3.1.3 Tepexpan The human remains of the so-called Tepexpan Man were recovered from sediments west of and near the town of Tepexpan in 1947 by Helmut de Terra, who gave it a late Pleistocene age given the apparent association with extinct megafaunal remains (De Terra 1947). At the time, the finding was of immense importance in prehistoric archaeology, as they were the oldest human remains in North America. However, it was later clear that the remains were laid in an intrusion into older sediments (González et al. 2015). Radiocarbon dating produced a date around 2000 year BP, which was deemed too young because of contamination with younger material at the molecular level (see González et al. 2003). A U-Th date placed it around 4700 year BP (see Sect. 11.2.3), which put the finding closer to an age indicated by its physical characteristics (Hernández-Flores and Serrano-Sánchez 2017). Recent archaeological prospecting and excavation in the area around the Tepexpan Man finding has provided an insight into important occupations, possibly also of sedentary populations (Acosta-Ochoa et al. 2017b). A layer containing
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11 From the Upper Pleistocene to the Agricultural Beginnings
artifacts dated 5140 ± 30 14C year BP (5800 cal year BP) appears in the stratigraphy across the paleolandscape (Acosta-Ochoa et al. 2017b). The middle Holocene general environment has been identified lakeshore environment (see the discussion in Sect. 5.3.1) with shallow alkaline waters surrounded by grass-dominated landscapes (Acosta-Ochoa et al. 2017b; Lamb et al. 2009) and seasonally inundated soils (Sedov et al. 2010). Close to the south of the site is the deltaic complex of the San Juan Teotihuacan, which should have presented a mosaic of landscapes (e.g., environment 2 in Fig. 8.11), possibly attractive to fauna and human populations. 11.3.1.4 Chicoloapan The Chicoloapan human remains (known as the Chicoloapan Man) were originally found in a locality northwest of San Vicente Chicoloapan in 1955. Using obsidian hydration on artifacts associated with the finding, the remains were dated between 7000 and 5600 years BP (Romano 1965), but a radiocarbon date on the remains proper produced an age of 4410 + 50 14C year BP (González et al. 2003). Although much younger than thought, the remains are still within the preceramic period (Acosta-Ochoa et al. 2021). Excavations at the site revealed that the stratigraphic level associated with the remains was a paleosol recognized as the “Totolcingo horizon” of the old stratifraphic scheme on which several lithic artifacts and stones had been used for grinding (Aveleyra-Arroyo de Anda 1967). Pollen data from the sediments around the finding showed an increase in grass pollen (Bopp 1961), which was interpreted as a sign of early farming (Aveleyra Arroyo de Anda 1967). The location and characteristics of the sediment described in the excavation suggest that this was an alluvial plain, perhaps part of the Santa Monica River, but relatively close to the lakeshore (Fig. 11.2). 11.3.1.5 Texcoco The “Texcoco Man” site is situated in the area of the Santa-Cruz and San Felipe, south of the present channel of the San Bernardino River, near the locality of a spring now dry. The findings were reported to archaeologists working at the nearby Tequexquinahuac site when workers digging for the construction of a radio tower discovered a human skull (Morett-Alatorre et al. 2004). The skeleton was recovered and studied, but no artifacts were found in association with it, and thus far, attempts to date the remains have been unsuccessful. Almost the entire skeleton lay in a depression, possibly of a paleochannel cut into older lacustrine deposits and filled in with lakeshore and alluvial sediments (Fig. 11.5; see also Fig. 5.5). Unfortunately, the remains did not produce material for absolute dating, though the physical dolicocephalic characteristics of the skull suggest an age probably similar to those of early or Middle Holocene findings (Acosta et al. 2017b; Morett-Alatorre et al. 2004).
11.3 Preceramic Societies Around the Lakes
267
Zone III
Zone I
Plow zone Historic alluvium
Projected grave area
Zone II
1 Sand-silt laminated
Three lacustrine clay units (jaboncillo) with erosional unconformities 1 Light green 2 Dark green 3 Reddish brown
1770±30 14C yr BP 2 Alluvial fill minor pedogenic development Surface at time of burial Zone IV Tlahuac Tephra (former GCB) c. 28-31 ka
3 Alluvial fill with minor pedogenic development 4 Alluvail fill with lenses of organic sediment and basaltic ash layer
Grave
Zones I
II
1 2 3
1770±30 14C yr BP Surface at time of burial
4 III
1 2 3
IV 1 meter
Fig. 11.5 Stratigraphy of the Texcoco Man locality based on descriptions by Morett-Alatorre (2004) with modifications and interpretation by the author. A hypothesized reconstructive sequence of site formation appears in Fig. 5.5. (Photograph courtesy of Luis Morett-Alatorre)
Although more studies of the stratigraphy in this area are needed, the current information suggest that surface at the time of the burial, however, is zone 3, which is a poorly developed soil on alluvium (Fig. 5.5). Nonetheless, correlation with other profiles in the area provides a general picture of the evolution of the landscape before and after the burial of the human remains, suggesting that the deposits where the man was buried post-date the early Holocene drying of Lake Texcoco, which
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11 From the Upper Pleistocene to the Agricultural Beginnings
caused streams to erode the Pleistocene lacustrine deposits, forming a paleochannel. However, the alluvial fill of the paleochannel coincides with fluvial aggradation caused by a rise in base level as the lake levels rose, signaling the return of moisture in the middle Holocene.
11.3.2 Environmental Change and the Path to Sedentarism and Agriculture The archaeological and paleoenvironmental record for the long transition from mobile groups to sedentary agricultural communities is still scarce in the Basin of Mexico. The more detailed studies at Zohapilco and San Gregorio Atlapulco provide substantial information valid for a sequence of cultural change in the freshwater lakes of the Chalco and Xochimilco basins. On the other hand, distribution of the other sites around Lake Texcoco, and particularly the more studied one at Tepexpan, provides clue to what these changes may have been like around the saline lakes. The existing paleoclimatic and paleoecological information, though still in low resolution and fragmentary, offers a general idea of the changes that may have accompanied the process of sedentarization and agricultural implementation. Paleoclimatic records indicate that dry conditions in the early Holocene resulted in persistent low lake levels in the Chalco-Xochimilco basins with predominantly alkaline conditions, while Lake Texcoco became considerably reduced, leading to the erosion of its bed. Despite these apparently unfavorable conditions, human presence in the Basin endured. The only human remains for this period are the Tlapacoya II man and the Tlahuac Man, both of which may have used the limited resources of the reduced southern lakes. Optimal climatic and environmental conditions returned sometime before 7000 year BP, despite some sudden fluctuations. These improved climatic conditions led to a more attractive aquatic environment in southern lakes, coinciding with the development of human communities of the Playa-1 and Playa-2 phases, during which a variety of resources existed in the aquatic areas and the surrounding forests. Climatic conditions became even better after c. 6500 year BP, perhaps permitting the more permanent occupation of the Atlapulco phase in Lake Xochimilco. A mid- Holocene eruption of the Popocatepetl Volcano affected this environment, though resilience under a favorable climate catalyzed the establishment of the Zohapilco occupation at Tlapacoya, which displays signs of sedentarism and subsistence from cultivated plants. The same climatic improvement that accompanied the optimal conditions during the Playa-1 and 2 phases in the southern lakes helped also in the recovery of aquatic environments in Lake Texcoco. These conditions attracted occupants around Lake Texcoco (Tepexpan, El Peñón de los Baños, El Peñón del Marqués, Texcoco, and Chicoloapan), although it is not clear what the ways of life were as little research has been done at those sites. Occupations at Tepexpan show human presence in an
11.3 Preceramic Societies Around the Lakes
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environment rich in aquatic resources, though strong evidence of farming is still not apparent. Nonetheless, it is possible that certain early agricultural activities occurred in the alluvial areas inland. Concurrently, artifacts and pollen associated with the Chicoloapan Man suggest that cultivated plants were consumed. Very likely, the area between Chicoloapan and Tepexpan became an attractive place as the regenerated Lake Texcoco and the deltas of the incoming rivers made available a variety of biotic resources while fertile alluvial soils provided the ground for incipient agriculture.
Chapter 12
The Lakes During the Agricultural Era
12.1 Climatic Changes, Lake Levels, and Settlements 12.1.1 Millennial and Centennial Climatic Changes The long-term evolution of the lakes of the Basin of Mexico depended on many factors, among which the combined effects of precipitation and evaporation are the most relevant in the hydrological dynamics of the lakes (Figs. 8.9, 8.10, and 8.11). Unfortunately, high-resolution records of this period inside the Basin of Mexico are nonexistent, which compels researchers to draw from regional paleoclimatic data. Thus, the δ18O records from speleothems in Juxtlahuaca Cave (Lachniet et al. 2017) and those from the sediments of Lake Aljojuca (Bhattacharya et al. 2015) became the most important bases for determining atmospheric moisture changes during the ceramic period in the Basin of Mexico. Fluctuations indicated by tree-ring data reveal periods of drought, but they have only included the most recent centuries of the agricultural period, especially the historical period (e.g., Stahle et al. 2000, 2011; Therrell et al. 2006; Lachniet et al. 2012, 2017; Burns et al. 2014; Villanueva-Diaz et al. 2014, 2015). Thus, they became important proxies for climatic reconstruction at decadal and centennial scales during the past millennium. Their results convene in the descriptions of environmental changes at the temporal scale of events described in Chaps. 13 and 14. Some of the low-resolution records of the agricultural period in the Basin of Mexico include pollen records from Lakes Quila and Zempoala and the Agua El Marrano valley (see Figs. 6.2 and 6.8). Additionally, the archaeological records provide data on sedimentation and landscape stability changes, which are correlated with archaeological and cultural changes (e.g., Cordova et al. 2022; Frederick and Cordova 2019; Cordova 2017; González-Arqueros et al. 2017; Sánchez-Pérez et al. 2013; Rivera-Uria et al. 2007; Frederick et al. 2005; McClung de Tapia et al. 2003; Solleiro-Rebolledo et al. 2003). © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5_12
271
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12 The Lakes During the Agricultural Era
Colonial 1800
1600
Lakes Xaltocan and Zumpango
b
Lake Texcoco Lake Chalco-Xochimilco
c
Artificial lake desiccation
d
60 50 40 30 20 10 0 -10
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Epiclassic Early Late Toltec Classic
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Terminal Formative A.D. B.C.
Late Formative 200
Xaltocan complex Growth of Tenochtitlan urban complex
Tlatel de Tepexpan El Tepalcate Buried shoreline sites Texcoco region
Late Aztec town and chinampa complexes L. Chalco Epiclassic sites
1800
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60 50 40
1400
1200
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Postclassic Pluvial
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Multidecadal trends
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-2 0
30 20 10 0
Lake levels gradually descending from Middle Holocene moist period ending c. 3700 BC
Regional rainfall proxies -10
-8
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Inferred trends of lake-level change
Conquest Interpluvial
1800
1400
Multiple-site occupation
Tlapacoya
0 2
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Single-site occupation
?
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Early Formative
1000
Terremote Tlaltenco
Toltec-Early Aztec settlements
Conquest Aztec Pluvial
3
800
Tlatel de Tequexquinahuac
Cuicuilco
-1
f
Middle Formative 600
Sites at Zacatenco and Ticoman
Multiple salt producing tlatels
Conquest
400
Conquest
-3 -2
δ18O (z-scores)
Early Aztec
Precipitation (mm/wet season)
2000
Late Aztec
Average solar spot number
Independent
e
Collapse of Teotihuacan Xitli Eruption (range of radiocarbon dates)
Foundation of Conquest Tenochtitlan
a
-2 0
1800
1600
1400
1200
1000
800
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400
200
AD-BC
200
400
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Fig. 12.1 Paleoclimatic scheme of various proxies for lake-level changes during most of the ceramic period. (a) Archaeological chronology and important events; (b) notable sites in and around the lakes of the Basin of Mexico; (c) general, nonquantitative lake-level trends in Lake Texcoco; (d) solar spot numbers (Solanki et al. 2004); (e) moisture changes from δ18O records from speleothems in Juxtlahuaca Cave (Lachniet et al. 2017); and (d) δ18O records from sediments in Aljojuca Lake. Gray bands indicate periods with low insolation and high moisture levels in one or the both records in panels e and f
The combination of high- and low-resolution records in a chart of paleoclimatic proxies provides the background of environmental and societal changes for the ceramic period (Fig. 12.1). Thus, the correlation of paleoclimatic, geoarchaeological, and cultural data leads to the construction of general trends in lake-level changes (Fig. 12.1c). It is important, however, to emphasize that these lake-level trends mainly represent those of Lake Texcoco. Nevertheless, high or low lake levels of Lake Texcoco most likely mean high or low lake levels of the other lake basins as well (see Fig. 8.11). The isotopic records from the Juxtlahuaca Cave and Aljojuca Lake show parallel trends in moisture levels despite minor differences (Fig. 12.1e, f). One such difference is observed in the Postclassic pluvial interval recorded in Juxtlahuaca, which does not appear in the Aljojuca records. One must consider that the nature of both records is different in terms of time of response to changes and sedimentation rates. Furthermore, their location with respect to the two sources of moisture, the Pacific Ocean and the Gulf of Mexico, is also possibly a matter of consideration in some of the disagreements.
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273
Although precipitation is an important aspect in the lakes, solar radiation may have also been an important factor for the balance of moisture in the lakes, especially because of its influence on evaporation (see Sect. 8.5.1). Although no studies have addressed the influence of solar irradiance changes, it is important to consider the solar spots, which are the proxy for reconstructing the amount of radiation produced by the Sun (Fig. 12.2d). The relationship between high moisture levels in the isotopic records and low levels of solar radiation is apparent (shaded bars in Fig. 12.1), notably during the Terminal Formative, Early Classic, Early Postclassic, and Aztec pluvial periods. A similar trend appears with the hike of precipitation during the late seventeenth century and early eighteenth century. However, this complex relationship perhaps requires further study for a better explanation of a possible relationship between atmospheric and sea temperatures and their relationship with the precipitation–evaporation balance in that part of the world.
12.1.2 Trends in Atmospheric Moisture and Lake-Level Fluctuations Moisture changes through the Middle and Late Formative periods suggest that lake levels were variable but not considerably high compared to those of later periods (Fig. 12.1c). Lake levels dropped during the Late Formative period and rose considerably during the transition to the Terminal Formative period. Then, during the transition to the Classic period, the lake levels rose quickly and remained high throughout most of the period. The generally stable and fairly moist conditions of the Formative period and the exceptionally wet conditions of the Classic period saw the development of the San Pablo black soil (SPBS) of the Teotihuacan region and the S1 of the Texcoco region (Sánchez-Pérez et al. 2013; Cordova 2017). This soil was a highly valuable resource to the cultures of the Classic period, particularly in the Teotihuacan valley (Sánchez- Pérez et al. 2013). This type of soil had earlier developed in the Chalco Basin but was subsequently eroded possibly due to the relatively high population pressure of the Middle and Late Formative periods (Frederick and Cordova 2019). The notable decline of moisture levels during the Epiclassic period resulted in declining lake levels that lasted through the Early and Middle Postclassic periods, though a short moist period has been recorded in the Juxtlahuaca for the Early Postclassic period. Evidence of a dry Epiclassic period appear indirectly in alluvial records, which also provide evidence of erosion on the piedmonts and flash flood sedimentation in the alluvial plains (Cordova and Parsons 1997; Frederick and Cordova 2019; Rivera-Uria et al. 2007; González-Arqueros et al. 2017). This suggests a dry period interrupted by sudden short moist periods, during which removal of sediments occurred on the least vegetated slopes, thus creating instability in the fluvial systems downstream (Cordova 2017). In connection with this instability, massive accumulations of fluvial sediment buried the S1 (or SPBS) soil horizon as in the example of Fig. 5.13b.
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Lake levels rose rapidly through the Late Postclassic period until the time of the conquest, perhaps reaching levels similar to those in the Classic period. These high moisture levels led to high lake levels reaching a peak in the mid-fifteenth century and thereafter perhaps declining, though remaining high until the time of the conquest (see Chap. 13). The historically documented low levels through the sixteenth century coincide with a drop in precipitation, which is evident in the two records, followed by a hike caused by a sudden and short return of moisture in the early seventeenth century, also historically documented (see Chap. 14).
12.2 Volcanism and Ecological Change 12.2.1 Volcanic Events and Population in the Holocene It is impossible to talk about the evolution of lakes and civilizations in the Basin of Mexico without references to constant volcanic activity. The southern part of the Basin, in particular, occupies an area where several eruptive events during the Holocene have been registered (Siebe and Macias 2004, Fig. 7), though not all of their tephras appear in the stratigraphic records of the lacustrine basins. The exception is perhaps the Upper Preceramic Plinian Eruptive Sequence (UPCES), which seems to have been the source of the so-called Pómez Marcadora Superior (PMS) detected at several localities in Lake Chalco and Lake Texcoco (see Chap. 6). However, volcanic activity in Popocatepetl during the ceramic period has been documented (see Sect. 12.2.2). Records of volcanic activity in the Chichinauhtzin monogenic volcanic field during the early and middle Holocene include those originating from the Tlaloc, Tlacotenco, Cuauhtzin, Hijo del Cuauhtzin, Teuhtli, Ocusacayo, and Guespalapa cones (Siebe et al. 2005). However, no evidence of their direct influence on the lakes and human populations exists, despite some layers of basaltic ash in some localities (see Sect. 6.1.3). The exception is the Xitle eruption, which had an apparent sound impact on the human and natural landscapes of the southern part of the Basin (see Sect. 12.2.2). Popocatepetl, the only currently active stratovolcano in the Basin, had several phases of activity during the ceramic period with occasional maximum events explosive enough to affect a broad area. These events, nonetheless, seem to have had more effects on the northern and eastern parts of the volcano and the immediate area, especially the piedmonts (Arana-Salinas et al. 2010; Plunket and Uruñuela 2011; Siebe 2000). Thus, to this day, no evidence exists of ancient settlements affected by these eruptions in the lacustrine realm or any other part of the Basin of Mexico.
12.2 Volcanism and Ecological Change
“El Pedregal” Xitle basaltic lava flow Pre-Xitle archaeological sites
San Jerónimo
M
Modern permanent streams
275
Coyoacan
San Angel
N
COPILCO
. na R ale d ag Estadio co Olímpico
M.A. Quevdo S Superama
19º 20’
C.U. C U
Baseball park
Metro Universidad
x Cerro Zacatepetl
. Eslava R
x
x Inbursa
Estadio Azteca
Tlalpan
LAVA FIELD OBSERVATIONS Lava flow direction Reports of pillow lavas Lava flow thickness less than 2 meters
x Xitle volcanic cone
Lava flow thicker than 20 meters
0
2600
2 km
99º 10’
2700
99º 10’
Fig. 12.2 The extent of the El Pedregal lava field in relation to Cuicuilco and Copilco with the modern permanent streams for reference
12.2.2 The Xitle Eruption and Its Impact on Cuicuilco’s Surrounding Landscape The eruption of the Xitle monogenic cone in the northwestern part of the Chichinautzin monogenic volcanic field formed an extensive basaltic lava field known as El Pedregal, a notable geomorphic feature in the southwestern part of Mexico City (Fig. 12.2). Two archaeological sites partially buried by the lava, Cuicuilco and Copilco, have become the focus of various investigations since the 1920s. The preliminary results of such early studies helped formulate the idea that the devastation caused by the Xitle eruption at the very end of the Formative period
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led to a migration of population to the northern part of the Basin, specifically to the Teotihuacan valley. A radiocarbon assay from deposits below the lava provided an age estimate of 2422+/−250 14C years BP (Arnold and Libby 1951) which waas widely accepted by the archaeological community, almost thus becaming a paradigm for decades. However, a series of research projects in the 1990s and early 2000s produced a broad range of absolute dates extending across several centuries before and after that original date (Urrutia-Fucuguachi et al. 2016; Lugo-Hubp et al. 2001; González et al. 2000; Siebe 2000; Pastrana 1997; Delgado et al. 1998; Cordova et al. 1994). Many of these dates were estimated from layers below the lava, usually from archaeological contexts or from paleosols (González et al. 2000; Siebe 2000). The implication of these provenience is that in many cases, the carbon used for dating came from contexts much older than the time of the eruption or soil horizons with older carbon, resulting in dates spanning several centuries with a fourth of them postdating the first date that pointed to the eruption before the growth of Teotihuacan (Cordova 2018). The youngest radiocarbon age, however, was not obtained from deposits below the lava but from a piece of charred wood embedded in ash near the cone of the Xitle volcano, resulting in an age estimate of 1670 + 35 BP (AD 245–315) (Siebe et al. 2005). The context of this date directly points to the occurrence of the Xitle eruption much later than originally believed, practically at a time when Teotihuacan and the northern part of the Basin were populated, thus suggesting that the eruption did not cause the migration of population northward. The late date eliminates the eruption of Xitle as the main cause for the abandonment of Cuicuilco and the migration of population to the northern parts of the Basin. Therefore, alternative explanations have been formulated to account for the shift of the population (see Manzanilla 2014), though the causes for the decline of Cuicuilco during the Terminal Formative do not yet have a convincing explanation. One possible explanation for the depopulation of the south prior to the Xitle eruption may lie in the volcanic activity of other volcanoes in the Chichinautzin area and the Popocatepetl volcano (Siebe et al. 2004). Two monogenic volcanic cones of the same type as Xitle erupted near the turn of the first millennium AD. One is the Jumento monogenic cone, located about 20 km southwest of Cuicuilco, whose eruptive event has been dated back to around 2000 BP (Arce et al. 2015a, b). The other is the Chichinautzin scoria cone, located approximately 30 km southwest of Cuicuilco, whose eruptive event has been dated back to 1835 BP (Siebe et al. 2005). Although these two volcanoes and their lavas are significantly distant from Cuicuilco, their eruptions could have affected part of the mountainous hinterland of the city. Yet, no convincing evidence in the archaeological and geoarchaeological records exists to support the possible effects of pre-Xitle volcanic eruptions on Cuicuilco. Volcanic activity in the Popocatepetl does not seem to be decisive because, as mentioned above, there is no evidence of any catastrophic impact on that side of the Basin of Mexico. Despite the controversy around the dates of the eruption and the time of Cuicuilco’s decline, it is evident that the Xitle lava flows considerably altered the
12.2 Volcanism and Ecological Change
277
landscape of the southwestern part of the Basin of Mexico. The impact of the eruption on the landscape around Cuicuilco can be assessed by reconstructing the paleotopography, paleohydrology, and preeruptive surface geology of the areas covered by the lava. These reconstructions can be achieved by interpreting the morphology of the lava, its thickness and structure, and the nature of the soils and sediments below it in places where they are exposed by quarrying (Lugo-Hubp et al. 2001; Cordova et al. 1994). The surface morphology and direction of the lava flows, their thickness, and underlying sediments provide clues to the preeruptive topography and landscape. Thus, the morphology of the lava in relation to the topography of the surrounding terrain suggests that the preeruptive landscape below the lava consisted of a series of fluvial valleys terminating in a fluvial plain that transitioned into the lacustrine plain (Fig. 2.3). The surface morphology of the lava flows provides the direction and sequence of the lava flows, which occurred depending on the paleotopography of the terrain over which they moved (see Medina-Jaen and Zamorano-Orozco 2011; Delgado et al. 1998) (Fig. 12.2). Thus, the flows first moved from the cone northward until it reached the Magdalena and Eslava river valleys, at which point it turned eastward toward Lake Xochimilco. Then, the lava flows bifurcated around Cerro Zacatepec, with one toward the south reaching the area of Cuicuilco and the other toward the north continuing eastward to the lacustrine plain. Additionally, other flows that reached other valleys descending from the Sierra de la Cruces, also moved northeast toward San Angel and Coyoacan (Fig. 12.2). The areas the center of the Ciudad Universitaria (the UNAM campus) and the baseball park were only partially covered by lavas, suggesting a high pre-erutpive topographic ridge that divided the catchments that flowed into Lake Xochimilco and Lake Texcoco (Fig. 12.3). In contrast, the lowest parts of the pre-eruptive landscape were west and south of Cerro Zacatepetl, and south of Metro Universidad, where the lava thickness is up to 30 meters. Furthermore, reports of pillow lavas in quarries spread between Estadio Azteca and Inbursa (Lugo-Hubp et al. 2001; González et al. 2000; Badilla-Cruz 1977) suggest that the lava flows came in contact with water, presumably of Lake Xochimilco. Therefore, it is possible that south of the delta, an embayment or inlet (i.e., estero) extended from the lake westward almost to the area south of Cuicuilco (Fig. 12.3). This layout of natural features suggests that the Curculio site, which includes the circular structure and the complex of buildings referred to as Cuicuilco B and C, was built on a spur penetrating the lake like a peninsula. Such a convenient location would have permitted the Cuicuilco complex to be near the lake but high enough to be protected from flooding. During the construction of the Inbursa financial complex in the late 1990s, several meters of sediments were exposed to the lava (González et al. 2000; Lugo- Hubp et al. 2001; Pastrana 1997). The sediments below the lava consisted of sequences of palustrine and lacustrine sediments alternating with apparent alluvial deposits (González et al. 2000; Lugo-Hubp et al. 2001). Additionally, canals cutting through a layer of peat were interpreted as chinampas (Pastrana 2018), though no details were provided on the stratigraphy. This finding is controversial, as there is no evidence elsewhere of chinampas contemporaneous with the occupation of
278
12 The Lakes During the Agricultural Era Alluvial soils Limit between elevated land (piedmont and hills) and alluvial plains
COPILCO
Reconstructed streams
Limits of lava field
x
aleo-Ma
P
?
