Biogenic Sedimentary Rocks in a Cold, Cenozoic Ocean: Neritic Southern Australia 3030639819, 9783030639815

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Noel P. James · Yvonne Bone

Biogenic Sedimentary Rocks in a Cold, Cenozoic Ocean Neritic Southern Australia

Biogenic Sedimentary Rocks in a Cold, Cenozoic Ocean

Noel P. James · Yvonne Bone

Biogenic Sedimentary Rocks in a Cold, Cenozoic Ocean Neritic Southern Australia

Noel P. James Kingston, ON, Canada

Yvonne Bone Adelaide, SA, Australia

ISBN 978-3-030-63981-5 ISBN 978-3-030-63982-2 (eBook) https://doi.org/10.1007/978-3-030-63982-2 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 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. Cover credit: A 70m high seacliff of Cenozoic limestone, basal white Eocene, overlying brown Oligocene and Miocene, at the Nullarbor Plain margin, Great Australian Bight, just west of Eucla, Western Australia. Photograph by Noel P. James This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

To the late Reg Sprigg & Kurt Kyser The Thinkers

Prologue

Carbonate rocks, because they are largely composed of components formed in seawater, can be repositories of unparalleled information about the history of our evolving planet. They are also critical repositories of paleobiological information, aquifers for freshwaters, host rocks for natural resources such as metallic ores and hydrocarbons, and storehouses of information about global change. Decoding critical information contained within ancient deposits is, however, difficult largely because of biotic evolution and diagenesis of these commonly soluble sedimentary rocks. This conundrum is potentially overcome by studying systems of deposition in the modern ocean together with older but still comparatively young lithified deposits whose components are relatively unchanged from those forming on the seafloor today. Southern Australia is profoundly important in this regard. It has been a cool-water carbonate depositional realm throughout most of the Cenozoic. More specifically, the modern offshore shelf is the largest such system in the modern world. This is so because it is meridional and does not cross latitude boundaries. The beauty of this extraordinary region, however, is that not only are cool-water carbonate sediments forming offshore today across the 2700 km long continental shelf, but that their rock equivalents are exposed as Cenozoic strata directly onshore (Fig. 1.1). This astonishing relationship allows direct comparison between modern and Cenozoic deposits but more important crucial aspects such as sequence stratigraphy, and early meteoric diagenesis that are only available in rock successions, can be assessed. The carbonates are exposed from Western Australia, across South Australia to Victoria, covering a distance of ~3 000 km. The rocks can be studied in roadside and railway cutbanks, in river valleys, in many building stone quarries, in steep seacliffs facing the Southern Ocean, and in numerous caves. These limestones and dolostones, because of such exposure, are often near large metropolitan centers, and hence some have been the subject of intense study for more than 70 years. They have recently become the topics of progressively more concentrated research because of their perceived unusual cool-water character and because they are active and potential hydrocarbon reservoirs, especially off Victoria. Such analyses have resulted in a quantum leap in our understanding of such deposits. vii

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Prologue

Furthermore the resulting scientific papers have allowed other workers to see ancient carbonates in a new light. This book is an attempt to assemble much of this recent research, together with our own works published in a wide variety of places, to act as a template for the interpretation of such similar rocks in the older geological record. Although a largescale synthesis by design, it is focused on our research in southern Western Australia and South Australia with the rocks in Victoria included from the studies of our colleagues. As the saying goes ‘write about what you know’. These colleagues are numerous, ranging from our university research students to our professional contemporaries who know more about these rocks than we shall ever do. Our most profound thanks must go to Jon Clarke, Peir Pufahl, Brian McGowran, Quinra Li, Colin Murray-Wallace, Malcolm Wallace, and in particular, the late Reg Sprigg. We shall especially treasure the intelligence and wisdom of our friend and co-researcher the late Kurt Kyser. We would be lost without the help of Anne Reekmann, Guy Holdgate, Steven Gallagher, Mark Benbow, Tony Belperio, Victor Gostin, Lindsay Collins, Pam Hallock, Roger Hocking, John Lindsay, Stelios Nicolaides, Pam Reid, David Feary, Bill Stuart, Paul Taylor, and Chris von der Borch. None of this would have been possible, however, without the numerous inquisitive and devoted research students such as Basim Shubber, Cody Miller, Jeff Lukasic, John Rivers, Justin Drummond, Laura O’Connell, Marina Joury, Nick Riordan, Paul Gammon, Peir Pufahl, and Tom Boreen. To anyone familiar with the Cenozoic succession in southern Australia it will quickly become obvious that we have followed a trail well traveled by others. Specifically, the marvelous overview in South Australia by Belperio (1995), the pioneering memoir on the Nullarbor by Lowry (1970), and the seminal synopsis of the southeast by McGowran and colleagues (1997, 2004) have been critical. Our analysis clearly uses these fundamental contributions, yet concentrates on the sedimentology and paleoceanography to arrive at an understandable synthesis. Such analyses would have been much less insightful without the knowledge gained over the last several decades during marine research on the modern offshore environment (James and Bone 2011). Images of the seafloor, analyses of sediments and biota, as well as integration with oceanographic parameters both widened our perspective and sharpened our observations resulting in more innovative interpretations of the rocks. The Australian Research Council and University of Adelaide grants to YB and Natural Sciences and Engineering Research Council of Canada grants to NPJ funded most of this research. The original manuscript was kindly reviewed and criticized by Brian Jones, and Jon Clarke, and skillfully technically edited by Isabelle Malcolm.

References Belperio AP (1995) Quaternary. In: Drexel JF, Preiss VP (eds) The geology of South Australia, Volume 2: the Phanerozoic. Geological Survey of South Australia, Mines and Energy South Australia, Bulletin 54, pp 219–280 James NP, Bone Y (2011) Neritic carbonate sediments in a temperate realm. Springer, Berlin, p 254

Prologue

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Lowry DC (1970) Geology of the western Australian part of the Eucla Basin. Geol Surv West Aust Bull 122:201 McGowran B, Holdgate GR, Li Q, Gallagher SJ (2004) Cenozoic stratigraphic succession in southeastern Australia. Aust J Earth Sci 51:459–496 McGowran B, Li Y, Moss G (1997) The Cenozoic neritic record in southern Australia: the biogeohistorical framework. In: James NP, Clarke JAD (eds) Cool-water carbonates: SEPM, Society for Sedimentary Geology, Special Publication 56, pp 185–203

Contents

Part I

Preamble

1 Introduction and Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.1 Scientific Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.2 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.3 Data Base . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.4 Book Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.1 Southern Australia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.2 Tectonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.3 Climate and Vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Cenozoic Depositional Basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.2 Eucla Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.3 St. Vincent Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.4 Murray Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.5 Otway Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Depositional Partitioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Successions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.1 Partitioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.2 Succession SA-1—Paleocene & Early Eocene . . . . . . . . . . . . 1.5.3 Succession SA-2—Middle Eocene to Early Oligocene . . . . . 1.5.4 Succession SA-3—Late Oligocene, Early, and Middle Miocene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.5 Succession SA-4 Late Miocene to Pleistocene . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

3 3 3 4 4 5 5 5 6 7 8 8 8 9 11 12 13 13 14 14 14 14

2 The Modern Carbonate Depositional Realm . . . . . . . . . . . . . . . . . . . . . . 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Modern Oceanography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21 21 22 22

16 17 18

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Contents

2.2.2 Current Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.3 Upwelling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.4 Embayments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.5 Antarctica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Sediments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Depositional Environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.1 Embayments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.2 Marginal Marine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.3 Inner Neritic (0-~ 60 mwd) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.4 Mid Neritic (60–140 mwd) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.5 Deep (Outer) Neritic (140–200 mwd) . . . . . . . . . . . . . . . . . . . 2.4.6 Upper Slope (200–500 mwd) . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part II

22 23 24 24 24 27 28 28 28 29 31 31 31

Sedimentary Successions

3 Succession SA2: Middle Eocene to Lower Oligocene—‘The Biogenic Shelf’ ~ 43-28 Ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Depositional Facies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 SA2.1—Middle Eocene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.1 Marginal Marine- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.2 Inner Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.3 Mid-Outer Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 SA2.2 Middle to Late Eocene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2 Terrestrial—Marginal Marine . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.3 Inner Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.4 Mid-Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.5 Slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 SA2.3 Late Eocene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.2 Marginal Marine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.3 Inner Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.4 Inner—Mid-Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.5 Mid—Outer Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.6 Outer Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.7 Slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 SA2.4 Early Oligocene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.2 Marginal Marine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.3 Inner Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.4 Inner—Mid Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.5 Mid-Outer Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.6 Outer Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

35 35 36 36 37 37 37 38 38 38 40 42 43 43 43 43 43 46 47 50 52 53 53 53 55 55 57 59

Contents

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3.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

60 61

4 Succession SA3: Late Oligocene—Middle Miocene—‘The Carbonate Shelf’ ~28–11 Ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.1 Depositional Facies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 SA3.1 Late Oligocene—Early Miocene . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Inner Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 Inner-Mid Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3 Mid-Outer Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.4 Slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Epicratonic Murray Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2 Facies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 SA3.2 Middle Miocene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.1 Terrestrial—Marginal Marine . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.2 Inner Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.3 Inner-Mid Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.4 Mid Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.5 Mid-Outer Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.6 Outer Neritic-Slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Epicratonic Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.2 Facies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.3 Padthaway Ridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

63 63 65 65 65 68 71 75 77 77 77 80 80 80 81 83 84 84 84 84 86 87 89 89

5 Succession SA4: Plio-Pleistocene—“The Shaved Shelf” ~10.4 Ma–5.2 Ka . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 The New Paradigm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.1 Plio-Pleistocene Chronology . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.2 Sub-Pliocene Unconformity . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.3 Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Depositional Facies—SA4.1 Pliocene-Early Pleistocene . . . . . . . . . 5.2.1 Lacustrine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.2 Marginal Marine-Inner Neritic . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.3 Slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Depositional Facies SA4.2 Mid–Late Pleistocene . . . . . . . . . . . . . . . 5.3.1 Marginal Marine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.2 Neritic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.3 Slope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.4 Bryozoan Mounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

93 93 94 95 95 96 96 98 103 104 104 110 111 112 112 113

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6 Diagenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Pre-Uplift Diagenesis (Subsidence Diagenesis) . . . . . . . . . . . . . . . . . 6.2.1 Eogenesis and Mesogenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.2 The Seafloor Diagenetic Environment . . . . . . . . . . . . . . . . . . . 6.2.3 Meteoric Diagenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.4 Dolomitization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.5 Mesogenetic Diagenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Post-Uplift Diagenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.1 Meteoric-Karst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.2 Telogenetic Karst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.3 Syngenetic Karst . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.4 Meteoric—Microscale Alteration . . . . . . . . . . . . . . . . . . . . . . . 6.3.5 Meteoric—Calcretes and Paleosols . . . . . . . . . . . . . . . . . . . . . 6.3.6 Telogenetic Calcretes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.7 Eogenetic Calcretes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.1 Synsedimentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.2 Meteoric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

117 117 118 118 119 122 122 124 126 126 128 134 134 135 137 137 138 138 139 140

Part III Analysis 7 Integration and Interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 SA2—Mid-Eocene to Early Oligocene—‘The Biogenic Shelf’ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.1 Tectonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.2 Oceanography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.3 Climate and Vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.4 Antarctic Glaciation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.5 Stratigraphic Sedimentology . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.6 Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 SA 3 Late Oligocene to Middle Miocene—‘The Carbonate Shelf’ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.1 Tectonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.2 Oceanography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.3 Climate and Vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.4 Glaciation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.5 Depositional Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.6 Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 SA4—Pliocene-Pleistocene—‘The Shaved Shelf’ . . . . . . . . . . . . . . . 7.4.1 Controls on Sedimentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.2 Tectonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.3 Oceanography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

145 145 146 146 146 148 148 149 152 152 152 152 154 154 155 158 158 158 159 160

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7.4.4 Glaciation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.5 Climate and Vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.6 Stratigraphic Sedimentology . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 Synopsis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Part IV Discussion 8 Sedimentary Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Subtidal, Meter-Scale Cyclicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.2 Glacial Eustasy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.3 Hydrodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.4 Seawater Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.5 Cenozoic Rhythms and Cycles . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Reef Mounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.2 SA2 Paleogene Bryozoan Mounds . . . . . . . . . . . . . . . . . . . . . . 8.3.3 SA4 Plio-Pleistocene Bryozoan Mounds . . . . . . . . . . . . . . . . 8.3.4 Models for Older Phanerozoic Reef Mounds . . . . . . . . . . . . . 8.3.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4 Trophic Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.2 Neritic Paleoenvironments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.3 Phosphates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 Biosiliceous Sedimentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5.2 Deposits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5.3 Late Eocene Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5.4 Sponges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5.6 Modern Equivalent? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6 Epicratonic Murray Basin Paleoenvironments . . . . . . . . . . . . . . . . . . 8.6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6.2 Climate Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6.3 Facies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6.4 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

173 173 174 174 174 175 176 177 182 182 182 182 183 185 185 186 186 187 188 189 190 190 190 191 191 192 193 194 194 194 194 195 195 195

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9 Global Comparisons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.2 Cenozoic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3 New Zealand . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4 Sedimentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.4.1 Diagenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5 Mediterranean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5.2 Sedimentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.5.3 Diagenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

201 201 202 202 202 202 203 204 204 204 206 206 206

Epilogue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

List of Figures

Fig. 1.1 Fig. 1.2

Fig. 1.3

Fig. 1.4

Fig. 1.5

Fig. 1.6

Fig. 1.7

Fig. 1.8 Fig. 1.9

Map of Australia illustrating location of the Cenozoic sedimentary basins along the southern margin . . . . . . . . . . . . . . . Geological map of southern Australia illustrating the major structural features and sedimentary basins (from James and Bone 2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Images depicting different stages in the separation of Australia from Antarctica (modified from Norvick and Smith 2001; James and Bone 2011) . . . . . . . . . . . . . . . . . . . . Map of the Eucla Basin, excluding offshore extension, but highlighting the Roe Plain and important towns and cities (based on Clarke et al. 2003) . . . . . . . . . . . . . . . . . . . . . Map of the St. Vincent Basin with inset at right detailing the fault-controlled embayments along the eastern margin and location of cross-section at A-A showing the general stratigraphy in the Willunga Embayment (modified from James and Bone [2008]. Outline of Pirie Basin is approximate after Alley and Lindsay [1995]) . . . . . . . . . . . . . . . . Map of the Murray Basin and general stratigraphy (modified from Lukasik and James 2006; Riordan et al. 2012) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Map of the Otway Basin indicating the approximate limit of Cenozoic sedimentary rocks inland and the various embayments separated by structural highs (constructed from Douglas and Ferguson 1988; Belperio 1995) . . . . . . . . . . . . Movement of Australia during the Cenozoic (after Feary et al. 1992; James and Bone 2011) . . . . . . . . . . . . . . . . . . . . . . . . Plot of Cenozoic depositional successions in southern Australia on the shelf and in adjacent epicratonic basins, against geologic time and the global sea level curve (modified from Quilty 1977; McGowran et al. 2004; James and Bone 2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

