Quaternary of South America and Antarctic Peninsula. Volume 4 (1986): With selected papers of the international symposium on sea-level changes and Quaternary shorelines São Paulo, 7-14 July 1986 9781000108385, 1000108384, 9781000131116, 1000131114, 9781000151534, 1000151530, 9781003079316, 1003079318

Citation preview

QUATERNARY OF SOUTH AMERICA AND ANTARCTIC PENINSULA VOLUME 4

PANOCHTUS TUBERCULATUS Owen

QUATERNARY OF SOUTH AMERICA AND ANTARCTIC PENINSULA With selected papers of the international symposium on sea-level changes and Quaternary shorelines Slio Paulo, 7-14 July 1986 Edited by

JORGE RABASSA Centra Austral de Investigaciones Cientfjicas, Ushuaia, Tierra del Fuego

VOLUME4(1986)

A.A.BALKEMA I ROTIERDAM I BOSTON I 1986

EDITORIAL BOARD

Arthur L. Bloom, Cornell University, Ithaca, USA

Edward B. Evenson, Lehigh University, Bethlehem, USA

Francisco Fidalgo, Universidad de La Plata, La Plata, Argentina

Alberto Rex Gonzalez, CONICET, Buenos Aires, Argentina

Calvin J. Heusser, New York University, New York, USA

Robert Hoffstetter, Museum National d'Histoire Naturelle, Paris,

France Ernest H. Muller, Syracuse University, Syracuse, USA Rosendo Pascual, Universidad de La Plata, La Plata, Argentina Enrique J. Schnack, Universidad de Mar del Plata, Mar del Plata, Argentina Carlos Schubert, Institute Venezolano de Investigaciones Cientificas, Caracas, Venezuela Luis Spalletti, Universidad de La Plata, La Plata, Argentina Kenitiro Suguio, Universidade de Sao Paulo, Sao Paulo, Brazil Mario E. Teruggi, Universidad de La Plata, La Plata, Argentina Eduardo P. Tonni, Universidad de La Plata, La Plata, Argentina Daniel A. Valencio, Univetsidad de Buenos Aires, Buenos Aires, Argentina

The texts of the various papers in this volume were set individually by typists under the supervision of each of the authors concerned.

ISSN 0168-6305 ISBN 90 6191 732 8

© 1986

A.A.Balkema, P . O.Box 1675, 3000 BR Rotterdam

For USA & Canada: A. A.Balkema Publishers, P.O.Box 230, Accord, MA 02018 Printed in the Netherlands

Contents

INTERNATIONAL SYMPOSIUM ON SEA-LEVEL CHANGES AND QUATERNARY SHORELINES 1 Kenitiro Suguio, Louis Martin, Jean-Marie Flexor & Antonio E . G. de Azevedo The Quaternary sedimentary deposits in the States of Par ana and Santa Catarina coastal plains

3

2 E. Boltovskoy & S. Watanabe QuaternarystratigraphyoftwocoresoffthecoastofPeru

27

3 B. Turcq, R . Coe & J . M. Froidefond Variability of beach ridges on the coast of Marica (Rio de Janeiro, Brazil)

45

4 M. Lointier & M. T .Prost Morphology and hydrology of an equatorial coastal swamp: Example of the Sarcelle swamp in French Guiana

' 59

5 J . A.Villwock, L.J.Tomazelli, E.L.Loss, E.A.Dehnhardt, N . 0 . Horn F 0 , F .A . Bachi & B . A.Dehnhardt Geology of the Rio Grande do Sul Coastal Province

79

6 Chalmers M. Clapperton & David E. Roberts Quaternary sea level changes in the Falkland Islands

99

7 Louis Martin, Jose M. L .Dorninguez & Kenitiro Suguio Consequence of relative sea-level changes during the Quaternary on sandy coastal sedimentation: Examples from Brazil

119

8 Federico I. Isla, Jorge L . Fasano, Laura Ferrero, Marcela A. Espinosa & Enrique J . Schnack Late Quaternary marine-estuarine sequences of the south­ eastern coast of Buenos Aires Province, Argentina

137

V

9 Marjorie Cseko Nolasco &Zelinda Margarida de Andrade Nery Leao The carbonate buildups along the northern coast of the State of Bahia, Brazil

159

10 M. T. Prost Aspects of the morpho-sedimentary evolution of French Guiana'scoastline

191

11 LouisMartin, KenitiroSuguio&Jean-MarieFlexor Relative sea-level reconstruction during the last 7, 000 yearsalongtheStatesofParanAandSantaCatarinacoastal plains : Additional information derived from shell-middens

219

12 IrariCarlos StalliviereCorrea Evidence of sea level fluctuation in the Rio·Grande do Sul Continental Shelf- Brazil

237

13 Pierre Perrin Geomorphic evolution of the catchment basin of MaricA (Rio de Janeiro) :An attempted correlation with sea-level variations

251

14 LianaMariaBarbosa, A. C.daSilvaPintoBittencourt, J .M. LandimDominguez &Louis Martin The Quaternary coastal deposits of the State of Alagoas : Influence of the relative sea- level changes

269

15 Jorge Rabassa, Calvin Heusser &Robert Stuckenrath New data on Holocene sea transgression in the Beagle Channel : Tierra del Fuego, Argentina

291

16 D.B.Scott, R.Boyd&F . S . Medioli Relative sea-level changes on a former glacial margin: Observed level and sedimentological changes vs theoretical models

311

VI

Selected papers of the international symposium on sea-level changes and Quaternary shorelines SaoPaulo, 7-14July 1986

Edited by KENITIRO suoufo

lnstituto de Geociencias, Universidade Federal de Silo Paulo, Brazil LOUIS MARTIN

ORSTOM, France & CNPq!ON, Rio de Janeiro, Brazil JORGE RABASSA

Centro Austral de lnvestigaciones Cientificas CADIC/CONICET, Ushuaia, Tierra del Fuego, Argentina

KENITIRO SUGuiO

Universidade de Siio Paulo, Brazil

LOUIS MARTIN

ORSTOM, France & Observat6rio Nacional, Rio de Janeiro, Brazil

JEAN-MARIEFLEXOR

Observat6rio Nacional, Rio de Janeiro, Brazil

1

ANTONIO E.G.DE AZEVEDO

Universidade Federal da Bahia, Salvador, Brazil

The Quaternary sedimentary deposits in the States of Parana and Santa Catarina coastal plains

ABSTRACT A detailed study, based on the interpretation of aerial photos, field surveys, radiocarbon dating and previous experience in Quaternary coastal researches along the States of S~o Paulo, Rio de Janeiro, Espfrito Santo, Bahia, Sergipe and AlagSas, allowed us to distinguish two generations of sandy terraces associated with two periods of sea-levels higher than today. The more internal deposits are related to a period when the relative sea-level reached a maximum of 8 m above the present level by about 120,000 years BP. Numerous radiocarbon ages made possible to correlate the more external deposits to the final part of the last great transgressive period, when the relative sea-level reached a maximum of 2.5 to 3.5 m above the present level by about 5,100 years BP. In the southern half of the State of Santa Catarina coastal plain, these sandy deposits have superficially been reworked by winds, giving rise to several generations of eolian dunes. The evolutionary scheme previously established for the State of Bahia may be suitably applied to the States of Parana and Santa Catarina coastal plains. RESUMO Urn estudo detalhado, baseado na interpreta9a0 de fotos aereas, levantamentos de campo, data9oes ao radiocarbono e experi~ncia previa em pesquisas do Quaternario Costeiro ao longos dos Estados de S~o Paulo, Rio de Janeiro, Espirito Santo, Bahia, Sergipe e Alagoas, nos permitiu distinguir duas geraf~es de terrafOS arenosos associados a dois periodos de niveis mari­ nhos mais altos que o atual. Os depositos mais internos est~o relacionados a urn periodo quando o nivel relative do mar atin­ giu urn maximo de 8 m acima do atual cerea de 120.000 anos passados. Numerosas data9oes ao radiocarbono permitiram

3

a

correlacionar os depositos mais externos parte final do ultimo grande periodo transgressive, quando 0 nivel relativo do mar chegou a urn maximo de 2,5 a 3,5 m acima do atual ha aproximadamente 5.100 anos passados. Na metado sul da planicie costeira do Estado de Santa Catari­ na, esses depositos arenosos foram superficialmente retrabalha­ dos pelo Vento dando Origem a varias gera~oes dA dunas eolicas. 0 esquema evolutivo anteriormente estabelecido para o Estado da Bahia pode ser adequadamente aplicado ~s planicies costeiras dos Estados de Parana e Santa Catarina.

INTRODUCTION The studied area is comprised between the southern extremity of Ilha do Cardoso (southern limit of the State of Sao Paulo 25°l3'S) and the town of Torres (northern limit of the State of Rio Grande do Sul = 29°20'S), as it is shown in Figure 1. Between Paranagua and the town of Laguna, the coastline has a N-S direction which changes to NE-SW direction southward. In some places, as in Paranagua area, the coastal plain is about 60 km wide but in other parts, Precambrian crystalline rock headlands or Parana Basin Paleozoic or Mesozoic sedimentary rocks reach the ocean.