Paleo-E
slava (?
)
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?
Alluvial plain
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x
1
?
2
s Inbursa
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ing Spr
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Baseball park Metro Universidad
(?) gdalena
Marshes
Deltaic plain
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C.U.
Estadio Olímpico
?
Alluvial plain
4
Pre-Xitli divide between the catchments of lakes Texcoco and Xochimilco
Marshes
Coyoacan
3
Deltaic plain Marshes
Marshes Lacustrine plain (Lake Xochimilco)
Estadio Azteca
s
Marshes
s
ing
Spr 0
2
s
ing
Spr
km 1 The Cuicuilco complex occupied a spur
3 The inlet is based only on the reported pillow
2 The lake inlet (estero) extended to the south
4 This was the most prominent interfluvial ridge.
surrounded by marshes and flood plains
of Cuicuilco. It was probably fed by springs.
lavas. It could have been larger
Copilco lay on it.
Fig. 12.3 General hypothetical reconstruction of the preeruptive landscape based on geomorphic and sedimentological information
Cuicuilco. However, if the finding corresponds to some form of early chinampas, then it could have been a series of raised fields roughly corresponding to the concepts of lakeshore or inland chinampas (see Sects. 9.3.2 and 10.2.4). Furthermore, the possibility of natural stream channels cutting through peat should not be discarded. Unfortunately, given the speed at which the Inbursa financial complex was built, detailed studies of such structures were not possible. The site of Copilco, near the northern edge of the lava field, was a village built on an interfluvial ridge formed by pyroclastic flows and alluvium of the so-called Tarango formation, evident in a pit dug at the location of a former Superama supermarket (Fig. 12.3). The interfluvial ridge reached the area of the M.A. Quevedo subway station, where under the lava, detrital materials indicate a stable surface (Ibarra-Arzave et al. 2019). In summary, this area, containing either lava of relatively shallow thickness or no lava at all, has formed an interfluvial elevation that extends from the university’s baseball park, across the Olympic Stadium, the Ciudad Universitaria, and the Copilco site to the Superama, to somewhere north of the
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279
M.A. Quevedo subway station, where it reaches the alluvial plains. This surface marks the divide between the former catchments of Lake Xochimilco and Lake Texcoco (Fig. 12.3). In view of the reconstructed paleolandscape (Fig. 12.3), it seems that the environs of Cuicuilco were reminiscent of the landscapes persisting on the eastern shore of Lake Chalco, where incoming rivers formed deltas and wetlands were fed by springs surround the southern part of the lake (Fig. 7.8). Therefore, the area around Cuicuilco had prime agricultural land and a variety of resources, all of which suddenly disappeared under the lava, perhaps making resettlement difficult.
12.3 The Formative Period 12.3.1 The Lakes and the Earliest Agricultural Villages In the archaeological chronology of the Basin of Mexico, the early sedentary communities that made utilitarian ceramics constitute the initial ceramic period or the early phase of the Early Horizon (Fig. 2.1). Unfortunately, very few sites have been studied for this period. Coapexco, situated at a high elevation in the southeastern part of the Basin, and Tlatilco, on the western piedmont, were two villages corresponding to this phase (Fig. 12.4). Known sites from this period in the lacustrine realm are rare, though the ones studied at Tlapacoya (i.e., Ayotla) (Tolstoy and Paradis 1970; Niederberger 1987) provide evidence of early agricultural life in the ceramic period. It is possible that the rarity of sites of this period of the lacustrine realm and its margins may have been due to burial by recent sedimentation or destruction by erosion, not to mention possible destruction by rapid expansion of urban sprawl. Although proxy data from Lake Xochimilco show that the late preceramic period (i.e., Playas 1–2, Atlapulco, and Zohapilco) experienced a relatively moist climate (Ortega-Guerrero et al. 2018b), it is not clear whether this optimal climatic trend continued through the Early Horizon. Still, one can infer that climatic conditions during this early ceramic phase were advantageous for agriculture. Pollen records from Tlapacoya indicate substantial transformation of vegetation (González- Quintero 1986; Niederberger 1987), which is indicative of ideal climatic conditions for farming.
12.3.2 Lacustrine Settlements Through the Formative Period During the Early Formative period (c. 1500–1050 BC), villages appeared in several ecological units of the Basin of Mexico, notably some that had been occupied earlier, such as Tlatilco and Coapexco, and the site of Altica on the piedmont west of the Teotihuacan valley (Fig. 12.4a). Conspicuously, the alluvial plain is void of
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12 The Lakes During the Agricultural Era
a
N
L. Zumpango
b
N Cerro Gordo
L. Zumpango
Cerro Gordo
L. Xatlocan
L. Xatlocan Teotihuacan Valley Cerro Chiconautla
Cerro Chiconautla Altica
Cuanalan
Sierra de Guadalupe
Sierra de Guadalupe
El Arbolillo Ticoman Zacatenco Tlatilco
Azcapotzalco
Lake Texcoco
Lake Texcoco
Tx-LF-14 (Tlatel de Tequexquinahuac) Tx-LF-13
Tx-LF-15
Tx-MF-13
Cerro Chimalhuacan
Ix-EF-3
Sierra de
Cuicuilco(?)
L. Xochimilco
atarina Santa C
Ix-EF-2
Ix-LF-8,9,10 & 11 ina Ix-MF-3 ta Catar
Copilco
Tlapacoya
Ix-EF-1 (Ayotla)
Sierra de Xo-LF-1-3 Xo-MF-1
Xo-EF-1 & 2
Tlahuac strait
L. Xochimilco L. Chalco
0
5 Km
10
Sierra Chichinautzin
Coapexco
0
San
Ix-MF-4 & LF-6
Cuicuilco
5 Km
10
Tlapacoya Ix-MF-1 & LF-2
Terremote-Tlaltenco Ch-LF-54
Xico
Ch-MF-15 & CH-LF-53
L. Chalco
Sierra Chichinautzin
Ch-MF-11 & Ch-LF-51 & 52
Temamatla
Fig. 12.4 (a) Early Formative and (b) Middle and Late Formative sites in the lacustrine realm of the Basin of Mexico. Major sites outside the lacustrine area are included for reference
Early Formative sites, but such sites may have also been deeply buried below recent sediment accumulations. Sites in the lacustrine realm appear in the Chalco- Xochimilco basin, especially around Tlapacoya and the strait connecting the two lakes, i.e., the strait of Tlahuac (Fig. 12.4a). Small settlements existed on the beds of the southern lakes proper, but, in many cases, their remains are mixed with materials of later occupations (Parsons et al. 1982). During the Middle Formative period (1050–550 BC), settlements occupied several ecological units of the Basin but only few in the lacustrine and lakeshore areas (Fig. 12.4b). Tlapacoya continued growing and intensifying its use of resources and trade (Niederberger 1976). However, one site with substantial information from excavation is Terremote Tlaltenco, located on the Tlahuac strait, which continued its growth into the Late Formative period (Serra-Puche 1988; Serra-Puche and Lazcano-Arce 2009), and others are some of the areas in and around the island of Xico in Lake Chalco (García-Chávez and Vélez-Saldaña 2008; Pulido-Méndez 1993; Parsons et al. 1982; Pulido). Although Cuicuilco was in full development at this time, no sites on the lakeshore nearby have been reported. However, based on the discussion above, many such lacustrine and lakeshore sites may be concealed below the lava field. Sites proliferated on or near the lakeshore around the base of the Sierra de Guadalupe, suggesting a strong connection with the lake, such as through the use of
12.3 The Formative Period
281
salt and other resources of the lake (Tolstoy and Paradis 1970; Tolstoy et al. 1977). Similarly, sites Tx-MF-13, north of the Cerro de Chimalhuacán, and Ix-MF-3, west of the Cerro de la Estrella, were perilacustrine sites possibly dedicated to salt extraction (Blanton 1972; Parsons 1971). However, elsewhere in Lake Texcoco and the northern lakes, sites from the Middle Formative period are practically absent. If the lake levels were high, then the sites may have been located toward the perilacustrine areas, where they would have most likely been concealed under recent alluvium deposits. Unfortunately, there are no regional records of moisture for the entire Middle Formative period, though a slight increase in lake levels apparently occurred toward the end of this period (Fig. 12.1). Moreover, the increase in population at the end of the Middle Formative period in the southern lake basins suggests that this may have been a relatively wet period (Frederick and Cordova 2019; McClung 2015). During the Late Formative period (550–200 BC), the increasing population in the whole of the Basin of Mexico resulted in the settlement of more sites in several areas previously unoccupied (Manzanilla and Serra-Puche 1987; Sanders et al. 1979). In the southern lakes, the Tlahuac strait continued to be occupied as did the shores on both sides of the strait. Concurrently, more settlements appeared in the area of Xico and the Amecameca River deltaic plain (Fig. 12.4b), including the alluvial plain of the Tlalmanalco River, where brickyard digging has exposed various sites of this period (Frederick and Cordova 2019). Late Formative sites in this region are usually small, as the larger settlements, presumably regional centers like Tlapacoya, Temamatla, and Cuicuilco, stood on high lands near the lakeshores. The lacustrine economy of the Middle and Late Formative periods is well known from Terremote Tlaltenco, a cluster of tlateles (Fig. 9.3), apparently inhabited year around and devoted to the exploration of aquatic resources but with an important agricultural component (Serra-Puche 1988). The question of possible chinampa agriculture in the southern lakes is still unanswered, as no concrete evidence indicates raised fields, despite the reported case south of Cuicuilco (see Sect. 12.2.2). In general, despite the possibilities of raised-field farming, no archaeological evidence exists to confirm it (Luna-Golya 2014). Late Formative settlements in Lake Texcoco appeared in various locations, especially in the southern part of its eastern shore, where Tlatel of Tequexquinahuac is one of the sites built on a deltaic complex (Cordova et al. 2022; Parsons 1971), and along the base of the Sierra de Santa Catarina (Blanton 1972). Perilacustrine settlements of this age occupied areas around the Sierra de Guadalupe and the alluvial plains of Tlalnepantla and Azcapotzalco (Sanders et al. 1979; Castillo-Mangas 2007; Sanders and Gorenflo 2007). In the Lake Xaltocan basin, sites were concentrated along the strait of Ecatepec, the western shores, and the low areas of the Sierra de Guadalupe (see Sanders and Gorenflo 2007). Most lacustrine sites in the basins of Lakes Texcoco and Xaltocan were tlateles, many of which are classified as salt production sites (Sanders and Gorenflo 2007; Blanton 1972; Parsons 1971), though some were clearly focused on other activities as is the case of Tlatel de Tequexquinahuac (Morett-Alatorre et al. 1999).
282
12 The Lakes During the Agricultural Era
12.3.3 The Terminal Formative-Classic Transition Viewed from the Lakes During the Terminal Formative period (c. 200 BC–AD 200), settlements in the Basin began to change dramatically, culminating in a shift of sites to the northern part of the Basin and in the eventual concentration of population in Teotihuacan (Nichols 2015; Manzanilla 2014). The factor that to this day dominates archaeological discourse concerning the Formative-Classic settlement shift to the north is whether the Xitle eruption in the south affected this migration, which is questionable in view of the radiocarbon dates associated with the eruption (see Sect. 12.2.3). Consequently, the main drivers of settlements northward may lie in other factors, such as environmental or sociopolitical factors. If the volcanic factor was in play, then it may have then been secondary. If one considers possible nonvolcanic environmental factors, then climatic change is perhaps one of the most important. Sanders et al. (1979) alluded to the possibility that moister conditions made lands in the northern part of the Basin, which were on the margin of enough rainfall, more attractive. The apparent sustained increase in precipitation during the first two centuries of the first millennium AD (Fig. 12.1e) may have catalyzed the changes in a series of causality relations that invited populations to settle in the former marginal lands of the north. Such a scenario, however, may not explain the apparent depopulation of the south. However, the move to the north did not mean depopulation of the south, as sites around Lakes Xochimilco and Chalco were still present through the Terminal Formative and Classic periods (Fig. 12.5). If the Xitle eruption occurred in the Early Classic period, then obviously many areas affected by lava flows and ash fall were probably abandoned, thus making the depopulation of the area a fact. However, the eruption was not the main cause for the migration of population northward, as this process began centuries later. One aspect that one must consider when looking at populations in the lacustrine and perilacustrine areas is the fact that increased moisture levels may have raised the levels of the lakes during the early centuries of the first millennium AD (Fig. 12.1c). Under such a scenario, many sites in the lacustrine and perilacustrine areas would have been inundated, which is a possible reason for settlers seeking land elsewhere. If the areas in the north were attractive because of the sustained increase in precipitation, then they could have moved there. However, despite the evidence in the paleoclimatic and geoarchaeological records of Lake Texcoco (Fig. 12.1c), this scenario is still conjectural. Despite the claims of “depopulation” during the Terminal Formative and Classic periods, many sites in the south remained occupied in the southern lake areas (Fig. 12.5). The Tlahuac strait and the Xico area seem to have been holding populations, despite the relative regional decline in those parts of the Basin (Fig. 12.5a). Surveys show that the intensity of the remains in these sites may be less than those in previous periods (Parsons et al. 1982). Ironically, the Terminal Formative site at Xico (Ch-TF-58) occupied the island and not the surrounding bed, as it did in previous periods (Fig. 12.5a), which may be a sign that the population moved to higher ground as the lake levels rose.
283
12.3 The Formative Period a
Areas with several settlements
L. Zumpango
N
b
L. Zumpango
Cerro Gordo
L. Xatlocan
Areas with several settlements Teotihuacan urban area
Zu-Cl-82
Zu-Cl-83
Cerro Gordo
L. Xatlocan
Teotihuacan
Teotihuacan
Cerro Chiconautla T-75
T-239
Cerro Chiconautla
TC-10 TC-3 Tlatel de Tepexpan TC-33
Cuanalan
Sierra de Guadalupe
Sierra de Guadalupe
El Risco
Tx-EC-1 & LC-2
El Risco
Lake Texcoco
Tlatelolco (?)
x
Tx-TF-46 (El Tepalcate)
Tx-EC-33-LC-19 Chicoloapan buried Early Classic site
Chapultepec
Tx-TF-44-45 Tx-TF-26, 27 & 28
Tx-EC-34-LC-20
Cerro Chimalhuacan
arina anta Cat
rra de S
Sie Cuicuilco
Ix-TF-3
Ix-TF-2
Tlapacoya Ch-TF-58
Ch-TF-63 Xico
5 Km
10
atarina
El Pedregal lava field
Ch-TF-58
L. Chalco 0
Cerro Portezuelo (Tx-EC-32-LC-18)
Ix-TF-12 Ix-TF-11
L. Xochimilco
Chapingo buried Classic site
Lake Texcoco
Azcapotzalco
Tx-TF-49
N
Sierra Chichinautzin
Santa C Sierra de Xo-Cl-5 Xo-Cl-1
L. Xochimilco
Ch-TF-57
Ch-Cl-56
Ch-Cl-51 Ch-Cl-49
L. Chalco Temamatla
0
5 Km
10
Fig. 12.5 Terminal Formative and Classic sites in the lacustrine and perilacustrine areas of the Basin of Mexico
During the Late Formative and Classic periods, in the Lake Texcoco area, shoreline sites still occupied areas of the bajada lakebed transition around the Sierra de Guadalupe and Sierra de Santa Catarina (Fig. 12.5). In the Texcoco region, lakeshore sites around the Chimalhuacán peninsula remained occupied, with El Tepalcate appearing as an isolated tlatel on the lakebed (Fig. 12.5a). However, its occupation appears to have ended during the Tzacualli phase, suggesting that its settlers could not raise the tlatel above the high lake level (Cordova et al. 2022). The Classic sites in most of the areas formerly occupied on the eastern shore of Lake Texcoco may have been abandoned as well. No Classic sites have been reported anywhere on the lakebed in this part of the lake. Sites for salt procurement and production were built on higher ground farther inland than in previous periods, as in the case of Early Classic occupation at the Tlatel de Tepexpan (Fig. 9.5) and areas nearby such as TC-3, 10, and 33; Tx-EC-1; and EC-3 (Fig. 14.4b). Unfortunately, recent alluvial accumulation has concealed the perilacustrine sites of this period. Geophysical evidence in the area of Chapingo (Rosado-Fuentes and Arciniega-Ceballos 2015) and findings in brickyards suggest that sites indeed existed in some parts of the alluvial plains (Cordova 2017). In particular, the Early Classic occupation in a section of Chicoloapan shows marks of impoundment and salinization, which could be interpreted as indicating a rise in the water table and possible impoundment (Fig. 5.13a).
284
12 The Lakes During the Agricultural Era
As sites in the lakebed and perilacustrine areas declined in the southern lakes and as Lake Texcoco shrank during the Terminal Formative-Classic transition, many new sites appeared near or on the shores of the northern lakes (Fig. 12.5a). In the northwest, north, and northeast of Lake Xaltocan, new rural communities appeared (Gorenflo and Sanders 2015; Parsons 2008). Their exact locations with respect to the lakeshore are not clear, but, in the case of Lake Zumpango, most sites seem to have been occupying Pleistocene lacustrine terraces or paleobeaches (Parsons 2008).
12.4 The Classic and Postclassic Periods 12.4.1 The Lacustrine Geography of the Basin of Mexico During the Classic Period During the Classic period, the Basin of Mexico experienced a shift in population to the northern half of the Basin, with the Teotihuacan valley having the highest concentration of population in the city of Teotihuacan itself (Manzanilla 2014; Sanders et al. 1979). The boundary of the higher concentration of settlements runs somewhere in the middle of the Texcoco survey region (Fig. 12.5b). On the west side of the Basin, that boundary runs somewhere between Tacuba and Mixcoac (González- Rul 2007). Thus, south of this roughly demarcated area, settlements were sparser and smaller than those in the north. The map of settlements during the Middle Horizon published by Sanders et al. (1979) shows that in comparison to the Middle and Late Formative and the Postclassic periods, Classic period settlements of the lacustrine and perilacustrine areas were scarce or, in most cases, completely absent. The only exceptions are the northern lakes, where concentrations of perilacustrine settlements appeared in areas previously unoccupied. The few small settlements around Lake Zumpango were limited to areas slightly above the lacustrine plain, on former beach berms, presumably of Pleistocene and Holocene (Parsons 2008; Frederick et al. 2005). Concentrations of small settlements (villages and hamlets) extended along the eastern and northeastern parts of Lake Xaltocan above the lacustrine plain and on the alluvial soils (Fig. 12.5b). Classic sites located on the northern shores of Lake Texcoco and the southwestern part of Lake Xaltocan (Fig. 12.5b) are small, tlatel-type settlements that are apparently salt-procuring stations (Sanders et al. 1979). These form a continuum with sites along the shoreline east of the Ecatepec strait and the delta of the San Juan Teotihuacan River (Fig. 12.5b). On the south shores, along the foot of the Sierra de Santa Catarina, Classic era sites are small and, like their counterparts in the north, slightly higher in elevation compared to previous and later sites reported by Blanton (1972). Classic ceramics have been found below Late Aztec structures in areas of the lakebed on the west side of Lake Texcoco, similar to the Classic ceramic styles recovered from sounding pits in Tlatelolco (González-Rul 1988). However, reports
12.4 The Classic and Postclassic Periods
285
are limited to ceramics without any association with structures or permanent occupations of the Classic age. These findings could have resulted from ephemeral occupations of insular areas during the Classic period or the ceramic fragments could have been present in the construction material brought in from the shores to build tlateles and platforms in the Postclassic period. In fact, near the closest shore is Azcapotzalco, an area with substantial Classic occupation (Fig. 12.5b), which could have been a source of earth for Classic ceramics. Another area with Classic ceramics on the bed of Lake Texcoco is the area between Mixcoac and the northern part of the Iztapalapa Peninsula, dubbed the “Mixcoac Isthmus” (González-Rul 2007), which does not seem to be associated with permanent settlements, as in Tlatelolco. However, salvage archaeology along subway lines 8 and 12 (Sánchez-Vázquez 1996), which cross this area of the lakebed, did not report Classic ceramics. Thus, it is most likely that the Classic ceramics reported by Gonzalez-Rul (2007) are found in several Aztec tlatel settlements in the area (i.e., Fig. 4.5). Therefore, like in the case of Tlatelolco, Classic ceramics in these areas could have been present in the earth collected from the mainland for the construction of Aztec tlateles.
12.4.2 The Lakes During the Epiclassic and Early Postclassic Periods The Epiclassic, the period that follows the fall of Tenochtitlan (c. AD 550), is characterized by a rearrangement of population throughout the Basin, especially by its regrouping into several settlement clusters. Sanders et al. (1979) recognize six settlement clusters for this period: the Teotihuacan valley Cluster, the Zumpango Cluster (north of Lake Zumpango), the Guadalupe Cluster (the area between Tenayuca and Cuautitlán), the Portezuelo Cluster (the southern end of the Texcoco survey Region), the Cerro de la Estrella Cluster, and the Xico Cluster (including the western shore of Lake Chalco). Some of these clusters included sites on the shores of the lakes or in some cases on the lakebeds themselves (Fig. 12.6a). Irrespective of whether they were associated with these clusters or not, some Epiclassic sites (or Early Toltec sites in some surveys) developed on sites previously occupied during the Classic period. These include some small sites at the base of the Sierra de Guadalupe facing Lake Texcoco, the areas around Xico Island in Lake Chalco, and the northern side of Lake Texcoco (Fig. 12.6a). Similarly, areas east of Lake Xaltocan, which is part of the Teotihuacan cluster, were occupied during the Epiclassic. Unfortunately, we know little about lacustrine Epiclassic sites, especially in the lacustrine realm. Surveys and excavations in the Xico area (García-Chávez et al. 2015; Pulido-Méndez 1993; Parsons et al. 1982) have revealed important structures built during this period. This cluster of settlements extended across the lake into the area of the Amecameca River, where Coyotlatelco ceramics, typical of the Epiclassic
286 a
12 The Lakes During the Agricultural Era
Single settlements or areas with several settlements
Zu-ET-23
N
L. Zumpango Cerro Gordo
Zu-LT-164 &165
b
Cerro Gordo
L. Zumpango
L. Xatlocan
L. Xatlocan
Cerro Chiconautla
Sierra de Guadalupe
Cerro Chiconautla
Sierra de Guadalupe Tx-ET-1
Tenayuca
Tenayuca
El Risco
Tx-LT-2 & 3
El Risco Tx-ET-16
Azcapotzalco
Ix-ET-10
Lake Texcoco
Ix-LT-36
Cerro Portezuelo
Ix-ET-14
Ix-LT-46
(Tx-ET-32)
Ix-ET-8
atarina
ta C
a de San
Sierr El Pedregal lava field Xo-ET-8 & 9 Xo-ET-2 Xo-ET-1
Xico
Ix-LT-25
Sierra de
El Pedregal lava field Ch-ET-28
Ix-LT-47
L. Xochimilco
5 Km
10
Ch-ET-24 & 25
Sierra Chichinautzin
0
5 Km
10
atarina
Santa C
Ix-LT-29 Xo-LT-1 Ch-LT-13 Ch-LT-90
L. Chalco 0
Tx-LT-4
Tx-LT-32-38
Azcapotzalco
Lake Texcoco
L. Xochimilco
Single settlements or areas with several settlements
Zu-LT-195 &196 Zu-LT-192 Zu-LT-197 Zu-LT-193 & 194
L. Chalco
Xico
Ch-LT-70-71 &76-80
Ch-LT-6
Sierra Chichinautzin
Fig. 12.6 Lacustrine and perilacustrine settlements during the (a) Epiclassic and (b) Early Postclassic (Late Toltec) periods
period, have been reported under the alluvial accumulations of the delta (Frederick and Cordova 2019) (Fig. 9.7). In the eastern Lake Texcoco basin, there seems to have been a reoccupation of the deltaic complex previously settled in the Formative period (e.g., the Tlatel de Tequexquinahuac) and other tlateles farther north along the shore (see Parsons 1971). It is likely that many of these newly occupied areas in the Epiclassic period were under water or threatened by flooding during the Classic period, as paleo-reconstructions of climate and lake levels suggest (Fig. 12.1). The Early Postclassic period corresponds to the Late Toltec (LT) period in the chronological schemes of some surveys. It is defined mainly by the presence of Mazapa ceramics, which are associated with dominance of the city of Tula (north of the Basin of Mexico). During this period, settlements in the Basin of Mexico were smaller and more dispersed than they were in the Epiclassic period, suggesting a general ruralization (Sanders et al. 1979). Early Postclassic settlements were more numerous on lakebeds than were those of the Epiclassic period. Presumably, lake levels were low, with only a minor short rise occurring during this period (Fig. 12.1). Some settlements of this period appeared in areas previously occupied during the Epiclassic period, but many others appeared in previously unoccupied areas (Parsons 2008). After a paucity of settlements during the Epiclassic period, some areas around Lake Zumpango were reoccupied, especially the Pleistocene sandy ridges located north and northwest of the lake (Parsons 2008) (Fig. 12.6b). Near the shores of Lake Texcoco,
12.4 The Classic and Postclassic Periods
287
minor concentrations of Late Toltec ceramics appeared, especially in association with the salt production sites in Lake Texcoco (Sanders and Gorenflo 2007; Litvak-King 1964; Mayer-Oakes 1959). Late Toltec ceramics also appear in various tlatel-type settlements in eastern Lake Texcoco (Fig. 12.6b), sometimes in single occupation, but sometimes mixed with earlier or later ceramic styles (Parsons 1971). In the southern basins, Late Toltec settlements extended to the Xico island, on the Tlahuac strait, and to some localities on the north and west shores (Parsons et al. 1982) (Fig. 12.6b).