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7

9

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12 13

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Fig. 1.10

Fig. 1.11

Fig. 2.1

Fig. 2.2 Fig. 2.3

Fig. 2.4

Fig. 2.5

Fig. 2.6

List of Figures

Eocene to Mid—Miocene chronostratigraphy and geologic formations in Eucla, St. Vincent, and Murray basins; major successions at left and subdivisions at right. Formations are in regular font, members in italics . . . . . . . . . . . . . . . . . . . . . . Eocene to Mid—Miocene chronostratigraphy and formations in embayments of the Otway Basin; major successions at left and subdivisions at right. Formations are in regular font, members in italics . . . . . . . . . . . . . . . . . . . . . . A sketch illustrating the autogenic and allogenic controls on carbonate sedimentation in basins along the southern Australian continental margin (from James and Bone 2011) . . . . A map of Australia and surrounding oceans highlighting the major current systems (from James and Bone 2011) . . . . . . . Seafloor sediments. a Bryozoan sands composed mainly of fenestrate and robust branching cheilostomes; Lacepede Shelf, water depth 90 m, cm scale; b Fine bryozoan sand composed mainly of delicate branching cyclostomes with floating large gastropods, water depth 180 m, c A mixture of coarse and fine bryozoans, gastropods, bivalves, and sponges, water depth 75 m, d Large whole and fragmented bivalves (mostly Katalysia and Donax ssp.), against a background of medium carbonate sand composed of Holocene and relict grains, water depth ~50 m, Lacepede Shelf, SA; e Corals and coral fragments from a stranded shelf edge reef complex, ~21–10 Ka, Lincoln Shelf, SA, 330 m water depth. f Deep outer shelf—upper slope (depth 320 m) composed of carbonate mud with a few pteropods and small gastropods, Lacepede Shelf, SA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Seafloor Sediments. a A suite of shallow water, Inner neritic benthic foraminifers, Lacepede Shelf. b Monaxon and triaxon siliceous sponge spicules, Lacepede Shelf. c Deep water outer shelf, coccolith-rich fine sand and silt, 410 m water depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stranded and relict particles. a Brown, relict grains formed during a previous sea level highstand and now mixed with light coloured Holocene grains, image 2 cm wide, Great Australian Bight, 80 m water depth. b Stranded branching coralline algae, originally deposited in shallow water 450 ky old Pleistocene Bridgewater Fm. aeolianites and filled with terra rossa clay (red) and volcanic ash (grey) in Comaum Quarry, S.A., cliffs~10 m high; d Surface fracturing, dissolution, and phase 7 red clay colluvium infill on Nullarbor Limestone, outcrop 10 m high, Watson Quarry; e Melton Limestone, Yorke Peninsula, an outcrop where roughly 50% of the limestone has been dissolved and vuggy porosity filled with red clay; cliff ~6 m high; f Marte Quarry in Gambier Limestone with numerous surface dissolution pipes filled with brown clay and overlain by Holocene volcanic ash (black), quarry wall ~15 m high . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Calcretes a Seacliff exposure of Pleistocene aeolinaite ~8 m high with well-lithified calcrete cap at top and poorly lithified calcarenite below, Cape Dombey Victoria; b Pleistocene 5 m high aeolianite exposure with several calcretes (at arrows) between aeolianite; c Multigeneration calcrete developed in aeolianite section 1.5 m thick; Cable Bay, S.A.; d Laminar calcite at the top of aeolianites, Marion Bay, S.A., image 5 cm wide . . . . . . . . . . . . . . . . . . . . . . . Rhizoliths and roots. a Numerous rhizoliths in Pleistocene aeolianite, Cape Spencer; cm scale; b Laminar calcrete developed around a tree root that has now vanished, pen scale 12 cm long . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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133

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Fig. 6.16

Fig. 7.1

Fig. 7.2

Fig. 7.3

Fig. 7.4

Fig. 7.5

Fig. 7.6

Fig. 7.7

Fig. 8.1

Fig. 8.2

Fig. 8.3

Fig. 8.4

List of Figures

Nodular calcrete along River Murray bank. a Hard laminar calcrete, with extensive nodular calcrete below, outcrop 4 m high; b Close view of nodular calcrete, cm scale; c Nodular calcrete where nodules have been broken to reveal laminar character, cm scale. d Broken nodules to reveal blackened calcrete core, Cape Spencer image width 8 cm . . . . . . Depositional succession SA2 placed against global sea level, general sediment composition and major events (modified from Quilty 1977; and McGowran et al. 2004) . . . . . . Sketch summarizing facies interpretation for all neritic deposits in Succession SA2. Formations are in regular font, members in italics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Depositional succession SA3 placed against global sea level, general sediment composition and major events (modified from Quilty 1977; and McGowran et al. 2004) . . . . . . Summary sketch of SA 3 formations and their interpreted neritic depositional environments. Formations are in regular font, members in italics . . . . . . . . . . . . . . . . . . . . . . . . . Summary sketch of Murray Basin SA3.1 and SA3.2 formations and their interpreted depositional environments on a centripital, epeiric ramp (from Lukasik et al. 2000) . . . . . . . Depositional succession SA4 placed against global sea level, general sediment composition and major events (modified from Quilty 1977; and McGowran et al. 2004) . . . . . . Summary sketch of SA 4 formations and their interpreted neritic depositional environments. Formations are in regular font, members in italics . . . . . . . . . . . . . . . . . . . . . . . . . A generalized sketch illustrating sequential development of a neritic, cool-water carbonate subtidal cycle. Letters correspond to the different parts of a given cycle that formed as the base of wave abrasion rose and fell (modified from James and Bone 1994) . . . . . . . . . . . . . . . . . . . . . A sketch showing the characteristics of an Abrakurrie Limestone subtidal cycle as in A above (modified from James and Bone 1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Characteristics and interpretations of meter-scale subtidal cycles and rhythms in Cenozoic strata from southern Australia (based on Boreen and James 1995) . . . . . . . . . . . . . . . . Stratigraphic column illustrating different parts of the Tortachilla Limestone and lower part of the Blanche Point Formation. Thickness of hardground-bound cycle units is shown at right (modified from James and Bone 2000) . .

136

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155

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159

160

175

176

178

179

List of Figures

Fig. 8.5

Fig. 8.6

Fig. 8.7

Fig. 8.8

Fig. 8.9

Fig. 8.10

Fig. 8.11

A comparison between interpreted epeiric ramp subtidal cycles in the Murray Basin (left) and subtidal cycles in neritic, open-shelf settings (right) on the Cenozoic continental margin (after, Lukasik and James 2003); T = transgression, R = regression, RSL = relative sea level . . . . . . . Seismic cross-section showing a bryozoan reef mound complex on the final clinoform breakpoint of an underlying siliciclastic delta complex in the Eucla Basin, Great Australian Bight; TWTB = two way travel time (modified from Sharples et al. 2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A sketch depicting interpreted Pleistocene bryozoan mound growth during a single glacial cycle from interglacial highstand to interglacial lowstand (modified from James et al. 2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A cross-plot of sea surface temperature and seawater chlorophyll content with appropriate environments wherein the different carbonate sediment associations are plotted; conditions present during southern Australian Cenozoic carbonate deposition is highlighted by a box (modified from Halfar et al. 2006; James and Lukasik 2010; James and Bone 2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The trophic resource continuum and correlative biotic, ecologic, and sedimentological information used to define trophic resources in the rock record (simplified from James and Lukasik 2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Princetown Nodule Bed in the Upper Oligocene Clifton Formation, near Princetown, Victoria. a Outcrop view of the nodule bed at base overlain by limestone, hammer scale 23 cm long; b Close view of the contact illustrating the nodules and overlying floatstone rich in pectenid bivalves and crinoid stems, cm scale at base; c Bedding plane view of nodules and intervening buff limestone, cm scale at left; d Cross-section of broken nodules showing the partially replaced core and intensely altered rim, cm scale; e Bedding plane of nodule bed with replaced pectinid bivalves (arrows) close view of C above, cm scale; f Bedding plane view illustrating replaced fenestrate (upper right) and robust columnar (lower left) bryozoans (arrows), cm scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blanche Point Formation. a Opal A sponge spicules, image width 25µm; b Close view of sponge spicule almost completely transformed to Opal CT lepispheres, image view, 15µm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Fig. 8.12

Fig. 9.1

Fig. 9.2

List of Figures

A sketch illustrating the relationship between inboard biosiliceous facies and outboard carbonate facies in late Eocene and early Oligocene neritic deposits of southern Australia (modified from James et al. 2016) . . . . . . . . . . . . . . . . . New Zealand; a Oligocene Limestone with extensive pressure solution stylolites, image 3 m across, b Te One Limestone (late Eocene), poorly lithified bryozoan grainstone, finger scale is 2 cm wide. c Onoua Limestone (Pliocene) globose Celleporaria sp. bryozoans in outcrop, d Momoe-a-toa Tuff (Pliocene), Cape Young, Chatham Island, numerous pectinids (Sectipecten sp.) and brachiopods in tuff; cm scale . . . . . . . . . . . . . . . . . . . . . . . . . . France, Provence, Saumane-Venasque, Miocene carbonates. a Cliff of cross-bedded, echinoid-bryozoan grainstone ~35 m high, about 1 km NE of Saumane b Tidal herringbone cross-bedded bryozoan-echinoid grainstone, NNE of Saumane, cliff is 8 m high. c Rhodolith rudstone, north of Marseilles, pen 15 cm long, d Large benthic foraminiferal grainstone, finger 1.5 cm wide . . . . . . . . . . . . . . . .

191

203

205

Part I

Preamble

Chapter 1

Introduction and Setting

Abstract The scientific approach herein is largely comparative because the same type of sediments that made up the Cenozoic strata are accumulating offshore today. The record was, however, controlled largely by changing oceanography, climate, tectonics, and the geohistory of Antarctica. The book focuses on the Paleogene and Neogene carbonate sedimentary rocks across southern Australia. The narrative is a combination of our own studies and those of previous workers. The book is structured in 4 parts. The latitude-parallel paleocontinental margin stretches ~2700 km from west to east. This margin was relatively quiescent in the Eocene and Miocene but upset by late Miocene uplift and exposure resulting in an entirely different depositional style in the Pliocene and Pleistocene. Climate evolved during the Cenozoic from early warm and humid to late cool and semi-arid. There are four separate depositional basins each with its own setting and geohistory. Strata are partitioned into discrete 4 successions, each with different parts. Keywords Continental margin · Cenozoic · Carbonates · Sedimentary basins

1.1 Overview As emphasized in the Preface, the book is a description and interpretation of Cenozoic cool-water carbonate sedimentary rocks that outcrop across southern Australia. This chapter is an introduction to the scientific approach, an outline of the database, and an overview of the book structure. To provide context for the rest of the volume the latter part of the chapter details the nature of the depositional basins, and partitioning of the extensive sedimentary sequence.

1.1.1 Scientific Approach The approach herein is entirely comparative. Biogenic components that make up these cool-water carbonate deposits are comparatively young, having not evolved greatly during the time period under examination. Thus, they can be directly © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 N. P. James and Y. Bone, Biogenic Sedimentary Rocks in a Cold, Cenozoic Ocean, https://doi.org/10.1007/978-3-030-63982-2_1

3

4

1 Introduction and Setting

AUSTRALIA Cenozoic Basins EUCLA BASIN o

30 S

ST. VINCENT BASIN

PERTH BASIN

OTWAY BASIN

MURRAY BASIN

GIPPSLAND BASIN

Fig. 1.1 Map of Australia illustrating location of the Cenozoic sedimentary basins along the southern margin

compared to their living counterparts, which makes interpretation both easier and more compelling. Although the deposits are similar to those offshore today, differences caused by changing oceanography, climate, and tectonics demand that they be assessed from a holistic perspective that differs somewhat from the modern setting. Thus, the scientific approach is in part actualistic and in part interpretative.

1.1.2 Scope The book focuses on Paleogene and Neogene carbonates exposed as outcrops in onland basins across Southern Australia, particularly the Eucla, St. Vincent, Murray, and Otway depocenters (Fig. 1.1). The Gippsland Basin was not analyzed because it is related to the Tasman Sea. The offshore sub-seafloor stratigraphy is only discussed when linked to the other basins.

1.1.3 Data Base The information described herein is a combination of our own detailed studies along with those of colleagues and research students over ~30 years. Most information from eastern parts of the Otway Basin has come from both the literature and our own examination of critical outcrops in Victoria.

1.1 Overview

5

Analyses are largely built on the previous painstaking biostratigraphy and chronostratigraphy of previous scientists. Our contributions are focused on the composition and interpretations of the rocks based on numerous field observations of more than 700 petrographic and geochemical analyses, together with fossil identifications and interpreted paleoecology. These rocks have been studied for over 70 years and inevitably there are a myriad of stratigraphic names. Named units are either ‘Formations’ in the formal sense or commonly named ‘Limestone’, ‘Sand’, or ‘Marl’ instead of Formation but have equal stratigraphic standing and are formally defined as equivalent to formations. These units are generally in Lower Case print. Some of these units also have members and they are designated in Lower Case italic print.

1.1.4 Book Structure The volume is in four parts. Part I is an introduction to the book itself, an overview of the Southern Australian setting focused on tectonics, oceanography, climate, modern carbonate depositional systems, and depositional basins, together with an outline of geohistory and past sedimentation as well as a précis of the different Cenozoic successions. Part II, the core of the volume, is a detailed documentation of Paleogene and Neogene stratigraphy, sedimentation, and diagenesis across the region framed in a geochronological context. Part III is an integration and interpretation of the depositional systems. Part IV is devoted to specific aspects such as cyclicity, reefs, biosiliceous sedimentation, and trophic resources with a final chapter comparing sedimentation in this region with similar coeval systems elsewhere.

1.2 Setting 1.2.1 Southern Australia Southern Australia (Fig. 1.1) stretches from Cape Leeuwin in Western Australia some 2700 km, between 32°S and 40°S, across the plains and Flinders Ranges of South Australia to the Otway Ranges and coasts of southern Victoria. The land is variable beyond simple description but is largely an agricultural and fishing region with two major large cities, Adelaide and Melbourne. The climate varies greatly but is mainly semi-arid except in the highlands where it is more humid. The coastline changes from spectacular sandy beaches to stunning seacliffs more than 100 m high, to tranquil shallow lagoons, to impressive rounded whalebacks of crystalline rocks. Cenozoic sedimentary rocks, the topic of this geological analysis, form most of these landscapes and seascapes.

6

1 Introduction and Setting

1.2.2 Tectonics Southern Australia is anchored by two major Precambrian cratons and bounded on the east by the Tasman Fold Belt System (Fig. 1.2), a series of Neoproterozoic to late Paleozoic continental margin and accreted terranes (Veevers 1984; Johnson 2004). The tectonic grain of southern Australia is predominantly north-south. This is a fragment of Gondwana that was truncated at right angles by the Southern Australian Rift System (Norvick and Smith 2001), an east-west, Mesozoic–Cenozoic structure involving rift and drift coincident with breakup of Australia and Antarctica (Fig. 1.3). Marginal rift basins and subsequent shelf deposits in this system comprise Jurassic to Cretaceous siliciclastic sedimentary rocks overlain by Cenozoic carbonates. The Murray Basin, as described below, is a structural depression just inboard of the passive continental margin and so is classified as an epicontinental basin. The passive continental margin was dramatically changed in the Late Miocene via tectonic inversion, wrenching, and compression (Sandiford 2003a, b; Hill and Exon 2004). Importantly, large segments of the inner continental margin and most epicratonic basins described herein were uplifted, variably deformed, and exposed. Deformation was most intense in Victoria and progressively less so westward (Dickinson et al. 2002; Sandiford 2003a). This tectonism was accompanied by Plio-Pleistocene volcanism (Price et al. 2003) largely restricted to Victoria. Such tectonics and accompanying seismicity continue today in South Australia (Greenhalgh et al. 1994) and Victoria with volcanism (the Newer Volcanics) in South Australia documented by native Australian oral tradition as recently as 1500 BP (Sheard 1986). ALBANY - FRASER PROVINCE

30o

EUCLA BASIN

GAWLER CRATON

YILGARN CRATON

DELAMERIAN FOLD BELT

TASMAN FOLD BELT SYSTEM

Perth PERTH BASIN

Adelaide BIGHT BASIN

SHORELINE

40o RECHERCHE BASIN

NEW ENGLAND FOLD BELT

SHELF EDGE

BREMER BASIN

MURRAY BASIN

LACHLAN FOLD BELT

Sydney

Melbourne GIPPSLAND BASIN

OTWAY BASIN

BASS BASIN

AUSTRALIA

SORRELL BASIN

TASMANIA

o

50

120o

130o

SOUTHERN AUSTRALIAN RIFT SYSTEM Cenozoic sediments and sedimentary cover rocks (local volcanics) Mesozoic and Cenozoic rift and passive margin sediments and sedimentary rocks

140o

150o

PRECAMBRIAN - PALEOZOIC CRATON Middle-Late Paleozoic crystalline volcanic and sedimentary rocks Neoproterozoic and Cambrian sedimentary rocks and volcanics

Cretaceous sedimentary rocks Jurassic syn-rift volcanic rocks

Archean, Paleoproterozoic and Mesoproterozoic metasediments, metavolcanics and granitoids

Fig. 1.2 Geological map of southern Australia illustrating the major structural features and sedimentary basins (from James and Bone 2011)

1.2 Setting

7 60ο

Australia

Greater India

V

Antarctica

Antarctica

a

Australia

Early Tithonian 145 Ma

b

Mid Cenomanian 95 Ma

80ο

ο

SOUTHERN AUSTRALIA RIFT SYSTEM

AUSTRALIA - ANTARCTICA 50 GULF V Australia V

Australia

V

V

Antarctica

c

Antarctica

Early Campanian 80 Ma

d

Mid Eocene 45 Ma

70ο

Normal crust

Thickened crust

Sea floor

Uplift

Thinned crust

Volcanic

Extensional depocentres

Spreading ridge

V

60ο

Volcanic center 1000 km

Fig. 1.3 Images depicting different stages in the separation of Australia from Antarctica (modified from Norvick and Smith 2001; James and Bone 2011)

Specifically, all of southern Australia is still undergoing strong E-W and SE-NW compression with evidence of tectonic activity through the Pliocene to the Holocene. Pliocene strandlines, for example, are displaced upward 200–250 m on the western side of the Otway Ranges (Wallace et al. 2005). During the Pleistocene the Eucla Basin (Fig. 1.1) was more or less tectonically stable whereas the gulfs and peninsulas of the St. Vincent Basin were a series of active horsts and grabens. The Murray Basin underwent gradual subsidence whereas the Otway Basin was, and is today, undergoing epirogenic uplift (Johnson 2004).