1 GEOLOGY OF THE COASTAL REGION In the States of Parana and Santa Catarina the coastal region is represented by an elongated strip of lowlands, limited eastward by the Atlantic Ocean and westward by the Serra do Mar and Serra Geral. Serra do Mar is usually composed of Precambrian crystalline rocks (gneisses and other metamorphic rocks, granites, etc) intruded by Mesozoic diabase dikes. The crystalline escarpment of Serra do Mar disappears in the south of Laguna (State of Santa Catarina), being replaced by the Serra Geral composed mostly of Mesozoic basaltic lava flows. Remnants of continental Neocenozoic deposits (Tertiary?) are widespread in these states, being characterized by the general afossiliferous nature and lack of key-beds. They are represented in the State of Parana by Alexandra Formation (Bigarellaet al., 1959), and in the State of Santa Catarina by Iquererim Formation (Bigarellaet al . , 1961), Canhanduva sequence (Bigarella and Salamuni, 1961), and Cachoeira layers (Bigarella, 1975). Quaternary deposits of the coastal region of these states are more or less directly related to submergence and emergence periods of Upper Pleistocene and Holocene. Among them, sandy ridges are widespread reaching a width of about 15 to 20 km, but they are discussed in more detail elsewhere.

4

Figure 1 . Location map of the stud i e d a r ea and l e g end of t he maps (Fig ur es 2- 6) .

5

2 PHYSIOGRAPHY OF THE COASTAL PLAINS

As a function of the physiography, it is possible to divide

the coastal region of the States of Parana and Santa Catarina

into three sectors (Figure 1):

a) Northern sector - This sector goes from Ilha do Cardoso

(25°l3'S) to the town of Barra Velha (26°40'S), which is

characterized by the occurrence of three great bays: Paranagua,

Guaratuba and Sao Francisco. The coastal plain situated at

the foot of the Serra do Mar escarpment presents its greatest

development within this sector.

b) Median sector - This sector is limited between the town of

Barra Velha and Garopaba area (28°00'S). This portion of the

coastline is characterized by the presence of Precambrian

crystalline rocks interrupting Quaternary coastal plains. This

sector is also characterized by the Santa Catarina Island,

where, for the first time, eolian dunes fields become

important.

c) Southern sector - This sector is comprised between Garopaba

area and the town of Torres (29°29'S), which is characterized

by vast coastal plains with extensive lagoons and paleolagoons.

This area is also characterized by frequent and important

eolian deposits belonging to several generations of dunes.

3 CLIMATE OF THE COASTAL PLAINS

The States of Parana and Santa Catarina coastal regions are

almost entirely characterized by a subtropical climate, with

cold winter and warm summer. While mean annual temperatures

are higher than 20°C in most of the Brazilian territory, in

these states they are less than l8°C. The mountainous areas

of the Serra do Mar and Serra Geral present the highest

precipitation values of Brazil, reaching frequently to maximum

precipitation higher than 5,000 mm/year in many places.

MARINE AND LAGOONAL DEPOSITS

A detailed study, based on the interpretation of aerial photos

and field surveys, supported by radiocarbon ages and previous

experience obtained studying coastal areas of the States of

Sao Paulo, Rio de Janeiro, Espirito Santo, Bahia, Sergipe and

Alagoas (Dominguez, 1983; Dominguez et al., 198la, l98lb, 1982,

1983; Bittencourt et al.,l979a, 1979b, 1982a, 1982b; Martin

and Suguio, 1975, 1976; Martin et al., 1978, 1979a, 1979b, 1980,

1981, 1982, 1983, 1984b, 1985, 1986; Suguio and Martin, 1976a,

1976b, 1978a, 1978b, 1982a, 1982b; Suguio et al.,l980, 1982,

1984a) allowed us to distinguish two generations of coastal

sandy deposits associated with two periods of high sea-levels.

The inner deposits began their sedimentation when relative

6

sea-level was about 8 m above the present level. Wood ~ragments sampled from argillaceous depo~its at the base of these sands have a minimum age of 35.000 years BP (Duarte, 1981). Though not any dating has been done, we think to be logical to assign an age of about 120,000 years BP to this high sea-level in comparison with the corals dated in the State of Bahia. In fact, sandy terraces to which is assignable the high sea-level of 120,000 years BP occur almost continuously from the State of Paraiba to Rio Grande do Sul. Thanks to several radiocarbon ages it was possible to assign the outer deposits to the final portion of the last great transgressive episode, whose maximum level has been attained about 5,100 years BP (Martin et al., this volume). There are also some marine gravel deposits which can be probably correlated with 120,000 years BP sandy terraces.

1 PROPERTIES AND DISTRIBUTION OF PLEISTOCENE MARINE TERRACES Presently these sandy terraces are whitish on the surface and brownish to blackish in the depth. The dark colours can be attributed to the presence of epigenetic organic matter which is impregnating the grains. Shallow marine origin of these deposits can be assured by the presence of Callichirus burrows, which can be attributed to marine arthropods whose life zone is the infratidal zone (Suguio and Martin, 1976b; Suguio et al., 1984; Rodrigues et al., 1984). This origin is also ensured by syngenetic sedimentary structures, like low-angle and herringbone cross-beddings. On the surface of the terraces it is possible to distinguish vestiges of alignments of ancient sandy ridges, which are much more dissipated than upon the Holocene terraces. This difference can be easily recognized on aerial photos (Martin et al., 1981). At the innermost portions of the coastal plains, the altitude of these terraces reach about 9.5 m, and oceanward, it declines until about 2.5 m, as in the Paranagua area near the contact with the Holocene terraces. Within the northern sector (Ilha do Cardoso - Barra Velha) the Pleistocene marine terraces are very well developed forming about 20 km wide band as in Paranagua and Joinville regions (Figures 2 and 3). They are much less developed within the median sector (Barra Velha - Garopaba) , when they are found only in the protected area at backside of massives of Precambrian crystalline rocks (Figures 4, 5 and 6). These terraces are once again developed within the southern sector (Garopaba- Torres), giving origin to 8 to 10 km wide band as in Sombrio area (Figure 9). In this sector they have superficially been reworked by wind and important fossil dune fields exist as in Laguna and Jaguaruna areas (Figures 4 and 5). On the other hand, in the Ararangua and Sombrio regions it is 7

CD

Fiqure 2 . Geological map of Baia de Paranagua area (State of Parana).

Figure 3 . Geologic map of Barra Velha region (State of Santa Catarina) .

9

possible to distinguish clearly the alignments of ancient sandy ridges (Figure 9).

2 PROPERTIES AND DEPOSITS

DISTRIBUTIO~

OF ANCIENT MARINE GRAVEL

In several places along the coastal plains of the States of Parana and Santa Catarina , there are some remnants of ancient marine gravel deposits. They represent ancient sea-levels clearly higher than it is today and they are older than the Holocene. There are no absolute ages for these deposits but it seems that most of them could be attributed to high sea­ level of 120,000 years BP. a) Morro do Sambaqui In Matinhos area (southern part of the State of Parana), between the Morro do Escalvado and Morro do Sambaqui, there is a restricted outcrop of an ancient marine gravel deposit which was probably originated through incipient reworking of a colluvial deposit by the waves . This deposit is situated between 12 and 13 m above the present sea-level and was described by Bigarella and Freire (1960). If the reconstruction of ancient sea-level done by Bigarella (1975) is correct, this level is higher than that of 120,000 years BP. However, until a more detailed study about this problem we prefer to correlate this deposit with the Pleistocene sandy terrace of 120,000 years BP. b) Porto da Passagem At the backside of the late Club de Caioba (State of Parana), there is also a gravel deposit formed through incipient reworking of a colluvial deposit (Bigarella, 1975). This deposit is recording an ancient sea-level about 8 m above the present level, so it is in agreement with the altitude of 120,000 years BP sea-level. Perhaps, the difference of altitude between the Morro do Sambaqui and Porto da Passagem gravel deposits could be explained by differences in wave energies in these places. c) Morro de Itajuba Between Barra Velha and Picarras, in northern portion of Morro de Itajuba, there is a gravel terrace originated by partial reworking of a regolith. Also in this case, the gravel deposit could record an ancient sea-level about 8 m above the present level (Bigarella, 1975).

10

Figure 4. Geologi c map of Picarras - Itajai region (State of Santa Catarina).

11

3 PROPERTIES AND DISTRIBUTION OF HOLOCENE MARINE AND LAGOONAL DEPOSITS a) Sandy deposits In the outer side of the Pleistocene marine terraces, and very frequently separated from them by swampy lowlands, there are lower sandy terraces commonly containing abundant mollusc shells which can be dated by 14C method and, under favourable conditions can give positions of ancient sea-levels. Differently from the Pleistocene marine terraces, these deposits are not in general impregnated by secondary organic matter. Alignments of sandy ridges are very conspicuously visible on aerial photos, mostly in northern and median sectors of the coastal plains, but intensive wind reworking affected the surfaces of the terraces in the southern sector. In the northern sector the Holocene marine terraces are much less developed than Pleistocene terraces. They are only 2 to 3 km wide and can frequently be reduced to a narrrow band as in the region between Ubatuba (Ilha de Sao Francisco) and the town of Barra Velha (Figure 3). They can be completely absent as in the Picarras area (Figure 4). The Holocene marine terraces are very discontinuous within the median sector but locally, they can be very well developed like in the Rio Itajaf-A~u valley (about 7 km wide), Tijucas region (about 5 km wide) and Enseada da Pinheira (Figures 4, 5 and 6). In the southern sector they have little development up to Morro dos Conventos, but they become more important with 5 to 6 km near the town of Sombrio (Figure 9). b) Clayey and/or silty deposits Around the bays of the northern sector (Paranagua, Guaratuba and Sao Francisco), as well as in the periphery of lagoons, southward from Ilha de Santa Catarina, there are more or less sandy clayey and/or silty deposits formed during the high sea-levels when the lagoonal extent was greater than today. They very frequently contain mollusc shells, which are sometimes so abundant, like in Laguna area, and economically exploitable. Similarly, related to the occurrence of paleo­ lagoons and paleobays there are numerous shell-middens, some of them of huge dimensions (about 50 m high).