12.4.3 Lacustrine Settlement Expansion During the Middle and Late Postclassic Periods The Middle Postclassic (Early Aztec) period corresponds to the Aztec I and II Black-on-Orange ceramic styles, whereas the Late Postclassic (Late Aztec) period corresponds to the Aztec III and IV Black-on-Orange ceramics (Fig. 2.1). However, in surface surveys, Early Aztec ceramic styles usually appear mixed with Late Aztec ceramic styles, which makes it difficult to map the locations and extent of the Early Aztec sites (Parsons et al. 1996), limiting the mapping of the latter only by the presence and absence of Early Aztec ceramics (Gorenflo and Garraty 2016) (Fig. 12.7). Many of the areas newly occupied during the Middle Postclassic period correspond to those later occupied by Late Aztec settlements, including Xochimilco, Tlahuac, Mixquic, Iztapalapa, Culhuacán, Xaltocan, and the areas around them (Fig. 12.7a). Although the Tenochtitlan settlement originated in this period, its evolution seems to be more complex and rapid than those of other lacustrine settlements (see Chap. 13). Lake Zumpango, however, has a paucity of Early Aztec sites, despite the large number of settlements at the Late Toltec and Late Aztec sites (Parsons 2008). Along with settlement expansion came the development of lakebed areas into chinampa fields, though much of it occurred during the Late Postclassic period, given the abundance of most of the Late Aztec ceramics and the support of radiocarbon dating (see Luna-Golya 2014; McClung Ávila-López 2006; Frederick 2007). The only exceptions were the chinampas around Xaltocan, dating from the Early Aztec to the Late Aztec period (see Morehart and Frederick 2014; Morehart 2012a). During the Late Postclassic (i.e., Late Aztec) period, settlements tended to occupy vast areas of the southern lakes and the western part of Lake Texcoco (Fig. 12.7b). Areas with a considerable number of settlements also include the northern, eastern, and southern shores, where many sites have been associated with salt production (Sanders et al. 1979; Blanton 1972; Parsons 1971) (Fig. 9.2), although many sites along the shores of Lake Texcoco seem to have had other purposes (see Cordova et al. 2022; Parsons 1971). In the southern lakes, numerous tlatel habitational sites within the chinampas were present, thus creating a large density of population in an apparently rural area (Luna-Golya 2014). Late Postclassic settlements in the lacustrine basins of the northern lakes are also substantial, with the eastern area of Lake Xaltocan fully developed into wetland agriculture and the western part having numerous salt-producing sites. Despite a
288
12 The Lakes During the Agricultural Era
a
Single settlements or areas with several settlements
N
Cerro Gordo
L. Zumpango Xaltocan
b
Single settlements or areas with several settlements
L. Zumpango
Cerro Gordo
Xaltocan
L. Xatlocan
L. Xatlocan Cuautitlan
N
Cerro Chiconautla
Cerro Chiconautla
Sierra de Guadalupe
Sierra de Guadalupe
Azcapotzalco Tenayuca
Tenayuca Huexotla
Azcapotzalco
Lake Texcoco Chapultepec
Coyoacan El Pedregal lava field
Culhuacan
L. Xochimilco Xochimilco
0
5 Km
10
a Sierr
anta
de S
Tlahuac
L. Chalco Sierra Chichinautzin
rina
Cata
Texcoco
Azcapotzalco Tlatelolco Lake Tacuba Tenochtitlan
Culhuacan
L. Xochimilco
Chalco
Xochimilco
0
5 Km
Texcoco
Iztapalapa
Coyoacan El Pedregal lava field
Huexotla
10
Sierra de
atarina
Santa C
Tlahuac
L. Chalco
Chalco
Sierra Chichinautzin
Fig. 12.7 (a) Middle Postclassic (Early Aztec) and (b) Late Postclassic (Late Aztec) settlements in the lacustrine and perilacustrine areas of the Basin of Mexico. (Simplified from Sanders et al. 1979; Parsons 2008)
paucity of sites in the previous period, sites proliferated around Lake Zumpango during the Late Postclassic period. However, here, one of the problems related to the settlements and the lake is that archaeological surveys did not cover areas under the waters of the new Lake Zumpango (Parsons 2008). Moreover, with no fully excavated sites in the area, it is difficult to make any connection between settlements and lake resources. Nonetheless, the high-density settlement patterns seen everywhere across the Basin of Mexico during this period seem to extend to large parts of the lacustrine basin (Sanders et al. 1979).
12.5 Patterns of Long-Term Appropriation of Lacustrine Environments 12.5.1 Settlement Patterns Across the Lacustrine Realm Settlement changes across the archaeological periods in the lacustrine and perilacustrine areas (Figs. 12.4, 12.5, 12.6, and 12.7) reflect the evolution of lacustrine space appropriation at centennial scales. The political, economic, and technological aspects involved in the process are complex and certainly intertwined with the
12.5 Patterns of Long-Term Appropriation of Lacustrine Environments
289
patterns of environmental change. Climatic change, as shown by regional proxies, also had consequences in the fluctuations over time and perhaps in the adaptation of settlements to lake-level fluctuations (Fig. 12.1). However, it is noticeable that while some areas are settled only in certain periods, others have a more recurrent settlement through various periods, an aspect that is important to discuss in the context of the aquatic environments of the ancient lakes of the Basin of Mexico (Fig. 8.11). The strait of Tlahuac has been an area of recurrent occupation since the Early Formative. The reasons for the preference of this part of the lake and the adjacent lakeshores are not clear. It could possibly have been an area with low lake levels, perhaps formed by a preexisting elevation between the lakes, or an area with a concentration of resources. In the latter case, it is possible that this location permitted access to the more vegetated and shallow Lake Xochimilco and to the more open and maybe deeper Lake Chalco, reminiscent perhaps of environment type 5 (Fig. 8.11). Two other areas of recurrent settlements in the southern lakes are Xico and Tlapacoya, which seem to have offered stable surfaces surrounded by productive wetlands, as exemplified by environment type 7 (Fig. 8.11). In the Lake Texcoco basin, the area with more continuous occupation is the bajada lakeshore surrounding the Sierra de Guadalupe, where most of the sites were occupied through most periods. Similarly, the bajada surfaces around the Sierra de Santa Catarina and the Cerro de Chimalhuacán seem to have had settlements through most periods. The bajada shores of the Cerro de Chiconautla were occupied, especially during the Terminal Formative, Classic, and Late Postclassic periods. All these regions around Lake Texcoco correspond to environment types 6 and 7 (Fig. 8.11), which are stable, flood-free zones for habitation close to aquatic resources, and possibly near springs. The area south of the San Juan Teotihuacan delta saw more occupation mainly during the Classic, Epiclassic, and Postclassic periods, suggesting an environment fluctuating between types 2, 3, and 4 (Fig. 8.11), though perhaps alluvial accumulation has been concealing other occupations. The eastern shore of Lake Texcoco was another deltaic area with multiple occupations, except for a gap during the Classic period. This area likely corresponds to environment type 4, although close perhaps to environment types 1, 2, and 3. In the northern lakes, permanent settlements do not seem to have occurred prior to the Terminal Formative. Although real aquatic settlements such as Xaltocan and Tonanitla date only to the Middle and Late Postclassic periods, lakeshore settlements seem to have been important through the Classic, Epiclassic, and Early Postclassic periods. The morphology of the shores, with evidence of the former (Pleistocene) lacustrine terraces, permitted settlements close enough to the lakes but high enough to avoid lake floods. Although we know little about the paleoenvironments of these two lakes, it is possible that several attractive environments existed, perhaps combining types 1 through 4 (Fig. 8.11). Unoccupied spaces in the lakes should also receive attention because of possible difficulties for settlement or because of site visibility. In case of the former, it is possible that certain physical difficulties existed for the lakes. As revealed by previous surveys (Parsons and Morett 2004; Ortuño-Cos 2015), the central interior of the lakebed area in Lake Texcoco was never fully settled, but they were still used for
290
12 The Lakes During the Agricultural Era
certain activities, namely, hunting, fishing, and ceremonies. Certainly, the problem with salinity may have been a deterrent, especially in contrast to the southern freshwater lakes, which overall had more continuous settlements (Figs. 12.4, 12.5, 12.6, and 12.7). However, it seems that infrastructure built during the Late Postclassic period had produced a solution to managing saline waters (see Chap. 13).
12.5.2 The Late Postclassic Appropriation of Lacustrine Spaces Unlike any of the previous periods, the Postclassic period saw the largest number of settled areas inside the lakes, a matter that reflects the high population density elsewhere in the Basin, as reflected in the data of the surveys (Manzanilla 2014; Sanders et al. 1979). However, the intriguing question here relates to the possible impact of adverse situations caused by the rise of lake levels (Fig. 12.1). In previous times, settlements would have moved out of the lakebeds during high lake-level stands, just like it occurred in the Classic period, and reoccupied them when the lake levels were low, similar to what occurred in the Epiclassic and Early and Middle Postclassic periods. However, the Late Postclassic settlement patterns seem to have been exactly the opposite. Thus, the question is “What led to the sudden move to control the lakes?” The answer to this question is complex, as many political, economic, technological, and environmental aspects converge in the process of human appropriation and control of the lakes. The social and political mechanisms behind this control of the environment through construction of infrastructure have been discussed, first from an “oriental despotism of Wittfogel” point of view (e.g., Palerm 1973) and then from a more ecological view (e.g., Sanders et al. 1979; Armillas 1971). However, more clues to the environmental and economic aspects have appeared with recent research and they are being interpreted under new theoretical lenses such as landesque capital and niche construction (Manuel Navarrete et al. 2019; Morehart 2016). Technological innovation and the widespread construction of infrastructure to control natural processes (e.g., floods, soil erosion, and loss of soil fertility) appear in other environments, especially in marginal lands. Examples of these are the reclamation of eroded slopes, which was also widespread in the Basin (Frederick and Cordova 2019; González-Arqueros et al. 2017; Cordova and Parsons 1997). In this sense, one can consider the swampy and saline areas of the lakes as “marginal lands” that needed to be reclaimed to accommodate the population and increase food productivity. The idea of the lakes as a marginal land goes against the view that the lakes were a blessing to the populations of the Basin, which is often cited in the literature. However, the idea of blessing may apply especially to the southern lakes, but not to the saline lakes, especially one with extreme changes like Lake Texcoco (Figs. 8.12, 8.13, and 8.14). Therefore, finding innovative ways to cope with difficult
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environments, in this case the swampy, saline, and rapidly changing lacustrine environments of the Basin, was imperative for survival, especially in the event of increasing population. Thus, although not possible to delve into greater details, Chap. 13 discusses some of the main environmental aspects surrounding this technological revolution in the lacustrine realm in the Late Postclassic period.
Chapter 13
Late Aztec Settlement, Hydraulic Management, and Environment
13.1 Prevailing Views and Questions About Tenochtitlan 13.1.1 The Environmental Significance of Tenochtitlan Central to the topic of lacustrine systems and civilizations in the Basin of Mexico is the development of insular urban complexes, dikes, and chinampas and the control of the hydrological flows of the lakes. The highest point in this development is without a doubt the construction of Mexico-Tenochtitlan, the insular settlement complex founded by the Mexicans in the early 1300s, which grew into one of the largest cities of the ancient New World. For this reason, the foundation and evolution of Tenochtitlan and the implementation of the hydraulic infrastructure that came with it deserve a chapter of their own. This means looking at historical and archaeological records as well as other sources of information that support or refute some of the established ideas and hypotheses of the origin and evolution of Tenochtitlan and its hinterland. When assessing the environmental history of Tenochtitlan, one must consider the entire lacustrine complex and its surrounding lands, something that is difficult to do due to the scarcity of data in some areas. Important in this process is also the climatic context, which exists in the form of global regional climatic proxies (Fig. 12.1). Additionally, non-archaeological data, especially geotechnical, geological, and geomorphological data, are relevant to the reconstruction of the environmental change of the city. Thus, in the sections below, the sources of information are discussed in the context of what is known from historical and archaeological sources. The final goal is a reconstructive model of environmental change surrounding the origin and development of the city and its surroundings, not as a fait accompli but as the theoretical basis for further research.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5_13
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13.1.2 Historical Sources Historical information of the foundation and development of Tenochtitlan can be obtained from several codices and historical accounts based on oral histories and the information in the codices. The codices include Códice Ramirez, Códice Boturini, Códice Mendocino, Códice Durán, and Códice Aubin and the Ordenanza del Señor Cuauhtemoc, among others (Mundy 2014, 2015; Matos-Moctezuma 2006; Gussinyer i Alfonso 2001; Valle 2000; Carballal-Staedtler and Flores-Hernández 1989b; Lombardo de Ruiz 1973). Historical accounts based on the codices and oral histories include the works by Hispanicized Nahua scholars (e.g., Alva-Ixtilxochitl 1975, 1977; Chimalpahin-Cuauhtehuanitzin 2003; Tezozomoc 1998) and Spanish historians (e.g., Motolinia 1990; Torquemada 1975; Durán 1897). Accounts by anonymous authors include the Anales de Cuautitlan (Anonymous 2004) and the Anales of Tlatelolco (Anonymous 2011). Regarding these sources, a large part of the historical information of Tenochtitlan falls within the field of ethnohistory, which is a dominant field in terms of reconstructing events before the conquest (see Chap. 2). Therefore, because most of the information on the events involving the foundation, development, and structure of the city fall within the field, their results deserve a special discussion (see Sect. 13.1.3). In addition to the sources mentioned above, the chronicles of the war of conquest provide information on the layout of the city and its hydraulic infrastructure (e.g., Aguilar 2018; Conquistador Anónimo 1941; Cervantes de Salazar 2007; López de Gómara 2006; Cortés 1985; Díaz del Castillo 1982; Sahagún 1830). Additionally, numerous litigation documents from the early years of the colonial rule also provide information on specific locations within the city (see Sánchez-Vázquez et al. 2007; Carballal Staedler and Flores-Hernández 2004; Lombardo de Ruíz 1973; Calnek 1972; Caso 1956). Furthermore, the map of Nuremberg (c. 1524) and the Uppsala map (c. 1554) (Figs. 1.5 and 1.6) provide a general picture of the locations and features in and around the Aztec capital.
13.1.3 The Ethnohistory and Archaeology of Tenochtitlan and Its Surroundings Despite divergences among scholars and sources, the most accepted date for the foundation of Tenochtitlan is the year 1325 (Mundy 2015; Lombardo de Ruíz 1973). Its twin city, Tlatelolco, founded in 1338, formed a single urban unit with Tenochtitlan after the latter was conquered in 1473 (Durán 1897; Torquemada 1975). As in the tradition of the time, the city was divided into wards known as campan in Nahuatl and parcialidades in Spanish. These wards were divided by the intersection of the main east-west and north-south streets into a central religious precinct. In turn, the campan were divided into smaller urban polities called barrios in Spanish and tlaxillacalli in Nahuatl.
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In Tenochtitlan, the four wards were Cuepopan, Aztacoalco, Moyotlan, and Teopan (also known as Zoquiapan), each with its own religious precinct (the triangles in Fig. 13.1). Each ward was subdivided into barrios based on close kinship ties at the level of calpulli (Caso 1956; Lombardo de Ruiz 1973; Gusinyer i Alfonso 2001). The locations of the barrios as known today represent localities claimed by their original groups after the conquest, except the area appropriated by the Spanish, known as La Traza, to build the Spanish city (Fig. 13.1). The names and locations of the former barrios fell into historical oblivion until Jose Antonio Alzate compiled information about them in the late eighteenth century and Alfonso Caso studied them in detail in the twentieth century (Mundy 2014). Despite name changes over time, the locations of the original barrios outside the Spanish Traza were identified using as reference the parishes that were originally constructed as churches over the temples of each original pre-conquest barrio (Caso 1956). Subsequent research studies with archival documents and archaeological excavations have refined some details related to the barrios (e.g., Lombardo de Ruíz 1973; Calnek 1972; González-Rul 1988; Gussinyer i Alfonso 2001; Sánchez- Vázquez et al. 2007; Mundy 2015). In addition to their importance in the history and urban political geography, such names often portray aspects of the landscape potentially useful in reconstructing the lacustrine landscape with its natural and cultural features. Outside the perimeters of Tenochtitlan Tlatelolco, extensive research studies have provided more details about the locations of insular settlements as well as the hydraulic infrastructure. Thus, using mostly historical references and features and names in the modern landscape, González-Aparicio (1968, 1973) reconstructed a map of the urban and suburban areas of Tenochtitlan (Plano Reconstructivo de la Región de Tenochtitlan). This map is so detailed and is backed by many sources that it has served as the main geographic reference. Figure 13.2 shows a simplified version of this highly detailed and dense original map of the western part of Lake Texcoco. Archaeological research works in the past five centuries have produced a great amount of information about features in the city, including ceremonial structures, residential units, markets, baths (temazcales), canals, and chinampas, which are important for the reconstruction of early life in the Aztec city. In much of the research, ethnohistorical and archaeological information have been combined in an effort to link the written and unwritten histories (Peralta-Flores 1996). Nevertheless, discrepancies between the archaeological findings and historical information occur, a matter that requires more investigation.
13.1.4 Research Questions To summarize the issues with the sources and their interpretations, this chapter focuses on three fundamental questions: (1) What was the lacustrine landscape of Tenochtitlan like before its foundation? (2) How did the city manage adverse natural
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Fig. 13.1 Wards (campan) and their barrios (tlaxillacalli) of Tenochtitlan. (Data were collected from Caso (1956), Lombardo de Ruíz (1973), and González-Rul (1988). The map is based on the work by Calnek (1972))
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conditions such as saline water and soil salinization and extreme events such as drying and flooding? (3) How did the city cope with drastic seasonal and decadal changes to maintain navigation and agriculture within its borders? The first question directly refers to the landscape conditions existing at the beginning of the fourteenth century in the western part of Lake Texcoco. In particular, the research conducted to answer this question has faced certain misinterpretations of some sources and misconceptions about the lake, some of which have been discussed in Chaps. 1 and 7. The second and third questions more specifically refer to the infrastructure and strategies adopted to cope with the short- and long-term dynamics of the lake. The answers to these questions require a review of the hydraulic infrastructure mentioned in the historical sources in the context of the dynamics of the lake discussed in Chap. 8.
13.2 The Original Landscape of Tenochtitlan 13.2.1 The Elusive “Primitive” Islands The idea that “primitive” or “original” islands served as locations of the Mexican settlements that grew to form Tenochtitlan appears in the modern maps of Tenochtitlan and in several written forms in the mass media and in some scholarly publications. However, because there is no historical precedent or empirical proof of existence of these islands, the idea of primitive islands should be deconstructed from its origin to its mention in the contemporary literature and maps. The idea of Tenochtitlan’s primitive islands must originate toward the end of the nineteenth century as there is no mention of them in earlier documents. A popular map of Tenochtitlan that is circulating in the social media and is cited in some publications on the Internet (reproduced in Fig. 13.3) holds some clues regarding the original idea of the primitive islands. Although some of these sources attribute this map to Carrera-Stampa’s (1949) compilation of maps, the map is absent in that publication. Interestingly, however, the map itself credits certain sources, some of which are impossible to trace (Fig. 13.3). One of the credited sources is “Téllez- Girón,” which is an error, as the likely source is Adrián Téllez-Pizarro, who published a study titled Apuntes sobre los cimientos de la Ciudad de Mexico in 1900. In his study, Téllez-Pizarro (1900) examined the deformation of the streets and buildings in Mexico City, which at the time was already apparent, as it is today. In this publication, he proposed that the uneven terrain below the city created by the original islands that predated the construction of Tenochtitlan was the cause of the deformation of the streets and buildings. Thus, using the distribution of deformations, he mapped the islands in the background of Tenochtitlan on a map that interestingly looks extremely similar to the popular map in question (Fig. 13.2). The implication of this study was that the Mexicans originally settled on these original,
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Fig. 13.3 A brief sketch of a popular map of Tenochtitlan circulating in the media. (Modified and adapted by the author)
supposedly natural islands, from where the city grew to form the Great Tenochtitlan. Nevertheless, Téllez-Pizarro never provided direct archaeological, geological, or any kind of empirical evidence to support the existence of such islands. Despite the lack of empirical proof, archaeologists and historians began adopting the idea of Tenochtitlan’s primitive islands. Consequently, the idea became grounded among scholars to the point that the islands appear in most reconstructive maps of the Basin’s lakes and of Tenochtitlan itself (Rovira Morgado 2016; Filsinger 2005; Niederberger 1987; González-Aparicio 1973; Calnek 1972; among others). The primitive islands are not mentioned in the histories of the foundation of Tenochtitlan in codices and chronicles written in early colonial times. There is also no empirical (archaeological, sedimentological, or geophysical records) evidence that supports the existence of such islands. From the point of view of lacustrine dynamics (discussed in Chap. 8), the existence of stable islands was not possible given the extreme lake-level changes (Figs. 8.13, 8.14, and 8.15). Unlike islands formed by rock promontories (e.g., Peñón de los Baños, Peñón del Marqués, Tlapacoya, and Xico), other types of islands would have been ephemeral, as they were formed by the abandoned levees of river channels, small bumps in the terrain caused by tectonic deformations and sediment banks (see Fig. 8.11). Thus, in the following sections, the existence of the primitive islands is challenged based on the original historical sources, toponyms, and stratigraphic geophysical records.