1.2.3 Climate and Vegetation A strong, mid-latitude, high-pressure cell dominates weather in Australia today. The high lies over the southern Australian coastline during summer resulting in the overall semi-arid climate. It shifts northward during winter, allowing a succession of lowpressure systems with accompanying rains and strong westerlies to sweep across the region, but the area is progressively most humid southward and eastward in Victoria and around Tasmania.

8

1 Introduction and Setting

There are essentially four types of vegetation on this isolated continent; (1) closed rainforest, (2) open forest or woodland, (3) heath scrub or Mallee, and (4) arid and semi-arid (White 1994). The latter is much like the sagebrush of western North America. The open forest and heath scrub are dominated by sclerophyll plants, a typically Australian floral type having vegetation (typically eucalypts, wattles and banksias) with hard, short, and often spiky leaves, which is a condition closely associated with low soil fertility. Pre-settlement vegetation in southern sub-humid/semi-arid margin of southern Australia was typically an open mallee (Eucalypt) scrubland. Scattered stands of belah, sugarwood, and native pine were present together with the mallee species. The understory usually consisted of low chenopod shrubs, Spinifex, or a variety of seasonal herbs and woody plants. A saltbush-bluebush steppe or low chenopod shrubland is more typical in the inland plains of SA, and the Nullarbor Plain. Hattersley (1983) records a marked shift in the abundance of C3 grasses in coastal regions, to C4 grasses in semi-arid regions and arid-inland through time, reflecting the transition from temperate coastal to interior climates. C4 plants are better adapted to higher temperatures and drier conditions than C3 species. Typically, C4 plants are grasses whereas C3 plants are trees and/or grasses.

1.3 Cenozoic Depositional Basins 1.3.1 Overview Cenozoic carbonate strata that form the core of this analysis are exposed across southern Australia in the Eucla, St. Vincent, Murray, and Otway basins (Fig. 1.1). Each of these basins has its own geohistory and thus distinct stratigraphic succession.

1.3.2 Eucla Basin This basin consists of the continental shelf and extends northward onshore between the Pilbara Craton to the west and the Gawler Craton to the east in the form of a vast, shallow, arcuate depression (Figs. 1.1, 1.2, and 1.4). The section along the narrow coastline in the west is called the Bremer Basin but in the light of recent nomenclature (Clarke 1993, 1994; Clarke et al. 2003) is herein referred to as the SW Eucla Basin. The Cenozoic section beneath the slope has been explored by Ocean Drilling Project Leg 182 and is also revealed in scattered petroleum exploration wells (Feary et al. 2004; Totterdell and Bradshaw 2004). The onshore portion forms the Nullarbor Plain (Lowry 1970), the world’s largest areal karst (Jennings 1962). Carbonates are exposed along formidable sea cliffs, in numerous caves beneath the Plain, and inland along the northern margin.

1.3 Cenozoic Depositional Basins

114

o

o

o

118

122

9 o

o

Western Australia

N

o

130

126

134

o

138

South Australia 28o

YILGARN CRATON NULLARBOR PLAIN

o

GAWLER CRATON

EUCLA BASIN

Kambalda

Eucla

Perth

o

Ceduna

Norseman

32

32

Roe Plain SOUTHERN OCEAN

Cape Leeuwin

Albany

500 Km

o

Adelaide

36

o

114

o

118

o

122

o

126

o

130

o

134

o

36

o

138

Fig. 1.4 Map of the Eucla Basin, excluding offshore extension, but highlighting the Roe Plain and important towns and cities (based on Clarke et al. 2003)

1.3.3 St. Vincent Basin The St. Vincent Basin Complex (Figs. 1.1, 1.5) is series of elongate, N-S Cenozoic grabens that overlie an Early Palaeozoic foreland basin and was a large, narrow, open gulf that faced the Southern Ocean during the Palaeogene and early Neogene (Lindsay and Alley 1995). The complex consists of the St. Vincent Basin, largely beneath Gulf St. Vincent and the marginal Pirie Basin, mostly beneath Spencer Gulf. The complex is now bounded on the east by the Mt. Lofty Ranges, part of the fold and thrust belt that was uplifted in the Neogene, and to the west by the Gawler Craton (Veevers 2000). Whereas much of the succession lies in the subsurface, excellent sections are exposed in two northeast–southwest-oriented half-grabens along the eastern shores of the gulfs (Fig. 1.5). The St. Vincent Basin itself comprises two sub-basins called the Noarlunga Embayment to the west and the Willunga Embayment to the east along the margins of the Mt. Lofty Ranges (Cooper 1979, 1985). The Cenozoic faults, possible reactivated older structures, developed when Australia began to drift away from Antarctica during the Middle Eocene and remain active to the present day. Tertiary strata are in places tilted against these structures (Dyson 1988; McGowran et al. 1997). The Willunga Embayment is 14 km wide at the present shoreline outcrop and cliffs extend inland in a NE direction some 26 km (Fig. 1.5). It is asymmetric, because of Neogene tectonics, such that the SW side is downthrown and fault bounded. The Noarlunga Embayment is 10 km wide at the entrance and extends inland 20 km in the same orientation. The basins to the north, the Adelaide Plains Basin, and Golden Grove Embayment are larger, but all deposits are subsurface with the record mainly as soft sediment.

10

1 Introduction and Setting

EYRE PENINSULA

MT . LO

FT Y R A N GES

ADELAIDE CITY

Fault

A'

Noarlunga Embayment

10 km

2

T. V

N

ST. VINCENT BASIN T

SPENCER GULF

Adelaide Plains Sub-Basin

IN CE N

YO RKE PENIN SUL A

PIRIE BASIN

LF GU

INVESTIGATOR STRAIT

S

see enlargement

1 Ba

KANGAROO ISLAND

cks tair sP

A

Metres

KTP 14

WLG 43 GULF ST. VINCENT

100

a ss a ge

LACEPEDE SHELF

50 km

200

Willunga Embayment A

WLG 40

WB-1

A'

WLG 37

WLG 42

0

-100

QUATERNARY

EOCENE Blanche Point Fm.

-200

OLIGOCENE-MIOCENE Piramimma Sand

-300

Tortachilla Lst. Maslin Sands

Ruwarung Mbr.

PERMIAN

Aldinga Mbr.

PRECAMBRIAN -CAMBRIAN

Cape Jervis Fm. -400

0

5 kilometres

Chinaman Gully Fm.

Fig. 1.5 Map of the St. Vincent Basin with inset at right detailing the fault-controlled embayments along the eastern margin and location of cross-section at A-A showing the general stratigraphy in the Willunga Embayment (modified from James and Bone [2008]. Outline of Pirie Basin is approximate after Alley and Lindsay [1995])

1.3 Cenozoic Depositional Basins

11

1.3.4 Murray Basin The Murray Basin (Fig. 1.6) is one of the largest (~450,000 km2 ) of the Cenozoic basins. It differs from all other continental margin basins described herein because it is comparatively shallow throughout and does not directly face the open ocean. Circumscribed by the Western Highlands and the Mount Lofty Ranges, the shallow epicratonic basin developed during the rifting of Australia from Antarctica in the mid- to Late Cretaceous (Veevers 1984, 2000; Veevers et al. 1991). The western half of the basin throughout the early Neogene was a wide (~520 to 410 km), shallow marine gulf with an epeiric sea character. The rocks accumulated approximately 200–500 km inboard of the continental shelf edge (Bone 2009). Margins of the epicratonic basin (Fig. 1.6) were rimmed on the northern and eastern sides by a wide (~100 km) belt of lagoonal and supratidal, non-evaporitic mudflats (Geera Clay) that trapped terrigenous sediments nearshore (Radke 1987; Brown and Radke 1989). The Padthaway Ridge, a structurally elevated Cambrian granitic and metasedimentary complex, formed an island archipelago along the wide, southern entrance of the Basin. This string of islands and submerged rocky

Fig. 1.6 Map of the Murray Basin and general stratigraphy (modified from Lukasik and James 2006; Riordan et al. 2012)

12

1 Introduction and Setting

highs absorbed open-ocean waves and swells, creating an expansive, semi-protected, shallow sea behind (Lukasik et al. 2000; Riordan et al. 2012). Internal forces (storms) and waves of limited fetch dominated the oceanography of this inland sea.

1.3.5 Otway Basin This basin is a ~300 km long, elongate depression-oriented NW-SE roughly parallel to the coastline (Fig. 1.7) and forms the inner part of the Cenozoic continental shelf (Douglas and Ferguson 1988; Birch 2003). The Western Highlands, a range of Mesozoic and older rocks, bound the Basin on the landward side. The structure is usually divided into western, central, and eastern sectors. Each sector consists of several subbasins or embayments separated by roughly oriented north-south structural highs (Fig. 1.7). The depressions are, from west to east, the Gambier Embayment, the Tyrendarra Embayment, the Port Campbell Embayment, and small Aire Embayment in the western sector with the Port Philip Embayment the Torquay Embayment in the central sector. The sub-basins are, respectively, separated by the Marino High and its southward extension the Dartmoor Ridge, the Warrnambool Uplift, and the Otway Ranges High (Fig. 1.7). The Gambier Embayment straddles the South Australia–Victoria border whereas the other embayments are wholly in Victoria. These depressions loose their identity and merge southward offshore.

Fig. 1.7 Map of the Otway Basin indicating the approximate limit of Cenozoic sedimentary rocks inland and the various embayments separated by structural highs (constructed from Douglas and Ferguson 1988; Belperio 1995)

1.4 Depositional Partitioning

13

1.4 Depositional Partitioning 1.4.1 Overview This section is a synopsis of sedimentation geohistory prior to a detailed documentation of the rocks in Part II. As stressed above the carbonates are entirely heterozoan (cf. James 1997). This is curious in a sense because even though the continent has changed position and drifted equatorward (Feary et al. 1992; Veevers 2000) over ~50 my of earth history (Fig. 1.8), the deposits have remained temperate in composition. This somewhat puzzling aspect is the result of two contrasting processes. Sediment deposition began during the Paleogene when global ocean waters were exceptionally warm, but because the region was at such high latitude, regional seawater was cool. The continent moved northward toward the equator throughout the Cenozoic until the region today lies in the mid-latitudes. At the same time, the global climate changed from the Late Cretaceous greenhouse mode to the present day icehouse mode. Thus, the ocean waters cooled even though the continent moved into equatorial latitudes. 0o

Present

10o

20o

Middle Oligocene 30o

Latitude oS

K/T boundary 40o

50o

Great Australian Bight 60o

P PLIO

0

MIOCENE

10

OLIGOCENE

20

30

EOCENE

40

50

PALEOC.

60

Time (Ma)

Fig. 1.8 Movement of Australia during the Cenozoic (after Feary et al. 1992; James and Bone 2011)

14

1 Introduction and Setting

1.5 Successions 1.5.1 Partitioning The combination of changing tectonics, ocean circulation, and climate has resulted in several discrete, although always cool-water, packages of slightly different carbonates. Large-scale packaging of the Cenozoic succession was first proposed by Quilty (1977) in Western Australia and this concept has been utilized, mostly via detailed biostratigraphy (McGowran et al. 1997, 2004; McGowran 2009), and applied across the region. There are now four recognized natural successions (Fig. 1.9) and these serve herein as a framework for sedimentological analysis; the basal one is siliciclastic and the three younger ones are mostly carbonate. Each succession is composed of several stratigraphic units, including major unconformities. These major stratigraphic units have been progressively refined with time (Hou et al. 2003; McGowran 2009) and can be correlated with third-order stratigraphic sequences. The term succession is used herein instead of sequence to avoid the constraints of sequence stratigraphic nomenclature and correlation. This is not to say that such precepts are not followed, as illustrated below. At present the major depositional packages are an amalgamation of all previous schemes but divided according to our own work and recent ODP drilling (Feary et al. 2004) on the slope. Designation is via lettered and numbered units (e.g., SA2.1) so as to clearly distinguish them from previous designations (Figs. 1.10 and 1.11).

1.5.2 Succession SA-1—Paleocene & Early Eocene These sedimentary rocks are mainly siliciclastic, reflecting physical sedimentation during late stages of rifting between Antarctica and Australia. They are not described in detail.

1.5.3 Succession SA-2—Middle Eocene to Early Oligocene As stressed by McGowran et al. (1997) this is the first record of widespread carbonate and biosiliceous sedimentation along the subsiding passive margin of southern Australia. Overall deposition took place in a wide sweep of settings from drowned paleovalleys, estuaries, and coal swamps to nearshore, neritic seafloors to offshore neritic shelf and slope paleoenvironments. The succession is easily divided into four parts. The basal two parts (SA2.1 and SA2.2—Middle and Late Eocene) comprise mainly neritic, and carbonates. The third succession (SA2.3—Late Eocene) is one of both biosiliceous sediments and carbonates. The upper part (SA 2.4—Early Oligocene) is mostly carbonates with lesser spiculitic deposits.

1.5 Successions

15

DEPOSITIONAL SUCCESSIONS SERIES

U

PLACENZIAN

L

PLEISTOCENE

ZANCLEAN

UPPER

5

+200

+100

0

-100

Sea level - Meters

HOLOCENE

PLIOCENE

0

STAGES

EUSTATIC CURVES

4

MESSINIAN TORTONIAN

MIDDLE

SERRAVALIAN

LANGHIAN

3 THIRD ORDER

BURDIGALIAN LOWER

Ma.