CHARACTERISTICS AND DISTRIBUTION OF MANGROVES AND COASTAL MARSHES Around protected margins of tidal channels and bays, where the tidal action is very conspicuous, there are mangroves and coastal marshes constituted dominantly by clayey silty

12

Figure 5 . Geologic map of Tijucas region (State of Santa Catarina) .

13

sediments very rich in organic matter. The southernmost limit of occurrence of mangrove swamps along the Brazilian coast is located at the southern extremity of the Ilha de Santa Catarina (Figure 6). There are more or less developed mangroves northward of this point, at the margins of the bafas de Paranagua, Guaratuba and Sao Francisco and around the Ilha de Santa Catarina. Southward, the typical mangrove trees are almost entirely replaced by grasses like Spartina.

QUATERNARY CONTINENTAL DEPOSITS OF THE STATES OF PARANA AND SANTA CATARINA COASTAL PLAINS

1 COLLUVIO-ALLUVIAL DEPOSITS The States of Parana and Santa Catarina coastal plains are also characterized by extensive continental deposits, essentially terrigenous of different origin and age. At the foot of the Serra do Mar escarpment there are colluvial ramps representing episodes of generalized mass-movement phenomena. The alluvial deposits are formed of gravels and clayey-silty sediments. In general, the coarse alluvial deposits are older than the fine alluvial deposits. Former deposits correspond to semiarid paleoclimatic conditions while the latter have been formed under present conditions. In certain areas, like Garuva, Joinville, Turvo and Praia Grande, these colluvio-alluvial deposits are particularly well developed and may be more ancient than the Quaternary.

2 EOLIAN DEPOSITS The coastal dunes are very well developed within the southern half of the State of Santa Catarina, mostly from the Ilha de Santa Catarina southward. It is possible to distinguish at least three generations of coastal dunes: a) ancient dunes, b) Holocene dunes fixed by vegetation and c) active dunes (Figure 7). a) Ancient dunes - They are mostly constituted by reddish coloured sands, covered by more or less dense vegetation and subjected to intensive pedogenetic processes. In some places it is possible to recognize the nature of the substrate, formed of Pleistocene marine sands. Obviously, they are more recent than 120,000 years BP. In other places, it is possible to lower than today. Then, they are older than 7,000 years BP.

14

Figure 6. Geologic map of Ilha de Santa Catarina (southern portion) area (State of Santa Catarina) .

15

Figure 7. Geologic map of Imbituba/ Laguna area (State of Santa Catar ina) .

16

.....

-

. F igure 8. Geologic map o f L aguna/Tub arao area (State of Santa Catarina)

.... CXl

Figure 9. Geologic map of Sombrio area (State of Santa Catarina)

b) Holocene dunes fixed by vegetation - These sands are composed of whitish to yellowish coloured sands. They rest upon Pleistocene or Holocene marine terraces, ancient dunes and ancient lagoonal deposits as, for example, in Laguna da Conceifao, Paulo Lopes and Garopaba do Sul areas. They are covered by vegetation and their migration stopped but they can be reactivated by antropic influence. c) Active dunes - They are formed only of whitish coloured sands and represent the outermost band of eolian deposits existing in the coastal plains.

3 FLUVIO-LAGOONAL DEPOSITS When a river flows into a lagoon, the fluvial sediments form an intralagoonal delta . Thus, during the past thousands of years, the Rio Tubarao constructed an intralagoonal delta with a considerable area, which partially filled the vast lagoon situated at south of Laguna (State of Santa Catarina). This delta is still active (Figure 8).

4 PEAT DEPOSITS Total or partial desiccation of ancient lagoonal areas as a consequence of relative sea-level drop gave origin to swampy lowlands favourable to form peat deposits . Similarly, some badly drained lowlands gave origin to peat deposits. Neither of them resulted in thicky deposits because vertical movements are practically null within Holocene time scale in these areas. Between Joinville and Itapocu, for example, there are extensive peat deposits presently covered by forest (Figure 3).

EVOLUTION OF THE STATES OF PARANA AND SANTA CATARINA COASTAL PLAINS DURING THE QUATERNARY The evolutive scheme developed for the State of Bahia littoral zone and valid for most of the eastern and southeastern coastal plains of Brazil, was scheduled with a great precision by Martinet al. (1983 and this volume). This model is constituted by eight stages: a) Sedimentation of Pliocene continental deposits (Barreiras Formation) ; b) Maximum of the Ancient Transgression (older than 120,000 years BP); c) Sedimentation of the post-Barreiras continental deposits; d) Maximum of the Penultimate Transgression (about 120,000 years BP); e) Construction of the Pleistocene marine terraces; 19

f) Maximum of the Holocene Transgression (about 5,100 years BP); g) Construction of intralagoonal deltas at the mouth of the most important rivers; h) Construction of the Holocene marine terraces. This model remains almost entirely valid for the States of Parana and Santa Catarina coastal plains. Stage 1 - Several continental deposits, locally named Alexandra, Cachoeira, Canhanduva and Iquererim (Bigarella, 1975), probably Tertiary in age, have been deposited under semiarid conditions (bajada environment). Stage 2 - There are not dated evidences of the Ancient Transgression in the area. However, the remnant of an ancient sandy marine terrace situated in Itapema could be related to the Ancient Transgression, as well as the ancient marine gravel deposits of Matinhos (State of Parana), whose summits are situated about 13 m above the present sea-level according to Bigarella (1975). This idea is reinforced by occurrence of sandy marine terraces older than 120,000 years in the State of Rio Grande do Sul (Villwock et al., this volume). Stage 3 - Continental deposits formed after the Tertiary and before the 120,000 years BP. Marine terraces are not still known in this area. However, probably the undifferentiated Quaternary deposits could be, at least in part, included within this stage. Stage 4 - During the maximum (about 8 m above the present deposits have been partially foot of the Precambrian rock

of the Penultimate Transgression level), the previous continental eroded and the sea reached the escarpments.

Stage 5 - Extensive sandy terraces have been formed after the maximum of the Penultimate Transgression along the States of Parana and Santa Catarina littoral zones. These deposits were superficially reworked by winds giving origin to huge eolian dune fields. Stage 6 - During the maximum of the Holocene Transgression, deeply eroded Pleistocene terraces were invaded by the sea with formation of many estuaries, bays and lagoons. Then, barrier island/lagoonal systems have been developed and paleoindians constructed many shell-middens at the border of these shallow-water bodies. Stage 7 - When the barrier-islands isolated the lagoons from the open sea, the rivers flowing into these lagoons constructed intralagoonal deltas. With exception of Rio Tubarao, which formed an intralagoonal delta filling up, in

20

part, the lagoonal system of the Laguna area (Figure 8), there are not any other extensive intralagoonal deltas in this area. Stage 8 - The maximum of the Last Transgression was followed by formation of sandy marine terraces. In southern half of this coastal plain the sandy deposits were superficially reworked by winds giving rise to important eolian dune fields. Some of dunes became completely inactive after being fixed by vegetation but others are still active.

CONCLUSIONS Like in the most part of the previously studied Brazilian littoral zones, the coastal plains of the States of Parana and Santa Catarina were also formed as a consequence of relative sea-level changes and paleoclimatic fluctuations during the Quaternary. Extensive sandy terraces record the regressive phases which followed the maximum levels of the two last transgressive episodes (120,000 and 5,100 years BP). While the maximum height of the Pleistocene Transgression was similar in the most of the studied Brazilian littoral zones (about 8 m), the altitude of the relative sea-level during the Holocene was clearly lower in these states than in other sectors. The southern half of the State of Santa Catarina is characterized by important eolian dune fields, where it is possible to recognize at least three generations of dunes. The oldest of them were deposited between 120,000 and 7,000 years E.P. The second generation is constituted by dunes formed after 5,000 years BP, which is inactive because it is fixed by vegetation. These dunes are locally covered by still active dunes.

ACKNOWLEDGEMENTS

a

It is a pleasure to thank Funda9a0 de Amaparo Pesquisa do Estado de S~o Paulo (FAPESP) for financial support (Processo 82/1818-7) during field surveys.