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13.2.2 Historical Sources and Archaeological Records Historical accounts are based on the codices, and the codices do not report or allude to the existence of islands prior or during the foundation of Tenochtitlan. In fact, they do not even point to a lake at the foundation site of Tenochtitlan but suggest a territory with groves of reeds, with the words carrizo, carrizales, espadañas, tule, and tulares appearing in many of them (e.g., Torquemada 1975: Book 2, 133–134; Duran 1897: Vol. 8, 41–43; Tezozomoc 1998: 59–60, 69; Chimalpahin- Cuauhtehuanitzin 2003: Quinta Relación: 35). In fact, most codices, however, portray the foundation of the city through abstract figures without really showing any island, focusing rather on the cactus and the eagle symbol, which, in most cases, is shown as growing out of the water (e.g., Códice Aubin; Códice Mendocino; Codice Ramírez). The only codex that depicts some details of the landscape of the western part of Lake Texcoco at the time of the arrival of the Mexicans is the Map of Sigüenza, a document owned by the sixteenth century historian Manuel Sigüenza y Góngora. The codex is a painting that shows the sequential events of the wanderings of the Mexicans that led to their final settlement in a vegetated marshy area. The map depicts the area settled by the Mexicans as only clumps of aquatic vegetation, seemingly tulares. It does not show any apparent islands in the vegetated lake, except the Peñón de los Baños, which is the only permanent island in the area. All the sources seem to agree on the establishment of a place of worship (tlalmomoztli) as the first central structure of the future city of Tenochtitlan (García-Quintana and Romero-Galván 1978; Lombardo de Ruíz 1973). It is understood from some passages that the construction of the tlalmomoztli required stakes and filling the area with earth (Códice Ramírez 1975: 27) and that the foundation of this structure had a square shape (Duran 1897: vol 1, 41). Therefore, the descriptions fit the construction of a platform (terraplén) corresponding to tlatel type 4 (Table 10.3, Fig. 10.4). The only description of a preexisting island is the location of Tlatelolco. Durán (1897), Torquemada (1975), and Motolinia (1990) agree that the initial location of Tlatelolco was a sandy promontory called Xaltilolco or Xaltelolco. The occurrence of an albarrada (dike) (Duran 1897: Vol.1, Chapters 5, 4) and a terraplén (Códice Ramírez 1975: 28) at this location suggests that this was an artificial structure that had been abandoned. It is possible that the Tepaneca (Azcapotzalco) who claimed this area as their territory had already built some structures. The description of the foundation site of Tenochtitlan suggests that the establishment of the earliest settlements in the marshy area on the western side of Lake Texcoco may have only been a simple colonization of a marshy area, which could be habitable by the construction of tlateles. The historical sources mention Mexicans exchanging products of the lake (fish and birds) for construction materials (Durán 1897; Códice Ramírez 1975; Torquemada 1975) (e.g., wood and stone) to build their tlatel settlements in the marshy area. Based on the historical descriptions, the early settlements of the soon-to-be Tenochtitlan consisted of small clusters of tlateles or artificial island complexes scattered across the marshes. In fact, González-Rul (1988) proposed a settlement sequence model in which these original settlements grew until their tlateles and
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Fig. 13.4 Schematic sequence of the growth and evolution of settlements into the different calpulli of Tenochtitlan (After González-Rul 1988) (a) before 1325, (b) by 1404, (c) by 1428, and (d) by 1446. The dots represent lacustrine settlements; the light gray surfaces represent the growth of settlements by gaining terrain on the water surface; and darker gray surfaces indicate areas of a higher concentration of land gained from the lake
chinampas coalesced to form a single urban unit (Fig. 13.4). Presumably, each of the original settlements was a group of tlateles settled by clans or groups related by kinship, which, through time, evolved into different calpulli (barrios) of the city (Fig. 13.1). Accordingly, it is not until the period 1428–1446, during the reigns of Itzcoatl and Moctezuma I that the city developed further into a single, connected urban area (Fig. 13.1d). Subsequently, as the city grew and the neighboring city of
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Tlatelolco was added, many changes in the dynamics of the lake influenced the layout of canals, dikes, and causeways (Lombardo de Ruíz 1973; Calnek 1972). Unfortunately, the archaeological records prove only the existence of chinampas, platforms, causeways, and buildings belonging to the later years of the city (see Sánchez-Vázquez et al. 2007). Most likely, many of these late constructions as well as intrusions caused by colonial or more recent constructions had obliterated the simple and poorly elaborated structures of the original settlements of the city. Nevertheless, the archaeological records fail to support the preexistence of natural islands, a fact that is apparent in most of the stratigraphic models of the salvage archaeological records (see Fig. 5.3).
13.2.3 The Original Landscape of Tenochtitlan Through Toponyms If settlement proliferation and expansion took the pattern presented in Fig. 13.4, and each of the original settlements was the center of a barrio, then it is possible to expect that some of their names would refer to natural features or environmental conditions. Noticeably, some of the toponyms of Tenochtitlan allude to the characteristics of water, springs, vegetation, minerals, or terrains. However, none of the toponyms that fall under this category refer to natural islands. Toponyms within the city often refer to events in the history of Mexican settlements or to the characteristics of the local vegetation, hydrology, or other natural features. Thus, a significant number of locality names refer to aquatic vegetation, especially those with the prefixes tul- (tollin: sedges) and aca- (acatl: reed). The Crónica Mexicayotl refers to the areas within the original settlement with names such as Toltzallan and Acatzallan, which translate to “in the middle of groves of aquatic vegetation” (Tezozomoc 1998: 62), and similar names for other localities. Among the names of the barrios, some refer to aquatic vegetation (e.g., Acatlan, Tolquechiuca, and Tultenco), wet meadows (e.g., Zacatlan, Tlalquechiuhca, and Tlaxcuititlan), muddy areas (e.g., Tzoquiapan), salt flats (e.g., Iztatla, Tequesquipan, and Atizapan), springs (e.g., Amanalco and Temazcaltitlan), and areas with channels (e.g., Ateponazco and Atlampa). These names are strongly suggestive of a landscape reminiscent of environment type 4 (Fig. 8.11), which rather than being an open lake was more a mosaic of wetlands. Interestingly, toponyms do not indicate names of open-lake areas, which is concordant with the sources, which suggests that it was rather a mosaic of marshes and channels with abundant vegetation.
13.2.4 The Stratigraphy Below the City Unfortunately, the subway lines that cross the center of the former city (lines 1, 2, and 3) produced no stratigraphic records. Nevertheless, if the stratigraphy had been recorded, then the shallow tunnel type of construction (Fig. 2.5) would have not
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reached the generally deep bottom of the cultural fill, normally at depths in the order of 12–14 m (Mazari et al. 1989; Santoyo-Villa et al. 2006). On the other hand, those subway lines for which there are stratigraphic records from salvage archaeology (i.e., lines 4, 8, and B) only cross the edges of the former Tenochtitlan, though they still show some relevant information about the ground where the former city was established. However, the stratigraphic records obtained through salvage archaeology show a complex cultural stratigraphy of fills, chinampas, and structures often standing on lacustrine clays or highly organic sediments (see Fig. 5.3). Not in a single case is there any indication of the stratigraphy of preexisting stable grounds that could be considered to be primitive natural islands. Some segments of lines 4 and 8 cross the eastern and western edges of the former Tenochtitlan. At some localities, they cut through Aztec structures whose foundations vary from place to place, but, in general, the stratigraphy shows that Late Aztec occupations (mainly marked by Aztec III pottery) were built directly on lacustrine clays (Fig. 5.3, models 4–8) or on layers of alluvial sand (Fig. 5.3, models 9, 11, 12, 14, and 16). The latter could have been sandy banks left by rivers or former beach deposits, perhaps reminiscent of the sand layers reported in the stratigraphy along subway line 5 (see Sect. 5.3.1), though in many cases it is not clear whether they had been deposited by alluvial channels or were sand trapped behind bordos or dikes, as is the case of Xaltilolco discussed above. Natural accumulations of sand deposited by rivers and reworked by waves could create landforms for settlements, as is the case of the Late Formative Tlatel de Tequexquinahuac (Fig. 9.3) on the eastern side of the lake. Layers of sand are reported in some of the layers above the lacustrine clay along subway line 5 (Carballal-Stadler and Flores-Hernández 1989a). In other salvage works, sand layers have appeared as epitomized, as in sections 14 and 16 of Fig. 4.17. According to the description of sediments in the reports, it is not clear whether that sand could have been alluvial sand, a beach ridge, or an artificial accumulation. However, supposing that some alluvial islets existed, they would not have been as round and large as those depicted on maps (e.g., Fig. 13.4) but elongated, small, scattered in the area, and generally more close to the shores. There are no deposits suggesting natural islands, unless artificial accumulations of earth raised the ground as reported at Magdalena de las Salinas, toward the eastern end of subway line 5. This locality has a tlatel structure that is one of the islands identified as Coatlayauhcan along the Tenayuca Causeway (see Fig. 13.2, location e5) (Carballal-Staedtler and Hernández Flores 1989a). This finding, among others, is consistent with the idea that the occupation of the marshy area of the western part of Lake Texcoco during the Aztec period was possible only through the construction of tlateles or platforms.
13.2.5 Geophysical and Geotechnical Research Studies Recent studies have shown that the differential deformation of the streets and buildings in Mexico City is linked to the existence of artificial islands (tlateles) and causeways as well as to other causes such as the shrinking of lacustrine clays due to
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water extraction (Mazari et al. 1989; Mazari 1996; Auvinet et al. 2017; Barba- Pingarrón 2008). Profiles of resistance and magnetometry show that below the buildings and streets in the historical center of the city, the layers of cultural deposits can reach up to 12 m (Mazari et al. 1989; Santoyo-Villa et al. 2006; Auvinet et al. 2017). In some localities, soft soil and a crust appear between the upper lacustrine clays (arcillas lacustres superiores) and the cultural deposits (Santoyo-Villa et al. 2006), but this does not prove the existence of an island; it could be a calcrete, perhaps similar to the one where the cultural deposits of the Tlatel de Tepexpan stand (see Fig. 9.5). Localities with reported apparent emergence of terrain, Churubusco (Huitzilopochco), Mexicaltzingo, Mixhuca, and other islands of the suburban hinterland of Tenochtitlan, also appear to be accumulations of cultural deposits directly on natural lacustrine layers (Auvinet et al. 2017) (Figs. 9.11 and 9.12). Therefore, it seems that most of the insular settlements around Tenochtitlan were not preexisting islands but tlateles built on lacustrine and palustrine grounds. Observations along line 5 show that the tops of the lacustrine deposits vary in depth, which suggests irregularities in the lacustrine ground (Carballal-Staedtler and Flores-Hernández 1989a). However, with constantly sinking ground and constructions above it, the anomalies may not be original. Irregularities of terrain in the lakebed existed, as in many parts of the lake, possibly caused by faulting (Santoyo- Villa et al. 2006). Furthermore, during the drying of Lake Texcoco in the Pleistocene– Early Holocene, stream erosion created topographic irregularities on the lakebed surface (see Sect. 5.2.2). There is no doubt that irrespective of whether they were tectonic or erosional, there were areas of different elevations in the lakebed at the time the Mexicans settled in the area of Tenochtitlan, but the differences in elevation would not have been large enough to constitute permanent islands, especially as the lake levels changed rapidly seasonally and through the years (see Chap. 8). Therefore, artificial constructions (i.e., tlateles) were necessary to elevate areas of the lake above seasonal flooding. It is worth mentioning that although Téllez-Pizarro (1900) attributed the deformations of the buildings and streets of the city center to preexisting islands, the idea is not far from the real cause, which is seen in the apparent emergence of terrain in areas of former tlateles and dikes (Fig. 9.11). The only difference is that these features were artificial and not natural islands. It is the difference between the clayey ground and the artificial accumulations that causes the deformations (Auvinet et al. 2017).
13.3 Hydraulic Technology, Floods, Navigation, and Agriculture 13.3.1 Water Flows Across the City and Its Surroundings The main challenge for the city was to stabilize lake levels to allow navigation or to prevent flooding during high levels. The initial strategy to prevent the flooding of dwellings by upgrading the ground by building tlateles and platforms was a
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short-term solution. However, as the city grew, larger buildings were constructed, and chinampa cultivation became more widespread, the city needed a more elaborate infrastructure, namely, dikes, causeways, bordo dams, and canals. While dikes and causeway-dike structures protected the city from flooding, they also retained water to maintain stable levels in canals for navigation and maintenance of chinampas. Canals, on the other hand, would also conduct water through the city and drain it to the lower parts of the lake. Reconstructive maps of the city show canals crossing the city generally in the west-east and north-south directions (Fig. 13.5). Thus, the canals flowing in the west-east direction conducted water along the westward gradient of the lakebed. Most probably, their original purpose, when the city was still a marshland, was to conduct the water from the incoming rivers to the lower part of the lake, as shown by the layout of the original canals crossing the marshland in the Map of Sigüenza. However, as the layout of the city became more complex, with dams and dikes, those canals may have conducted water across the city from west to east. In contrast, the north-south canals may have served to distribute the waters of the main west-east canals sidewise, allowing water to reach certain areas for canoe transit, or as part of the drainage system out of the city. The general gradient of the ground, which led the flow of water eastward, also explains why the main dikes (Nezahualcoyotl’s, Ahuizotl’s and the Iztapalapa and Tepeyac causeway dikes) were needed to retain freshwater in the city (Fig. 13.2). However, the locations of each of these structures should be comprehended in terms of the changing nature of the lake during the 200 years of the city’s existence (see Sect. 13.4). The main canals crossing the city from west to east (Fig. 13.5) also follow the gradient toward the deeper lake basin, suggesting that the flow of water was eastward, perhaps in times of low lake levels. In fact, after the conquest, some of these canals still carried the waters of the incoming rivers through the city, as shown in many of the late colonial maps of Mexico City (see Lombardo de Ruíz 1996; Apenes 1943). The gravity issue with the water flowing east may not be the only reason for building north-south structures as the area of Tenochtitlan was subjected to strong currents and surges. As discussed in the tendency of the water to flow along the west-east gradient, the area of Tenochtitlan was undoubtedly exposed to the surges.
13.3.2 The Dikes of Nezahualcoyotl and Ahuitzotl The construction of a dike that divided the waters of Lake Texcoco is one of the most prominent aspects of hydraulic engineering during the apogee of Tenochtitlan. Most sources agree that during the reign of Moctezuma I (who reigned from 1440 to 1469), floods plagued the city, especially a major one that occurred around 1449, and that the Mexican King asked King Nezahualcoyotl of Texcoco for help (Duran 1897; Torquemada 1975). This is how Torquemada described its construction: Estacáronla toda muy espesamente. las cuales estacas (que eran muy gruesas) les cupieron de parte a los tepanecas. coyohuaques. xochimilcas; y lo que más espanta es la brevedad con que se hizo. que parece que ni fue oída ni vista la obra, siendo las piedras con que se hizo todo de güijas muy grandes y pesadas y trayéndolas de más de tres y cuatro leguas de
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0
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Other features:
A. Iztapalapa D. Iztapalapa canal B. Tepeyac E. Atarazanas C. Nonoalco-Tacuba (docks/embarcadero) D. Tacuba
A Main streets and causeways Dikes Canals City limits (estimated)
Main royal and/or ceremonial precincts Ceremonial precincts of the great quarters (campan) Chinampa site
Fig. 13.5 Tenochtitlan Tlatelolco with their wards (i.e., parcialidades or campan), causeways, and locations of a selected number of wards referring to the aspects of the lacustrine landscape and water management. (Adapted from Calnek (1972) with modifications by the author) alli; con que quedó la ciudad por entonces reparada, porque estorbó que el golpe de las aguas salobres no se encontrase con esotras dulces. sobre que estaba fundada la ciudad. (Torquemada 1975; Book 2, XLVII, 219) [It was lined up tightly with thick wooden posts that they obtained from the Tepanecas, Coyohuaques, and Xochimilcas; and it did not take too long to build it. It was made by placing [in between the lines of stakes] pebbles and large stones brought in from more than
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three or four leagues [12–16 km] away. Once finished, it [the dike] prevented the clash between freshwater and saline waters (translated by the author).]
Based on this description, most maps trace the extent of the dike from the Tepeyac causeway to Iztapalapa, passing somewhere between the eastern outskirts of the city and El Peñón de los Baños (Fig. 13.3). Furthermore, given the mention of a dike broken by the locals in the area of Iztapalapa during one of the campaigns of the conquest war in early 1521 (see Chap. 14), González-Aparicio (1968), on his map, connected the dike with the supposed dike mentioned in this locality east of Iztapalapa (Fig. 13.3, locations 13 h and i). However, other than the dike mentioned in this incident in Iztapalapa, there are no references of Nezahualcoyotl’s dike anywhere in the chronicles of the war of conquest. The brigantines sailed directly into their first targets south of Tenochtitlan without any obstacles. Although the dike was not mentioned in the war chronicles, the map of Nuremberg, which accompanied the second letter of Hernan Cortés to King Charles V, shows what seems to be the dike (Fig. 1.5). The dike on this map appears with some gaps, which could have been openings through which the brigantines could have sailed. However, with such gaps, the dike would not have had any importance in preventing flows of water. Paradoxically, the map of Uppsala (map of Santa Cruz), prepared about 30 years after the conquest, shows the dike as a continuous structure across the lake (Fig. 1.6). Moreover, several early colonial documents concerning floods and drainage of the lakes mention the dike, often as dique de los indios (the Indians’ dike), though it seems that they refer more to the past and not to a functioning dike (Candiani 2014). In the1870s, the engineer Tito Rosas recognized the remains of a dike in the landscape attributed to the ancient dike, but the area was later obliterated by the growth of the city, making the localization of the feature difficult (Auvinet et al. 2017). Then, with the help of eighteenth century maps, Jose Luis Lorenzo (1974) tried to place the location of the feature originally identified by Tito Rosas within the matrix of the growing city (see the location on the map in Fig. 2.4). Later, plans for archaeological salvage for the construction of line 5 of the subway (Fig. 2.5) aimed at targeting the remains of the dike without success (Carballal-Staedler and Flores-Hernández 1989a). However, geophysical studies identify areas of high sedimentation west of a line paralleling the location of the dike, suggesting a feature that retained sediments (Carballal-Staedler and Flores-Hernández 1989a). Based on the idea that water flowed westward, it is possible that rivers deposited large amounts of sediments in that area as the lake receded, topping any remains of the dike with sediments. However, other scholars suggest that the dike had already been scavenged for materials for the construction of the early Spanish city (Ramírez 1976; Candiani 2014). That the dike was not in use at the time of the war of conquest is a possible explanation for its disappearance and lack of importance in the chronicles of the conquest (Lorenzo 1974). One possible cause of its abandonment as a dike could have been changes in the dynamics of the lake due to the lowering of its water level. This suggestion concurs with the proposal of Lachniet et al. (2012, 2017) who state that the construction of the dike was a response to high lake levels caused by the exceptionally wet period called the Aztec pluvial in the mid-fifteenth century. Subsequently,
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the same authors suggest that the slow but continuous decline in the water level was due to drying that culminated in the droughts of the sixteenth century, making the dike lose its functionality. Interestingly, it is during this period that a new dike (Ahuizotl’s dike) was built near the city, which supports the idea that its construction may have responded to the hydrology of the lake. Information on the dike built at the end of the Ahuizotl’s reign (1486–1502) exists in various historical documents and coincides with floods in the city, particularly with the one in 1499 (Candiani 2014). Like his predecessor, Ahuizotl asked one of the Texcocan kings to help with the engineering of the project; thus, Nezahualpilli (Nezahualcoyotl’s son) directed its construction (Durán 1897; Torquemada 1975). The dike bordered the city on its eastern flank and connected with the Iztapalapa and Tepeyac causeways (Fig. 13.5), which also served as dikes, thus making a continuous north-south wall dividing this part of the lake. Although most sources attribute the purpose of the construction of the dikes to protecting the city from flooding, it is evident that they had other functions, especially protecting the waters of the city from the incursion of salty water from the eastern part of the lake and preventing the freshwater from leaving the city. As Hernan Cortés put it in his description, “el agua buena va hacia la mala” [the good water goes to the bad] (Cortés 1985: 71). Similarly, Fray Toribio Motolinia described the “old city,” referring to Tenochtitlan, as surrounded by freshwater, “y la dulce entra en la salada porque esta mas alta” [and the freshwater flows into the saline water because the former is higher] (Motolinia 1990: 144). In this process, water flowed through the gaps in the causeway dike, “y aquella calzada tiene cuatro ojos con sus puentes por donde sale de la agua dulce a la salada mucha agua” [and that causeway had four orifices with their bridges, through which freshwater goes to the saline water in large amounts] (Motolinia 1990: 144). Thus, this description suggests that the flow of freshwater tended to be dammed before the water reached the saline side of the lake across the structure linked to Ahuizotl’s dike. Interestingly, after decades of abandonment following the conquest, Ahuizotl’s dike was reinforced in the late sixteenth century as a measure to protect the Spanish city from floods. This new revamped dike took the name of Dique de San Lázaro (San Lazaro dike), after the locality of the embarcadero formerly known as Tetamazolco (Fig. 13.2, location f8) and Atarazanas (Cervantes de Salazar 2007). The San Lazaro dike appears on the map of Uppsala (Fig. 1.5) and is definitely a structure that persisted with reinforcement through most of the colonial period.
13.3.3 Infrastructure in the Shadow of Large Dikes and Causeways The point that is important to recognize is that the protection provided by Ahuizotl’s dike and the Iztapalapa and Tepeyac causeway dikes would not have been enough to control the water in the entire city. Therefore, smaller dikes and bordo dams would have been needed, particularly to divert the water from the west-east canals into the
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north-south canals. Clues to some small dike or bordo structures inside the city can be obtained from some of the chronicles, especially the mention of albarradas inside the city. Bernal Díaz del Castillo (1982) makes numerous references to albarradas gained by the Spanish army in their advance through the city, suggesting smaller dikes inside the urban area. However, such dikes could have been some sort of platform dikes (Fig. 9.14b) corresponding to type 6 platforms (Table 10.1; Fig. 10.1). Bordo dams would have been useful in the agricultural areas of the city or around smaller, insular settlements outside the city, especially when, in some cases, localities combined the production of salt and chinampa agriculture, two activities that would have implied the separation of saline water from freshwater. Correspondingly, for this purpose, the strategy should have involved a series of water compartments (see Sect. 13.3.4) as indicated by the C1, C2, and C3 compartment types in the model of water management in saline lakes (Fig. 10.13). These compartments would have been the key for maintaining chinampa agriculture within the city and its surrounding areas, which is another important aspect of discussion in the development of Tenochtitlan.
13.3.4 The Chinampa Systems in the Western Part of Lake Texcoco The chinampa system of Tenochtitlan is mentioned in numerous studies of sixteenth century cadastral documents and city ordinances (Carballal-Staedtler and Flores- Hernández 1989a, b; Calnek 1972, 1973). Based on early colonial documents, Calnek (1972) placed localities of chinampas on the map of the city, resulting in chinampas in all four wards but with the largest concentrations in Moyotlan and Teopan (Fig. 13.5). Then, the question is how were these chinampas associated with houses, to which an answer appears in some documents. The frequently cited Map on Maguey Leaf shows a pattern of isolated houses associated with a group of chinampas, though it is not clear what part of the city the map represents (Calnek 1973). However, another reconstruction of the chinampas and platforms with houses were in rows (e.g., Fig. 9.14b). Therefore, the settlement’ chinampa patterns may have varied in the city. Unfortunately, the excavated chinampas cover such small areas that it is difficult to study the patterns. The only case of a large excavated chinampa field is the chinampas of the Colonnia Transito, which would correspond to the southeastern part of the barrio of Ateponazco (within Teopan) (Dirección de Medios de Comunicación INAH 2016). Although the description shared to the public is minimal, it gives an idea that dwellings were next to the chinampas, suggesting, perhaps, the pattern represented in the map of Maguey. In any of the examples, historical or archaeological, the area occupied by chinampas was much larger than that occupied by nonagricultural features (dwellings, civic and religious structures, and marketplaces). As for the shape of the chinampas, they are highly consistent with the long and narrow types typical of the chinampas elsewhere in the Basin. Depictions of the chinampas on the map on Maguey Leaf and
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other documents (see Calnek 1972, 1973) and the layout of the Ateponazco chinampas (Dirección de Medios de Comunicación INAH 2016) suggest that the land-towater ratio was low, like their contemporaneous chinampas in Iztapalapa and the southern lakes (see Sect. 9.3.2). Presumably, the construction techniques, especially the use of aquatic vegetation and mud from canals, would have been similar to those described in historical sources and shown in archaeological contexts elsewhere in the Basin of Mexico. However, because the chinampas in Tenochtitlan and the surrounding settlements were in a saline lake, the strategies of water management were different from those in the southern lakes. More specifically, the issues concerning chinampas in Lake Texcoco were (1) securing freshwater, (2) preventing soil salinization, and (3) maintaining a stable lake level. In the Iztapalapa area, the chinampa system seems to have relied, as Palerm (1973) suggested, on a nearby sources of water, whether canals conveying it from reservoirs or the southern lakes. Evidence of water conveyed from freshwater sources to chinampas in saline lakes has a precedent in the case of Xaltocan, where chinampas are even older than those in the rest of the Basin (Morehart 2012b). However, the supply of freshwater to chinampas in Tenochtitlan is more complicated given the size of the fields. Unfortunately, to this point, no satisfactory explanation exists, though the hypothetical system of watertight compartments originally proposed by Palerm (1973) seems to be a way to manage water and prevent salinization, especially with the use of bordos (see Sect. 9.5.1). This, however, could be a local solution, especially for smaller areas such as Iztapalapa; in Tenochtitlan, the freshwater compartments would have needed major structures to supply water (see Sect. 10.3.2). A full-scale system to “desalinize the lake,” so to speak, for the development of the chinampa system in Tenochtitlan would have required solving several hydrological issues, the procurement of freshwater and the prevention of flooding by saline water. The first issue could have been solved on a small scale by building bordo dams around springs. As the city grew, however, it was probably necessary to secure water from other sources, perhaps from springs and streams inland, for which bordo canals (Fig. 10.6) would be needed, similar to the canals that brought water to Xaltocan’s chinampas (Fig. 9.15). The second issue, which is preventing the flooding of fields by saline waters, involved building bordos around the fields and eventually large dikes and causeways. In this case, the eastward gradient of the lakebed ground may also have helped, as it enabled keeping freshwater at a higher level. The dikes and the secondary structures (i.e., smaller dikes and bordo dams and sluice gates) would have kept the water from flowing eastward, prevented water from building up, and protected the fields from surges from the east. Such structures would have solved the third part of the problem by maintaining stable water levels for the chinampa fields and navigation canals. Another aspect that is still under debate relates to the date when the inhabitants of Tenochtitlan began their chinampa farming. Although there is a widespread assumption that chinampas existed in the area from the time of the foundation of the city, the chronological sequence for the development of chinampas does not exist in
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the historical and archaeological records. Certainly, the fact that the Mexicans paid tribute to Azcapotzalco in the form of nursery rafts with various crops already planted in them (Torquemada 1975: Book 2, XV, 142–143) may suggest that some form of aquatic agriculture existed from the early days of Tenochtitlan. However, the widespread use of chinampas seems to have occurred much later, probably toward the end of Itzcoatl’s reign (1427–1440), when, after defeating Azcapotzalco, the Mexicans gained full control of the freshwater sources in the mainland and hydraulic projects in the city began (Lombardo de Ruíz 1973: 65). This development agrees with the urban development of the city proposed by González-Rul (1988), who considered the years 1428–1446 to be the time when the physically isolated calpulli became interconnected into a single urban center (Fig. 13.4c, d). Purportedly, those empty aquatic spaces between islands were filled in with chinampa fields.