15

MIOCENE

10

20

AQUITANIAN

SECOND ORDER

UPPER LOWER

30

OLIGOCENE

25 CHATTIAN

RUPELIAN

UPPER

35

40 MIDDLE LOWER

50

PRIABONIAN BARTONIAN

EOCENE

45

2

LUTETIAN

PRESENT SEALEVEL

YPRESIAN

55

Fig. 1.9 Plot of Cenozoic depositional successions in southern Australia on the shelf and in adjacent epicratonic basins, against geologic time and the global sea level curve (modified from Quilty 1977; McGowran et al. 2004; James and Bone 2011)

16

1 Introduction and Setting

Fig. 1.10 Eocene to Mid—Miocene chronostratigraphy and geologic formations in Eucla, St. Vincent, and Murray basins; major successions at left and subdivisions at right. Formations are in regular font, members in italics

1.5.4 Succession SA-3—Late Oligocene, Early, and Middle Miocene This was perhaps the acme of cool-water carbonate deposition across the region, and encompassed the whole shelf. The preceding middle Oligocene is represented by a major unconformity corresponding to a global lowstand, with very little sedimentation but extensive erosion. The succession itself is in two parts. Part SA3.1 (latest Oligocene–Early Miocene) is a classic cool-water system whereas Part SA3.2 is a highstand that corresponds to warm-water deposition during the Middle Miocene Climatic Optimum (MCO).

1.5 Successions

17

EOCENE-MIOCENE STRATIGRAPHY OTWAY BASIN EMBAYMENTS Gambier

Tyend

Pt. Pt. Campbell Campbell E

Aire

Pt. Phillip

Torquay

Pre-Pliocene Unconformity

L

SA 4

PLIO

0

Green Point

Camel -back

Gellibrand

Greenways

Clifton .

Yellow Bluff Fynsford Gellibrand

Gellibrand Clifton

Maude

Demon’s Bluff

Demon’s Bluff

Narrawaturk

Dilwyn

EOCENE M

SA 2

Calder River

Eastern View

Zeally

Point Addis

3.2

Celleporaria

Batesford

Peubla

Jan Juc

Glen AireClay

Brown’s Creek

Narrawaturk 40

Fishing Point

Demon’s Bluff

Castle Cove

L

30

Naracoorte Port Campbell Port Campbell Coleville Muddy . Creek Bochara

Gambier Lst

My

E

20

OLIGOCENE E L

SA 3

MIOCENE M

10

Werribbee

3.1

2.4 2.3 2.2

Johanna River

Eastern View

2.1

50

MAJOR LITHOLOGY Limestone

Sandstone

Marl

Spiculite

Fig. 1.11 Eocene to Mid—Miocene chronostratigraphy and formations in embayments of the Otway Basin; major successions at left and subdivisions at right. Formations are in regular font, members in italics

1.5.5 Succession SA-4 Late Miocene to Pleistocene Tectonic inversion along the southern margin fortunately exposed these older successions for examination but restricted carbonate sedimentation to marginal marine, lacustrine, and slope paleoenvironments (Murray-Wallace 2018). Most neritic deposits were stripped by repeated ravinement and so the shelf is now composed of Pleistocene sediment on SA-3 or older limestones. Part SA4.1 (Pliocene—Early Pleistocene) accumulated during an early Pliocene sea level rise and overall warming followed by initial global glaciation. SA4.2 records late Pleistocene deposition and reflects dramatic glacioeustatic sea level fluctuation.

18

1 Introduction and Setting

References Alley NF, Lindsay JM (1995) Chapter 10, Tertiary. In: Drexel JF, Preiss WV (eds) The geology of South Australia, Vol. 2: the Phanerozoic. South Australia Geological Survey, Bulletin 54, pp 151–217 Belperio AP (1995) Quaternary. In: Drexel JF, Preiss VP (eds) The geology of South Australia, Volume 2: the Phanerozoic. Geological Survey of South Australia, Mines and Energy South Australia, Bulletin 54, pp 219–280 Birch WD (2003) Geology of Victoria, 23. Special publication—Geological Society of Australia, 842 pp Bone Y (2009) Geology and geomorphology. In: Jennings JT (ed) Natural history of the Riverland and Murraylands. Occasional Publications of the Royal Society of South Australia Inc., The University of Adelaide Press, Adelaide, pp 1–49 Brown CM, Radke BM (1989) Stratigraphy and sedimentology of mid-Tertiary permeability barriers in the subsurface of the Murray Basin, southeastern Australia. J Aust Geol Geophys 11:367–385 Clarke JDA (1993) Stratigraphy of the Lefroy and Cowan palaeodrainages, Western Australia. J R Soc West Aust 76:12–23 Clarke JDA (1994) Evolution of the Lefroy and Cowan palaeodrainage channels, Western Australia. Aust J Earth Sci 41:55–68 Clarke JDA, Gammon PR, Hou B, Gallagher SJ (2003) Middle to Late Eocene stratigraphic nomenclature and deposition in the Eucla Basin. Aust J Earth Sci 50:231–248 Cooper BJ (1979) Eocene to Miocene stratigraphy of the Willunga Embayment. South Australia Geological Survey, Report of Investigations 50, p 81 Cooper BJ (1985) The Cainozoic St. Vincent Basin–tectonics, structure, stratigraphy. In: Lindsay JM (ed.) Stratigraphy, palaeontology, malacology: papers in honour of Dr. Nell Ludbrook. Special Publication. Department of Mines and Energy, South Australia, pp 35–51 Dickinson JA, Wallace MW, Holdgate GR, Gallagher SJ, Thomas L (2002) Origin and timing of the Miocene-Pliocene unconformity in southeast Australia. J Sediment Res 72:288–303 Douglas JG, Ferguson JA (eds) (1988) Geology of Victoria. Geological Society of Australia, Melbourne, VIC, p 663 Dyson IA (1988) Estuarine facies of the North Maslin Sand and South Maslin Sand, Maslin Beach. MESA 11:42–46 Feary D, Boreen TD, James NP, Bone Y, Birch G, Lanyon R, Shafik S (1992) Preliminary post-cruise report, Rig Seismic Research Cruise 1991, sediments of the Great Australian Bight. Bureau of Mineral Resources, Southern Margin Project 121.27, pp 163 Feary DA, Hine AC, James NP, Malone MJ, Hine AC, Feary DA, Malone MJ, Andres M, Betzler C, Brooks GR, Brunner CA, Fuller M, Molina Garza RS, Holbourn AE, Huuse M, Isern AR, James NP, Ladner BC, Li Q, Machiyama H, Mallinson DJ, Matsuda H, Mitterer RM, Robin C, Russell JL, Shafik S, Simo JA, Smart PL, Spence GH, Surlyk FC, Swart PK, Wortmann UG (2004) Leg 182 synthesis; exposed secrets of the Great Australian Bight. In: Proceedings of the Ocean Drilling Program, Scientific Results (CD ROM) 182 Greenhalgh SA, Love D, Malpas K, McDougall R (1994) South Australian earthquakes, 1980–92. Aust J Earth Sci 41:483–495 Hattersley PW (1983) The distribution of C3 and C4 grasses in Australia in relation to climate. Oecologia 57:113–128 Hill PJ, Exon NF (2004) Tectonics and basin development of the offshore Tasmanian area incorporating results from deep ocean drilling. In: Exon NF, Kennett JP, Malone MJ (eds) The Cenozoic Southern Ocean: tectonics, sedimentation, and climate change between Australia and Antarctica. American Geophysical Union, pp 19–42 Hou B, Frakes LA, Alley NF, Gammon P, Clarke JDA (2003) Facies and sequence stratigraphy of Eocene valley fills in Eocene palaeovalleys, the eastern Eucla Basin, South Australia. Sed Geol 163:111–130

References

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James NP (1997) The cool-water carbonate depositional realm. In: James NP, Clarke MJ (eds) Cool-water carbonates. SEPM Special Publication, pp 1–20 James NP, Bone Y (2008) Carbonate-biosiliceous sedimentation in early Oligocene estuaries during a time of global change, Port Willinga Formation, St. Vincent Basin, southern Australia. In: Lukasik J, Simo JA (eds) Controls on carbonate platform and reef development. SEPM Special Publication 89, pp 231–253 James NP, Bone Y (2011) Neritic carbonate sediments in a temperate realm. Springer, Dordrecht, Heidelberg, London, and New York, p 254 Jennings JN (1962) The limestone geomorphology of the Nullarbor Plains (Australia). In: International congress of speleology. Bari, pp 371–386 Johnson D (2004) The geology of Australia. Cambridge University Press, Cambridge, p 276 Lindsay JM, Alley NF (1995) St Vincent Basin. In: Drexel JF, Preiss VP (eds) The geology of South Australia, Vol. 2: the Phanerozoic. South Australia Geological Survey, Bulletin 54, pp 163–172 Lowry DC (1970) Geology of the western Australian part of the Eucla Basin. Geol Surv West Aust Bull 122:201 Lukasik J, James NP (2006) Carbonate sedimentation, climate change and stratigraphic completeness on a Miocene cool-water epeiric ramp, Murray Basin, South Australia. Geol Soc Spec Publ 255:217–244 Lukasik JJ, James NP, McGowran B, Bone Y (2000) An epeiric ramp; low-energy, cool-water carbonate facies in a Tertiary inland sea, Murray Basin, South Australia. Sedimentology 47:851– 881 McGowran B (2009) The Australo-Antarctic Gulf and the Auversian facies shift. In: Koeberl C, Montanari A (eds) The late Eocene Earth—hothouse, icehouse, and impacts. Geological Society of America Special Paper, pp 215–240 McGowran B, Holdgate GR, Li Q, Gallagher SJ (2004) Cenozoic stratigraphic succession in southeastern Australia. Aust J Earth Sci 51:459–496 McGowran B, Li Q, Moss G (1997) The Cenozoic neritic record in southern Australia: the biogeohistorical framework. In: James NP, Clarke JAD (eds) Cool-water carbonates. Special Publication—SEPM, pp 185–203 Murray-Wallace CV (2018) Quaternary history of the Coorong coastal plain, southern Australia. Springer International Publishing, Cham, Switzerland, 229 pp Norvick MS, Smith MA (2001) Mapping the plate tectonic reconstruction of southern and southeastern Australia and implications for petroleum systems. APPEA J 41:15–35 Price RC, Nicholls IA, Gray CM (2003) Cainozoic igneous activity. In: Birch WD (ed) Geology of Victoria. Geological Society of Australia, Special Publication 23, pp 362–375 Quilty PG (1977) Cenozoic sedimentation cycles in western Australia. Geology 5:336–340 Radke BM (1987) Sedimentology and diagenesis of sediments encountered by Victoria Department of Mines, Piangil West-1, Murray Basin, southeastern Australia, Australia Riordan NK, James NP, Bone Y (2012) Oligo-Miocene seagrass-influenced carbonate sedimentation along a temperate marine paleoarchipelago, Padthaway Ridge, South Australia. Sedimentology 59:393–418 Sandiford M (2003a) Geomorphic constraints on the late Neogene tectonics of the Otway Range, Victoria. Aust J Earth Sci 50:69–80 Sandiford M (2003b) Neotectonics of southeastern Australia; linking Quaternary faulting record with seismicity and in situ stress. In: Hillis RR, Muller RD (eds) Evolution and dynamics of the Australian Plate. Geological Society of Australia, Special Publication 22, pp 101–113 Sheard MJ (1986) Some volcanological observations at Mount Schank, southeast South Australia. Geol Surv S Aust Q Geol Notes 100:14–20 Totterdell JM, Bradshaw BE (2004) The structural framework and tectonic evolution of the Bight Basin. Pet Explor Soc Aust Spec Publ 2:41–61 Veevers JJ (1984) Phanerozoic earth history of Australia. Oxford geological sciences series 2. Clarendon Press, Oxford, UK, 418 pp

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Veevers JJ (2000) Billion-year earth history of Australia and neighbours in Gondwanaland. Gemoc Press, Sydney, p 388 Veevers JJ, Powell M, Roots SR (1991) Review of seafloor spreading around Australia, 1. Synthesis of patterns of spreading. Aust J Earth Sci 38:373–389 Wallace WW, Dickinson DJA, Moore DH, Sandiford M (2005) Late Neogene strandlines of southern Victoria: a unique record of eustasy and tectonics in southeast Australia. Aust J Earth Sci 52:279– 297 White ME (1994) After the greening: the browning of Australia. Kangaroo Press Pty. Ltd, Kentworth, NSW, Australia, 288 pp

Chapter 2

The Modern Carbonate Depositional Realm

Abstract The sediments being deposited offshore today are heterozoan and a modern benchmark for the older Cenozoic deposits. Modern oceanography is characterized by cool waters, a series of complex currents, and seasonal upwelling. Neritic sediments are composed of extraclasts, mainly relict and stranded particles, together with biofragments mostly from living bryozoans, benthic foraminifers, mollusks, echinoderms, brachiopods, coralline algae, and siliceous sponges. Depositional environments range from large nearshore embayments to marginal marine systems to the wide neritic realm. Tidal sand shoals, seagrass meadows, macroalgal forests, coralline pavements, rippled sand barrens, and rocky reefs typify the inner neritic zone above fair weather wave base. The middle neritic seafloor between fairweather wave base and storm wave base is characterized by rippled sands, subaqueous dunes, and rocky reefs. The deeper outer neritic environment, only disturbed by occasional storms, is a zone of muddy locally reworked sediment. The upper slope is largely a burrowed mud barren. Keywords Heterozoan · Oceanography · Biofragments · Neritic environments · Sediments

2.1 Introduction This chapter is a brief overview of modern carbonate deposition and environmental controls (Fig. 2.1) present across the southern margin of the continent, based largely on the monograph by James and Bone (2011). The modern shelf, with no marginal barrier, has attributes of both open shelves and ramps (James and Jones 2016). The narrative concentrates first on modern oceanography and the influence of nearby Antarctica. The sediments are then described and related to major depositional settings such as large embayments or gulfs, and various sectors of the neritic shelf.

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 N. P. James and Y. Bone, Biogenic Sedimentary Rocks in a Cold, Cenozoic Ocean, https://doi.org/10.1007/978-3-030-63982-2_2

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Fig. 2.1 A sketch illustrating the autogenic and allogenic controls on carbonate sedimentation in basins along the southern Australian continental margin (from James and Bone 2011)

2.2 Modern Oceanography 2.2.1 Overview Ocean waters on the continental shelf are largely subtropical and separated from the cold Antarctic ocean by the Subtropical Convergence Zone (Fig. 2.2). There is unimpeded zonal water circulation from the west (West Wind Drift). The sea state is swell-dominated with high wave heights (> 2.5 m) and long period swells (10–20 sec). Storm wave base is estimated to lie on average at ~ 60 m water depth (mwd) whereas swell wave base extends to ~ 140 mwd.

2.2.2 Current Systems Current systems are strongly affected by climatic seasonality. The autumn change from an easterly to westerly wind pattern results in a change of Eckman transport and a switch in coastal currents. The regimen is over all downwelling but with local, cool summer upwelling. Near surface environments are affected by two current systems. The Flinders Current System (Fig. 2.2) is an upwelling-favorable northern boundary current that extends from the surface to ~ 800 mwd and flows from south of Tasmania northward and westward generally outboard of the shelf edge to Cape Leeuwin. It is composed of Antarctic Intermediate Water and Subantarctic Mode Water that is cool, well oxygenated, and with moderate nutrient levels.

2.2 Modern Oceanography 120°E

110°E

23 130°E

140°E

INDONESIAN SOUTH EQUATORIAL FLOWTHROUGH CURRENT

150°E

10°S

EAST AUSTRALIAN CURRENT 20°S

AUSTRA AUSTRALIA LIA

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30°S

LEEUWIN CURRENT

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WEST WIND DRIFT

WARM CURRENT

40°S

ZEEHAN CURRENT

TEMPERATE CURRENT

COOL CURRENT

SUBTROPICAL CONVERGENCE ZONE COLD CURRENT

Fig. 2.2 A map of Australia and surrounding oceans highlighting the major current systems (from James and Bone 2011)

The Leeuwin Current System (Cresswell 1991) is a seasonal (autumn and winter) phenomenon that flows in the opposite direction eastward at depths of < 200 m along the entire length of the continental shelf edge. It is composed of relatively warm, nutrient-depleted subtropical surface waters, and generally prevents upwelling. The system comprises Leeuwin Current waters in the west, South Australian Current waters in the center, and Zeehan Current waters in the east (Middleton and Bye 2007).