REFERENCES Bigarella, J.J. 1975. Topics for discussion (International Symposium on the Quaternary). Boletim Paranaense de Geo­ ciencias. 33:171-276. Curitiba. A Bigarella, J.J. & Freire, S.S. 1960. Nota sobre a ocorrencia de cascalheiros marinhos no literal do Parana. Boletim Universidade do Parana, Geologia. 3:22. Curitiba. Bigarella, J.J. & Salamuni, R. 1961. Ocorr~ncia de sedimentos

21

"' A continentais na regiao litoranea de Santa Catarina e sua significa9ao paleoclimatica. Boletim Paranaense Geografia, 4/5:179-187. Curitiba. Bigarella, J.J.; Marques Filho, P.L. & Ab'Saber, A.N. 1961. Ocorrencia de sedimentos remanescentes nas fraldas da Serra do Iquererim (Garuva, SC). Boletim Paranaense Geografia, 4/5:82-93. Curitiba. Bigarella, J.J.; Salamuni, R. & Marques Filho, P.L. 1959. Ocorr~ncia de depositos sedimentares continentais no litoral do Estado do Parana (Forma9ao Alexandra) . Instituto Biologia e Pesquisas Tecnologicas, Notas Preliminares e Estudos. 1:7. Curitiba. Bittencourt, A.C.S.P.; Dominguez, J.M.L.; Martin, L. & Ferrei­ ra, Y. de A. 1982a. Evolu9ao do "delta" do Rio Sao Francisco (SE/AL) durante o Quaternario - Influecia das varia9oes do nivel do mar. Atas IV Simposio do Quaternario no Brasil, p.49-68. Rio de Janeiro. Bittencourt, A.C.S.P.; Martin, L.; Dominguez, J.M.L. & Ferrei­ ra, Y. de A. 1982b. 0 Quaternario Costeiro do Estado de Ser­ gipe. XXXII Congresso Brasileiro Geologia, Boletim 2 (Breves Comunica9oes), p.92. Salvador. Bittencourt, A.C.S.P . ; Martin, L.; Vilas-Boas, S. & Flexor, J. M. 1979a, Quaternary marine formations of the coast of the State of Bahia, Brazil. Proceedings 1978 International Symposium on Coastal Evolution in the Quaternary, 232-253. Sao Paulo. Bittencourt, A.C.S.P.; Vilas-Boas, G.S.; Flexor, J.M. & Martin, L. 1979b. Geologia dos depositos quaternaries do litoral

do Estado da Bahia. Textos Basicos, 1:1-21. Salvador .

Dominguez, J.M.L. 1983. Evolu9ao quaternaria da planicie costeira associada foz do Rio Jequitinhonha (BA) - Influ~ncia das varia9oes do nivel do mar e da deriva litor~nea de sedimentos. Disserta9~0 de Mestrado, Instituto de Geocien­ cias, Universidade Federal da Bahia, 73pp. Salvador. Dominguez, J.M.L.; Bittencourt, A.C . S . P. & Martin, L. 198la. Esquema evolutivo da sedimenta9ao quaternaria nas fei9oes deltaicas dos rios Sao Francisco (SE/AL), Jequitinhonha (BA), Doce (ES) e Paraiba do Sul (RJ). Revista Brasileira de Geo­ ci~ncias. 11:227-237. Sao Paulo. Dominguez, J.M.L.; Bittencourt, A.C.S.P. & Martin, L. 1985. 0 papel da deriva litorgnea de sedimentos arenosos na cons­ tru9ao das planicies costeiras associadas a desembocaduras dos rios Sao Francisco (SE/AL), Jequitinhonha (BA), Doce (ES) e Paraiba do Sul (RJ). Revista Brasileira Geoci~cias, 13:98-105. SRo Paulo. Dominguez, J.M.L.; Martin, L. & Bittencourt, A.C.S.P. 198lb. Evolu9ao Paleogeografica do delta do Rio Jequitinhonha du­ rante o Quaternario - Influ~ncia das varia9oes do nivel do mar. IV Simposio Quaternario no Brasil, Atas, 69-82. Rio de Janeiro. Dominguez, J.M.L.; Martin, L.; Bittencourt, A.C.S.P.; Ferrei­

a

22

ra, Y. de A. & Flexor, J.M. 1982. Sobre a validade da utili­ za~ao do termo delta para designar as planicies costeiras associadas as desembocaduras dos grandes rios brasileiros . XXXII Congresso Brasileiro Geologia, 2 (Breves Comunicas:~es): p.92. Salvador. Duarte, G.M. 1981. Estratigrafia e evolu~ao do plane costeiro norte da Ilha de Santa Catarina. Dissertayao de Mestrado, Universidade Federal do Rio Grande do Sul. Martin, L.; Bittencourt, A.C.S.P.; Flexor, J.M. & Vilas-Boas, G.S. 1984a. Evid~ncia de urn tectonismo quaternario nas costas do Estado da Bahia. XXXII Congresso Brasileiro Geologia, Anais 1:19-35. Rio de Janeiro. Martin, L.; Bittencourt, A.C.S.P. & Vilas-Boas, G.S. 1981. Differenciation sur photographies aeriennes des terrasses sableuses pleistoc~nes et holoc~nes du littoral de l'~tat de Bahia (Bresil). Photo-Interpretation, 3: fasc. 4/5. Paris. Martin, L.; Bittencourt, A.C.S.P. & Vilas-Boas, G.S. 1982. Primeira ocorrencia de corais pleistoc~nicos da costa brasi­ leira - Data9ao do maxima da penultima trangress~o. Ciencias da Terra. 1:16-17. Salvador. Martin, L.; Bittencourt, A.C.S.P.; Vilas-Boas, G.S. & Flexor, J.M. 1978. Introdu~ao ao estudo do Quaternario do literal da Bahia, trecho Salvador-Ilheus. Revista Brasileira Geoci~ncias, 9:309-320. Sao Paulo. Martin, L.; Bittencourt, A.C.S.P.; Vilas-Boas, G.S & Flexor, J.M. 1980. Mapa geologico do Quaternario Costeiro do Estado da Bahia. Governo do Estado da Bahia, SME, 2 folhas escala 1:250.000, texto em ingl~s, portugu~s e frances, 57pp. Salva­ dor. Martin, L.; Dominguez, J.M.L.; Suguio, K.; Bittencourt, A.C.S.P. & Flexor, J.M. 1983. Schema de la sedimentation quaternaire sur la partie centrale du littoral bresilien. Cahier ORSTOM, Serie Geologie, 13(1) :59-81. Paris. Martin, L.; Flexor, J.M. Blitzkow, D. & Suguio, K. 1985. Geoid change indications along the Brazilian coast during the last 7,000 years. Proceedings vth International Coral Reef Congress, Tahiti, 2. Martin, L.; Flexor, J.M.; Vilas-Boas, G.S.; Bittencourt, A.C.S.P & Guimaraes, M. M.M. 1979a. Courbe de variation du niveau relatif de la mer au cours de 7000 derni~res annees sur un secteur homog~ne du littoral bresilien (nord de Salvador). Proceedings 1978 International Symposium on Coastal Evolution in the Quaternary, 264-274. Sao Paulo. Martin, L. & Suguio, K. 1975. The State of Sao Paulo coastal marine Quaternary geology - The ancient strandlines. International Symposium on the Quaternary Proceedings, Acade­ mia Brasileira de Ci~ncias. 47:249-262. Rio de Janeiro. Martin, L. & Suguio, K. 1976. ttude preliminaire du Quaternaire marin - Comparaison du littoral de Sao Paulo et Salvador, Bresil. Cahier ORSTOM, Serie Geologie. 8:33-47. Paris. Martin, L.; Suguio, K. & Flexor, J.M. 1979b. Le Quaternaire

23

marin du littoral bresilien entre Cananeia (SP) et Barra de Guaratiba (RJ). Proceedings 1978 International Symposium on Coastal Evolution in the Quaternary, p.296-331. Sao Paulo. Martin, L.; Suguio, K. & Flexor, J.M. 1986. Relative sea-level reconstruction during the last 7,000 years along the States of Parana and Santa Catarina coastal plains - Additional information derived from shell-middens. This volume. Martin, 1.; Suguio, K.; Flexor, J.M.; Bittencourt, A.C.S.P. & Vilas-Boas, G.S. 1980. Le Quaternaire marin bresilien (littoral pauliste, sud-fluminense et bahianais). Cahier ORSTOM, Serie Geologie. 9(1) :95-124. Paris. Martin, L.; Suguio, K.; Flexor, J.M.; Dominguez, J.M.L. & Azevedo, A.E.G. 1984b. Evolu9ao da planfcie costeira do Rio Parafba do Sul (RJ) durante o Quaternario - Influencia das varia9oes do nfvel do mar. XXXIII Congresso Brasileiro Geolo­ gia, Anais 1:84-97. Rio de Janeiro. Rodrigues, S . de A.; Suguio, K. & Shimizu, G.Y. 1984. Ecologia e paleoecologia de Callichirus major SAY (1818) (Crustacea, Decapoda, Thalassinidea). Anais Sem. Reg. Ecol. 4:499-519. Sao carlos (SP). Suguio, K. & Martin, L. 1976a. Brazilian coastline Quaternary formations - The States of Sao Paulo and Bahia littoral zone evolutive shemes. International Symposium on Continental Margins of Atlantic Type, Anais Academia Brasileira de Ci~n­ cias. 48:325-334. Rio de Janeiro. Suguio, K. & Martin, L. 1976b. Presen9a de tubos fosseis de Callianassa nas forma9oes quaternarias do litoral paulista e sua utiliza9ao na reconstru9ao paleoambiental. Boletim IG, Institute de Geoci~ncias, USP. 7:17-26. Sao Paulo. Suguio, K. & Martin, L. 1978a . Quaternary marine formations of the State of Sao Paulo and southern Rio de Janeiro. Proceedings 1978 International Symposium on Coastal Evolution in the Quaternary Special Publication 1, 55pp. Sao Paulo. Suguio, K. & Martin, L. 1978b. Mecanismos de genese das planf­ cies sedimentares quaternarias do litoral do Estado de S~o Paulo . XXIX Congresso Brasileiro Geologia, Anais 1:295-305. Ouro Preto. Suguio, K. & Martin, L. 1982a. Progress in research on Quaternary sea-level changes and coastal evolution in Brazil. Symposium on Holocene Sea Level Fluctuations: Magnitude and Causes. Department of Geology, University of South California, p.l66-181. Columbia. Suguio, K. & Martin, L. 1982b. Significance of Quaternary sea­ level fluctuations for delta construction along the Brazilian coast. Geo-Marine Letters . 1(3/4) :181-185. Suguio, K.; Martin, L. & Dominguez, J.M.L. 1982. Evolu9ao do "delta" do Rio Doce (ES) durante o Quaternario - Influencia das varia9oes do nfvel do mar. IV Simposio Quaternario no Brasil, Atas: p.93-116. Rio de Janeiro. Suguio, K.; Martin, L.; Dominguez, J.M.L. & Bittencourt, A.C.S. P. 1984a. Quaternary emergent and submergent coasts ­