13.3.5 The Lacustrine Landscape Beyond Tenochtitlan There is much less knowledge of the hydraulic infrastructure in Lake Texcoco outside the area around Tenochtitlan, especially east of Iztapalapa and El Peñón de los Baños. However, it is possible that although not on the scale of the western part of the lake, hydraulic infrastructure existed in the eastern part of the lake. If the sources attribute most of the engineering of the hydraulic system around Tenochtitlan to Kings Nezahualcoyotl and Nezahualpilli, both rulers of Texcoco, then it would be ironic if some form of infrastructure did not exist in the Texcoco side of the lake. Canals and gardens, especially in the part of the lake near the city of Texcoco, are known (Alva-Ixtilxochitl 1975). Unfortunately, most of the possible infrastructure lies below the alluvial deposits of the colonial age and lamas, which extend over the lakebed (see Fig. 5.12). Nonetheless, areas around Nexquipayac Atenco have documental information (e.g., Fig. 2.10) and prospects for documenting the special uses of water and soil for agricultural purposes through the study of soils and sediments (Cordova et al. 2021). In the northern lakes were some structures of which we know little, despite their mentions in historical documents (Strauss 1974). Most recorded dikes and canals in these basins are of colonial age, often associated with infrastructure for flood protection or as part of the desagüe works (Candiani 2014; García-Chávez 2018). If pre-Hispanic hydraulic works existed in the Lake Zumpango basin, then they were probably destroyed by colonial construction works or were concealed under recent alluvial deposits or the waters of the modern lake. The only area with known hydraulic structures is the area around the island of Xaltocan, where a causeway, canals, and chinampas appear in the archaeological records (Morehart 2012a; Morehart and Frederick 2014). Other parts of the lake possibly had structures that would have prevented influxes of salt water, according to the soil profiles from the western part of the lake. If a structure existed to separate these two parts of the lake, then it would have run somewhere from Xaltenco to the foot of Cerro Chiconautla through the tlatel formed by Tonanitla, though only exhaustive geoarchaeological research would test this hypothesis.
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The Late Aztec lacustrine landscape of the southern lakes is better known through documental works (Ramirez 1976; Rojas-Rabiela 1974) and through surveys, excavations, and historical research studies (Frederick and Cordova 2019; McClung de Tapia and Acosta-Ochoa 2015; Luna-Golya 2014; Medina-Jaén 2008; Serra-Puche and Lazcano-Arce 2009; Avila-Lopez 2006; Parsons et al. 1982; Armillas 1971). The most notable hydraulic feature of this area is the Tlahuac dike, which connects the island of Tlahuac with the northern and southern shores. This dike also served to regulate the waters of the two lakes, especially preventing the flooding of Lake Xochimilco by the waters of Lake Chalco when its water levels increased (Candiani 2014; Rojas-Rabiela 1974). Similarly, the dike prevented the waters of Lake Xochimilco from flowing eastward when the water levels of Lake Chalco, whose bed lay lower, dropped (Humboldt 1811; Orozco y Berra 1864). In essence, the dike prevented the flooding or sudden draining of the chinampa system in Lake Xochimilco. Additionally, causeways connected Xochimilco and Mixquic with the mainland, though it is not known whether they also had a role in regulating water levels. Overall, the bulk of chinampa agriculture was found to be concentrated in the southern basins, a reason why in some sources, their inhabitants are referred to as Chinampanecas. The existence of springs, one of the main reasons for its persistent freshwater conditions, and the relative safety from river floods and sudden lake- level changes, would have enabled chinampa agriculture without the problems faced by the inhabitants of the other lakes. By the end of the Late Aztec period, the area of the lakes under chinampa cultivation would have been at its greatest extent. Going by some of the maps produced using aerial photographs and ground surveys (Luna-Golya 2014; Parsons et al. 1982; Armillas 1971), it could be easily concluded that somewhere between 50% and 80% of the area of the southern lakes was cultivated and settled.
13.4 The Development of Tenochtitlan as an Environmental Dynamic Process 13.4.1 A Dynamic Environmental Model Beyond the historical narratives, often grounded in mythological events, several studies have called for alternative explanations for the environmental origin of Tenochtitlan, especially linked to climatic changes (Berres 2000; Lachniet et al. 2012, 2017). An environmental perspective of the foundation and evolution of the city, however, should not leave out the historical events in ethnohistorical sources and archaeological records. Moreover, knowledge about the construction of hydraulic infrastructure, despite being limited, should serve as the basis for an environmental model of the evolution of settlements in Lake Texcoco. Bearing in mind this inclusive view of the sources, a model of the possible origin of the city can be placed
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in the context of lake dynamics (see Chap. 8). Therefore, the first aspect to consider in the elaboration of the environmental history of Tenochtitlan is its location within the Lake Texcoco basin, particularly in relation to the lake’s topography, layout of features, and the recurrent flows of water (Fig. 13.6). Keeping the model in Fig. 13.6 in mind, the first aspect to notice is that despite being a saline body of water, the western and southwestern parts of Lake Texcoco benefited from an influx of large volumes of freshwater from the rivers. In part, this influx has to do with the hydrology of the Sierra de las Cruces, its piedmont, and the alluvial plain, where fractures providing water from springs and river catchments are relatively larger than those for most of the rivers descending from the Sierra Nevada (Fig. 3.12, hydrographic zones II and III). Moreover, the relatively narrow alluvial plain of this part of the basin enabled a faster transition between the alluvial and lake realms, thus characterizing this shore as a mosaic of fluvial and lacustrine features such as channels, esteros, and vegetated marshes and swamps (e.g., environment 4 in Fig. 8.11). In contrast, the eastern side had a wider plain and a lower gradient with smaller streams, which led to the development of environments more conducive to open salt flats, which, with fewer springs, would have been less attractive for aquatic settlement. Certainly, the lack of land for the Mexicans and the political geography of the Basin in the thirteenth and fourteenth centuries played a role in initiating the earliest settlements in the marshes of the western part of the lake. Yet, if it had been possible, then such settlements could have occurred farther away from their enemies (e.g., Azcapotzalco and Culhuacan). Nevertheless, the more habitable marshes of the western part were more attractive despite being at the gates of the enemies. The western part of the lake would have been ideal not only because of the influx of freshwater but also because the deeper part of the lake was east of El Peñón de los Baños, making the lakebed in the western part dip gently to the east. This slope was evidently important, as freshwater could be utilized before it flowed into the lower area where it would mix with saline water. Nonetheless, this general model would have had to not only accommodate seasonal hydrological fluctuations but also changes in the longer term according to multi-decadal fluctuations in precipitation.
13.4.2 Long-Term Changes in the Evolution of the City With the premise that the west-east gradient of the lakebed in the western part of Lake Texcoco and the inputs of freshwater, it is possible to reconstruct the possible hydrological changes that occurred before, during, and after the collapse of Tenochtitlan and into the first century of the Spanish Mexico City, roughly encompassing ca. 1200–1650 (Fig. 13.7). This model illustrates the hydrological stages that occur under high or low lake levels in the western part of Lake Texcoco, where palustrine and lacustrine conditions can be reconstructed for certain historical events (Fig. 13.7a, e). The basis of the climatic background, as discussed in Chap.
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Physical characteristics Larger stream catchments Narrow alluvial plain Gentler lakebed gradient
Smaller stream catchments More extensive alluvial plain Steeper lakebed gradient
Faster delivery of larger amounts of freshwater and sediments to the lake. Fluvial ediment accumulation and vegetation extend farther away from the shore
Slower delivery of freshwater and sediments to the lake. Fluvial sediment accumulation and vegetation are closer to the shore
Catchment divide
Catchment divide
Alluvial plain
Alluvial plain
Alluvial plain Alluvial plain
Catchment divide
More springs More permanent streams with large discharge Less saline water and more sources of freshwater
Fewer springs Mostly intermittent streams resulting in lower discharge More saline waters and fewer sources of freshwater
Resulting conditions for lake appropriation:
Higher natural diversity Better conditions for building settlements and control of freshwater flows for wetland agriculture whiile having access to salt
Lake
SYMBOLS Influx of water from other lakes
Deeper area of the lake (based on its historical recession) Rocky islands (peñones)
Lower natural diversity Building settlement only near the shore, and difficulties for managing freshwater. though larger potential for salt production
Saline Freshwater
Incoming streams Permanent Seasonal Intermittent/ ephemeral
Fig. 13.6 Diagrammatic model that compares the western and eastern parts of Lake Texcoco in terms of conditions for the development of lacustrine settlements and chinampas
13.4 The Development of Tenochtitlan as an Environmental Dynamic Process Colonial
a
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FW Freshwater SW Saltwater
Flow or water forces
*Hydrological stages in the west part of Lake Texcoco based on decadal lake level stands IV Shallow lake with deep parts. Saline water forces its way westward mixing with freshwater during certain times of the year III Shallow lake with fresh water moving eastward. Occasional saline water invasions from the east. Easy navigation across the lake. II Marsh with springs and fresh water moving eastward. Navigable natural channels (esteros) or dugout canals I Saltflat with springs
Fig. 13.7 The evolution of Tenochtitlan’s landscape: (a) projected lake-level changes in the western part of Lake Texcoco from c. AD 1200 to 1650, indicating hydrological stages (Roman numerals) and events (Arabic numerals). Comparison with δ18O records from (b) speleothems in Juxtlahuaca Cave (Lachniet et al. 2017) and (c) sediments in Aljojuca Lake (Bhattacharya et al. 2015; Lachniet et al. 2017). (d) Solar irradiation curve based on sunspot numbers (Data from Solanki et al. 2004). Events marked in panel a appear in panel c, in a sequence from top to bottom: (1) before 1325; (2) growth of the city still under Azcapotzalco rule; (3) around the time of Itzcoatl’s rule; (4) construction of Nezahualcoyotl’s dike during Moctezuma’s I reign; (5) construction of Ahuizotl’s dike; (6) the war of conquest; and (7) lake drying during the rule of Viceroy Velasco the Elder
12, came from regional precipitation proxies (Fig. 13.7b, c) as well as the sunspot number (Fig. 13.7d), which is a proxy for solar irradiance (Solanki et al. 2004). The latter is the closest proxy that could help understand evaporation in the hydrological cycles of the lakes of the Basin (see the discussion in Sect. 8.5). The decades preceding the founding of Tenochtitlan seem to have coincided with a low lake stand caused by lowered precipitation, which had perhaps prevailed since the collapse of Tula (Lachniet et al. 2017). Therefore, the lake level of the far western part of the lake may have been low enough to expose the ground, making it a wetland, consistent with the descriptions of reeds and sedge fields in the sources. During this time and in the early days of the city, settlements consisted of tlateles in the swamps (Fig. 13.7e, 1). In the subsequent decades, levels began to rise, reaching a high point in the mid-fifteenth century. Perhaps, it is at this time that tlateles were upgraded and structures built, mainly small dams (bordos), to manage the freshwater flowing from the west to the deepest part of the basin in the east (Fig. 13.7e, 2). As discussed above, the first half of the fifteenth century saw a faster development, probably with the first chinampas, which could be a problem as the bordos were not enough to contain the floods of saline water from the east, as the lake levels were
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rising (Fig. 13.7e, 3). The problem was partially, if not fully, resolved with the construction of Nezahualcoyotl’s dike (Fig. 13.7e, 4), which prevented the mixing of waters, high on both sides due to increased precipitation and low evaporation, and provided low insolation. Precipitation slowly declined in the mid-to-late 1400s, with some deep droughts (Therrell et al. 2006). Although new floods occurred at the turn of the century, lake levels were already low, and the Nezahualcoyotl dike had lost its functionality, as the lake levels were in decline and a dike had to be placed elsewhere. Thus, the construction of Ahuitzotl’s dike and the reinforcement of the Tepeyac and Iztapalapa causeways protected the city from extreme flood events, at a time when freshwaters in the west were maintained at a stable level by raising them slightly above the saline water levels (Fig. 13.7e, 5 and 6). Breaking the dikes, as done during the war and siege of Tenochtitlan in 1521, resulted in the mixing of the waters, though levels were still high enough for the Spanish vessels (brigantines) to navigate (see Chap. 14). Subsequently, the dikes and causeways became apparently obsolete during the period of prolonged drought from 1524 to around 1550 (Fig. 13.7e, 5 and 6). This indicates neglect on the part of the colonial authorities, who were unaware of the long-term dynamics of the lake. Thus, in view of the extreme low lake levels of this drought period, Viceroy Luis de Velasco I (who ruled from 1550 to 1564) ordered the redirection of the Cuautitlan River into Lake Texcoco for the purpose of raising the water level and allowing canoe traffic to supply the city with needed goods (Candiani 2014). This situation changed in the early and later parts of the sixteenth century when rains again increased and possibly evaporation levels declined with the slow decline of sunspots (Fig. 13.7a–d). It was in the first half of the seventeenth century that the disastrous floods that afflicted the city occurred (see Chap. 14). In summary, the diagrams of Fig. 13.7 portray in general terms what the lake- level trends were and how they affected the area where Tenochtitlan was founded until its collapse and replacement by the Spanish-founded Mexico City. Furthermore, this model shows how the city had to adapt to the long-term (decadal) dynamics of the lake—therefore, the view presented here provides a history of the city as an environmental process. However, the centuries before and after the life of the city are interesting to see as they show the pre-urban development and the consequences of changing the management of water in the lake. The model presented here contrasts with the static views of the lakes portrayed by contemporary maps and histories of the lacustrine realm of the Basin of Mexico (see discussions in Chap. 7).
13.4.3 Seasonal Hydraulic Dynamics in the Context of Long-Term Lake-Level Changes One aspect to consider when looking at the development of the hydraulic infrastructure during the Postclassic period in the lakes of the Basin is the lacustrine dynamics throughout the year. In other words, the network of dikes and canals would have had
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to adapt to the natural seasonal cycles of the lake (Fig. 8.13) and the seasonal strong currents (Fig. 8.7) and occasional surges. Consequently, the north-south dikes (Ahuizotl’s and Nezahualcoyotl’s) would have created modifications in the seasonal flows of water in the lake to protect the city from incursions of saline water at times when the levels rose in the wet season, especially when currents from the east pressed against the city (Fig. 8.7b, c). Similarly, these dikes would keep water inside the city to enable navigation and chinampa cultivation when the levels dropped in the dry season. Likewise, the southern causeway-dike (Huitzilopochco- Mexicaltzingo-Iztapalapa) would have protected the city from flooding by the southern lakes, while, perhaps, redirecting water to the Iztapalapa chinampas, though the latter case is still hypothetical. As discussed in Sects. 13.3.2 and 13.4.1, the two north-south dikes were not contemporaneous, as they were constructed at different times in history, perhaps responding to different lake levels. Therefore, as proposed by Lachniet et al. (2012, 2017), Nezahualcoyotl’s dike operated at a time when the lake levels reached a high peak. Thus, it seems that some internal infrastructure existed within the city for flood protection during Itzcoatl’s rule, but it was not enough to protect the city from sudden high lake-level stands during the rule of Moctezuma I (Lombardo de Ruiz 1973). Nezahualcoyotl’s dike should have protected the city from floods, especially those coming from the northern lakes, which, in turn, received large amounts of water from the Avenidas de Pachuca and Cuautitlan rivers that cascaded into Lake Texcoco across the northern lake basins and the strait of Ecatepec. However, the dike may have also been useful during other times of the year to prevent the mixing of saline water and freshwater, which would have affected the city, especially during sudden flash floods or surges caused by strong winds. It is perhaps for this reason that the chinampa system did not develop until the construction of Nezahualcoyotl’s dike. There is then the possibility that west of the dike, the water levels were higher than those on the east side and the opposite occurred in the dry season. Therefore, it is probably unlikely that the dike had openings during its functional life. Canoes navigating to and from the east side would have had to unload and reload their cargo. Through the 1470s and 1480s, perhaps the dike was not necessary as the water levels dropped so the water flowed naturally eastward, as it normally would. The openings may have existed already at the time of the Spanish conquest, perhaps as represented in the map of Nuremberg (Fig. 1.5), which would explain how the brigantines would move into the city without the barrier of a dike (see Chap. 14). Ahuizotl’s dike may have been necessary during lower lake levels but it had no use during sudden hikes of lake levels by short periods of abundant rain (Fig. 13.7). Ahuizotl’s dike had the practical function of keeping the water levels within the city stable while protecting it from incursions of saline water from the west. The reason for it being closer to the city may be explained in terms of the convenience of using the already-constructed north-south causeways as dikes (Tepeyac and Iztapalapa). Like its predecessor, Ahuizotl’s dike would regulate waters on both sides and keep saline waters from flooding the city during the lake-level rise in the wet season, while serving as a dam to keep the freshwater at a stable level in the west during the dry season. As we know through the chronicles of the conquest, the causeway had
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gaps, which could be used by canoes, but could also be blocked to prevent water from draining into the lower areas during low levels. Given that the lakes underwent tremendous long-term changes (e.g., Figs. 8.14 and 8.15), the dikes had a limited life. Dikes and bordos had to be constantly upgraded, relocated, or abandoned. It is not surprising then that Nezahualcoyotl’s dike lasted a few decades, until it became obsolete given the hydrological changes related to the changes in atmospheric moisture. Ahuizotl’s dike was functional when the Spanish arrived in 1519, but, as we know, it had no use during the drought period of 1524–1550 and had to be upgraded afterward when the wet years returned (see Chap. 14). This sequence of infrastructure changes shows that in contrast to the idea of stable lakes, the highly dynamic lakes of the Basin required an extremely dynamic strategy for water control.
Chapter 14
The Lakes After 1519: War, Floods, and Drainage
14.1 The Lacustrine Landscapes of the War of Conquest 14.1.1 The Strategic Importance of Insular Settlements The lakes of the Basin provided a large part of the subsistence to the inhabitants of the Basin while serving as a means of communication and trade between the settlements on the shores. However, it was evident that the growth of large insular settlements and the constant warfare among them implied some changes in the distribution of settlements. Thus, insular settlements such as Xochimilco, Tlahuac, Mixquic, Xaltocan, and Tlatelolco Tenochtitlan developed with the lakes’ water around them as defense. Over time, however, many of these settlements became subdued by others. Thus, at the time of the arrival of the Spanish in 1519, Tenochtitlan was the only sovereign insular settlement and one that was well-protected from its enemies. According to the chronicles, Tenochtitlan was an insular city that was connected to the mainland by a series of causeways with drawbridges and defensive towers (Cortés 1985; Bernal Diaz del Castillo 1982). In the context of this insular strategic position, the importance of naval defense became clear through the existence of canoes crafted for use in warfare (Biar 2017; Favila-Vázquez 2011). The Spanish conquerors were tested by the hardships of battling canoes before and during the siege of Tenochtitlan, despite having guns and the much larger European craft. The chronicles also describe the difficulties that the Spanish army and its allies faced when moving along the causeways while being attacked from canoes. The debacle of the Sad Night (June 30, 1520) is an example of how effective the attacks from the canoes were, as dozens of Spanish and their allies were massacred trying to reach the mainland during their flight from the city along the Tacuba causeway. Early experiences with battling the defenders of an insular city led the Spanish to build their own navy of brigantines, which, though a herculean task, was one of the main reasons for their success in taking the city (Gardiner 1956). Certainly, the © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5_14
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conquerors had other advantages: the number of native allies, availability of gunpowder, and the unintentional but devastating spread of smallpox that decimated a large number of their Mexican adversaries (Escalante-Gonzalbo 2004). Nonetheless, the difficulties with the aquatic environment during the war were the first obstacles that the Spanish encountered in a series of other predicaments that were soon to come in their quest to dominate the Basin of Mexico. After the war, a clash of two civilizations occurred for the dominance of the dynamics of the lakes, as one alien nonaquatic culture tried to establish itself in an aquatic environment that the native culture knew well. For this reason, this cultural transition in the lakes of the Basin of Mexico is important to observe in terms of the history of civilizations in lacustrine environments.
14.1.2 A Battlefield Geography (1519–1521) Descriptions of the events of the conquest appear in firsthand and secondhand sources. Firsthand sources directly originated from participants in the events, namely, Hernán Cortés, Bernal Díaz del Castillo, Francisco de Aguilar, and an anonymous conqueror (Aguilar 2018; Cortés 1985; Díaz del Castillo 1982; Conquistador Anónimo 1941). Secondhand accounts were written in later decades by authors who obtained information from primary sources and informants (e.g., Cervantes de Salazar 2007; López de Gómara 2006; Sahagún 2002; Torquemada 1975; Durán 1897). Additionally, reviews of related documents provide information about the settings and events not recorded in the chronicles but obtained from dispersed sources of information (e.g., Clavijero 1974; León-Portilla 1959; Gardiner 1956, 1958). Battlefield geographies customarily use maps to portray battle sites and the movements of armies with respect to elements of the landscape. This practice is problematic for the Basin of Mexico, given the many aspects of historical cartography and misconceptions about the former lakes (see Chap. 7). Nonetheless, an approximation based on the existing information and careful avoidance of known geographic blunders permits the depiction of the most relevant events of the conquest of the lacustrine area and the siege and taking of Tenochtitlan. Thus, these events were placed on the map, which has been the cartographic basis throughout the previous chapter, known as the map of Niederberger (1987) with features reported in the map of González-Aparicio (1968) and the urban geography of Calnek (1972, 1973) and further modifications by the author (Figs. 14.1, 14.2, and 14.3). The maps include events spanning from the first visit of the Spanish and ending in the Sad Night (Noche Triste) flight and the Battle of Otumba (Fig. 14.1), events of the campaigns preceding the attack on Tenochtitlan (Fig. 14.2), and those of the main assault and siege of the city (Fig. 14.3). For some aspects of the campaigns, the details to place them exactly where the events occurred are lacking. For example, the exact location of the capture of Cuauhtémoc, who fled Tlatelolco in a canoe, is not known, though a landmark around Tepito marks the place where Cuauhtémoc, the captured last king of the Mexicans, was presented to Hernan Cortés.