2.2.3 Upwelling Upwelling of waters from the Flinders Current occur in summer but are localized to the Bonney Shelf, off Kangaroo Island, near the mouth of Spencer Gulf, and along the western coast of Eyre Peninsula. There is no upwelling during winter because of the strong westerlies (Richardson et al. 2018).

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2.2.4 Embayments Spencer Gulf and Gulf St. Vincent (Fig. 1.5) are inverse estuaries in which strong summer heating and evaporation form saline waters at the head of each gulf. These waters cool in winter and flow oceanward as dense, saline, bottom currents.

2.2.5 Antarctica Antarctica, located at the South Pole, today lies some 4500 km south of Australia, but was once joined to the continent, and has had an important, if far-field influence on oceanography, climate, and deposition throughout the Cenozoic. Different parts of Antarctica have had different glacial histories. The present Antarctic Ice Sheet comprises an East Antarctic component grounded largely above present sea level and a West Antarctic component grounded mostly below sea level. Marine-based (West Antarctic) ice sheets are considered relatively unstable. There is evidence from around Antarctica that, although East and West Antarctic climates were coupled in the past, changing approximately in phase, the climate of West Antarctica (including the Antarctic Peninsula) has varied about a consistently warmer baseline (e.g. Kennett and Barker 1990; Zachos et al. 1992). Although East Antarctic glaciation started at 35 Ma (Early Oligocene) or earlier, West Antarctic glaciation probably began much later ~ 14 Ma (Late Miocene).

2.3 Sediments Sediments are a typical heterozoan, (James 1997) cool-water carbonate suite of largely benthic biofragments (Figs. 2.3, 2.4). The major constituents are extraclasts, relict and stranded grains, together with associated contemporaneous skeletons. Extraclasts are siliciclastic sand (mainly quartz), relict grains, and Cenozoic carbonate particles (James and Bone 2011). Relict particles (Fig. 2.5) are variably abraded biofragments, whose intraskeletal pores are filled with brown carbonate and Fe-oxides, formed largely during Marine Isotope Stage (MIS) 3 (50–20 Ka) in a suite of extremely shallow lagoonal settings (James 1997; Rivers et al. 2007; Rivers et al. 2008). Stranded components are particles that formed in shallow water but were abandoned during the Holocene sea level rise (Fig. 2.5). Cenozoic grains comprise late Pleistocene carbonates, older Quaternary carbonate fragments, and Tertiary limestone pieces. The sediment-producing organisms that create biofragments are cool-water throughout, ranging from subtropical to cool-temperate. There are no warm-water or tropical elements; no ooids, no coral reefs, insignificant calcareous green algae, although there are extensive muddy tidal flats. The biofragments are mostly from

2.3 Sediments

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a

b

c

d

e

f

Fig. 2.3 Seafloor sediments. a Bryozoan sands composed mainly of fenestrate and robust branching cheilostomes; Lacepede Shelf, water depth 90 m, cm scale; b Fine bryozoan sand composed mainly of delicate branching cyclostomes with floating large gastropods, water depth 180 m, c A mixture of coarse and fine bryozoans, gastropods, bivalves, and sponges, water depth 75 m, d Large whole and fragmented bivalves (mostly Katalysia and Donax ssp.), against a background of medium carbonate sand composed of Holocene and relict grains, water depth ~50 m, Lacepede Shelf, SA; e Corals and coral fragments from a stranded shelf edge reef complex, ~ 21–10 Ka, Lincoln Shelf, SA, 330 m water depth. f Deep outer shelf—upper slope (depth 320 m) composed of carbonate mud with a few pteropods and small gastropods, Lacepede Shelf, SA

mollusks, bryozoans (Bone and James 1993), echinoderms, brachiopods, coralline algae, and siliceous sponges (Figs. 2.3f, 2.4). The microbiota are mainly small benthic foraminifers and coccoliths, but with local large benthic protists signaling warmer subtropical waters.

26 Fig. 2.4 Seafloor Sediments. a A suite of shallow water, Inner neritic benthic foraminifers, Lacepede Shelf. b Monaxon and triaxon siliceous sponge spicules, Lacepede Shelf. c Deep water outer shelf, coccolith-rich fine sand and silt, 410 m water depth

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2.4 Depositional Environments

27

Fig. 2.5 Stranded and relict particles. a Brown, relict grains formed during a previous sea level highstand and now mixed with light coloured Holocene grains, image 2 cm wide, Great Australian Bight, 80 m water depth. b Stranded branching coralline algae, originally deposited in shallow water 140 mwd (sensu Pomar 2021).

Fig. 2.6 A sketch illustrating the major energy and temperature interfaces and hydrodynamic zones on an open ocean shelf

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2.4.1 Embayments Two elongate, N-S oriented marine embayments, Spencer Gulf and smaller Gulf St. Vincent (Fig. 1.5), extend inland into the continental interior. They are both floored by heterozoan carbonates and add to the diverse spectrum of deposits in this realm (Shepherd and Sprigg 1976; Burne and Colwell 1982; Gostin et al. 1988; Fuller et al. 1994; Belperio 1995; O’Connell et al. 2016). Both are shallow, Spencer Gulf < 60 mwd, Gulf St. Vincent < 35 mwd, warm temperate (~ 10-28°C), and metahaline (38–46‰ salinity), with inverse estuarine circulation. Clockwise circulation brings low salinity marine waters up the west coast. It rapidly increases in salinity (up to 47‰) at the gulf head during the summer, cools during winter, and flows down the east coast and out to sea as a dense saline seafloor brine. Sediments are primarily fragments of bivalves, large and small benthic foraminifers, bryozoans, coralline algae, crinoids, and echinoids that accumulate in six environments, muddy tidal flats, seagrass meadows, patchy seagrass sand flats, rhodolith pavements, open sand-gravel plains, and muddy deeper seafloors below the euphotic zone (James et al. 2008; James and Bone 2011; O’Connell et al. 2016). Gulf St. Vincent sediments are a mix of in situ carbonate and clay from the nearby Mt. Lofty Ranges, whereas those in Spencer Gulf are wholly carbonate. Luxuriant seagrasses grow to ~ 30 mwd. Bivalves are the most common biota.

2.4.2 Marginal Marine The marginal marine environment comprises high-energy beaches, linear calcareous dune complexes, muddy tidal flats in large protected embayments, saline lagoons between aeolian ridges, and saline lakes associated with these lagoons (James and Bone 2011).

2.4.3 Inner Neritic (0-~ 60 mwd) This zone is above fairweather wave base with seafloor environments (Figs. 2.6, 2.7) such as tidal sand shoals, seagrass meadows, macroalgal forests, coralline pavements, rippled sand barrens, and rocky outcrops (rocky reefs). It is a setting of constant wave agitation, sediment production but little accumulation, winnowing, abrasion, and bioerosion. The locally quartzose but dominantly skeletal sands and gravels are mainly composed of bivalves, large and small benthic foraminifers, coralline algae (articulated and rhodoliths) and low diversity bryozoans. Living rhodolith pavements are densest at ~ 30 mwd and locally to 50 mwd but some have been recovered to 90 mwd.

2.4 Depositional Environments

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a

b

c

d

e

f

Fig. 2.7 Modern Seafloor, Lacepede Shelf images. a Lush growth of the seagrass Posidonia sp., 5 meters water depth; Divers N. George and J. Bone-George; b Lush growth of the macroalga Phyllospora sp. and Ecklonia sp. at 3 m water depth; c Seafloor at 120 mwd, of mostly brown bryozoans and surrounding bryozoan carbonate sand, courtesy CSIRO; d Growth of calcareous algae Metagoniolithon and Syarthrophyton and the macroalga Caulerpa at 3 m water depth; e A rocky seafloor with encrusting corallines, abalone (Haliotis) and Ecklonia, water depth 36 m, f Prolific growth of bryozoans, serpulids, encusting corallines, sponges and asteroids on the rocky seafloor at 18 m water depth

2.4.4 Mid Neritic (60–140 mwd) The seafloor here lies below fairweather wave base but is subject to frequent reworking by storms and long period swells. It is a seafloor zone characterized by rippled sand, subaqueous dunes, and rocky reefs (Fig. 2.8). The biofragmental sands

30 Fig. 2.8 Modern seafloor images. a Rippled bryozoan sand on middle neritic seafloor at 138m water depth, Lacepede Shelf; image width in foreground 1.5m, courtesy CSIRO; b Numerous crinoids each about 1m high at 310m, water depth, NW Tasmania Shelf, image courtesy CSIRO; c Deep outer neritic seafloor of carbonate mud and sparse bryozoan growth, Lacepde Shelf; foreground image width 1.5 m, at 359 m water depth

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2.4 Depositional Environments

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and gravels are dominated by bryozoans, brachiopods, and infaunal bivalves but with bryozoans as the most important sediment producers. The sediments are typically burrowed, reduced by bioerosion, and locally cemented to form hardgrounds.

2.4.5 Deep (Outer) Neritic (140–200 mwd) The seafloor at these depths is only disturbed by exceptionally intense storms or large swells and is thus a zone of muddy, locally reworked sediment that is characterized by suspension settling, bioerosion, and burrowing. The sediment (Figs. 2.4b, c, 2.8) is mostly fine skeletal muddy sand to mud whose larger particles are generally delicate branching bryozoans (although a wide spectrum of growth forms can be present) and sponge spicules.

2.4.6 Upper Slope (200–500 mwd) Wholly below storm and swell wave base sedimentary processes here are pelagic fallout and sediment gravity flows. The seafloor sediment is largely a burrowed mud barren (Figs. 2.3, 2.4, 2.8) with scattered growth of sponges and diminutive bryozoans.

References Belperio AP (1995) Quaternary. In: Drexel JF, Preiss VP (eds) The geology of South Australia: the Phanerozoic vol 2. Geological Survey of South Australia, Mines and Energy South Australia, Bulletin 54, pp 219–280 Bone Y, James NP (1993) Bryozoans as carbonate sediment producers on the cool-water Lacepede Shelf, Southern Australia. Sed Geol 86:247–271 Burne RV, Colwell JB (1982) Temperate carbonate sediments of northern Spencer Gulf, South Australia: a high salinity ‘foramol’ province. Sedimentol 29:223–238 Cresswell GR (1991) The Leeuwin Current–observations and recent models. In: Pearce AF, Walker DI (eds) The Leeuwin Current. J. R. Soc. W. Aus, 1–14 Fuller MK, Bone Y, Gostin VA, von der Borch CC (1994) Holocene cool-water carbonate and terrigenous sediments of Southern Spencer Gulf, South Australia. Aust J Earth Sci 41:353–363 Gostin VA, Belperio AP, Cann JH (1988) The Holocene non-tropical coastal and shelf carbonate province of Southern Australia. Sed Geol 60:51–70 James NP (1997) The cool-water carbonate depositional realm. In: James NP, Clarke MJ (eds) Cool-water carbonates. SEPM Special Publication, pp 1–20 James NP, Bone Y (2011) Neritic carbonate sediments in a temperate realm, Southern Australia. Springer, Dordrecht Heidelberg London New York, p 254 James NP, Jones B (2016) Origin of carbonate sedimentary rocks. Wiley, Oxford, UK, p 483 James NP, Martindale RC, Malcolm I, Bone Y, Marshall J (2008) Surficial sediments on the continental shelf of Tasmania, Australia. Sed Geol 211:33–52

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Kennett JP, Barker PF (1990) Latest Cretaceous to Cenozoic climate and oceanographic developments in the Weddell Sea, Antarctica: an ocean-drilling perspective. In: Barker PF, Kennett JP (eds) Proceedings of the Ocean Drilling Program, Scientific Results, pp 937–960 Middleton JF, Bye JAT (2007) A review of the shelf-slope circulation along Australia’s Southern Shelves: Cape Leeuwin to Portland. Prog Oceanogr 75:1–41 O’Connell LG, James NP, Doubell M, Middleton JF, Luick J, Currie DR, Bone Y (2016) Oceanographic controls on Shallow-Water temperate carbonate sedimentation: Spencer Gulf, South Australia. Sedimentol 63:105–135 Pomar L (2021) Chapter 12, Carbonate systems. In: Scarselli N, Jurgen A, Chiarella D, Roberts DG, Bally AW (eds) Regional Geology and Tectonics: Principles of Geologic Analysis. Elsevier, Netherlands, pp 235–311 Richardson LE, Middleton JF, Kyser TK, James NP, Opdyke BN (2018) Water masses and their seasonal variation on the Lincoln Shelf South Australia. Limnol Oceanogr 63:1944–1963 Rivers JM, James NP, Kyser TK (2008) Early diagenesis of carbonates on a Cool-water carbonate shelf, Southern Australia. J Sediment Res 78:784–802 Rivers JM, James NP, Kyser TK, Bone Y (2007) Genesis of palimpsest cool-water carbonate sediment on the continental margin of southern Australia. J Sediment Res 77:480–494 Shepherd SA, Sprigg RC (1976) Substrate, sediments and subtidal ecology of Gulf St. Vincent and Investigator Strait. In: Twidale CR, Tyler MJ, Webb BP (eds) Natural history of the Adelaide region. R. Soc. S.A., 161–174 Zachos JC, Breza JR, Wise SW (1992) Early Oligocene ice-sheet expansion on Antarctica: stable isotope and sedimentological evidence from Kerguelen Plateau, Southern Indian Ocean. Geol 20:569–573

Part II

Sedimentary Successions

Chapter 3

Succession SA2: Middle Eocene to Lower Oligocene—‘The Biogenic Shelf’ ~ 43-28 Ma

Abstract The succession ranges in age from middle Eocene to early Oligocene and is divided into four parts. Carbonate deposition was at first confined to the west but by the early Oligocene extended into the Otway Basin. SA2.1—Middle Eocene strata, are largely marginal, inner, and mid neritic siliciclastics passing outboard into carbonates with deep water bryozoan mounds. SA2.2—Mid to Upper Eocene rocks are mostly similar with carbonaceous inboard terrestrial facies and mid-neritic bryozoanrich limestones. SA2.3—Uppermost Eocene neritic deposits are quite different with not only biofragmental carbonates but also extensive biosiliceous, spiculitic sediments. SA2.4—Lower Oligocene deposits are dominantly carbonate but again with extensive spicules and chert. By this time carbonate deposition had also begun to take place in western parts of the Otway Basin. Keywords Eocene-Oligocene · Carbonates · Siliciclastics · Neritic · Spiculites

3.1 Overview This was a period of dramatic global change characterized by ocean water cooling, beginnings of Antarctic glaciation, initiation of Circum-Antarctic Current flow, high sea level, thermohaline global ocean circulation, and the first extensive neritic carbonate deposition in southern Australia (Fig. 1.10). Strata are named ‘the biogenic shelf’ because both biogenic siliceous and carbonate sediments accumulated on the shelf at this time. The Eocene-Oligocene boundary within this succession is an unconformity marked by sea level fall and profound erosion. This feature coincided with opening of the Tasman Gateway, establishment of the Circum-Antarctic Current, and the initiation of extensive Antarctic glaciation (Francis et al. 2008; Scher et al. 2015).