24

Comparison of the Holocene sedimentation in Brazil and south­ eastern United States . Anais Academia Brasileira Ci£ncias. 56(2) :163-167. Rio de Janeiro. Suguio, K.; Martin, L. & Flexor, J.M. 1980. Sea-lev el fluctuations during the past 6,000 years along the coast of State of Sao Paulo . In: N.A. M~rner (ed.) Earth rheology, isostasy and eustasy, p.471-486. John Wiley & Sons. Suguio, K.; Rodrigues, S. de A.; Tessler, M. G . & Lambooy, E.E. 1984b. Tubos de ophiomorphas e outras feifoes de bioturba9ao na Forma9ao Cananeia, Pleistoceno da planicie costeira de Cananeia-Iguape, SP. In: L.D . Lacerda et al. (org . ) Restin­ gas: origem, estrutura, processes: p.lll-112 . Niteroi (RJ). Villwock, J.A . ; Tomazelli, L.J.; Loss, E.L.; Denhardt, E . A . ; Horn Filho, N.O.; Bachi, F.A. & Dehnhardt, B . A. 1986. Geology of Rio Grande do Sul coastal province. This volume.

25

E.BOLTOVSKOY & S. WATANABE

Museo Argentina de Ciencias Naturales 'B. Rivadavia' & Conicet, Argentina

2

Quaternary stratigraphy of two cores off the coast of Peru

ABSTRACT On the basis of a quantitative analysis of planktonic Foraminifera, eight Quaternary climatic zones were identified in co re 3-5 and ten in core 3-6 (USNS ELTANIN, Peruvian continental slope). Four different approaches were used for the construction of the paleoclimatic curves: l. Warm water vs. cold water ratio of entire assemblaqes. 2. Ratio of Globoquadrina dutertrei vs . G. pachyderma (sin.), 3. Ratio of G. dutertrei vs. Globorotalia inflata and 4. Globigerina bulloides si nistral vs. dextral fractions . In order to compensate for patchy data due to natural (deposition, preservation) and procedural (sampling, subsampling, counting) biases, the ratios were calculated on the basis of smoothed figures (averaging each three consecutive discreet values, except at the ex tremes, where two values were considered). The first of the four approaches mentioned above yielded the mo s t reliable results, but th e c urves in question lacked adequate resolution. The ratio between G. dutertrei and G.pachyderma(sin.) results in a curve essentially concordant with the former but with much more spectacular changes, thus providing a more clear-cut ' separation between the climatic events reflected. The climate-induced foraminiferal changes analyzed are synchronous in the Pacific and Atlantic Oceans. It is believed that the stratigraphic range of Globorotalia pseudopima should be rai sed to the Quaternary, inclusively. Reworked Pliocene, Miocene, Quaternary and Oligocene specimens were found at most levels.

RESUMEN Del analisis cuantitativo realizado con foraminiferos planc­ -tonicos de los testigos 3-5 y 3-6 del USNS ELTANIN, del talud continental peruana, fueron identificadas ocho zonas climaticas

27

pleistocenicas en el primer testigo y diez en el segundo. Se emplearon cuatro diferentes relaciones para la reconstruccion de las curvas paleoclimaticas: 1 . Relacion entre la asociacion de especies de aguas calidas y de aguas frias. 2. Relacion entre Globoquadrina dutertrei y Globoquadrina pa­ -chyderma (sin . ) . 3. Relacion entre Globoquadrina dutertrei y G. inflata. 4 . Rela~ion entre Globigerina bulloides sinistral y dextral. Para compensar los datos individuales de cada muestra que podrian no ser representatives, debido a la condicion natural de la depositacion, preservacion, etc. del material y trata­ -miento del mismo (muestreo, submuestreo, conteo), dichos da­ -tos se promediaron considerando para cada uno tres valores consecutivos, excepto para los extremes, donde son considera­ -dos solamente dos valores. El primero de esos cuatro proce­ -dimientos, mencionados arriba, proporcion6 un resultado mas confiable, aunque la curva en cuestion carece de una adecuada resolucion. De la relacion entre G.dutertrei y G.pachyderma(sin) se deduce una curva concordante con la primera, pero con cam­ -bios mucho mas espectaculares, asi provee de una mas clara y neta separaci6n entre los eventos climaticos reflejados. El clima inducido de los carnbios de las asociaciones de foramini­ -feros estan sincronizados en el Oceano Pacifico y Oceano Atlantico. Esta admitido que el rango estra.tigrafico de Globo­ -rotalia pseudopima debe ser elevado hasta el Cuaternario inclusive. Ejemplares resedimentados del Plioceno, Mioceno y Oligoceno fueron encontrados en distintos niveles.

INTRODUCTION The detailed study of planktonic foraminifers in piston cores obtained from the sea bottom is of great interest because it allows reconstruction of climatic and hydrological changes that have taken place in a given area during the last geological epochs . . Many of such studies have been carried out on a great number of Atlantic Ocean cores, but relatively very few cores have been studied from the Pacific. The main objectives of this study are: 1 . The qualitative and quantitative study of the planktonic foraminifers of two piston cores retrieved off the Peruvian coast. 2. The establishment of their biostratigraphic zonation. 3. The determination of the age of the deposits recovered. 4 . The assessment of the present paleoclimatic changes. 5. Comparison with analogous results from the South Atlantic Ocean. This report is a contribution to the International Geological

28

?igure 1 . Locati on of cores.

Correlation Project (PIGG/UNESCO N° 201 "Quaternary of South America").

MATERIAL AND METHODS The cores studied were retrieved in~id-June, 1962, during the third cru ise of the oceanographic research vessel USNS ELTANIN (National Science Foundation, USA). Their geographic location, lengths and type of sediment are as follows: Core 3-5: l6°03'S; 76°46'W; 2835 m; 793 cm; clay Core 3-6: l6 °0l'S; 76°47'W ; 2780 m; 1003 cm ; clay Core 3-5 was sampled at 10 cm intervals (total of 80 samples) , whereas core 3-6 was sampled at somewhat less regular intervals (total of 95 samples). After the sediments were washed through a 0.062 mm sieve, from the poorest samples all foraminifers were picked, whereas from those with abundant material 200-400 individuals were selected at random. A total of 20,785 foraminifers were picked from core 3-5 and 27,965 from core 3-6. Approximately 7% of these were unidentifiable due to their sma ll size (evidently 29

Plate I 1. Globigerina bul1oides, f. typica; core 3-5, depth 0-2 cm. 2. Globigerina bulloides, f. trilocularis; core 5-3, depth 0-3 cm. 3. Globigerina digitata; core 3-5, depth 391-393 cm. 4. Globigerina falconensis; core 3-5, depth 121-123 cm. 5. Globigerina quinqueloba; core 3-5, depth 101-103 cm. 6. G1obigerina utilisindex; core 3-5, qepth 41-43 cm. 7. Globigerina utilisindex; core 3-5, depth 161-163 cm. 8. Globigerina utilisindex; core 3-5, depth 161-163 cm. 9. Globigerina cf. tecta; core 3-5, depth 441-443 cm. 10. Globige_rina rubescens; col'e 3-5, depth 381-383 cm. 11. Globigerinita clarkei; core 3-5, depth 61-63 cm.

30

~nmature) and/or ?OOr preservation. Thus, this report is based on somewhat over 45,000 specimens. Samples with less than 100 individuals (1, 2, 3, 22, 29, 12, 31 and 37 in core 3-5, and 29, 31, 32, 33, 35, 36, 37 and 52 in core 3-6) were excluded from the subsequent discussions and analyses.

GENERAL CHARACTERISTICS OF THE FAUNA FOUND A total of 54 taxa (sp. and subsp.) were identified in both cores. Table I and II summarize lists of the foraminifers found in cores 3-5 and 3-6, respectively, and their stratigraphic and quantitative distribution. The assemblages of both cores are practically identical. The dominant species are: Globigerina bulloides, s.l., G. quinqueloba, Globigerinita glutinata, G1oboquadrina dutertrei, G. pachyderma s. str., G. pachyderma pacifica, G1oborota1ia inflata and G. pseudopima. In most samples, although i.n considerably less number, were found also Globigerinoides ruber, G1oboquadrina hexagona and Orbu1ina universa. In still considerably smaller quantity, but in relatively many samples, was recorded Globorotalia truncatu1inoides. In addition, we also recorded very few specimens of G1oboro­ ta1ia tosaensis, transitional forms between G. tosaensis and G. truncatulinoides and between G1oborota1ia margaritae and G. eastropacia, G1obigerina umbilicata, Globorotalia crotonen­ sis, G. puncticulata, Globigerinoides ob1iquus and Orbu1ina sutura1is. Not cited herein are many species recorded as isolated specimens; however, they are included in tables I and I I.