14.1 The Lacustrine Landscapes of the War of Conquest Citlaltepec
Citlaltepec
November 1519-July 1520 N
a
321 December 1520-April 1521
b
Spanish route after the Sad Night. Early July 1520
January-February 1521 March on Xaltocan and Tacuba Teoloyucan Xaltocan
To Tlaxcala RTT
Otumba
Cuautitlan
Cuautitlan Campaign continues twoards Tacuba with the purpose of sounding terrain for a future attack on Tenochtitlan
Above 2500 m 2300-2500 m 2250-2300 m
Tenayuca
Below 2250 m
Popotla Tacuba
RTT
Texcoco
Atarazanas
Cortés-Moctezuma meeting place
Coyoacan Culhuacan
Brigantine
Arrival of Cortés’s army in the Basin of Mexico. November 1529
10
Texcoco Huexotla Coatlinchan
Mixquic Tlalmanalco Ayotzingo
Coatepec
RTT
Coyoacan Campaign conitnues to the western shore
Chalco
5 Km
Corés establishes its base of operations against the Mexica in Texcoco
Tenayuca
Battle or skirmish
Cuitlahuac (Tlahuac)
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Acolman
Iztapalapa defenders break a dike to flood the Spanish army
Attacks by canoe RTT Retreat to Texcoco
Iztapalapa
Mexica warriors in canoes come to Xaltocan’s help
Second unsuccessful attempt to take Tacuba Tacuba Tlatelolco Tenochtitlan
Spanish flee the city during the Sad Night. June 30, 1520 Brigantines sail with Moctezuma to Tepepolco
N
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Iztapalapa campaign Culhuacan January 1521
5 Km
Mexica canoe attack Xochimilco
Chalco
Cortés moves to Texcoco on the last day of 1520
Xochimilco Tlalmanalco To Campaigns in 10 campaign Spring 1521 Cuauhnahuc, Spring 1521
Fig. 14.1 Events of the conquest in the lacustrine area: (a) November 1519 to June 1520 and (b) December 1520 to April 1521 Fig. 14.2 Events of the war against Tenochtitlan during April and May 1521
April 28-May 30 1521 Alvarado moves to Chapultepec to cut of water supply to Tenochtitlan and takes Tacuba, May 1521
Tenayuca
5 Km
N
Brigantines launched on April 28, 1521 Then, weeks of training on water
Texcoco Brigantine Shipyard flotilla sails towards Canal Tepepolco. May 30, 1521
Azcapotzalco Tepeyac Tacuba
0
Tlatelolco Tenochtitlan
Chapultepec
Olid moves to Coyoacan May 1521
Hundreds of canoes sail towards Tepepolco
Tepepolco Iztapalapa
Cortés takes the island and from the hilltop gains a better view of the enemy forces
Sandoval moves to take Iztapalapa
Ground attack
Battle or skirmish
Naval attack and siege
Brigantine
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a N
May 30-early June 1521
b August 1521
N
Tacuba
14 13
Mexica-held territory
Tlatelolco
12
8
11
9
Tacuba
2
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7
6
5
Coyoacan
Acachinanco Ground attack Naval attack and siege Battle or skirmish Brigantine
2
Acachinanco Xoloc
km
1 4
Tepepolco
3
Iztapalapa Huitzilopochco Culhuacan
0
5 km
1 Naval battle won in favor of the Spanish. Brigantine force splits. 2 Canoe forces fail to repeal Spanish advance and retreat to the city 3 Sandoval pushes through Iztapalapa 4 Brigantines help Olid and Sandoval to secure the southern causeways 5 Cortés takes the Acachinanco fortress 6 Breach of a dike. Brigantines sail to aid Alvarado in Tacuba. 7 Brigantines navigate north with Sandoval 8 Sandoval takes Tepeyac and secures the causeway 9 Brigantines sail to secure other causeways. The naval siege of the city begins 10 Brigantines join forces with Alvarado to take the Tacuba causeway. 11 Cortés’s forces adavance from the south 12 Alvarado’s forces join Cortés from the west 13 Brigantines break intoT latelolco harbor and land at the market 14 Cuautemoc escapes, but is aprehended by Holguin. War ends
Fig. 14.3 (a) Events from May 30 to the middle of June 1521 and (b) events leading to the surrender of Cuauhtémoc on August 13, 1521
14.1.3 Lacustrine Dynamics and Features in the Chronicles of the Conquest Historical sources refer to several natural and cultural features of the lakes and their dynamics, which for the most part have not been analyzed from a geographic point of view. The cultural features described by the chronicles of the conquest include dikes, causeways, islands (tlateles), and chinampas, some of which have been compiled and discussed in previous works (Candiani 2014; Carballal-Staedtler and Flores-Hernández 1989b; Rojas-Rabiela 1974; Palerm 1973). Therefore, in this
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section, some extracts of the chronicles are discussed in the context of the aspects presented in the second part of this book, mainly the configuration of the lakes, salinity, and natural features. In terms of the dynamics of the lakes, Cortés (1985) and the conquistador Anónimo (1941) portray the general idea of a freshwater lake and a saline lake, although it is not clear whether the former meant only the southern lakes or it included the western part of Texcoco. However, Cortés (1985: 71) mentioned that the freshwater flowed into the saline water and that the flow went from behind Ahuizotl’s dike and the Iztapalapa and Tepeyac causeways to the western part of the lake (see Sect. 13.3.2). The chronicles report that the Spanish took over the Iztapalapa causeway on May 30, 1521 (Fig. 14.2); they broke it to get their brigantines to the other side, namely, into the freshwater side of the lake. Perhaps, after this event, they sealed the broken gap, though there is no reference of this, other than the fact that, constantly, the Mexican defenders broke the causeways and that the Spanish attackers repaired them. The existence of Lake Xaltocan during the war is evident in the description of the battle as displayed in Fig. 14.2. Bernal Díaz del Castillo also describes the existence of esteros communicating between it and Lake Texcoco. He relates that “Mexico habia enviado escuadrones de gente de Guerra a Saltocan para les ayudar, los cuales fueron en canoas por unos hondos esteros” (To help Xaltocan, Mexico sent squadrons of warriors, who came in canoes along deep esteros) (Díaz del Castillo 1982: 332). This comment suggests that the esteros were in the strait connecting Lakes Xaltocan and Texcoco and were most likely deep natural wetland channels like the ones depicted in Fig. 8.10b. Despite the mention of Lake Xaltocan, the existence Lake Zumpango and the strait connecting it to Lake Xaltocan is not mentioned. However, some sources suggest that the movement of troops between Texcoco and Tacuba during some campaigns was through Citlaltepetl (e.g., Cervantes de Salazar 2007; López de Gómara 2006; Clavijero 1974; Orozco y Berra 1880), which implies a route around the northern flank of Lake Zumpango (Figs. 14.1 and 14.2). Therefore, it is easy to think that the area of Lake Zumpango and the strait connecting it to Xaltocan was not a passable route, perhaps because it was a swampy terrain. Nevertheless, the northern route through Citlaltepetl could also have been a strategic measure to avoid areas easily reached by the Mexicans in canoes, similar to what occurred during the battle of Xaltocan (Fig. 14.1). Among the many geographic aspects of the war of conquest, one of the most intriguing is the operation of the brigantines in the shallow waters of Lake Texcoco during the assault on and siege of the city (Fig. 14.3). The most intriguing part is that the throwing of the brigantines into the lake and the first assault occurred in May, which is the end of the dry season, a time when lake levels would have been at their lowest. Even during the early part of the rainy season, levels would still be low enough, at least through the first weeks of the battle in June. Nevertheless, it is likely that the brigantines were small and designed for navigating in shallow waters (see Sect. 14.1.4). Moreover, at least Torquemada (1975: 267) and Sahagún (1830: 40) mention that Cortés sounded the waters of the lake before the attack. Although they do not mention dates, it is likely that the sounding occurred in the days between the
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launching of the vessels from the shipyard in Texcoco (April 28) and the day of the first assault on the Mexicans (May 30). If that was the case, then the Spanish vessels would have followed a route along the deepest parts of the lake. Similarly, there is no mention in any of the sources, during the siege, of any difficulties in navigation due to the shallow waters or any brigantines running aground. Therefore, despite the breaking of the causeways by the Mexicans for slowing the advance of the attackers, the western part of the lake was still navigable. Although the seasonal low levels may have been a problem for navigation, the overall levels of the lake may have been high, as the years and decades preceding the war of conquest were relatively wet. Regional proxy precipitation data support the idea of high lake levels from around 1490 to the early 1520s (Fig. 13.7). In fact, floods during the end of Ahuizotl’s reign and through Moctezuma’s II reign were frequent and catastrophic (see Ramirez 1976). Therefore, under a prolonged wet period, lake levels at the end of the dry season would not have been as low as they normally were (see the models in Figs. 8.13 and 8.14). Most of the sources describing incidents involving the brigantines during the siege of the city provide a picture of the lacustrine landscape, especially an aquatic environment with groves of aquatic vegetation. Among many incidents were ambushes that the Mexicans carried out by planting stakes at the bottom of the lake to block the passage of brigantines, while the attackers hid in the nearby reeds. Once a brigantine was jammed in the stakes, the ambushers came out of their hideouts, attacked, and boarded the vessel, sometimes carrying prisoners as well. The accounts of these incidents indicate that the lake around Tenochtitlan was to a certain point vegetated with tulares and carrizales, which contrasts with the visual and cartographic depictions of a Tenochtitlan surrounded only by clear spaces with only water.
14.1.4 The Brigantines and the Naval Battle of Lake Texcoco Despite the importance of the brigantines in the Spanish success in the war of conquest, historical sources provide little detail about the vessels themselves. Additionally, discrepancies and inconsistencies among the sources and historical accounts exist in terms of the construction, shape, size, and capability of the vessels. The primary inconsistency regarding shape and size lies in the term itself. In terms of sixteenth century vessels, a brigantine was a ship with two masts, and, like its contemporaries, the nao and the caravel, it had towers or bridges at the bow and stern (Romero 2017). However, the sources from the conquest mentioned at least four oars on each side of the vessel, a description inconsistent with that of an early sixteenth century brigantine, which did not use oars (Gardiner 1956). The descriptions given in all sources seem to suggest that the vessels looked more like a galley, more properly a fifteenth century Portuguese fusta. The latter is a type of galley of a small draft with one mast, sails, and oars. Such a vessel is characterized as being fast and able to operate in shallow waters (Matthew 1988). In fact, the word fusta appears five times in Cortés’s letters to King Charles V (Cortés 1985).
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A series of documents referring to a litigation Martín López, the builder of the brigantines, filed against Cortés for his excessively unfulfilled promises provide general descriptions of the construction and dimensions of the brigantines (Gardiner 1956, 1958). The estimated dimensions of the largest ship (the captain’s ship) and those of the rest of the fleet (Gardiner 1956: 68) indicate relatively small vessels (Fig. 14.4b, c). Noticeably, the low draft (approximately half a meter) would enable them to navigate in shallow waters. The vessels maintained a beam wide enough to
a
b
c
Fig. 14.4 (a) Cortés’s brigantines as depicted in Bernardino de Sahagún’s Florentine Codex, Book 12 (Sahagún 2002), sketched by the author. Reconstruction of the (b) flagship “La Capitana” and (c) the rest of the brigantines, based on dimensions provided by Gardiner (1956). Marks in the horizontal and vertical scales represent 1 m
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accommodate oarsmen and had space for movement between them, while being narrow enough to navigate across constricted gaps in causeways and canals. None of the chronicles of the conquest mention any instance of any brigantines running aground or the impossibility of navigating in any areas around the city. In fact, the siege was heavily enforced from all directions to prevent the smuggling of food or water into the city, and most authors concur that despite the attacks, the brigantines could navigate into the city along its canals. As always, a mud captain on the bow would fathom the waters (Gardiner 1956), which perhaps helped avoid shallow areas where the vessel could run aground. It is important to remember that by the time of the battle, the Spanish were already familiar with the lake. During his stay at Cortés’s in Tenochtitlan, between November 1519 and June 30, 1520, Martín López built four brigantines (Gardiner 1958). The chroniclers mentioned that on one occasion, they even invited Moctezuma for a sail to Tepeapulco (Díaz del Castillo 1982) (Fig. 14.1). The fact that the Mexicans did not impede the construction of the vessels meant that they did not suspect any intention on the part of the Spanish to use the brigantines for strategic purposes. However, it is likely that Cortés had the four brigantines built to escape by water in case of an attack or to fathom the waters of the lake in case of a future naval siege (Gardiner 1956). When relations with the Spanish deteriorated, the Mexicans burned the brigantines, forcing the Spanish and their allies to flee via the Tacuba causeway on the night of June 30, 1520 (Fig. 14.1), causing the debacle of the Sad Night, an event that reassured Cortés that a naval attack was the only way to defeat the Mexicans and conquer their city. After a series of battles outside the Basin of Mexico, the 13 brigantines for the final battle were crafted in Tlaxcala using nearby wood sources and implements of iron and sails salvaged from ships that had landed in Veracruz, including some of those that Cortés had destroyed in previous months. With no lakes in the immediate surroundings of Tlaxcala, the waters of the Zahuapan River were dammed with stones to recreate the shallow conditions of Lake Texcoco to test a prototype of the brigantines under construction (Gardiner 1956). The brigantines were then disassembled and carried to Texcoco, where they were reassembled and launched on April 28, 1521. The choice of Texcoco as the shipyard and naval base to launch the brigantines into the lake is clear based on its physical location. Bernal Díaz del Castillo (1982: 315) discussed two options for a shipyard and a naval base, Ayotzingo and Texcoco. Ayotzingo had canals that were better suited for a shipyard, but it was too far from the target of the campaign with many lacustrine towns in between. Texcoco, on the other hand, though more difficult for a port, had the advantage of being closer to both Tlaxcala and the target. Besides, to carry the ships from the shipyard in town and launch them into Lake Texcoco, a zanja (canal) and an estero (inlet or bay) were required (Díaz del Castillo 1982: 315). Additionally, the Texcoco choice was the better one, as a rift in the Texcocan royal family provided an opportunity for an alliance against the Mexicans (López de Gómara 2006; Clavijero 1974). The exact location of the shipyard in Texcoco has been lost with time, but clues to its possible location in chronicles and documents as well as the Aztec
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archaeological reconstruction of the city can help identify possible locations of the shipyard and the canal used to launch the brigantines. A monument in Texcoco indicates the locality, though historians believe that it is in the wrong place (CrucesCarvajal 2015) and that it is possible that the location is within the grounds of the main palace in the city as hinted by Cortés (1985). Scattered archaeological data, written descriptions in various historical sources, and colonial maps have been the basis for reconstructing the Late Aztec city of Texcoco (Coronel-Sánchez 2005). With this information, it is possible to locate the shipyard and the possible places of the canal and the estero mentioned by Bernal Diaz del Castillo (1982), though this task will require other sources as well as geomorphological and sedimentological work.
14.2 Dynamic Lakes, Floods, and Drainage 14.2.1 A Non-Lacustrine Society Settles on the Lake One of the big mistakes made by the Spanish conquerors was to build the capital city of New Spain, Mexico City, on the ruins of Tenochtitlan. The problem with this decision was that the Spanish knew practically nothing about the dynamics of the lakes and the past developments that led native settlers to build settlements according to the dynamic changes of the lakes. In particular, the dikes, bordo dams, canals, and other features were destined to regulate water levels throughout seasons and through periods of extremely low or high lake levels. Although Cortés first considered establishing the seat of the Spanish rule in Coyoacan, he soon changed his mind, turning the construction efforts to the seat of Aztec power (Candiani 2014). The construction of the Spanish city went ahead without any provisions to deal with the aquatic environment, however, in contrast to the Aztec city that it meant to replace. The dikes, which had been destroyed during the war, were not rebuilt, but their materials were used for the construction of the new city (Candiani 2014). Moreover, the construction of the Spanish city converted many of the canals of the Aztec city into streets by filling them with rubble (Jiménez- Vaca 2017), which reduced the capacity of the city’s ground to drain properly, especially in times of water excess. Not only did the Spanish lack familiarity with the lacustrine conditions around the city but the construction and expansion of the new city also occurred at a time when lake levels began to drop during a period trending toward dryness as evident in some of the historical sources (e.g., Motolinia 1990; Torquemada 1975; Códice Aubin 1963) as well as in proxy records from tree rings and oxygen isotopes (Stahle; Lachniet et al. 2012, 2017; Bhattacharya et al. 2015) (Fig. 13.7). Motolinia (1990) considers the year 1524 as the beginning of the drying period, when the lakes began to shrink, consistent with the paleoclimatic records (Fig. 13.7). During the advanced phase of this drought period, the city began to face some
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problems, especially with the traffic of canoes at a time when supplies to the city still depended on navigation routes. Given this situation, during the governance of Viceroy Luis de Velasco (who ruled from 1550 to 1564), attempts to prevent the drop in water levels included the elimination of the former infrastructure to contain the lake and the diversion of the Cuautitlan River to its former course (Candiani 2014). Such a move had disastrous consequences when climatic trends reverted to wetter conditions. In 1553, copious rains made the lakes swell, with the first known flood of the city occurring within the period of the Spanish rule (Ramirez 1976). This flood prompted the authorities to repair some dikes and take other measures such as reinforcing some dikes that were only a patch over a major problem (Candiani 2014). However, subsequent copious rain events, especially the 1580 flood, alerted the government and the Spanish Crown to act on a more lasting solution, which happened to be the draining of the lakes out of the basin or the so-called desagüe (Gurría-Lacroix 1978). The herculean project of desagüe was given to Enrico Martínez, a man who held the title of royal cosmographer. Despite having no proper experience in hydraulic technology, Martínez began directing the construction of a tunnel through the northwestern divide of the Basin, a project that was known as the Tunnel of Huehuetoca, where the Tajo de Nochistongo is now located (see Fig. 3.11a). However, authorities and residents debated over the usefulness of the expensive and long project, especially during years without extreme rain events, when the flood problem was not apparent. At times, the project had to be halted either for technical or for political and economic reasons. Copious rains returned in the early years of the seventeenth century, thus pressuring the colonial government to carry on with the project. Digging the tunnel in the area of Nochistongo proved to be difficult due to conditions of the rock and difficulties with labor, which heavily depended on Indian workers (Candiani 2014). The floods of 1604 and 1607 were particularly catastrophic and made the digging of the tunnel more difficult. Thus, given the high cost and slow pace of the project, alternatives were sought, and additional infrastructure was built to protect Mexico City. With the idea that the Cuautitlan and Avenidas de Pachuca rivers were the culprits in most floods, the San Cristobal dam (i.e., Albarradón de Ecatepec) was built at the strait connecting the northern lakes with Lake Texcoco (García-Chávez 2018). Soon, however, it was clear that the problems lay elsewhere, as waters from the southern lakes contributed to the flooding, thus prompting the building and reinforcement of dams in the south (Candiani 2014). Similarly, the incoming rivers contributed to swelling of the lake during periods of abundant rain, thus leading the government to dam some of the large rivers. The San Juan Teotihuacan River was dammed at a narrow pass south of Acolman by the Presa de Acolman, and the Avenidas de Pachuca was dammed upstream with the construction of the Presa del Rey (Gurria-Lacroix 1978; Ramírez 1976). All these measures, however, did not help solve the problem, as floods kept occurring. Once the tunnel of Nochistongo began to function, it was riddled with problems, especially eventual collapses that backed up the water and made repairs more difficult (Candiani 2014). Frustration with the inefficiency of the costly tunnel led to
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even more discord between authorities, colonists, and the Spanish Crown, which sought to solve the problem by sending Adrian Boot to Mexico in 1614 to devise a solution to the flood problem. Boot was from the Low Countries where there had been a long tradition of floodwater management with dikes (López 2012). His role in the project in Mexico was ambiguous, as it was not clear whether he was going to team up with Martínez to solve the problem or replace him as the head of the desagüe projects. In a sort of friendly clash with Martínez, Boot presented an extremely different point of view. While Martínez continued to support the idea of draining rivers and lakes out of the Basin (see details in Candiani 2014), Boot proposed a series of dikes and management of the water without full drainage. It is interesting that his proposal was not very different from the water management techniques that had existed in the Aztec period, except that it included European technology such as windmill- powered pumps, mechanical scoops, cranes, and other devices (López 2012). The innovations to the system that came with European technology may have included use of water from the rivers for inland irrigation and for gristmills. However, the political environment of the New Spain and Mexico City governments at the time led to disagreements between those who supported Boot’s new idea and those who supported the full drainage (desagüe) proposed by Martínez, with the latter prevailing. Differences between rulers, however, did not help in solving the problem. Viceroy Diego Carrillo y Pimentel, Marqués de Gélves (who ruled from 1621 to 1624), was skeptical of the desagüe projects and ordered their cessation and the destruction of the dike preventing the Cuautitlan River from reaching the new Lake San Cristobal, a decision that had disastrous consequences later on (Candiani 2014). Although his successor, Rodrigo Pacheco y Osorio, Marqués de Cerralbo (who ruled from 1624 to 1635) tried to rectify the problem, it was too late. In 1629, rains were copious at a time when previous years and the current year had already seen unusually high amounts of rain. In August of that year, the situation became critical, and the lakes grew to levels never seen in previous flood events (García-Martínez 2004; Everett-Boyer 1975). The city was completely flooded and remained underwater for 4 years, losing some of its inhabitants, who moved to other cities including Puebla, which had already been considered as a candidate for the capital of New Spain (Candiani 2014; García-Martínez 2004). The viceroy, Marqués de Cerralbo, proposed moving the city to Tacubaya, on the west lakeshore, a project that received fierce opposition from some guilds in the city and from the Church, which had already invested heavily in the construction of churches and monasteries in the city (Candiani 2014). The problem, of course, was that building a new city would require money and large amounts of labor that, at this point, were not available after the disastrous decimation of the Indian population by epidemics (Gibson 1964). In the end, the unfortunate decision for the city and the capital of the viceroyalty to remain in its place brought about consequences that plague the city to this day. As the water receded, some authorities became confident that the city could still be saved and continued supporting the construction of dikes and repairs to the existing ones and the continuation of the drainage projects in the northwest part of the
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Basin. Martínez did not live very long after the big flood, and the desagüe projects were transferred to other parties. However, subsequent works solved the problem only temporarily; some decisions made the problem worse, and some planned projects were unattainable or unrealistic. The problem dragged on through the rest of the colonial period and the early decades of independence. In summary, the first 120 years of colonial rule in the Basin of Mexico were plagued by events and a series of wrong decisions that reflected the unfamiliarity of the new ruling society, the Spanish, with the aquatic environment. Coming from an area of rather dry lands, the Spanish were not readily aware of the necessity of managing water in a territory like the Basin of Mexico as the Aztec predecessors had done in previous centuries. The ideas for managing water proposed by Adrian Boot, who developed his skills in wetland country, seemed strange to the Spanish authorities, even though his ideas would have been successful. Unfortunately, the number of desagüe projects continued to drain the coffers, putting an exhausting burden on taxpayers and taking a toll on the indigenous slave labor, with no solution to the flood problem in sight.
14.2.2 The Colonial Desagüe Projects The flood of 1629 marked a turning point in the fate of Mexico City in terms of floods. The idea of leaving the city in its current state prevailed, a move that required the continuation of the desagüe projects. Enrico Martínez was removed from the project and later died. The subsequent work fell under the administration of the Jesuits under the leadership of Andrés de San Miguel, who continued the improvement of the Huehuetoca tunnel and other projects to defend the city from floods (Gurría-Lacroix 1978). The Huehuetoca tunnel project was reactivated and its maintenance continued, but the internal collapses also continued. A decision to make the tunnel an open-air conduit was passed, thus creating the Tajo de Nochistongo, which exists to this day (Fig. 7.6). The tunnel, however, only carried the waters of the Cuautitlan River and the excess water from Lake Zumpango, thus diminishing the amount of water that flowed south into the other lakes. This small amount drained from the lakes was not enough to spare the city from floods, as the problems with excess water in extreme events lay elsewhere. Some proposals even considered draining the Amecameca to the south, whereas others proposed finding natural tunnels in the lakebed, the latter being proposed by Antonio Alzate (see Candiani 2014; Ramirez 1976; Rojas- Rabiela 1974). Floods continued to occur occasionally, returning with a higher frequency in the mid-eighteenth century, when other proposals appeared (e.g., Cuevas Aguirre y Espinosa 1748). Interestingly, the same dynamics of abandonment of the projects and negligence of the infrastructure occurred in decades of the quiescence of weather extremes, returning only at times when catastrophic floods hit the city and large estates owned by influential persons. The idea of draining Lake Texcoco
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directly to the north began to be discussed, resulting in the construction of a canal under the direction of Ignacio Castera, thus receiving the name Canal de Castera (Gurría-Lacroix 1978) (see location in Figs. 7.2 and 7.6). However, because of the differences in elevation between the bed of Lake Texcoco and the Tajo de Nochistongo, Castera’s project failed. Thus, the Spanish rule officially ended in 1821 with the problem of lake flooding unsolved.