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 N. P. James and Y. Bone, Biogenic Sedimentary Rocks in a Cold, Cenozoic Ocean, https://doi.org/10.1007/978-3-030-63982-2_3

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EOCENE - EARLY OLIGOCENE STRATIGRAPHY EUCLA - ST. VINCENT BASINS PIRIE BASIN

Ooldea Barton Sand Sand Pallinup Princess Royal Naranup Norseman

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Rogue Port Julia

Ruwarung Aldinga Chinaman Gully Blanche Point

Khasta Wilson Bluff

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Hampton

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Spiculite

Fig. 3.1 Eocene to Oligocene SA2 chronostratigraphy and formations in Eucla, St. Vincent, and Murray basins; subdivisions at right. Formations are in regular font, members in italics

3.2 Depositional Facies As stressed above, widespread biogenic deposition, particularly in the west, really began with the major sea level rise near the Lutetian-Bartonian boundary (~ 42 Ma) (Fig. 1.10) in the Middle Eocene (Prothero and Bergren 1992). This style of sedimentation would be the dominant motif throughout much of the following Eocene. Early Oligocene deposition was similarly typified by cool-water neritic carbonate accumulation in the west and locally in the east (McGowran et al. 1997). Strata are divided into four distinct units (Figs. 3.1 and 3.2) with chronological similarities across southern Australia.

3.3 SA2.1—Middle Eocene These strata (Figs. 3.1, 3.2) are largely subsurface and so not well documented. Carbonates are only present in the Eucla and St. Vincent basins, all coeval Otway Basin deposits are siliciclastic.

3.3 SA2.1—Middle Eocene

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EOCENE-OLIGOCENE STRATIGRAPHY OTWAY BASIN EMBAYMENTS Tyend

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Pt. Phillip

Aire

Greenways

Narrawaturk Marl

Demon’s Bluff Narrawaturk Marl

Torquay

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MAJOR LITHOLOGY Limestone

Sandstone

Marl

Spiculite

Fig. 3.2 Eocene to Oligocene SA2 chronostratigraphy and formations in embayments of the Otway Basin; subdivisions at right. Formations are in regular font, members in italics

3.3.1 Marginal MarineNorth Maslins Sand: These inboard quartzose sands in the St Vincent basin are cross-bedded with scattered plant-bearing lenses. The sediments are interpreted to have accumulated in environments ranging from deltaic to braided river to fluviolacustrine (Alley and Lindsay 1995).

3.3.2 Inner Neritic Hampton Sandstone: This 30–50 m thick sandstone is present across the Eucla Basin shelf. A thin basal conglomerate is overlain by limonite-stained, quartzose, glauconitic sand, and sandstone with rare bryozoans (Li et al. 2003) is interpreted as an open marine deposit.

3.3.3 Mid-Outer Neritic Wilson Bluff Limestone: The lower part of this unit and unnamed equivalents on the Eucla Basin slope are all subsurface in petroleum exploration wells and ODP Leg 182 cores. The oldest slope unit cored during ODP Leg 182 (Package No. 1, Feary et al. 2004-40 Ma—Middle-Late Eocene) is a thin, quartzose, biofragmental grainstone to

38

3 Succession SA2: Middle Eocene …

sandstone. Planktic foraminifers indicate largely warm-water deposition. Equivalent shelf facies of the neritic basal Wilson Bluff are glauconitic marls. Large bryozoan mounds grew on top of underlying siliciclastic delta deposits along the shelf edge during initial flooding at ~ 43 Ma (Sharples et al. 2014). The structures extend ~ 500 km along strike with individual reef mounds ~ 75 km thick, 5 km wide and 60–250 km in length. Reefs contain 8 species of cyclostomes and a similar number of cheilostomes, and together comprise ~ 5–10% of the rocks. The mounds were eventually buried by extensive prograding shelf carbonates (see Chapter 8).

3.4 SA2.2 Middle to Late Eocene 3.4.1 Overview The middle part of the Wilson Bluff Limestone is poorly known. The exposed rocks everywhere else in the Eucla Basin (Fig. 3.1) are a lower suite of siliciclastics and lignites and an upper package of minor carbonates that accumulated along inboard flooded paleovalleys and inundated shelf. Whereas the inboard succession in South Australia (Eucla Basin) is a series of quartzose barrier islands, there is no such system in Western Australia. The succession in the St. Vincent Basin is similar. Basal deposits are sandstones together with inboard lignites that pass upward and outboard into carbonates. Coeval strata to the east in the Otway Basin are all siliciclastics.

3.4.2 Terrestrial—Marginal Marine Werrilup Formation: These basal siliciclastics and lignites (Fig. 3.3) accumulated in non-marine and marine environments along Western Australian margins of the Eucla Basin, especially in the palaeovalleys (Clarke et al. 2003). Sediments are bivalverich sandstones with abundant bryozoans and echinoids whose shells are highly abraded and rounded. There are several 1–5 m thick layers of bryozoan grainstone. All carbonates are completely dolomitized. Maralinga Formation: Roughly coeval massive to locally laminated carbonaceous (gravelly) sands, with black, carbonized wood and leaf fragments make up much of the basal facies in the eastern parts of the Eucla Basin (Clarke et al. 2003). Lignitic facies accumulated in a coastal–estuarine plain, and these non-marine, siliciclastic, paludal sediments are interpreted as being deposits of aggrading fluvial plains, estuarine channels, or even swamps (Alley et al. 1999). The inner shelf in the Eucla Basin was a local series of barrier islands (Ooldea Sand), leeward lagoons, and flooded paleovalleys (Fig. 3.4). Ooldea Range barrier

3.4 SA2.2 Middle to Late Eocene

39

Fig. 3.3 A series of cores penetrating mid-late Eocene deposits at Blue Dam on the shores of Lake Cowan north of Norseman, Western Australia illustrating lignites of the Werrilup Formation; each core section is 2 m in length

island sands were backed by a series of leeward lagoons and swamps. The quartzose barrier complex indicates that any longshore drift was from northwest, suggesting an overall westerly vector to winds during the Late Eocene (Benbow 1990). Paling Limestone: Lagoonal and flood-tidal deltas in the lee of the Ooldea Range along the NE side of the Basin in South Australia also contain thin glauconitic and carbonaceous limestones with abundant bryozoans, mollusks, echinoids, benthic foraminifers, ostracodes, coralline algae, and sponge spicules. The unit occurs opposite passes through the Ooldea Range and was deposited either because these areas of the lagoon had normal salinity, or were composed of shelf carbonate swept into the lagoon and accumulated as flood-tidal deltas (Clarke et al. 1996). South Maslin Sand: These sands (Fig. 3.5) in the St. Vincent Basin overlie and are intercalated with brown coals and lignitic siliciclastic sediments of the inboard Clinton Formation. The marginal marine deposits are glauconitic, carbonaceous, and pyritic. They contain a sparce marine biota of bryozoans, gastropods, echinoids, bivalves, benthic foraminifers, and sponge spicules; together with local goethite pellets. Aggregates of goethite and glauconite together with clay are common. The

40

3 Succession SA2: Middle Eocene …

WA

SA

N

Late Eocene Shoreline

Paleovalley

Lagoon

EUCLA BASIN

Mid-Eocene Ooldea Barrier

Lo

Late Eocene Paling-Barton Barrier

ng

sh

or eD

rif

t

Eucla Group Carbonates Miocene Coast Lagoon Eucla GREAT AUSTRALIAN BIGHT 0

Km.

100

Fig. 3.4 Mid-Late Eocene lithofacies map of the eastern Eucla Basin showing location of coastlines, paleovalleys systems, and major shoreline barriers (simplified from Benbow 1990; Alley et al. 1999, Hou et al. 2003)

upper contact with the Tortachilla Limestone is a zone of late-stage, intensive dissolution and leaching which has been interpreted as an unconformity, but the evidence is equivocal (James and Bone 2000). Clinton Formation: Landward brown coals and carbonaceous siliciclastic sediments are localized to the very inboard northern and eastern sides of the St. Vincent Basin. They overlie the North Maslin Sands and underlie the South Maslin Sands but in the far north inboard are intercalated (Belperio 1995; Holdgate and Clarke 2000).

3.4.3 Inner Neritic Norseman Limestone: These marine carbonates (Figs. 3.1, 3.6, 3.7) filled wide, deep embayments, or shallow nearshore flats in the Eucla Basin and consisted of three facies; 1. Coarse, basal bryozoan grainstones are dominated by corallines and bryozoans but also contain common echinoid tests and spines, bivalves, gastropod molds, calcareous sponges, and benthic foraminifers (Clarke et al. 1996). Calcareous and siliceous spicules are rare; but molds of possible aragonitic green algae are present locally (Cockbain 1969). The depositional environment is interpreted to

3.4 SA2.2 Middle to Late Eocene

41

a

b

c

d

Fig. 3.5 Tortachilla Limestone, Maslins Beach, Adelaide. a South Maslin Sand (MS) overlain by Tortachilla Limestone, (T) section ~8 m thick; b Tortachilla Limestone (T) overlain by Blanche (BP), J. Matear scale (circled); c Burrows filled with green sediment (arrows) in earlier light grey— coloured grainstone, 20 cm long hammer head scale; d Gastropod mold floatstone between burrows in C, image 5 cm wide

Fig. 3.6 Detailed stratigraphy of the Norseman Formation (based on Clarke et al. 1996)

42

3 Succession SA2: Middle Eocene …

Fig. 3.7 Norseman Limestone, Lake Cowan, WA; Cross-bedded, coarse bryozoan grainstone; hammer scale 23 cm long

have been relatively tranquil and either shifting sands or fixed substrates in waters 10–20 m deep. 2. Overlying current-bedded, coarse, variably dolomitized bryozoan sands have ebb-dominated southward-directed paleocurrents (170°–200°). They are thought to have accumulated in water depths of 10–40 m with macroalgae or seagrasses, like those growing off the coast of southern Australia today (cf. James et al. 2009). 3. Fine-grained bryozoan-echinoid grainstone facies are locally present in paleovalley centers. They also contain the bivalve Chlamys, infaunal and epifaunal echinoids, gastropods, and brachiopods. The large benthic foraminifers Crespinina sp and Amphistigina sp. (Clarke et al. 1996), implying warm waters, are conspicuous, but not common.

3.4.4 Mid-Neritic Tortachilla Limestone: Carbonates in the Willunga and Noarlunga sub-basins (Fig. 3.5) are a comparatively thin (~ 3 m), coarse grained, quartzose, biofragmental, bryozoan ± mollusk calcarenites comprising several stacked, m-scale depositional cycles (see Chapter 8, Fig. 8.4) with hardground caps that represents a long time period (James and Bone 2000). Lithification, aragonite dissolution, and the filling of molds by sediment and cement point to extensive early marine and meteoric diagenesis (see Chapters 6 and 8). Mullloowurtie Formation: Equivalent rocks in the Noarlunga Basin to the west are fossiliferous calcarenites and glauconitic orthoquartzitic sands (Stuart

3.4 SA2.2 Middle to Late Eocene

43

1970). Both facies are intensively burrowed and diagenetically altered. Burrowing by decapod crustaceans is locally so intense that it almost obliterates cross-beds. Carbonates are a quartzose, bryozoan—mollusk floatstones-rudstones with pectens, turitellid gastropods, and bryozoans. Bryozoans are typically fragments of articulated branching cyclostomes and cheilostomes, with accessory flat-robust branching cheilostomes. Echinoid fragments and spines, large and small benthic foraminifer tests and mollusk shells (bivalves and gastropods) are common.

3.4.5 Slope ODP Leg 182 slope facies Package 11 (39–37 Ma Late Eocene) (Li et al. 2003) is a calcareous ooze and wackestone with warm-water planktic foraminifers.

3.5 SA2.3 Late Eocene 3.5.1 Overview Basal lithologies are well exposed in the Eucla and the St. Vincent basins. It is assumed that Wilson Bluff middle limestones comprise transgressive shelf facies but are not exposed. By contrast, the upper parts of the formation are well exposed in the cliffs that face the Great Australian Bight, in caves beneath the Nullarbor Plain, and locally offshore in the St. Vincent Basin. Inshore facies comprise barrier sands with the carbonate and siliceous spiculites in the Eucla and St. Vincent basins. Deposits in the Otway Basin are again mostly siliciclastics, except in the far eastern Aire District (Fig. 3.2).

3.5.2 Marginal Marine Upper Ooldea Sand: This sand forms the Paling–Barton Ranges, a series of younger barrier island complexes (Figs. 3.4, 3.8), inboard of the Ooldea Range proper (Clarke et al. 2003). The unfossiliferous unit, however, does not as yet have good age control.

3.5.3 Inner Neritic Pallinup Formation: This unit includes all biosiliceous spicular marine sediments of this age along the margin of the Eucla Basin in Western Australia (Gammon et al. 2000a; Gammon et al. 2000b). There are four informal members, typically

44 Fig. 3.8 Ooldea Sand, near Lake Ifould, S.A. a Exposure along railway line, J. Clarke scale; b Paling Limestone (P) at base with overlying brown Ooldea sand and buff calcrete horizons (arrows), section 5 m thick, c highly weathered Precambrian overlain by dark, Ooldea Sandstone; section 3 m thick, Lake Ifold, SA.; scale divisions = 2 cm

3 Succession SA2: Middle Eocene …

a

b

P c

PC

3.5 SA2.3 Late Eocene

45

conglomeratic sand in the lowermost unit, sand in the second, and spicular muds in the third and fourth units. These informal members can be recognized along the length of southwest Western Australia (Gammon et al. 2000b). A fifth, uppermost, member, the Fitzgerald Member, is ~ 20 m thick, and consists mainly of spongolite, spiculite, and muddy spiculite (Fig. 3.9). Body fossils of lithistid sponges are locally abundant, forming sponge rudstones with a spiculite matrix. Calcareous biota is sparse and dominated by mollusks (epifaunal bivalves), with fewer large fenestrate bryozoans, brachiopods, and echinoids in a spiculitic matrix. The trace-fossil assemblage is mostly Thalassinoides and Chondrites. Mscale cycles in the upper part comprise spiculite grading up into glauconitic mudstone capped by a firmground. The opal-dominated biota occurs on the landward side of palaeotopographic barriers formed by bedrock highs that would have been rocky reefs and islands in the Eocene sea (see Chapter 8, Fig. 8.12). Farther offshore, in sub-shoreface, more open marine outer-archipelago sites, calcareous fossil molds rapidly increase and sediments pass outboard into calcareous muddy spiculite and then into Wilson Bluff Limestone, bryozoan limestones, and marls described below. The coeval Princess Royal Member further west in Western Australia accumulated in estuaries formed by the marine flooding of paleovalleys (Clarke 1993; Gammon et al. 2000b). Paleovalley successions consist of a thick basal terrestrial lignitic

a

b

c

d

Fig. 3.9 Pidinga Frm—Fitzgerald Member; a Spongolite Quarry at Norseman, W.A., P. Gammon scale; b Outcrop with numerous sponges (arrows); lens cap scale 5 cm diameter; c Large demosponge, cm scale d Large demosponge (S), smaller digitate sponges (arrows), coin 2.5 cm diameter

46

3 Succession SA2: Middle Eocene …

claystone sharply overlain by marine spiculitic mudstone that overall coarsens and cleans upward to muddy spiculite and finally pure spiculite. Local, thick, trough cross-bedded sandstone, or spiculite facies represent estuarine channels. The unit is most extensive in the upper reaches of the paleovalleys. Loose sponge spicules from soft-bodied sponges dominate, with only rare rigidbodied sponges. Both diatom and sponge taxa within estuarine facies indicate relatively normal marine salinity (Gammon et al. 2000a, b). Calcareous fossils are scarce apart from a few gastropods and bivalves in channel sandstones. Kasta Formation: Coeval Khasta Formation sediments in the eastern Eucla Basin of South Australia are fine to medium-grained sandstones and siltstones, with parallel and ripple laminations, flaser and lenticular bedding, marine trace fossils, and up to 25% siliceous sponge spicules. Heavy minerals are common. The trace-fossil assemblage inland is dominated by Skolithos, although Thalassinoides is present locally. Body fossils of lithistid sponges are also present although not in the abundance that characterize the Fitzgerald Member of the Pallinup Formation (Clarke et al. 2003).