The following species, evidently reworked from other strata, were recorded in very limited numbers: Globorotalia acostaen­ sis, Globigerinoides bulloideus, Globigerina cf. tecta and G. utilisindex.

12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24.

Globigerinita humi1is; core 3-5, depth 441-443 cm. Globigerinita iota; core 3-5, depth 51-53 cm. G1obigerinita glutinata; core 3-5, depth 111-113 cm. Globigerinita g1utinata; core 3-5, depth 441-443 cm. Globigerinita glutinata; core 3-5, depth 191-193 cm. G1obigerinita uvula; core 3-5, depth 61-63 cm. G1obigerinel1a aequilateralis; core 3-5, depth 531-533 cm. Globigerinel1a aequilateralis; core 3-5, depth 531-533 cm. Globigerinoides e1ongatus; core 3-5, depth 401-403 cm. Globigerinel1a calida praecalida; core 3-5, depth 11-13 cm. Globigerinella calida praecalida; core 3-5, depth 51-53 cm. Globigerinoides ruber; core 3-5, depth 381-383 cm. Globigerinoides ruber; f. pyramidalis; core 3-5, depth 461­ 463 cm. 25. Globigerinoides obliquus; core 3-5, depth 681-683 cm.

31

PALEOCLIMATIC ZONES Four types of relationship were used for the assessment of paleoclimatic variations. 1. Ratio between specimens of typically warm water and typically cold water specimens. The former consist of : Globi­ gerina digitata, G. rubescens, Globigerinella aequilateralis, Globigerinoides conglobatus, G. elongatus (f. typica and f. pyramidalis), G. ruber (f. typica and f. pyramidalis), G. sa­ cculifer, G. tenellus, G. trilobus, Globoquadrina conglomerata, G. dutertrei, G. hexagona, Globorotalia eastropacia, G. menar­ dii, G. neoflexuosa, G. tumida, Orbulina universa, Pulleniati­ na obliquiloculata and Sphaeroidina dehiscens. The following foraminifers were included in the typically cold water group: Globigerina bulloides (f. typica and f. trilocularis, dextral and sinistral specimens), G. quinqueloba, Globigerinita clar­ kei, Globoquadrina pachyderma (f. typical and f. superficiaria; only sinistrally coiled of both forms), Globorotalia inflata, G. scitula (f . typica and f. gigantea) and Orcadia riedeli. 2. Ratio between the population of two species only, namely of a typical representative of warm water: Globoquadrina dutertrei and of a typical cold water species: Globoquadrina pachyderma (sinistral). 3. Ratio between the population of the same warm water species Globoquadrina dutertrei and a cold water representative: Globo­ rotalia inflata. 4. Ratio between the sinistral and the dextral specimens of Globigerina bulloides, s.l. It is well known that this ratio has a well-pronounced tendency to increase with the temperature decrease. In order to compensate for patchy data due to natural and/or procedural biases (preservation, sampling, counting, etc), the ratios were calculated on the basis of smoothed figures, i.e., averaging each three consecutive values (except at the extreme, where two consecutive values were taken into account). Thus, four paleoclimatic curves were derived for each core. The first two showed great coincidence and, since they appeared to be the only reliable ones, only they are illustrated in figure 2. However, there is a difference between them, namely, the curve based on entire assemblages is somewhat smoother and of less resolution, whereas the one derived from two species 1 only is sharper and thus provides more clear-cut differences between the changes involved. Re s ults obtained with the use of the curve based on the relationship between Globoquadrina dutertrei and Globorotalia inflata are not reliable and not clear; probably because of insufficient numbers of G. inflata. This curve is not included in figure 3. The ratio between the sinistral and dextral specimens of Glo­ bigerina bulloides yielded a rather irregular pattern which is not in accordance with the other curves. This result was

32

surprising, since the ratio in question is consistent with c limat ic variations and has been used with prior success for South Atlantic sediments in paleoecological surveys (Boltovskoy, 1973). The curve obtained from the above mentioned ratio is not shown in figure 3.

HYDROLOGICAL ENVIRONMENT A detailed review of the hydrology of the area under discussion was published by Burkov et al. (1971). According to these authors, cores 3-5 and 3-6 are located near the boundary dividing two hydrological structures: the Subtropical Oriental Structure to the north, and the Peru-Chilean Structure to the south. In the former they recognized: a) Surficial Water Mass (0­ be·tween 50 and 75m) ; 1 7°-20°C; 35.0-35. 2%0 ; northwestern movement.. b) Subtropical Orientrl Surficial Water (between 50 and 75 ­ 400 m); 9°-l6°C; 34.7o/oq southward movement. c) Antarctic Intermediate Water Mass ( 400 m); 5.5°C; 34.50 ­ 34.55o/o~ northward movement. The Peru-Chilean Structure consists of:

a) Surficial Water (0- 80 m); l6°-l7°C; northward movement.

b) S~bantarctic Surficial Water Mass (80-200 m); ll°C; 34.1­ 34. 7°/0 0 ; northward movement.

c) Subtropical Surficial Water (200-400 m); 8°-ll°C; 34.55­ . 34.800k~ southward movement. d) Antarctic Intermediate Water Mass ( 400 m) ; northward movement. Since both cores are located in the vicinity of the boundary

between these hydrological structures, the paleoclimatic

changes shift the above mentioned boundary. As a consequence,

subtropical and subantarctic waters (with their corresponding

faunas) will vary in influence, which, in turn, will be

reflected in the fluctuation of the thanatocoenosis found in

cores 3-5 and 3-6.

PREVIOUS WORK The most interesting studies for our report are those by Blackman and Somayajulu (1966), Blackman (1966) and Wiles (1967). In the first two papers, the authors analyzed 55 cores retrieved from the southeastern Pacific Ocean. These cores were considerably shorter than ours (12 to 526 cm) . Of these 55 cores, three (DWBG-100 and DWBG-114) are located very close to our cores (3-5 and 3-6). Blackman and Somayajulu were able to identify five cl imati c zones in the first two cores and six in core DWBG-114. They did not correlate their zones with the well-known Pleistocene interglacial and interstadial epochs, but were able to determine the absolute ages of the sediments

33

Plate II 1. 2. 3. 4. 5. 6. 7. 8.

Globigerinoides sacculifer; core 3-5, depth 31-33 cm. Globigerinoides tenellus; core 3-5, depth 441-443 cm. Globigerinoides trilobus; core 3-5, depth 41-43 cm. Globoquadrina dutertrei; core 3-5, depth 131-133 cm. Globoquadrina dutertrei; core 3-5, depth 121-123 cm. Globoquadrina dutertrei; core 3-5, depth 551-553 cm. Globoquadrina pachyderma; core 3-5, depth 751-753 cm. Globoquadrina pachyderma, f. superficiaria; core 3-5, depth 351-353 cm. 9. Globoquadrina pachyderma, f. superficiaria; core 4-19, depth 22-24 cm.

34

studied . As for the study by Wiles (1967), an important disagreement with his result concerning the interpretation of the sinistrally coiled Globoquadrina dutertrei is discussed in the systematic part of the present paper.

GEOLOGIC AGE The upper 48 cm of both cores are apparently of Holocene age. At this depth the paleoclimatic curves of both cores show a very sharp change from a warm-temperate to a cold fauna. Thus, the rate of sedimentation during the Holocene was about 4.4 cm/ 1,000 years. The paleoclimatic curves of cores 3-5 and 3-6 are in good agreement, but the Pleistocene sedimentation rate of the former ~eems to be somewhat lower. Eight climatic zones can be identified in core 3-5 and ten in core 3-6, however, climatic changes are not as sharp as in the case of Holocene/Pleistocene boundary. All of the zones are undoubtedly Pleistocene, because, as is mentioned above, typical (although rather rare) specimens of Globorotalia truncatulinoides were recorded throughout both sequences. We suppose that these deposits are late Pleistocene in age. However, since no absolute ages could be derived, exact rates of sedimentation in this area are lacking. In addition, many samples of both cores contained high proportions of re­ worked and displaced foraminifers, thus precluding any

10. Globoquadrina pachyderma pacifica; core 3-5, depth 341­ 513 cm . 11. Globoquadrina pachyderma pacifica; core 3-5, depth 341­ 513 cm. 12 . G1oboquadrina pachyderma pacifica; core 3-5, depth 341­ 513 cm. 13. G1oboquadrina pachyderma pacifica; core 3-5, depth 541­ 543 cm. 14. Globoquadrina pachyderma pacifica; core 3-5, depth 581­ 583 cm. 15 . G1oboquadrina hexagona; core 3-5, depth 341-513 cm. 16. Globoquadrina hexagona; core 3-5, depth 341-513 cm. 17. Globoquadrina hexagona; core 3-5, depth 341 - 513 cm. 18. G1oboquadrina hexagona; core 3-5, depth 341-513 cm. 19. Globorotalia crassaformis; core 3-5, depth 751-753 cm. 20. Globorota1ia crassaformis; core 3-5, depth 461-463 cm. 21. G1oborota1ia inflata; core 3-5, depth 481-483 cm. 22. Globorotalia inflata; core 3-5, depth 591-593 cm. 23 . Globorotalia scitula; core 3-5, depth 491-493 cm. 24. Globorotalia scitula; vars.; core 3-5, depth 531-533 cm.