14.2.3 The Desagüe After Independence The decade-long War of Independence (1810–1821) resulted in a total abandonment of the desagüe projects and negligence of the infrastructure to protect the city from floods. Two years after independence, José María Mora (1823) published a report on the condition of the desagüe and the flood protection infrastructure that needed to be repaired. However, the political instability that followed prevented any concrete action. This period of inactivity in the desagüe and flood protection extended into the Mexican–American War (1848–1849) and the wars that led to the French invasion (1864). Under the Second Empire, Maximilian I (who ruled from 1864 to 1867) issued new directives to solve the flood problem and revive the idea of desagüe, placing the project under the direction of the engineer Francisco de Garay. The best picture of the situation of the lakes and existing canals at the beginning of the project appears in the map published in the 1860s by Francisco Díaz-Covarrubias (a simplified version of the map is displayed in Fig. 7.2). Catastrophic floods in the late 1860s created a focused interest on solving the problem, which was taken over by the liberal governments that succeeded the Second Empire. Consequently, through the 1870s and 1880s, proposals were reviewed and a series of studies were conducted to assess a large-scale project for draining the lakes via tunnels excavated through the mountains in the north to drain the water into the Tula River (Lemoine-Villicaña 1978). The digging of the Tequixquiac Tunnel began in the 1870s under the direction of the engineer Tito Rosas. However, the main problem was in getting the water from the lakes to the tunnel, a difficult task given the much lower elevation of Lake Texcoco and the southern lakes with respect to the entrance of the tunnel. Francisco de Garay, who had worked on the original project under the Second Empire, evaluated the situation and, in a report and a series of detailed maps now held in the Francisco Orozco y Berra Map Collection at the Meteorological Observatory of Tacubaya, proposed the integration of canals that would conduct the water to the tunnels (Garay 1888). Thus, the construction of the Gran Canal (aka Gran Canal del Desagüe) to conduct part of the waters from the Lake Texcoco Basin to the Tequixquiac Tunnel began under the rule of Porfirio Díaz, who lend strong support to the project (Tortolero-Villaseñor 2015). Lacking the technology and machinery for the project, the Mexican government contracted an English company (Lemoine-Villicaña 1978). Finally, on March 17, 1900, President Díaz, in a ceremony, inaugurated the
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combined drainage system of the Gran Canal and the Tequixquiac Tunnel, putting an end to the almost 400-year-old attempt to drain the lakes out of the Basin. The Gran Canal collected the water from the western catchments of Lake Texcoco, and the overflow of water from the southern lakes via the Canal de la Viga and Canal Nacional, which also collected water from the Amecameca River. The Gran Canal also collected water from Lakes Xaltocan and San Cristobal and the Avenidas de Pachuca River (see Figs. 3.11, 7.6, and 7.8). Later, the Canal del Sur (aka Río de la Compañía) drained other tributaries of Lake Chalco. This project resulted in the total desiccation of Lakes Xaltocan, San Cristobal, and Chalco and a considerable reduction in the size of Lake Texcoco (see Fig. 7.7), whose remains were fed by the streams from the eastern catchments (see Fig. 3.12). The project certainly permitted the use of land in the former bed of Lake Chalco, which benefitted the haciendas in the area owned by persons close to the Díaz regime (Tortolero-Villaseñor 2015). The vast areas of the dried-up Lake Texcoco became salinized and idle until a project to create an agricultural park initiated efforts to sell lots, which in the end failed because of the impossibility of preventing salinization (Espinosa-Castillo 2008). Later, in the twentieth century, companies extracting salt and other minerals were established in the northern part of the lakebed, for example, the famous Sosa Texcoco. Similarly, vast areas of the former beds of Lakes Xaltocan and San Cristobal were salinized and, without having any possibility of use for farming, were finally taken over by marginal urban neighborhoods.
14.3 The Desiccation of the Lakes in Retrospect 14.3.1 The Prediction and Realization of an Ecological Disaster The ecological disaster caused by the desiccation of the lakes became evident throughout the twentieth century. In addition to the loss of habitats for aquatic and avian species, the problem with blowing dust afflicted the population of the city, especially during the windy season in February and March. The dust problem was the least of all problems, as poor drainage during the rainy season caused flooding in some of the new neighborhoods. The clayey nature of the ground was also problematic for constructions, especially because of shrinking of clays caused by water extraction, thus causing subsidence and damage to buildings and urban infrastructure. The lacustrine clays, especially those still saturated, are the cause of magnification of seismic waves that result in more damage in the former lacustrine plain (see Auvinet et al. 2017). Among other changes is the alteration of local climatic patterns, discussed in Chap. 3, as areas of wetland were replaced by barren soil and concrete. The elimination of the wetlands also led to ecological changes, especially the destruction of
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habitats for migratory and local birds and large numbers of aquatic species. To this problem, one must add the disruption of traditional aquatic ways of life of the indigenous inhabitants. The disaster was not a surprise, as several voices had warned authorities of the possible consequences of draining the lakes. Alexander von Humboldt had assessed the situation of the city and the surrounding lakes and, at the time of his visit to Mexico in 1803, presented a critical opinion of what had been done in terms of desagüe. Among other things, Humboldt pointed out the big mistake of building the Spanish city in the same location as the Aztec capital, which was designed to accommodate the lacustrine conditions, as well as the consequences of the projects, which had already created problems with the soil and caused diseases around Lake Texcoco (Humboldt 1811). During the final planning for draining the lakes, Francisco Díaz-Covarrubias (1876) warned of possible environmental consequences of draining Lake Texcoco completely. He later proposed a project to contain the lake with dikes, a scheme that was not much different in purpose from the one implemented on a smaller scale a century later with the construction of Lake Nabor Carrillo (Figs. 1.2 and 2.11b). Then, once the desagüe project was close to completion, Fernando Altamirano (1895) warned of possible alterations to climate and the risks that the exposed lakebed may pose in terms of diseases, particularly in case of strong winds. Remarkably, all these predictions turned out to be correct. Alternatives to draining the lakes existed even in the early colonial years. Adrian Boot proposed the management of the lakes with dikes and wind pumps, which fell to deaf ears as, by then, the total drainage idea had gained momentum in the government and society (Candiani 2014; López 2012). Soon after the disastrous flood of 1629, a large sector of the society and even the Spanish Crown were supportive of moving the city out of the lake to the shores (García-Martínez 2004; Everett-Boyer 1975). It is not clear, however, whether the outcome of this move would have been ideal. The city would have been saved from floods, but the lake would most likely have been polluted with the city’s wastewaters, which, in turn, would have damaged the ecosystem of the lake and affected the residents of the city, though, perhaps, proper management of the black water out of the basin could have solved the problem. The long-term disaster brought about by the desiccation of the lakes, in tandem with the rapid and disorderly growth of the metropolitan area, has now reversed the views of the former lakes. Thus, projects of restoration such as those in Lake Zumpango, parts of Lake Xochimilco, and Lake Texcoco have been proposed and implemented with varying degrees of success. In particular, the restoration of Lake Texcoco has been controversial. Proposals for restoring the lakes in the twentieth century such as the Plan Lago de Texcoco in the 1980s (see Cruickshank-García 1998) were received with hope by the science community and the environmentalist movement but were met with disbelief by the authorities. A plan for the Lake Texcoco Ecological Park was first proposed in the present century, later discarded in favor of constructing an airport, and, then, again revived, and the Lake Texcoco Ecological Park (Parque Ecológico Lago de Texcoco) is under construction at the
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time of this writing. However, the post-desagüe history of the lakes is a long and complex one that falls outside the scope of this book.
14.3.2 Water Management or Drainage? A History of Adaptive Decisions One must understand that the recurrent patterns of problems and actions concerning the management of the lakes have always been approached from the point of view of the city and never really from the point of view of the lakes, their ecosystems, and the peoples whose livelihoods depended on the resources of the lakes. To this day, programs to restore parts of the lakes are approached from the point of view of the city, though some small-scale projects view the ecological aspect, something that is relatively new in the human–lake relations in the Basin of Mexico. Nonetheless, the environmental history of the lakes from the early agricultural societies to the final desagüe (c. 1900) varied in relation to the changing attitudes toward the lakes. Such attitudes can be mapped in the framework of three trends: do nothing, manage the lakes, or drain them (Fig. 14.5). During pre-Hispanic times, the process of adaptation was lengthy and in tandem with long- and short-term fluctuations, thus practically doing nothing about controlling the water flows of the lakes. During this period, settlements in Lake Texcoco and in the northern lakes were sparse and temporary and, in many areas, nonexistent, except for the perilacustrine areas above and outside the lakebed (Figs. 12.4, 12.5, and 12.6). During the same period, settlements in the southern lakes were more recurrent but concentrated only in certain areas of the lakebed. It was not until the Middle and Late Postclassic periods that large-scale water management permitted settlement and farming inside the lakes across most of the lacustrine realm (Fig. Fig. 14.5 Views of the lakes and their problems before the desagüe and in modern times. The solid line indicates the path of trends and actual actions, and the intermittent lines indicate proposals that never made it to action
MANAGE
Conquest 1521
Late Postclassic Period
Adrian Boot’s proposal
Enrico Martínez 1550 1610’s 1620’s Flood of 1555
Diaz-Covarrubias proposal Flood of 1629 1700
Proposal to move the 1821 city outof the lake INDEPENDENCE
DO NOTHING
1800 1860s1870s 1880s 1890s
1900
DRAIN
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12.7). It is evident that efforts to control the lake led to managing water flows through the hydraulic infrastructure and permitted urban and rural development in areas of the lakes that had not been settled in previous periods. During the first three decades after the conquest, the attitude reverted to doing nothing and the hydraulic infrastructure was neglected or destroyed. This attitude changed after 1550, when the return of extreme rainfall events caused flooding in the city. After that, there was vacillation between draining the lakes, managing their waters with the hydraulic infrastructure, or doing nothing and letting the system work on its own. Despite these vacillations, the dominant trend was toward drainage. Nonetheless, it is important to point out that there were proposals (dotted arrow lines) that could have changed the fate of the lakes and the city if they had been implemented (Fig. 14.5). The most important proposal was a move toward the management of the water without drainage or with limited drainage, as proposed by Adrian Boot in the 1610s. Then, the proposal of the Marqués de Gélves to dismantle the infrastructure and leave the system alone meant a trend toward doing nothing, a decision that was detrimental, as it left the city unprepared for the floods to come. However, there were other proposals for minor projects, which usually veered toward variations of the methods for draining the lakes. Then, during the War for Independence and the subsequent political instability of the early independence period, the drainage project and existing infrastructure were temporarily abandoned, indicating a rather unintentional shift toward doing nothing. Once the idea of drainage returned in the second half of the nineteenth century, the proposal of Francisco Díaz-Covarrubias (1876) to keep the lakes but contain them in dams was an idea looking toward water management. However, at this point, the direction toward drainage had begun to gain momentum, ending with the final drainage of the lakes in 1900. In the twentieth century, new attitudes toward the remaining bodies of water and the dry lakebeds appeared, especially toward reviving the existing water bodies and creating new ones. This can be seen in some projects of the late twentieth century such as Lake Nabor Carrillo and the most recent reconstruction of Lake Zumpango, the regeneration and protection of some habitats in Lake Xochimilco, and the creation of the Lake Texcoco Ecological Park. However, the contemporary attitudes between restoring and protecting the remaining lakes and the full desiccation and development of the dry lakebeds are perhaps worth analyzing in another publication.
Chapter 15
Lacustrine Systems and Societies in the Basin of Mexico
15.1 The Lakes of the Basin of Mexico 15.1.1 The Overall Picture of the Lacustrine Realm The former lakes of the Basin of Mexico were shallow bodies of water occupying tectonic depressions without an outlet for basins draining into the sea. Precipitation and mostly torrential stream water and spring water were the main sources of water for the lakes. The markedly seasonal nature of precipitation and high evaporation rates resulted in significant lake-level changes throughout the year. Additionally, multiyear extreme dry or wet events caused long-term lake-level changes. Thus, this highly dynamic situation presented many challenges to the inhabitants in using resources from the lakes. Nonetheless, through the ages, the surrounding populations adapted to these conditions and controlled part of the flows of water for their benefit. In contrast to the characteristics described above, many contemporary scholars perceive the ancient lakes of the Basin of Mexico to be deep and stable bodies of water that are interconnected as if forming a single lake (e.g., Fig. 1.4a). This inaccurate view has its origin in multiple semantic and cartographic errors and false assumptions that were established during the past and present centuries (see Chap. 7). Nevertheless, ancient cartography and historical references, as well as geological and geomorphological evidence, support the idea of shallow and highly variable bodies of water often separated and not connected as a single large lake. However, each lake basin had its own characteristics and dynamics, which are important to recognize when reconstructing their aquatic environments. The following sections detail the natural aspects of each lacustrine basin as well as the benefits and difficulties they presented to human use and settlement.
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15.1.2 Lake Texcoco Lake Texcoco was the largest and the lowest of the five lakes, which meant that during extreme wet conditions or events, it would receive large amounts of overflow water from the other lakes, which meant extensive flooding of the areas on its margins. Conversely, during prolonged dry conditions, the incoming water would be trapped in the thresholds between lake basins, creating a deficit of water coming into Lake Texcoco. Historical records provide descriptions of lake changes under extreme dry and wet conditions during the first century of the colonial period, before the lakes began to recede through the works of desagüe. Extreme dry conditions between c. 1524 and 1550 led to the drying of many parts of the lake and problems in navigation, whereas extreme wet events between 1604 and 1629 led to lake expansion and flooding of agricultural lands and Mexico City itself. These examples show the two extremes conditions that the native settlers experienced cyclically in the past. Consequently, because of these extreme dynamics, Lake Texcoco was certainly the most difficult one to tame. To make matters more difficult, its waters were saline, alkaline, and heavy in minerals, which represented an advantage for the procurement of salts and other evaporitic minerals but made other economic activities or permanent settlements extremely difficult. Eventually, however, its inhabitants managed to control the lake at least partially with the help of hydraulic infrastructure, thus permitting the establishment of lacustrine towns and vast areas of chinampa agriculture. Despite its problems, sedimentological and geomorphological records suggest that the lake was highly diverse, with several microenvironments existing in the areas of springs, river mouths, and deltas, behind sand bars, and in the areas where freshwater could be naturally or artificially trapped (see Chap. 8). This diversity of aquatic environments represented areas of concentration of vegetation and fauna, which, as represented in chronicles and maps, seemed to attract settlers to certain parts of the lake. This high diversity of habitats created niches for human habitations, which explains the high concentration of recurrent settlements in certain areas of the Basin (Figs. 12.4, 12.5, 12.6, and 12.7). The deep prehistoric past of the lake is much less known, though limited paleolimnological, paleoecological, and sedimentological data (see Chaps. 4, 5, and 6) provide a general picture of lacustrine changes through the Upper Pleistocene and Holocene. The combined data show that during this part of the prehistoric period, Lake Texcoco was for the most part a shallow lake, except for certain times in the Pleistocene when climatic and hydrological conditions permitted the lake to grow and become deeper. However, the scarcity of absolute ages of most deposits does not permit pinpointing these periods, though it is evident from the data that around the last glaciation (marine isotope stage 2 (MIS 2)), the lake developed relatively high levels (see Chap. 5). The causes for those unusually high and stable levels are not known, though data from Lake Chalco suggest that it had to do with the balance between precipitation and evaporation caused by low temperatures (see Chap. 6).
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15.1.3 Lakes Chalco and Xochimilco It is difficult to separate the two southern lakes, as they occupy practically the same basin and generally form a continuum, except for the existence of the artificial island of Tlahuac and dike across the strait. According to observations by Alexander Humboldt and others after him in the nineteenth century, water flowed from Chalco to Xochimilco during the wet time of the year and in the opposite direction in the dry time of the year. Therefore, the function of the Tlahuac dike was to regulate the flow in both ways during times of wet or dry conditions, a necessity to maintain the water of canals and chinampas at a stable level. In view of this fact, it is possible that during long-term dry periods, the strait of Tlahuac was completely dry or not fully inundated, which may explain the large number of settlements during most archaeological periods in this area (Figs. 12.4, 12.5, and 12.6). The numerous springs in the Basin provided large amounts of freshwater that would have offset the high evaporation rate of the waters during the dry season or prolonged dry periods, thus maintaining freshwater conditions and relatively stable levels throughout the year. Most likely, the freshwater conditions led to the lakes being more vegetated and with more abundant fauna than the saline lakes to the north. All together, these conditions explain the relatively more obvious abundance of settlements in the early agricultural period and through the ceramic period (Figs. 12.4, 12.5, and 12.6). Furthermore, the freshwater and abundant vegetation made it an ideal place for chinampa agriculture, a system that developed throughout most of the lake area and survived to a large extent through the colonial and independent periods. Unlike other lake basins, there is more information on the prehistoric past of the southern lakes. Several stratigraphic studies with reliable dates provide information on the fluctuations of Lake Chalco going back to 160,000 years BP. The evolution of the lakes during this period is complex as it was influenced by climatic and volcanic factors. Nonetheless, the data suggest that a combination of low spring and summer temperatures resulted in relatively deeper and less alkaline lakes (see Chap. 6). Nonetheless, despite periods of high stands, they were relatively shallow lakes, which is coherent with the fact that high lake levels would reach the seam connecting with Lake Texcoco from where water would flow to the latter. Nonetheless, there is a possibility of Lake Texcoco reaching the seam and inundating Lake Xochimilco, though no studies have confirmed such an event.
15.1.4 Lakes Xaltocan and Zumpango The geographic extent and the hydrological characteristics of the northern lakes are less known. Cartographic and historical documents, especially the chronicles of the war of conquest, provide a confusing picture of the northern lakes. While some maps and documents only provide proof of the existence of Lake Xaltocan (Fig. 2.8), others show both lakes being practically disconnected from each other and
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from Lake Texcoco (Fig. 1.6). Seventeenth century maps show more details of the area, but the lakes appear behind dams evidently constructed during the colonial period (e.g., Figs. 7.3 and 7.4). This leaves many questions regarding the size and nature of the lakes in the pre-conquest times unanswered. They could have been just wetlands, but it is not clear whether they formed a continuum of wetlands or were connected by a stream. Soils along the area between the two lakes suggest that these were marshes (see Sect. 5.3), despite lacustrine clay appearing deeper below the soils, though these seem to be the lacustrine clays of the Pleistocene age that appear elsewhere in the Basin. Early historical sources, especially those of the sixteenth century, mention the island of Xaltocan and its chinampas, though the word lake (i.e., laguna) is never mentioned, which perhaps suggests that these were wetlands. Besides, the existence of chinampas already suggests that the lake basin was transformed, which leaves the lakes or wetlands open. The prehistoric past of the northern lakes is much less known than that of the other lakes, though there are indicators in the geology and surrounding landforms of periods of high stands during the Pleistocene in a manner similar to the one described for Lake Texcoco. First, thick layers of lacustrine clay show that at several times during the Pleistocene there was a large lake, probably covering the basins of both lakes (Fig. 4.13). Second, lacustrine terraces in the northwestern shores of Lake Xaltocan support the idea of high lake stands, though no exact dates can be derived from these features. Additionally, clay depths in the strait of Ecatepec suggest that during the high stands in the Pleistocene, Lake Xaltocan was fully connected to Lake Texcoco (Fig. 4.13). Presumably, the Pleistocene era’s large lake occupying the modern basins of Lakes Xaltocan and Zumpango was divided into the two modern lake basins first by the progradation former deltaic system at Xaltenco, thus creating a narrow strait connecting the two lakes (Fig. 5.10).
15.1.5 The Good, the Bad, and the Ugly of the Lakes A romanticized view of the disappeared lakes of the Basin of Mexico in modern times has distorted the true historical nature of the former lacustrine systems. From a pragmatic and critical perspective of the paleoecological, archaeological, and historical aspects, the lakes were both a blessing and a curse for their inhabitants. On the one hand, the lakes provided a variety of resources for their subsistence and a means of communication via canoes, and, on the other, their rapidly change nature, sometimes unpredictable, presented immense difficulties for extensive use of resources, especially in the context of demographic pressure. This description is not unique to the lakes of the Basin of Mexico, as other ecosystems in antiquity around the world also showed a similar paradox. The case of the Nile in Egypt is a good example, as it proved to be a blessing for agriculture, whereas catastrophic floods and low water levels, which unless were known beforehand and controlled, proved to be a curse or an impediment for stable settlements. Like the case of the lake
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inhabitants of the Basin of Mexico, the ancient Nile settlers were able to control, with certain efficacy, the flows of water to their advantage. This blessing-and-curse situation that the native inhabitants faced was practically unknown to the Spanish colonial society that settled in the Basin of Mexico in the sixteenth century. The disastrous droughts and floods that the Spanish faced were nothing new. The difference was that their predecessors had developed the land and, most importantly, their city according to the short- and long-term changes that characterized the lakes. On the one hand, the Spanish neglected the hydraulic infrastructure or in some cases destroyed it. On the other, they built a city that was not suitable for an aquatic environment. Adrian Boot, a native of the Low Countries, proposed a scheme to manage the lakes differently and more accordingly to coexist with the aquatic environment (Fig. 14.5). The Spanish authorities and settlers, perhaps accustomed to dry environments, dismissed the proposal. This brings about the hypothetical question: If the Dutch had colonized Mexico, would they have managed their settlements in the lakes better? In summary, in the context of the history of human–lake relations in the Basin of Mexico, one can see that the “good” side of the lakes is that they were ecosystems that provided benefits to wildlife and were a source of livelihood for certain societies under proper management and a certain limit of population growth and distribution. The “bad” side is that, like in any natural system, things can go wrong; natural disasters are unavoidable, and unpredictable extreme fluctuations in their cycles can be detrimental to human populations. The “ugly” side is that population pressure and mismanagement of the lacustrine systems can lead to horrific consequences to the human society and the ecosystems.
15.2 The Development of a Lacustrine Culture and Technology 15.2.1 Lacustrine Subsistence Archaeological and ethnohistorical evidence of the use of lacustrine resources is abundant and strongly supports the view that communities in and around the lakes depended on several biotic and non-biotic resources. Paleobiological research works on preceramic and ceramic settlements suggest that despite the development of agriculture and distant trade, food products from the lakes remained extremely important in the diet of the local populations of the Basin. Parsons (2010) explains this phenomenon as a replacement for nutritious foods that other cultures would get from domesticated animals or the so-called “pastoral niche.” The utilization of mineral resources from the saline lakes is another aspect that seems to have persisted through time in the Basin, notably with the procurement and processing of salt and tequesquite. However, water salinity presented other problems, particularly once agriculture reached the lakeshores and lakebeds. As
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discussed in Chap. 5, there is some evidence that soil salinization in the perilacustrine area was a problem when lake levels rose. It was also problematic when population pressure pushed populations to occupy lacustrine spaces. However, this issue deserves more discussion, particularly concerning wetland agriculture in saline lakes, with the cases of Lake Xaltocan and the western part of Lake Texcoco.
15.2.2 The Development of Wetland Agriculture It appears that the establishment of chinampas in the Basin of Mexico was late compared to similar systems of raised fields in other parts of Mesoamerica. The earliest evidence of chinampas supported by radiocarbon dating shows that the system was already in place in the early Aztec period in Lake Xaltocan, perhaps as early as AD 1200 (see the dates in Morehart and Frederick 2014). In the southern lakes, the few radiocarbon dates and the widespread association of chinampas with Aztec III point to their construction practically within the Late Postclassic period (Avila-Lopez 2006; Frederick 2007). Interestingly, though the southern lakes are best known for their ancient chinampa systems, the oldest chinampas seem to have developed in Lake Xaltocan. Although no radiocarbon dates exist for the chinampa systems of Tenochtitlan and Iztapalapa, they all seem to be associated with Aztec III pottery, which suggests a Late Postclassic age (Sánchez-Vázquez et al. 2007; Avila-Lopez 2006). In fact, the widespread chinampa system of Tenochtitlan may not have been built earlier than the 1420s given some historical indicators, particularly in terms of city planning (see the discussion in Sect. 13.3.4). One aspect that is important here is that the chinampa system depended on the control of changing lake levels and water flows through dikes and canals (Armillas 1971). Archaeological records to date support this premise as most of the known systems of canals and dikes date back to the Late Aztec period. However, as suggested by several authors, certain forms of less risky drainage agriculture may have been practiced earlier (Niederberger 1987), although no evidence of such early chinampa systems exist in the current archaeological records. Certainly, there is a possibility that early chinampa systems were destroyed by construction of more recent settlements and chinampa systems or that older chinampa systems became part of the palimpsest of features in the archaeological records. However, no study to date has focused on studying this possible scenario.
15.2.3 Lakes as Marginal Land and the Postclassic Demographic Phenomenon The unprecedented spread of settlements on the lakebeds that took place during the Late Postclassic period (Fig. 12.6) occurred in conjunction with the proliferation of settlements across the Basin of Mexico. Sanders et al. (1979) interpreted this growth
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and spread of settlements as part of the same wave of demographic growth across the Basin, hinting at the possibility of the need for space and areas to increase productivity. Although their idea has not been proven wrong, it does call for the question: “Why did the settlement expansion take place in the lakes?” Sanders et al. (1979: 177) observed that many of the areas that were newly occupied during this period were “marginal land,” implying areas with low rainfall and poor soil or terrains that were difficult to cultivate. These marginal lands included the low rainfall areas of the semiarid northern part of the Basin, which were occupied and farmed with the implementation of irrigation (Nichols 2015). Areas with difficult terrains such as inclined slopes and rocky substrates and areas with shallow soils were occupied and farmed through the implementation of terracing and check dams (Nichols 2015; Evans 1990). Such areas mostly include the piedmonts, some isolated hills, and the recent basalt lavas (McClung et al. 2003; Cordova 1997; Cordova and Parsons 1997; Evans 1990). Concurrently, with their counterparts on dry land, lacustrine and wetland areas were functionally “marginal lands” because they were areas where cultivation and habitation were not possible without some form of infrastructure. Thus, in parallel with the reclamation of marginal land areas with terracing, check dams, and inland irrigation, lakes and swamps were reclaimed with the implementation of dikes, canals, and several smaller structures that permitted large-scale chinampa agriculture and settlement. One also must keep in mind that the appropriation of the lakes occurred at a time when lake levels, particularly that of Lake Texcoco, tended to rise (Figs. 12.1 and 13.7). Before then, the number of the few settlements that existed on lakes and lakeshores fluctuated, apparently in tandem with lake-level fluctuations (see Chap. 12). This dynamics suggests that in addition to environmental changes (including climatic and hydrological changes), the development of the lacustrine infrastructure involved social changes and the implementation of new technological changes beyond anything seen before (see the next section).