3.5.4 Inner—Mid-Neritic Kingscote Limestone: The lower part of this formation on Kangaroo Island in the St. Vincent Basin (Fig. 3.10) is biostratigraphically equivalent to the inboard Tortachilla Limestone and Blanche Point Formation and best correlated with the upper part of the Wilson Bluff Limestone (James et al. 2016). The rocks are either echinoderm-serpulid floatstones with a fine bioclastic echinoderm/bryozoan grainstone/packstone matrix, or serpulid worm grainstones. There are large and small benthic foraminifers, some of which were photosymbiotic protists indicating local subtropical ocean waters. Large fossils are mostly clypeasters and spatangoids, pectin bivalves, and infaunal bivalves; bryozoans are ubiquitous and rhodoliths are abundant near the base. Meter-scale storm tempestites are typical. The sediments are interpreted to have accumulated in a seaway developed between a series of mid-shelf islands. The unit is truncated at the top by a subaerial erosional karst unconformity with a flat scoured subaerial exposure surface (Fig. 3.10) with Fe-staining and meteoric cements (James et al. 2016) equivalent to that below the Chinaman Gully.

3.5 SA2.3 Late Eocene

47

b

a

o E

c

e

d

f

O

E

Fig. 3.10 Kingscote Formation Kangaroo Island—a Type section at Kingscote, lower Eocene (E) carbonates overlain by upper Oligocene limestones (O); J. Matear scale (Circled); b Close view of Eocene echinoid spine floatstones, image 10cm wide. c Large infaunal echinoid in fine biofragmental grainstone-packstone, image 9 cm wide; d Clypeaster floatstone-rudstone, image 9 cm wide; e Fibularia rudstone, cm scale; f Contact between Eocene (E) and Oligocene (O) strata, image 50 cm wide

3.5.5 Mid—Outer Neritic Blanche Point Formation: These well-studied Upper Eocene strata (Figs. 3.11, 3.12) present in both the Willunga sub-basin and Noarlunga sub-basin, are coccolith marls, spiculitic marls, and spiculites, all locally rich in glauconite, turritellid gastropods, and sponges. The biosiliceous sediments, most of which are marls in this succession, comprise several facies (James and Bone 2000); (1) Fossiliferous glauconitic marl:

48

3 Succession SA2: Middle Eocene …

Fig. 3.11 Stratigraphic column of the Tuketja and Gull Rock members of the Blanche Point Formation illustrating the major lithologies (numbered) and macrofossil distribution (modified from James and Bone 2000)

Sediments contain glauconite and a diverse macrobiota, including turritellids and local clusters of arborescent bryozoans. The Cibicides/ Uvigerina foraminiferal ratio (C/U ratio) is usually high, indicating a dominance of epifaunal protists. The rocks are floatstones to local rudstones, with a matrix of variably coccolith-rich, glauconitic, spiculitic, and microbioclastic packstone ± wackestone, (2) Glauconitic marl: These deposits have a relatively sparse macrobiota, usually pectinid bivalves and occasional nodular/arborescent bryozoans (Celleporaria), and are conspicuously burrowed and

3.5 SA2.3 Late Eocene Fig. 3.12 a Blanche Point Formation (BP) and overlying Hallet Cove (HC) sandstones ~ 50 m high; Maslins, Adelaide, S.A.; b Gastropod floatstone with many snails preserved; image 10 cm wide; c Carbonate mudstone with intact demonsponge above finger, image 10 cm wide

49

a

HC

BP

b

c

50

3 Succession SA2: Middle Eocene …

glauconitic. The C/U ratio remains high. The sediment is a coccolith-rich, spiculitic, microbioclastic packstone ±wackestone, (3) Burrowed marl: These sparsely glauconitic microbioclastic wackestones are virtually devoid of macrobiota but have conspicuous burrows. The C/U ratio is generally low, indicating a dominance of infaunal benthic foraminifera. Sediments in the Noarlunga sub-basin just to the west are mostly siliciclastic with poorly constrained biostratigraphy. Strata are correlative with the Throoka Silts on Yorke Peninsula that are paralic to lagoonal deposits with plant remains. The Paraminna Sand Member is the inboard equivalent to all of the Blanche Point Formation. It is a well-sorted glauconitic, quartzose sand with indistinct cross-bedding and wood fragments, that is sparsely fossiliferous. All depositional environments are interpreted as relatively shallow water and low energy, reflecting the variable impedance of a basin-entrance archipelago of carbonate highs (e.g., Kangaroo Island) and a low energy Australia-Antarctica Gulf. Marls and spiculites are interpreted to have formed in an overall estuarine circulation system under a humid climate. Basinal waters, although well mixed, were turbid, yet subphotic near the seafloor. Finally, carbonate diagenesis throughout is minor, with much aragonite still present, but early opal-A alteration and silicification is extensive, except in the spiculite, which is still opal-A. Browns Creek Formation: Although mostly not exposed in the Gambier Embayment except as parts of the Narrawaturk Formation, the ~ 50 m-thick, fine-grained, mollusk-rich, Brown’s Creek Formation is exposed in the Aire District in the central region of the Otway Basin (Fig. 1.7). The sediment is sandy clay to clayey marl to pebbly mudstone with Fe-stained quartz, local glauconite, and abundant carbonaceous particles. The uppermost few meters are a bryozoan marl. Particularly conspicuous are the gastropod Turritella (Spirocolpus) aldingae and the small bivalve Limpopsis chapmani. This unit is essentially a siliciclastic version of the Blanche Point Formation in the St. Vincent Basin (Abele et al. 1988).

3.5.6 Outer Neritic Wilson Bluff Limestone: Where exposed in the Eucla Basin these rocks everywhere stand out from overlying carbonates because of their white color and overall fine grained, soft, poorly cemented nature (Fig. 3.13). From a distance the limestones strongly resemble Cretaceous chalks and have occasionally been described as such. Bedding boundaries, highlighted by chert nodules and replaced fossils, enhances this resemblance. Bedding in this upper part of the unit is generally sub-horizontal, except along seacliffs in the western Eucla Basin, where it is locally inclined. The rocks are mostly bryozoan floatstones but with numerous complete to compacted entire echinoid tests and spines, and local whole brachiopods, especially Terebratula sp. together with serpulid worms. The coccolith- and spicule-rich matrix

3.5 SA2.3 Late Eocene

51

b

a N AB WB

c

d

e

f

Fig. 3.13 Wilson Bluff Formation; a Seacliff at Eucla with white Wilson Bluff (WB) overlain by dark Abrakurrie Limestone (AB) and Nullarbor Limestone (N); cliff height ~50 m; b Thick, soft, spiculitic wackestones overlain by rhythmically bedded bryozoan packstones and chalks; cliff 10m high; c Alternating, recessive bedded wackestone—mudstone and more resistant layers of well cemented bryozoan floatstone with numerous chert nodules, section ~10 m thick; d Bryozoan wackestone-floatstone with numerous delicate branching cyclostome bryozoans, finger 1.0 cm wide; e Cross-section of large demosponge, cm scale.; f Diver examining the echinoid-rich Wilson Bluff Limestone in Pannikin Cave, Nullarbor Plain, image courtesy Cave Exploration Group, South Australia

is a fine microbioclastic packstone to wackestone with conspicuous delicate bryozoan fragments and whole planktic foraminifers. Glauconite is present but not abundant. Bryozoans are mostly foliose and delicate branching types with numerous encrusting and articulated branching growth forms (Cockbain in Lowry 1970). Bivalves such as Chlamys, Spondylus, and the oyster Notostrea lubra are common.

52

3 Succession SA2: Middle Eocene …

Fig. 3.14 Lapped chert by indigenous Australians from Wilson Bluff Formation; image 8 cm wide

Spondylus in the upper part is interpreted as a tropical form. Both planktic and benthic foraminifers are present. Planktic protists form about half of the total biota in lower marls but are many fewer in the upper limestone. Chert nodules, generally decameter-size but locally up to 3 m across, are scattered throughout with locally silicified sponges in the west. There is enough chert in the unit that weathered pieces were knapped by local indigenous peoples (Fig. 3.14) The type section at Wilson Bluff (Lowry 1970) and Point Culver, consists of; (1) 40 m of chalky bryozoan packstone to floatstone with chert nodules and abundant oysters (Notostrea sp) at the top, (2) 14m of chalky bryozoan packstone, no chert, and (3) 2m of well-cemented bryozoan floatstone with abundant large brachiopods (Terebratula subcarnea). M-scale cycles of calcareous marl grading up to coarser bryozoan, echinoid, serpulid grainstone occur at the top.

3.5.7 Slope Slope deposits cored in Leg 182 (Package 111; 36.5–35 Ma—Latest Eocene; Li et al. 2003) are fine-grained ooze with clay-rich ooze interbeds. Deposition is interpreted to have been in waters > 300 m deep and is correlated with the SA2.3. Foraminifers throughout suggest cooling ocean waters with increased nutrients and silica contents.

3.6 SA2.4 Early Oligocene

53

3.6 SA2.4 Early Oligocene 3.6.1 Overview By the early Oligocene carbonate deposition had finally reached eastward into the Gambier and Aire sub-basins of the Otway Basin (Fig. 3.2). Although well exposed there they are not present in the Eucla Basin, having been removed by post-early Oligocene erosion. Furthermore, the top of underlying succession SA2.3 in the St. Vincent Basin is truncated by an erosional unconformity that is present on the mainland and on Kangaroo Island.

3.6.2 Marginal Marine Chinaman Gully Formation: The Eocene-Oligocene boundary here is placed at the erosional base of the Chinaman Gully Formation (McGowran et al. 1992). This 2–10 m thick, varicolored to dark, carbonaceous pyritic quartzose sand, silt, and clay in both the Willunga and Noarlunga sub-basins basins (Figs. 3.15, 3.16) contains lignite, carbonaceous silts, and clays inland. Sedimentation is interpreted to coincide with rising baselevel, inasmuch as uppermost silts and clays are intensely burrowed and contain a few marine fossils. This unit is interpreted as a series of freshwater paleoswamps, bogs, and coastal marshes that were transgressed by an estuarine lagoon facies (Reinson 1992; Lindsay and Alley 1995; Dalrymple 2011).

Fig. 3.15 A diagrammatic cross-section down the axis of the Willunga and Noarlunga embayments, St. Vincent Basin illustrating the Early Oligocene sedimentary succession (modified from James and Bone 2008)

54 Fig. 3.16 a Chinaman Gully Formation, composed of red and grey sandstone and marl; field book scale (20 cm); b Aldinga Mbr, Willunga Formation; cross-bedded calcareous sands, 10 cm scale divisions on pole; c Aldinga Mbr. Willunga Formation, Close view of bryozoans rudstone, image 10 cm wide

3 Succession SA2: Middle Eocene …

3.6 SA2.4 Early Oligocene

55

3.6.3 Inner Neritic Port Vincent Limestone: The lower Oligocene to lower Miocene open shelf limestone (Shubber et al. 1997) is ~ 100 m thick along the western side of the St. Vincent Basin and is divided into three informal members. The one lower Oligocene member consists of two facies: (1) friable bryozoan packstones-rudstones locally rich in large miliolid benthic foraminifers, coralline algae, echinoids, bivalves gastropods, and brachiopods and (2) lenses of bryozoan-bivalve (Chlamys) floatstone that are locally dolomitized. They are interpreted to have accumulated in inner shelf settings, likely comparatively low energy. Willunga Formation—Aldinga Member: Terrestrial sediments of the Chinaman Gully Formation in the St. Vincent Basin are sharply overlain by a 2–3 m thick white to Fe-stained, cross-bedded, quartzose sand and sandstone (Fig. 3.16). Basal beds of this transgressive unit are granule to coarse-grained sand with abundant bryozoans. The sand is planar cross-bedded up to angles of 20° that are regionally bidirectional; most indicate current directions from the N or SW. These are locally overlain by trough cross-beds, 2–4 cm thick, with flow directions from the N and NNE, mud drapes, and thin layers of wave ripples with mud drape indicating tidal deposition. Most bryozoans are articulated branching, delicate branching, and flat robust branching, with minor fenestrate types. Sands in both embayments contain the large benthic foraminifers Linderina, Halkyardia, and Masslinella (James and Bone 2008) and coralline algal rods. The bryozoans also include Densipora, a form that today grows only epiphytically on seagrasses. Rogue Formation: The upper part of this coeval unit on Yorke Peninsula has two units (Stuart 1970). The thin, ~ 1 m thick lower unit, the Port Julia Greensand Member is a burrowed sandstone with numerous Fe-oxide grains, abundant bivalves (pectens), and gastropod molds. It is overlain by a brown siliciclastic sand with pectens, bivalves, bryozoans, and sponges. The overlying Rogue Formation is similar to the lower part. These two units are coeval with the Aldinga and Ruwarung members of the Port Willunga Formation to the east.

3.6.4 Inner—Mid Neritic Kingscote Limestone: The upper three units of limestones on Kangaroo Island form a ~ 10 m-thick succession overlying the erosional subaerial erosion surface on top of late Eocene unit 1 (Lindsay and Alley 1995; James et al. 2016). The mostly crossbedded, variably quartzose limestones (Fig. 3.17) are principally bryozoan-mollusk grainstones and rudstones with accessory echinoids, and serpulids. The numerous benthic foraminifers are all cool-water protists. Many units are thoroughly burrowed by Skolithos or Thalassinoides.

56 Fig. 3.17 Kangaroo Island—Oligocene; a Meter-scale cycles separated by subaerial exposure surfaces (arrows), 10cm scales on stick (circled); b Bipolar cross–bedded bryozoan grainstone; 20 cm pen scale at top; c close view of bryozoan grainstone in previous images; image 20 cm wide

3 Succession SA2: Middle Eocene …

a

b

c

3.6 SA2.4 Early Oligocene

57

M-scale cycles of basal bryozoan grainstone-rudstones grade upward to mollusk rudstone that is capped by a Fe-stained Thallassinoides hardground. Some of the hardgrounds have attributes of meteoric exposure surfaces. The numerous and diverse bryozoans comprise a wide spectrum of growth forms compatible with the high-energy nature of the sediments. By contrast, the dominance of large robust branching Celleporaria sp. bryozoans near the top of the Kingscote Limestone point toward more tranquil and mesotrophic conditions. Although corallines are ubiquitous, their low numbers imply relative water opacity. Paleocurrent measurements suggest a tidal-dominated regimen wherein the currents were flood-dominated. The upper several meters of the Kingscote Limestone is a planar-bedded burrowed packstone-grainstone with many attributes similar to those in the coeval Willunga Formation inboard. This could be interpreted as the basal part of a mostly now eroded transgressive system.