35

Plate III 1. G1oborota1ia eastropacia; core 3-5, depth 461-463 cm .

Detail of wall of figure 2 .

2. Globorotalia eastropacia; core 3-5, depth 461-4 63 cm . 3. Globorotalia eastropacia; core 3-5, depth 441-443 cm . 4. Globorotalia margaritae/ eastropacia; core 3-5, depth 451­ 453 cm. 5. Globorotalia margaritae; core 3-5, depth 371-373 cm. 6. Globorotalia margaritae; core 3-5, depth 70-72 cm. 7. Globorotalia margaritae; core 3-5, depth 70-72 cm. 8. Globorotalia menardii; core 3 -5, depth 401-403 cm . 9. Globorotalia menardii neoflexuosa; core 3-5, depth 31­ a3 c m.

36

correlation of the climatic zones identified with the Pleistocene interglacial and interstadial epochs described for other areas. In low latitude areas, these correlations are especially difficult because of the low intensity of the faunistic changes caused by climatic shifts. Yet, the location of the Holocene/Pleistocene boundary, as well as the general character of the paleoclimatic curves presented in this report, are in good agreement with those for the southwestern Atlantic (Boltovskoy, 1973). This suggests that the glaciation events were synchro~ous in both areas (southeastern Pacific and southwestern Atlantic). A similar conclusion was also reported by Blackman & Somayajulu (1966) and Blackman (1966).

SYSTEMATIC PART Table I and II summarize the faunistic data obtained. Plate I includes photographs of some of the species identified. Most of the taxa recorded have been repeatedly described and illustrated before, and therefore do not need further treatment. A few, however, deserve some brief comments. Globigerina utilisindex Jenkins and Orr, 1973. The occurrence of this species in cores 3-5 and 3-6 is rather enigmatic . Our specimens are identical with the primary types and we have no doubts as to the certainty of our iden.tifications. However, G. utilisindex was described from the early Oligocene, and, as far as we know, this species has not yet been found in the Neogene or the Quaternary. Our specimens were most probably reworked, but strangely enough, no benthic foraminifers of Oligocene age

10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24.

Globorotalia pseudopima; core 4-19, depth 22-24 cm. Globorotalia pseudopima; core 4-19, depth 22-24 cm. Globorotalia pseudopima; core 3-5, depth 341-513 cm. Globorotalia pseudopima; core 3-5, depth 121-123 cm. core 3-5. depth 161-163 cm. Globorotalia -p seudopima; ­ Globorotalia tosaensis/truncatulinoides; core 3-5, depth 791-793 cm. Globorotalia tosaensis/truncatulinoides; core 3-5, depth 481-483 cm. Globorotalia truncatulinoides; core 3-5, depth 681-683 cm. Globorotalia tumida; core 3-5, depth 211-213 cm. Orbulina bilobata; core 3-5, depth 121-123 cm. Orbulina suturalis; core 3-5, depth 151-153 cm. Orbulina suturalis; core 3-5, depth 141-143 cm. Orcadia riedeli; core 3-5, depth 731-733 cm. Pulleniatina obliquiloculata; core 3-5, depth 541-543 cm. Sphaeroidinella dehiscens; core 3-5, depth 41-43 cm.

37

Figure 2. Paleoclimatic curves: Broken line - ratio between warm water and cold water foraminiferal assemblages. Solid line - ratio between Globoquadrina dutertrei and G.pachyderma (sin.). Dotted line- denotes samples which contained insufficient numbers of c limatic indicator species.

were f o und in the samples surveyed. Globoquadrina dutertrei (d'Orbigny), 1839. This species js widely distributed and is well known as being very predominantly de~trally coiled. However, we found in core 3-5 (between samples 13 and 20), and in core 3-6 -~betw een samples 12 and 24) that 38

Tab le I. Verti c al di s tri b uti on o f p lank t oni c f o raminif e r s .i n cor e 3-5.

Table I. Continued.

Table 2. Vertical distribution of planktonic foraminifers in core 3-6 .

Table 2. Continued.

the proportions of the sinistral form in the population of G. dutertrei were very high oscillating between 17 and 75%. In a core located in the same area, Wiles (1967) also found in some portion of his core a high percentage of sinistral form. However, according to Wiles, these sinistral specimens were among cold water fauna, thus indicating low temperatures, whereas in cores 3-5 and 3-6 the samples containing high proportion of sinistral forms were characterized by a warm water assemblage and evidently belong to the warm temperature zone. Globoquadrina pachyderma pacifica Boltovskoy and Watanabe. This new subspecies was described by Boltovskoy and Watanabe (in press, Rev. Espan. Micropal.) on the basis of material from the two cores discussed in this paper. Its most typical feature is the very high dorsal side. Globorotalia eastropacia Boltovskoy, 1974. This species is undoubtedly closely related to G. theyeri Fleisher, 1974. However, since the former lacks a keel and its porosity covers the entire test, whereas G. theyeri, according to Fleisher, has a thin imperforate keel, we prefer to treat both foraminifers separately. In addition (although this is not of taxonomic importance), G. eastropacia is always dextral, whereas G. theyeri is sinistral. Globorotalia pseudopima Blow, 1959. This foraminifer is widely considered as a typical pre-Quaternary representative. However, since in cores 3-5 and 3-6 it is present in Quaternary deposits i~ large numbers, and mostly in an excellent state of preservation, we suggest that (at least in the southeastern part of the Pacific Ocean) its vertical distribution should be extended to include the Quaternary.

ACKNOWLEDGEMENTS The authors are very grateful to Mr Dennis Cassidy, curator of the Antarctic Research Facility at Florida State University (Tallahassee, USA), for providing the samples used in this study and for reading a draft copy of the manuscript. REFERENCES Blackman, A. 1966. Pleistocene stratigraphy of cores from the southeastern Pacific Ocean. Univ. California, San Diego (unpublish. PhD thesis). Blackman, A & Somayajulu, B.L.K. 1966. Pacific Pleistocene: faunal analyses and geochronology. Science, 154:886-889. Boltovskoy, E. 1973. Estudio de testigos submarinos del Atlan­ tico Sudoccidental. Rev. Mus. Argent. Cienc. Nat., Geol., 7 (4): 215-340.

43

Burkov, V.A ., Panfilova, S.G., Moiseev, L.K. & Zubin, A.B. 1971. Circulation and water masses of the Southeastern Pacific. Tr. Inst. Okeanol., 89:9-32 (in Russian) . Wiles, W.W. 1967. Pleistoc~ne changes in the pore concentration of a planktonic foraminiferal species from the Pacific Ocean. Progr. Oceanogr., 4:153-160.

44

B.TURCQ

ORSTOM, Departamento de Geociencias, Universidade de Stio Paulo, Brazil

3

R.COE

Departamento de Geoqufmica, Universidade Federal Fluminense, Niteroi, Brazil J.M.FROIDEFOND

Universite de Bordeaux/, Departement de Geologie & Oceanographie, IGBA/CNRS, Talence, France

Variability of beach ridges on the coast of Marica (Rio de Janeiro, Brazil) ABSTRACT Inventory of morpho-sedimentary units on a 35 km trench of the coastline of the State of Rio de Janeiro allowe d the identification of three beach-ridge generations . The first one is characterized by low undulations and me dium size well- s orted sands. It was formed during a pleistocene high sea level period whi c h, in contrast to the present, exhibited lower littoral dynamics. The sec ond and third generations are well defined beach ridges separated by a flat trough. They were edificated at 5000 years BP and 3500 years BP respectively, via similar littoral dynamics acting at present. Coalescence of the latter ridges was observed at their eastern premises . This variation of shoreline orientation may be attributed to slight hydro­ dynamic changes, to wind action and/or to neotectonic movements. The latter seems to be the most pausible process responsible for coalesc e nce.

RESUMO 0 estudo das unidades morfo-sedimentares da reg1ao de Marica, no Estado do Rio de Janeiro, possibilitou a identificayao de tres gera9oes de cordoes arenosos. A primeira geray~o apresenta· se bastante erodida, corn altitudes medias n~o ultrapassando 4 m. Esses cordoes mais antigos sao testemunhos de uma transgressao pleistocenica cuja caracterfstica reflete uma dinamica litoral menos intensa do que a atual . A segunda e a terceira gerayoes sao caracterizadas por cordoes bem definidos, separados por uma estreita depressao, notadamente na parte oeste. Esses cordoes mais recentes foram edificados ha 5000 AP e 3500 AP respectivamente, atraves de uma d i namica similar) atual. Observa-se no setor leste, uma coalescencia desses cor~oes. A variayao de orienta~ao da linha de costa deve-se a pequenas mudanyaS da hidrodinamica, a fenomenos eolicOS e a

45

fen6menos neotectonicos, sendo este ultimo, provavelmente, mais atuante.

0

INTRODUCTION Extended sandy coastal plains, named "Restingas", represent about 5000 km of the ~razilian littoral zone (Lacerda et al., 1984). These plains are usually covered by beach ridge, in some cases reworked by sand dunes. These features were the result of the last sea level lowering. This was shown by various systematical studies and also numerous radiocarbon datings which enabled the construction of a detailed pattern of sea level fluctuations since 6000 years BP (Suguio et al.l979, Martin et al., 1980, 1983). Although the formation of these beach ridges are clearly related to periods of higher sea level and smooth regressions thereafter, little is known about the mechanisms involved in their construction. A recent study has shown that the ridge patterns may reflect a record of past marine hydrodynamical and climatic changes (Martinet al., 1984). This paper presents a detailed study of a simple small-scale beach ridge system near Rio de Janeiro. The factors responsible for the variability of beach ridges will be discussed in term of temporal and regional changes.