15.2.4 Environmental and Technological Thresholds Archaeological records and historical sources provide evidence that the maximum development of infrastructure to control the waters of the lakes in favor of settlement and agriculture occurred in the Postclassic period. This development contrasts with the development of the irrigation infrastructure in Mexico, which began developing in the Formative period (see Doolittle 2011). Then, the question is “why did the agricultural development of the lakes take so long compared to that of marginal lands elsewhere?” Although some scholars made observations and provided some hypotheses to the explain the development of the lakes (e.g., Sanders et al. 1979; Palerm 1973; Armillas 1971), there is no full explanation of the process in terms of an integrated view regarding environmental constraints, social organization, and technological change.
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Throughout the analysis of lacustrine dynamics and cultures across different time scales in the chapters of this book, it has become evident that technology played an important role in the development of cultures in an aquatic environment. Therefore, it is evident that the societies that inhabited the lakes came to adapt to the dynamics of the lakes and wetlands and eventually were able to control the water and energy flows through a network of structures, which in this book are referred to as lacustrine cultural features (i.e., hydraulic infrastructure and landesque capital). To reflect this relationship, Fig. 15.1 presents three levels of technological advances in relation to natural lacustrine features and processes. The upper and right sides and the upper right corner represent the influence of natural processes (tectonics, sediment accumulation, and natural erosion), whereas the lower and left sides and the lower left corner represent the cultural processes (removing and accumulating materials) of transformation of the lacustrine environment. The inside of the diagram shows the techno-environmental levels divided by two developmental thresholds. The levels mark the relative dominant influence of natural or cultural processes as well as the degree of dominance of cultural processes (digging and accumulating) over natural flows (e.g., floods, lake surges, or lake drying). In view of this framework, each techno-environmental level is
Fi
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t T Level 1 hr Erosional Level 2 esho ld
Aggradational
Seasonally exposed lakebed
Th
re Level 2
Level 3
sh
ol
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Deltaic channels Inlets
Canals Tlateles Embarcaderos
Fluvial sediments redistributed by Deltaic deposits currents and waves
Resuspension sediments
Swamps
Sand bars Beach deposits
Tulares Faulting and Organic spring deposits sediments Early forms Removal Shoals and elevated of raised (negative surfaces Canal networks Faulting features) Chinampas Tlateles Straits Lacustrine Springs agricultural Chinampa Tlatel complexes complexes Rock complexes promontories Insular settlements Dike systems Lacustrine ? urban Causeways and complexes aqueducts
Integration
Tectonic and Volcanic
Accumulation (positive features)
Natural processes
Natural lacustrine landscapes
Cultural processes
Anthropogenic lacustrine landscapes
Fig. 15.1 Techno-environmental levels and thresholds in the transformation of the lacustrine realm of the Basin of Mexico in pre-Hispanic times
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characterized by the level of construction and integration, with the highest level of integration closer to the lower left corner of the diagram (Fig. 15.1). Level 1 implies technological change in the dependence on natural processes, whereas level 3 means the dominance of cultural over natural processes and level 2 the influence of both more or less equally. For example, in level 1, the construction of a tlatel could be achieved by using a preexisting natural feature (e.g., a deltaic channel levee or a beach ridge), whereas the building of a large artificial complex of tlateles and platforms required some form of control of natural processes with canals and dikes. In other words, level 3 mostly involves structures with a high level of complexity (see Sect. 10.2.3), involving large amounts of labor, material, and technology. The model considers two thresholds between the techno-environmental levels, implying a push in technological innovation and organization. The crossing of the thresholds, however, is not unidirectional; failure or environmental change could revert the system to a lower level, meaning that although a threshold may have been crossed with technological advances, abandonment or extreme events could push the system back to a lower technological level. Crossing the first threshold may have occurred many times after the early days of agriculture, perhaps even before the ceramic periods. Certainly, lake-level fluctuations influenced this crossing of thresholds back and forth as well as the reorganization of political and social structures. The crossing to level 3, however, occurred in the lacustrine realm of the Basin of Mexico only once, during the Late Postclassic period and perhaps beginning in the late Middle Postclassic period. Therefore, the key to understanding the apparently unusual case of the widespread occupation of lakebeds in the Late Postclassic period is the evolution of technological innovation, a matter that requires discussion and conceptualization. Interestingly, under the Spanish colonial rule, the system depicted in the model became obsolete, as the new ruling society failed to maintain the previous system of lake management (see Chap. 14). Instead, the next level that the Spanish colonial society opted for was draining the lakes, which was a technological change in its own way, but not within the lines of the model in Fig. 15.1. The new political establishment were undecided about whether to maintain and further develop the old system, do nothing and abandon the lake, or drain the lakes and develop the empty basins (Fig. 14.1).
15.2.5 The Origin and Development of Tenochtitlan It is ironic that the urban development of Tenochtitlan and its satellite lacustrine settlements occurred in a “marginal” environment, where practically no settlements existed before. In part, this development in the saline environment of Lake Texcoco (as per the discussion in Sect. 15.2.3) occurred in response to the convergence of circumstantial natural events with social and technological changes. On one hand, the hydrological changes geared by climatic events between the sixteenth and seventeenth centuries played a role in facilitating the settlement of the western part of Lake Texcoco (Fig. 13.7), and, on the other, political forces drove a group of people
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to take advantage of those environmental changes. These changes may have catalyzed the development of the technology needed to control the dynamics of the lakes. Therefore, the development of Tenochtitlan and its satellite settlements was an environmental dynamic process that accompanied the evolution of a civilization. The environmental dynamic model that explains the evolution of Tenochtitlan and its satellite settlements (see Sect. 13.4) does not conflict with the traditional history based on ethnographic sources, namely, those alluding to a series of mythical and religious events. Instead, the model is an alternative approach to the events proposed in the sources. The sources themselves, if read with an environmental focus, do support many aspects of the model. One of such aspects is the fact that the original settlement of the city was not a lacustrine one but probably various settlements in a palustrine environment, which over time became impounded by a lake naturally as lake levels rose and artificially as the construction of dikes created a rather lacustrine environment (see the sequence in Fig. 13.5e). In other words, the Mexicans settled in a marshy area, but, by the time the Spanish arrived, the site was surrounded by the lake by means of natural processes and artificial control of water flows. In fact, 20 years after the conquest, the lake had once again become a marsh, and, a century later, the lake completely flooded the Spanish city. These were the natural cycles that the lake underwent throughout its history. Similarly, the model does not conflict with archaeological data, as the model itself draws on some important aspects found through archaeological research. The fact that most of the cultural layers belong to the Late Postclassic period, with only few of the Middle Postclassic, suggests that the area had no sizable settlements before. Many of the Late Postclassic settlements lie directly on lacustrine and palustrine deposits and not on preexisting islands. Such “primitive islands” were a misunderstanding of a study in the early 1900s, which has been carried over in the literature to the present.
15.3 Prospects for Research on the Lakes of the Basin of Mexico Throughout the chapters of this book, it has become evident that there are several large gaps in our knowledge of the natural, cultural, and environmental aspects of the prehistoric and historic lakes. Nonetheless, each chapter points to areas of research that have proven effective in bridging the gaps of the general knowledge of the former lakes of the Basin to establish proper questions for future collaborative research projects. Unfortunately, the growth of the urban areas has been so rapid that many opportunities to study certain parts of the system are disappearing in front of our eyes every day. However, there are some geographic windows where urban development has not advanced quickly, though the threat of future urban sprawl is latent. Similarly, salvage archaeology in the city must recover as much relevant
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information as possible but within the frame of a robust conceptual model and by applying the appropriate technology for recording information that otherwise could be lost to the city and time. Many of the gaps can be breached in several ways, through field research within the geographic windows and salvage archaeology opportunities in urbanized areas as well as through more ethnographic and experimental research and modeling using empirical data based on paleodata and modern analogues. With the available resources and the present knowledge of the lakes, the types of research needs and suggestions for future studies of the lakes are listed below. • Proper study of lake-level fluctuations at decadal and centennial scales using references in archaeological settlements and key areas, where lakeshore environments, particularly beach deposits, may be found, and correlating them with high-resolution paleoclimatic data. • Application of diverse proxies, in the Pleistocene and early Holocene, for paleoecological reconstruction in Lakes Texcoco, Xaltocan, and Zumpango, where there is a tremendous gap in paleoecological and paleolimnological information. • Refinement of time resolution in some systems, especially in environments with megafauna. • Application of various methods of absolute dating as a means of corroborating dates. • Study of transitional depositional systems, especially deltaic systems, as they seem to have created diverse ecosystems. • Study of various aspects of sedimentation and erosion in the lakes with the use of modern analogues and simulation models. • More stratigraphic and geomorphological research on the northern lakes, particularly Lake Zumpango, as we know little about its natural and cultural history. • Archaeological surface reconnaissance of areas not formerly surveyed, bearing in mind aspects of erosion and sedimentation, as in many areas of the lakeshore, sites lie buried under alluvium. • Research in the aspects of lacustrine management, especially in saline lakes, where, as we know, there are areas where freshwater could be utilized, whereas in others, salt could be produced, a matter that can be tackled through experimental research and modeling. • Study of the various aspects of construction and maintenance of the hydraulic infrastructure, tlateles, platforms, and buildings, using either experimental research or modeling. • Use of early aerial photography and late historic cartography to recreate areas of the lakes before the rapid urbanization (from the 1950s to the present). • Studies of the recent deformation and sinking of the ground as a way to reconstruct the ancient paleotopography of the lakes. • Corroboration of historical references and maps with archaeological and geoarchaeological data. • Diffusion of research to change or replace the currently established paradigms that point to static lakes with one that emphasizes the idea of dynamic lakes that evolved in the context of natural and cultural processes.
Abbreviations
AGN AHCM
Archivo General de la Nación (National General Archives) Archivo Histórico de la Ciudad de México (Historic Archives of Mexico City) CDMX Ciudad de México (Mexico City’s political entity or state) CONACULTA Consejo Nacional para la Cultura y las Artes (National Council for Culture and Arts) CONAGUA Comisión Nacional del Agua (National Waters Commision) ENAH Escuela Nacional de Antropología e Historia (National School of Anthropology and History) INAH Instituto Nacional de Antropologia e Historia (National Institute of Anthropology and History) UNAM Universidad Nacional Autónoma de México (National Autonomous University of Mexico) SEP Secretaria de Educación Pública (Secretary or Ministry of Public Education). STC Sistema de Transporte Colectivo (Collective Transportation System; authority in charge of Mexico City’s subway and transportation authority) TEO Túnel Emisor Oriente (Eastern Drainage Tunnel; latest deepest drainage system in the Basin of Mexico). TMVB Transmexican Volcanic Belt. TSZ Ten
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5
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Glossary
Acalli (also acalle) Nahuatl for canoe. Acequia Canal or ditch, usually for irrigation. In the Basin of Mexico, the term was also used for navigation canals. Also see apantli. Acocil (plural, acociles) A crustacean, usually. Adoratorio Shrine or altar. Ahuauhtli (or ahuauhtle) Insect eggs usually deposited on the leaves of grass in shallow waters. Albarrada Originally, a fence, but used in Colonial Mexico to refer to a dike, causeway, or dam. Albarradón A dike, usually a large one. Almácigo (also almáciga) Nursery bed where seeds are planted. Apantli (also apantle) Nahuatl for canal or ditch. Barranca (plural: barrancas) A deep ravine.Bergantín. Brigantine. A vessel with two masts. In the lexicon of the War of Conquest, it designated a vessel of much smaller dimensions built for the battle and siege of Tenochtitlan. Bandolero Literally, gang member or bandit. In the context of the southern lakes, it referred to floating islands of vegetation that blocked waterways. Bordo Dam or small dike constructed as protection from floods or to retain water; also, river channel levee. Caliche Hardened calcareous sediment or calcrete. Calzada Causeway. Camellón (plural, camellones) Colonial Spanish name for chinampas; also used for cultivated terraces on slopes. Campan Nahuatl word to refer to the four wards of a city, in this case Tenochtitlan. Carrizo Reed grass. Carrizal A grove of reeds (see carrizo); sometimes used to refer to groves of aquatic grass or grass-like plants (see tular). Charal (plural: charales) Species of small fish in the Atherinidae family. Chinamitl Fence or enclosure, especially one made of canes, reeds, or stakes. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5
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Glossary
Chinampa Elevated crop bed made of a combination of lake muck, leaves, sod, ash, and diatomite, built in shallow waters or swamps. The beds are often bordered by stakes or small trees. The term comes from chinamitl, which is the enclosure of stakes around the bed, and -pa, suffix particle indicating location. Céspedes Although today the term is used to mean lawn or sod, in the early times in the Basin of Mexico, the term was used to refer to wet meadows composed of grasses, sedges, and bulrushes. The term refers also to blocks of this sod cut from wet meadow vegetation, which were used in the c onstruction of dikes, bordos, causeways, and even chinampas in pre-Hispanic and Colonial times is amply documented. Ciénega Wetland or mire, territory seasonally or permanently wet. Cinta Floating vegetation, either floating aquatic plants or floating remains of plants dislodged from the shore. Their use in the layering of chinampas is documented through the Colonial and modern periods. Códice. Codex In Mesoamerica, códices are documents depicting historic events, royal lineages, and modes of life in a pictorial way on traditional native or European paper. However, these codices also have notations or entire pages written in the native language and/or in Spanish. Desagüe Literally, drainage. In the history of the Basin of Mexico, it refers to the century-long drainage of the lakes out of the basin. Dique Dike. Ejido Communal or public land belonging to a rural settlement or village. Since the Mexican Revolution, the term has been used for land expropriated from large estates and given to peasants and commoners. Embarcadero Docking or mooring place, or a simple cove to protect navigation craft. Entarquinamiento Deliberate flooding of a field with muddy water from a stream or canal to add moisture and nutrients. See also tarquín. Espadaña Cattail (Typha spp). Estero Estuary, derived from the Latin estuarium. Modern Spanish, however, uses the word estuario to refer to an estuary, though some colloquial Spanish might still use estero to refer to estuario. The Royal Academy of the Spanish Language also refers the term estero to an inland area inundated by water from a river and with dense vegetation (RAE 2021), with the main example from the region of northern Argentina. In the lakes of the Basin of Mexico, esteros are water inlets formed by fluvial channels inundated by high water, usually navigable and protected, more appropriately called inlets in English (Chapter 8). Hoyo (also hoya) A deep part of a river or a lake. In the wetlands in the Basin of Mexico, it may refer to a pond. Islote A small island, usually natural, but also artificial. In the archaeological literature of the Basin of Mexico, it may also refer to a tlatel. Jaboncillo The term refers to layers of lacustrine clay, usually green, with a high capacity for water retention (between 200 and 400%). The term derives from jabon (soap) and roughly implies soapy, a soapy-like feeling at touch, or highly slippery when wet.
Glossary
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Juncal Community of bulrushes and sedges. See juncia. Juncia Bulrush (Juncaceae family) or sedge (Cyperaceae family). Lama Loam or loamy soil. Its usage in the rural areas of Mexico refers to loamy soil deposited by stream flooding, especially in cultivated fields. See also entarquinamiento and tarquín. Montículo Mound, usually artificial; can be interchangeable with tlatel and terremote. Peregrinación Pilgrimage; in Aztec history, referring to the migration of the Mexica from their ancestral land to the location where they founded their capital city (Tenochtitlan) in the western part of Lake Texcoco. Requezón (or requesón) Literally it translates as ricotta cheese. In the lacustrine realm of the Basin of Mexico, it referred to dried insect (Elyris hians) used as food and fertilizer. Its name comes from its smell similar to ricotta cheese (requesón, in Spanish). Salinero A person dedicated to the extraction and processing of salt; from salina or a salt evaporation pond. Sementera A plot of cultivated land. Tarquín Sediment or soil derived from the deliberate flooding of a river on a crop field. See entarquinado and lama. Temazcal From Nahuatl, temazcalli, hot bathhouse. Traditional Mesoamerican bathhouse used for ceremonial or healing purposes. It is a lodge similar to sweat houses in other cultures, where steam is produced by pouring water on heated rocks, usually also using aromatic or medicinal herbs. Terraplén An earthen platform, usually flat; may also refer to earth filling in a depression to flatten the ground. Terremote (or torremote) Mound, often an artificial islote; synonymous with tlatel and montículo. Tepetate Nahuatl, tepetlatl. Hardened deposit that silcretes, calcretes, or endurated horizons in soils. The termmay also be used for an indurated volcanic ash deposit. Tequesquite Nahuatl, tequixquitl. A soft rock of several minerals (e.g., sodium chloride, sodium carbonate, sodium sulfate, and potassium carbonate) often precipitated on the ground after waters evaporate from a lake. Its pre-Hispanic use was in cooking, especially to soften corn dough for tortillas and tamales. After the conquest, it had other uses, especially as an ingredient in gunpowder and in construction materials. Tezontle Nahuatl: Tezontli. Basaltic scoria. Usually red, porous rocks used in construction. Tlatel (or tlaltel) Nahuatl, tlaltelli. Constructive mound built on a permanently or seasonally inundated surface; often interchangeable with monticulo, torremote, and islote. Tlateles are multipurpose structures for temporary or permanent settlement. They can be built inland, but in the archaeological jargon, the word refers to mounds in the lacustrine environment. Tlaxilacalli Sector of a city, barrio, or parcialidad. Tolvanera Dust storm.
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Glossary
Tular (plural, tulares). Community of aquatic vegetation composed of sedges, cattails, and bulrushes. See tule. Tule Nahuatl, tollin. Aquatic monocot plant, usually in the family of sedges (Cyperaceae), cattails (Typhaceae), and bulrushes (Juncaceae). Zacatonal Nahuatl, zacatl (grass). Used mainly for the alpine grass community of tufted grasses in the mountains of central Mexico.
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Index
A Ahuizotl (Ahuizotl’s dike), 219, 305, 308, 315, 317, 318, 323 Ajolote, 72, 218 Albarrada, albarradón, 227 Amecameca river, 41, 117, 164, 202, 203, 229, 235, 281, 285, 332 Ayotzingo, 41, 42, 215, 234, 235, 326
214, 216, 236, 247, 274, 294, 295, 305, 307, 315, 317, 319–327, 335, 340 Cuautitlan, 53, 61, 62, 93, 157, 159, 161, 166, 179, 191, 204, 257, 294, 316, 317, 328–330 Currents, 47, 59–61, 80, 109, 146, 158, 160, 170, 173–176, 178, 179, 182, 188, 215, 232, 267, 305, 317, 329, 330, 342
B Balderas Man, 27, 259 Beach (Beach deposits), 107–111, 303, 347 Brickyards, 103, 114–117, 281, 283 Brigantines, 23, 214, 215, 236, 307, 316, 317, 319, 323–327
D Deltas, 41, 111, 114, 117, 169–172, 176–180, 183, 187, 198, 202, 204, 218, 229, 235, 256, 269, 277, 279, 284, 286, 289, 338 Diatoms, 13, 70, 80, 128–131, 135, 172, 252–254
C Canal de la Viga, 43, 151, 214, 234, 240, 332 Carrizales, 300, 324 Céspedes, 208, 219–221, 247 Chicoloapan Man, 261, 266, 269 Cinta, 208, 220, 221 Codex Xolotl, 38, 39, 151, 161 Codice Florentine (Florentine Codex), 9, 72, 73, 325 Codice Mendocino (Mendoza Codex, Codice Mendoza), 294, 299 Codices, 9, 37–40, 45, 294, 299, 300 Conquest, 8, 10, 17, 23, 39, 40, 145, 150–152, 154, 157, 161, 162, 166, 168, 183, 212,
E Embarcadero, 201, 215, 235, 237, 308 Entarquinamiento, 117, 121 G Gran Canal del Desagüe, 53, 156, 164, 165, 331 H Huatepec, 109, 111, 115, 174, 182, 185, 188, 216, 217, 262 Huehuetoca, 50, 328, 330
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022 C. E. Cordova, The Lakes of the Basin of Mexico, https://doi.org/10.1007/978-3-031-12733-5
379
380 I Iztaccihuatl, 15, 49, 56, 128, 137–139, 253 Iztapalapa, 33, 152, 153, 173, 174, 188, 210, 211, 213, 216, 219, 223, 230, 235, 246–248, 285, 287, 305, 307, 308, 310, 311, 317, 323, 342 Iztapalapa causeway, 37, 219, 234, 316, 323 L Laguna, 47, 152–157, 166, 172, 211, 212, 225, 237, 240, 340 Landesque capital, 290, 344 M Magdalena River, 182 Mammoths, 103, 115, 117, 119, 173, 255, 257–259 Megafauna, 12, 253–263, 347 Mexicaltzingo, 103, 151, 164, 205, 234, 304 Mixhuca fault, 77, 82, 87, 94 Moctezuma, 301, 305, 315, 317, 324, 326 Mooring Embarcadero N Nezahualcoyotl (Nezahualcoyotl’s dike), 18, 47, 155, 236, 305, 307, 315–318 Nezahualpilli, 308, 311 Nochistongo, 328 Nuremberg map, 17, 19, 294, 307, 317 P Paleolimnology, 13 Pantitlán, 94 Peñón de los Baños, 94, 95, 163, 174, 179, 182, 185, 188, 262, 268, 299, 307, 311, 313 Peñón del Marqués, 88, 157, 182, 188, 261, 262, 268, 299 Peñón woman, 27, 259, 261 Pollen, 13, 80, 128–131, 135, 136, 139, 140, 251–253, 255, 266, 269, 271, 279 Popocatepetl, 15, 49, 56, 127, 128, 137, 254, 268, 274, 276
Index S Salvage archaeology, 10, 33, 80, 255, 285, 303, 346, 347 San Lazaro (San Lazaro dike), 43, 156, 214, 308 Santa Catarina Graben, 77, 82, 87, 94 Santa Isabel Iztapan, 27, 204, 257, 259 Solonchaks, 66 Subway, 34–36, 55, 80, 94, 101, 109, 152, 188, 215, 230, 237, 258, 278, 279, 285, 302, 303, 307 T Tacuba, 43, 257, 284, 323 Tacuba causeway, 319, 326 Tajo de Nochistongo, 11, 50, 53, 61, 149, 328, 330, 331 Tarango formation, 123, 278 Tecocomulco, 60, 61, 80, 129, 130, 162 Tenochtitlan, 8, 17, 22, 23, 33–35, 38, 39, 43, 46, 63, 74, 82, 94, 117, 145, 152, 155, 157, 162, 173, 175, 187, 196, 198, 199, 205, 211–213, 215, 216, 218–220, 229, 230, 232, 233, 237, 242, 246–248, 285, 287, 293–305, 307–321, 324, 326, 327, 342, 345–346 Tepeapulco, 262, 326 Tepetzingo, 121, 182, 185, 204, 216, 217, 262 Tepexpan, 12, 27, 32, 80, 108, 119, 128, 129, 140, 173, 185, 187, 188, 202, 204, 230, 232, 254, 257, 259, 261, 265–266, 268, 269, 283, 304 Tepeyac causeway, 234, 241, 305, 307, 308, 323 Tephrochronology, 82, 125–128 Tequesquite, 95, 160, 183, 341 Tequixquiac tunnel, 61, 331, 332 Terremote Tlaltenco, 13, 36, 198, 199, 201, 215, 220, 223, 281 Tlahuac, 17, 104, 125, 126, 152, 156, 158, 164, 191, 199, 205, 252, 253, 261, 268, 280–282, 287, 289, 312, 319, 339 Tlapacoya, 12, 27, 80, 107, 108, 119, 126, 127, 140, 182, 185, 188, 212, 253, 255, 257–259, 261–263, 265, 268, 279–281, 289, 299 Tlatelolco, 8, 33, 39, 197, 198, 215, 232, 237, 284, 285, 294, 295, 300, 302, 306, 320 Tocuila (Tocuila mammoths), 94, 128, 173, 204, 232, 257, 259
Index Tulares, 68, 182, 187, 198, 231, 234, 300, 324 Túnel Emisor Oriente (TEO), 61, 77, 78, 91 Túnel of Huehuetoca, 157, 160 U Uppsala map (De la Cruz Map), 18, 20, 21, 38, 146, 151, 161, 294, 307, 308
381 X Wittfogelian model, 290 X Xitle (volcano and lava), 124, 182, 274–279, 282