GEOGRAPHICAL AND GEOMORPHOLOGICAL SETTING The studied area is a 35 km long trench of the coast, 30 km east of Rio de Janeiro, near the city of Marica, at about 23 Lat. S. and 43.long. E .• The morphology of this coastal region is dominated by crystalline massifs. They are remains of the South Atlantic opening and form the typical landscape of Rio de Janeiro (Figure 1). The diagram was constructed by numerical treatment of topographic data according to Froidefond and Berthois (1979). The coastal plains lie at the base of these mounts, formed by fluvial and lagoonal sediments, bordered by beach barriers. The inner shelf is a perfect morphological continuity to the coastal plain. A more detailed geomorphological description of the studied area is depicted in Figure 2. The crystalline massifs exhibit a SW-NE orientation. They form the landheads of the barrier beaches and inner shelf islands. A hilly lowland extends between the crystalline massifs and the coastal plains. The hills are remnants of dessicated Tertiary erosion surfaces and are, in general, composed of altered gneisses. The beach barrier adopts a tombolo shape in the region close to the Marica islands.

46

Figure 1. Computer b l ock-diagram showing the topographic f~tures of the Rio de Janeiro area.

MORPHO-SED IMENTARY UNITS Aeria l photographs at a 1/20 000 scale allow a better definition of the morpho- 3 edimentary units of the coasta l plain (Figure 3) . Hills and crysta ll ine massifs are grouped under the term "complex basement ".

VALLEY FLATS The ~ain va ll eys of the lagoonal tributaries li e between the crysta lli ne massifs. The fluvia l rteposits formed flat surfaces that were fun ctioning as the f l ood plains of the rivers and, in part, also of the lagoons. In tnis l ast case the high lagoonal levels are wel l marked on the aerial photographs (Figure 3).

47

Figure 2. Computer block-diagram depicting area

geomorphological aspects of Lagoa de Mar ica

rigure 3 .

Morph o - sedi m entar~

un i ts of Mari c a coasta l plain.

LAGOONAL BEACH RIDGES The formation of small-s c ale beaches on lagoon shores is a common process . Such beach ridges existed at the periphery of the actual lagoons. They are formed of very well sorted medium sand. Ancient lagoonal beach ridges, with the same morphological and lithological characteristics, were also recognized . This is another indication of the prevailance of higher lagoonal levels in the past. These higher levels are probably related to high sea levels and/or may also be due to the recent draining of this region (Coe et al., 1986).

LAGOONAL CLIFFS Around the lagoons the hills of alterated rock are cut by cliffs up to 20 m in height . The actual hydrodynamics of the lagoon are not expected to create such cliffs. On the other hand, the gneisses, whose alteration is largely older than the holocene transgression, are not resistant enough to be directly eroded by the sea in such an irregular pattern. These cliffs were probably carved during an older stage of the lagoon by a stronger hydrodynamic forcing than the actual one. This was probably due to a larger access of the lagoon to the open sea (Coe et al., J. 986).

FIRST GENERATION BEACH RIDGES A series of small amplitude beach ridges lies in the western part of the studied area, between a large valley flat and the beach barrier (Figure 3). Their altitude is low (4 m). They are composed of medium sized sand. These ridges are strongly eroded and, at some place, overlain by lagoonal beach ridges.

SECOND AND THIRD GENERATION RIDGES The beach barrier per se is composed of two well defined beach ridges. They are considered as two distinct beach ridge generations. The second generation ridge (the landward one) adopts a multiple crest pattern in the western part of the studied area. It disappears progressively in the eastern part where the third generation ridge overlies the second. The two beach ridges are composed of coarse sand. The second generation ridge is 9 to 12 m high, the third 4 to 11 m. The ridge elevation is strongly dependant on wind reworking. A flat trough separates the two ridges in the western region. On the northern sidP., the trough edge is modeled by numerous sand spits (Figure 3). These spits do not prevail on the southern side where a sharp contact between the flRt trough and the

so

steep side of the third generation ridge exists. The shoreward side of this ridge is, in contrast, smooth and prolongated by the actual beach.

GRANULOMETRICAL STUDY In order to conduct a better characterization of the three ridge generations, we realised samplings along: the two well defined ridges of second and third generation, the best marked crest of the first generation ridges and the berm of the actual beach. These sediments are dominantly quartzose. Each sample was submitted to granulometrical analyses on a standard US seaving set. Positions of the sampling points and granulometrical results are exposed on Figure 4. Sediments of the second and third generation ridge and of the present berm are well sorted coarse sands. Their mean diameter decreases eastward as also evidenciated by Mueheet al.,(l977) on the present beach. The standard deviation (SD) decreases in th e same direction. The skewness (Sk) reaches very high values in the coarse sand zone (3 in millimetric system or -3 in phi system) and faces a marked decrease in the zone located landward of Marica islands. The granulometry of the second and third generation ridge and of the present berm exhibits very similar patterns. The first generation ridges are composed of well sorted medium sand and also show high skewness. The short length of these ridges do not allow any identification of granulometrical gradients.

DISCUSSION l CHRONOLOGY OF BEACH RIDGE EDIFICATION The beach barriers of the Rio de Janeiro coast commonly present two well defined beach ridges. Datations realised in Araruama, eastward of the studied area (Coe, 1984) and in Jacarepagua, westward of the studied area (Maiaetal., ~. 984) indicate that these two ridges correspond to the high sea levels of 5000 years BP (second generation ridge) and 3500 years BP (third generation ridge) -see Martinet al., this volume-. As the second generation ridge corresponds to the higher level of the holocene transgression, the first generation must then be related to an older transgressive event. These ridges, typified by a low relief and an eroded aspect, are similar to those observed in Bahia (Martin et al.., 1981) and Santa Catarina States (Suguio et al., this volume). Bahia State ridges were dated at 120 000 years BP (Martin et al., 1982). The great granulometrical difference between the first ridge generation

51

Figure 4 . Granulo metr i cal c haracte r istic s of beach ridge s i n Marica.

52

and the others shows that the pleistocenic swells from south­ west to southeast were consistently weaker than the present ones.

2 THE LAST TRANSGRESSIVE MIGRATION Muehe (1984) proposed the existence of a last transgressive event in this region. His main argument is supported by the past existence of a lagoon in the flat trough between second and third generation ridges. The sand spit observed on the shoreward face of the second generation ridge seems to be lagoonal cuspate spits (Zenkovitch, 1959). Such morphology is observed in lagoons between the two holocenic beach ridges in other regions of the Rio de Janeiro State (Coe, 1984; Maiu et al., 1984). The presence of lagoonal organic mud under a 20 cm thick sand layer in the flat trough south of Marica lagoon (Lacerda personal communication) corroborates Muehe's hypothesis. In this case, sand spits are expected to occur also on the third generation ridge edge, facing symmetrically the cuspate spits of the second generation ridge. The lack of these spits is interpreted as the result of recent transgressive migration of the third generation ridge. The second and third generation ridges observed in the whole studied area (Figure 3) present different orientations, the second generation being progressively overlain by the third in an eastward direction. This implies a past variation of the shoreline orientation. In the eastern part of the studied area, close to Guarapina lagoon, the third generation beach ridge also overlies lagoonal mud of this lagoon. This fact fits in with a reorientation of the coast and with a possible transgressive dislocation of the third generation ridge between 3500 years BP and present.

3 FACTORS OF BEACH RIDGE MIGRATION Several mechanisms may explain the variations of shore orientation. The most likely are: 1. A variation of the do~inant swell orientation, 2.. An effe-::t of wind whicll would _thrust the third generation ridge over the second one ("this translation could be hi::rher in the east zone where the sand is finer) and, 3. An effect of neotectonism.

The pattern of swell formation in this part of the South

Atlantic Ocean is little known. Some visual observations (Muehe, 1979) reveal that swells from south (44%) and southwest (39%) are dominant. These swells are initiated by the strong winds resulting from the passage of polar fronts. The influence of the southerly swells can be S 50 m below to> 60 m above that of the present day. "Drowned" river valleys commonly terminate at c - 50 m OD. Raised beach sediments occur at 1-4 m, 2-4 m, 6-8 m, 20-25 m, and at 60+ m. Those at 2-4 m and 6-8 m are younger than 4000 BP; the others pre-date a period of peri­ glacial solifluction older than c 26000 BP. The 20-25 m and 60+ m beaches may have formed during interglacial periods. The absence of large Quaternary glaciers on the Falkland Islands precludes a glacio-isostatic origin for the beaches. The Holocene beaches may be due to hydro-isostatic effects but are higher than predicted by the geophysical model possibly because of tectonic uplift. The 20-25 m and 60+ m beaches are believed to indicate late Quaternary uplift of the Falkland Islands.

RESUMEN: CAMBIOS DE NIVEL DEL MAR EN LAS ISLAS MALVINAS EN EL CUATERNARIO Hay evidencia en las Islas Malvinas que el nivel del mar duran­ te el Cuaternario varia desde -50 m a +60 m. Valles fluviales "inundados" terminan comunmente a -