3.6.5 Mid-Outer Neritic Gambier Limestone: This Oligo-Miocene limestone (Fig. 3.18) outcrops onshore, where it is ~ 250 m thick but ranges up to 700 m in drillholes (Li et al. 2000). It is divided into three members which are, upward; (1) Greenways Member (lower Oligocene), (2) Camelback Member (upper Oligocene), and (3) Green Point Member (middle Miocene (Fig. 3.2)). The limestone is mostly marl to calcisiltite with the sections punctuated by several calcirudites and calcarenites in the westernmost part of the Otway Basin (James and Bone 1989; James et al. 1991; Li et al. 2000). Parts of the formation are dolomitized. Large skeletons are generally brachiopods, gastropods, and bivalves. Sand and finer particles are mostly bryozoans, benthic and planktic foraminifers, and echinoderms. More specifically, coarse sediments are dominated by a wide variety of bryozoans. Fine sediments are; (1) microbioclastic with numerous cyclostomes, (2) chalks and cyclostome mudstones and packstones containing conspicuous planktic foraminifers, and, (3) marls similar to 2 but with more clay. Chert is common in the fine-grained units. Most of the limestones are interpreted as mid to outer shelf, 50–200 mwd deposits. Greenways Member: The 40 m-thick lower Oligocene limestone above a basal unconformity is a thin basal transgressive, fine- to coarse-grained packstone to grainstone with a wide variety of bryozoans and variable numbers of echinoderm and benthic foraminifer particles. Most of the unit is a cyclostome bryozoan mudstone to wackestone with minor benthic foraminifers, echinoid particles and conspicuous planktic foraminifers. The top is an erosional unconformity (James and Bone 1989; James et al. 1991; Li et al. 2000). Willunga Formation—Ruwarung Member: The bulk of the overlying Willunga Formation (Figs. 3.19, 3.20) consists of lithologies that change upward from richly fossiliferous clay floatstones (up to 40% clay) to clay-rich floatstones, with chert

58

3 Succession SA2: Middle Eocene …

Fig. 3.18 Gambier Limestone, Camelback Member, Mt. Gambier area S.A. a Building stone quarry (people scale) with extensively karsted limestone in background; b Quarry wall of Gambier Limestone bryozoan wackestone; J. Rivers scale, circled; c Close view of bryozoan grainstone in previous image composed of delicate branching cyclostomes, image width ~4 cm; d Cross-bedded bryozoan grainstone, 23 cm hammer scale (circled); e Large Celleporaria bryozoan, image width 6 cm. f Bedding plane of numerous pectens; cm scale

nodules, to an upper unit of grainy quartzose floatstones (> 30% fine-medium sand) with numerous chert nodules (James and Bone 2008). Floatstones are rich in epifaunal elements such as large and diverse bryozoans (e.g., Celleporaria spp., various fenestrates, and encrusting forms), pectenid bivalves, echinoid spines, and locally large brachiopods. Scolicia textures grainy beds whereas muddy layers, particularly the tops of clay beds, are burrowed by Thalassinoides. Sand-size carbonate grains are mostly bryozoan remains, benthic foraminifer tests, echinoid pieces, and coralline algae (articulated) fragments in shallow water facies.

3.6 SA2.4 Early Oligocene

59

Fig. 3.19 Willunga Formation, Willunga Embaymnet, a Ruwarung Member, composed of wellbedded bryozoan floatstone and fossiliferous clay-rich floatstone; cliff ~ 8 m high, b Close view of outcrop in A composed of alternating well-burrowed (Thallassinoides) beds and structureless units; 10 cm units on scale; c Large Celleporaria sp. bryozoan in marl, d Numerous fenestrate cheilostome bryozoans, in floatstone, image 6 cm wide

Siliceous sponge spicules locally form as much as 50% of the sediment. Although generally molds, some spicules are still opal-A, whereas others are replaced by opal-CT lepispheres or microquartz (see Chapter 8, Fig. 8.11). Narrawaturk Formation: These carbonates in the Otway Basin (Fig. 3.2) are a series of high-energy, locally siliciclastic, inner shelf facies that pass up-section to mostly deeper water, lower energy, mid- to outer shelf bryozoan marls, calcisiltites, and chalks. The locally glauconitic sediments with many foraminifers are punctuated by storm events and minor shallowing intervals. Post-depositional dolomitization, however, has locally obliterated much depositional fabric.

3.6.6 Outer Neritic Castle Cove Limestone: The Late Eocene—Early Oligocene deposit in the Otway Basin is a ~ 25 m thick unit of quartzose limestones, clays, and marls with conspicuous planktonic foraminifers implying deep water, neritic deposition.

60

3 Succession SA2: Middle Eocene …

a

b

c

d

Fig. 3.20 Willunga Formation, Noarlunga Embayment. a Echinoid grainstone, image 7 cm wide; b Gastropod rudstone composed of snail molds, image 8 cm wide; c Bedding plane of numerous Thalassinoides burrows; hammer 13 cm long; d Chert nodule in bryozoan wackestone, hammer 23 cm long

Glen Aire Clay: This Otway Basin unit is a ~ 20 m-sandy thick clay, with numerous quartzose, limonitic, limestone interbeds, and a capping pyritic bryozoan clay. The clay contains numerous conspicuous bivalves (Limopsois), gastropods, and planktonic foraminifers again suggesting deep neritic depositional conditions.

3.7 Summary The Middle Eocene to Lower Oligocene Biogenic Shelf deposits consist of four packages. SA2.1 (Middle Eocene) inboard siliciclastics grade outboard into neritic bryozoan-rich carbonates and slope bryozoan reef mounds. SA2.2 (Middle to Upper Eocene) strata have a similar facies disposition but terrestrial sediments are lignites. SA2.3 (latest Eocene) is characterized by abundant biosiliceous spiculites and associated carbonates. SA2.4 (Lower Oligocene) strata consist of abundant carbonates but with reduced biosiliceous deposits.

References

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References Abele C, Kenley PR, Holdgate G, Ripper D (1988) Otway Basin. In: Douglas TJG, Ferguson JA (eds) Geology of Victoria. Geological Society of Victoria, pp 272–302 Alley NF, Clarke JDA, Macphail M, Truswell EM (1999) Sedimentary infillings and development of major tertiary palaeodrainage systems of south central Australia. Spec Publ Int Assess Sediment 27:337–366 Alley, NF, Lindsay, JM (1995) Tertiary. In: Drexel JF, Preiss VP (eds) The geology of South Australia, vol 2. Geological Survey of South Australia, Bulletin 54, pp 151–215 Belperio, AP (1995) Quaternary. In: Drexel JF, Preiss VP (eds) The geology of South Australia, vol 2: the Phanerozoic. Geological Survey of South Australia, Mines and Energy South Australia, Bulletin 54, pp 219–280 Benbow MC (1990) Tertiary coastal dunes of the Eucla Basin. Aust Geomorpho 3:9–29 Clarke JAD, Bone Y, James NP (1996) Cool-water carbonates in an Eocene tide-dominated palaeoestuary, Norseman Formation, Western Australia. Sed Geol 101:213–226 Clarke JDA (1993) Stratigraphy of the Lefroy and Cowan palaeodrainages, Western Australia. J R Soc Western Aust 76:12–23 Clarke JDA, Gammon PR, Hou B, Gallagher SJ (2003) Middle to Late Eocene stratigraphic nomenclature and deposition in the Eucla Basin. Aust J Earth Sci 50:231–248 Cockbain, AE (1969) Dasycladasean algae from the Werillup Formation, Esperance, Western Australia, Geological Survey of Western Australia Annual Report 1968 Dalrymple, RW (2011) Tidal depositional systems. In: James NP, Dalrymple RW (eds) Facies models 4. Geological Association of Canada special publication No. 6, St-John’s, Newfoundland, pp 201–231 Feary, DA, Hine, AC, James, NP, Malone, MJ, Hine, AC, Feary, DA, Malone, MJ, Andres, M, Betzler, C, Brooks, GR, Brunner, CA, Fuller, M, Molina Garza, RS, Holbourn, AE, Huuse, M, Isern, AR, James, NP, Ladner, BC, Li, Q, Machiyama, H, Mallinson, DJ, Matsuda, H, Mitterer, RM, Robin, C, Russell, JL., Shafik, S, Simo, JA, Smart, PL, Spence, GH, Surlyk, FC, Swart, PK, Wortmann, UG (2004) Leg 182 synthesis; exposed secrets of the Great Australian Bight. Proceedings of the Ocean Drilling Program, Scientific Results (CD ROM) 182 Francis JE, Marensi S, Levy R, Hambrey M, Thorn VC, Mohr B, Brinkhuis H, Warnaar J, Zachos JC, Bohaty S, DeConto R (2008) Chapter 8 from Greenhouse to Icehouse—the eocene/oligocene in Antarctica, Developments in Earth and Environmental Sciences. Elsevier, Amsterdam, pp 309–368 Gammon P, James NP, Clarke JDA (2000a) Eocene spiculites and spongolites in Southwestern Australia: not deep, not polar, but shallow and warm. Geo 28:855–858 Gammon PR, James NP, Clarke JDA, Bone Y (2000b) Sedimentology and lithostratigraphy of upper Eocene sponge-rich sediments, Southern Western Australia. Aust J Earth Sci 47:1087–1103 Holdgate G, Clarke JDA (2000) A review of tertiary brown coal deposits in Australia—their depositional factors and eustatic correlations. Am Asso Pet Geo Bull 84:1129–1151 Hou B, Frakes LA, Alley NF, Gammon P, Clarke JDA (2003) Facies and sequence stratigraphy of Eocene valley fills in Eocene palaeovalleys, the eastern Eucla Basin, South Australia. Sed Geol 163:111–130 James NP, Bone Y (1989) Petrogenesis of Cenozoic, temperate water calcarenites, South Australia: a model for meteoric/shallow burial diagenesis of shallow water calcite sediments. J Sed Petrol 59:191–203 James NP, Bone Y (2000) Eocene cool-water carbonate and biosiliceous sedimentation dynamics, St. Vincent Basin. S Aust Sed 47:761–786 James NP, Bone Y (2008) Carbonate-biosiliceous sedimentation in early Oligocene estuaries during a time of global change, Port Willunga Formation, St.Vincent Basin, southern Australia. In: Lukasik J, Simo JA (eds.), Controls on carbonate platform and reef development. SEPM Special Publication 89, pp 231–253

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James NP, Bone Y, Brown KM, Cheshire N (2009) Calcareous epiphyte production in cool-water carbonate depositional environments; Southern Australia. In: Swart P, Eberli G (eds) Advances in carbonate sedimentology. International Association of Sedimentologists Special Publication 41, pp 123–148 James NP, Bone Y, Kyser TK (1991) Shallow burial dolomitization of mid-Cenozoic, cool-water, calcitic, deep-shelf limestones, southern Australia. AAPG Bull 75:602 James NP, Matenaar J, Bone Y (2016) Cool-water Eocene-Oligocene carbonate sedimentation on a paleobathymetric high, Kangaroo Island, Southern Australia. Sed Geol 341:216–231 Li Q, James NP, McGowran B (2003) Middle and late Eocene Great Australian Bight lithobiostratigraphy and stepwise evolution of the southern Australian continental margin. Aust J Earth Sci 50:113–128 Li Q, McGowran B, White MR (2000) Sequences and biofacies packages in the mid-Cenozoic Gambier Limestone, South Australia: reappraisal of foraminiferal evidence. Aust J Earth Sci 47:955–970 Lindsay JM, Alley NF (1995) St Vincent Basin. In: Drexel JF, Preiss, VP (eds) The geology of South Australia, vol. 2 The Phanerozoic. South Australia Geological Survey Bulletin 54, pp 163–172 Lowry DC (1970) Geology of the Western Australian part of the Eucla Basin. Geo Surv W Aust Bull 122:201 McGowran B, Li Q, Moss G. (1997) The Cenozoic neritic record in southern Australia: the biogeohistorical framework. In: James NP, Clarke, JAD (eds) Cool-Water carbonates. Special Publication—SEPM, pp 185–203 McGowran B, Moss G, Beecroft H (1992) Late Eocene and Earlyt Oligocene in South Australia: local neritic signals of global oceanographic changes. In: Prothero DR, Bergren WA (eds) EoceneOligocene Climatic and Biologic Evolution. Princeton University Press, Princeton, New Jersey, pp 64–83 Prothero DR, Bergren WA (eds) (1992) Eocene-Oligocene climatic and biotic evolution. Princeton University Press, Princeton, New Jersey, USA, p 568 Reinson, GE (1992) Transgressive barrier island and estuarine systems. In: Walker RG, James NP (eds) Facies Model. Geological Association of Canada, St. John’s, Newfoundland, Canada, pp 179–194 Scher HD, Whittaker JM, Williams SE, Latimer JC, Kordesch WE, Delaney ML (2015) Onset of Antarctic Circumpolar current 30 million years ago as Tasmanian Gateway aligned with westerlies. Nat Res Lett 523:580–583 Sharples AGWD, Huuse M, Hollis C, Totterdell JM, Taylor PD (2014) Giant middle Eocene bryozoan reef mounds in the Great Australian Bight. Geo 42:683–686 Shubber B, Bone Y, James NP, McGowran B (1997) Warming-upward subtidal cycles in mid-tertiary cool-water carbonates, St. Vincent Basin, South Australia. Spec Publ Soc Sed Geo 56:237–248 Stuart WJ Jr (1970) The Cainozoic stratigraphy of the eastern coastal area of Yorke Peninsula, South Australia. Trans R Soc S Aust 94:151–178

Chapter 4

Succession SA3: Late Oligocene—Middle Miocene—‘The Carbonate Shelf’ ~28–11 Ma

Abstract This period, Late Oligocene to Middle Miocene, was one of carbonate depositional along the entire continental margin. Following a mid-Oligocene sea level fall, Upper Oligocene deposition was cool-water throughout with extensive heterozoan deposits in all neritic environments as well as the epicratonic Murray Basin. The middle Miocene was much different with comparatively warm ocean waters resulting in numerous large benthic foraminifers, abundant coralline algae, and even local reef-building corals in the deposits. The Murray Basin deposits accumulating in a centripetal ramp system also had local photozoan facies. Keywords Oligocene-Miocene · Carbonate · Warm ocean · Murray Basin · Ramp

4.1 Overview This was a time of continuous carbonate deposition across the entire southern continental margin of Australia (Figs. 4.1 and 4.2), including the epicratonic Murray Basin, and it is so named ‘the carbonate shelf’. It was the last such extensive deposition in the south Australian Cenozoic. Sedimentation took place in two distinct stages SA3.1 (Late Oligocene—Early Miocene) and SA3.2 (Middle Miocene). There is an excellent outcrop record of largely neritic deposition because the rocks were uplifted and exposed soon after deposition. This subsequent late Miocene tectonic disturbance was, however, most intense in the St. Vincent Basin and the eastern Otway Basin. As a result, much of the middle and some of the early Miocene strata there was removed via uplift and erosion. Thus, the record of deposition during SA3.2 is largely preserved in the Eucla and Murray basins together with the Gambier and Pt. Philip embayments of the Otway Basin.

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 N. P. James and Y. Bone, Biogenic Sedimentary Rocks in a Cold, Cenozoic Ocean, https://doi.org/10.1007/978-3-030-63982-2_4

63

64

4 Succession SA3: Late Oligocene …

OLIGOCENE - MIOCENE STR ATIGRAPHY EUCLA - ST. VINCENT - MURRAY BASINS PIRIE BASIN

EUCLA BASIN W MARGIN

INBOARD

E MARGIN

CENTRAL

MURRAY BASIN

ST. VINCENT BASIN OUTBOARD

10

30

Upper Mannum Port Vincent

Abrakurrie

3.2

3.1

Lower Mannum

Ruwarung Willunga

My

Melton

E

20

Pata Bryant’s Creek Cadell Glenforslan Finniss

Garford

Colville

OLIGOCENE E L

SA 3

MIOCENE M

Nullarbor

Ettrick Aldinga

Upper Kingscote

2.4

MAJOR LITHOLOGY Limestone

Sandstone

Spiculite

Marl

Fig. 4.1 Late Oligocene—Early Miocene SA3 chronostratigraphy and formations in Eucla, St. Vincent, and Murray basins; subdivisions at right. Formation names in normal font, member names in italics

OLIGOCENE - MIOCENE STRATIGRAPHY OTWAY BASIN EMBAYMENTS Gambier

30

Tyend

Pt. Campbell

Pt. Campbell E

Port Naracoorte Campbell Port Colville Muddy Campbell Creek Bochara Green Point Gellibrand Gellibrand Camel -back

Gambier

My

E

20

OLIGOCENE L

SA 3

MIOCENE M

10

Clifton

Nirrandra

Clifton

Demon’s Bluff

Aire

Pt. Phillip

Torquay Yellow Bluff

Fynsford

Gellibrand

Fishing Point Batesford Calder River

Maude Demon’s Bluff

3.2

Zeally

Point Addis

Peubla Celleporaria Clay

Jan Juc

3.1

Glen Aire

MAJOR LITHOLOGY Limestone

Sandstone

Marl

Spiculite

Fig. 4.2 Late Oligocene—Early Miocene SA3 chronostratigraphy and formations in embayments of the Otway Basin; subdivisions at right. Formation names in normal font, member names in italics

4.1 Overview

65

4.1.1 Depositional Facies The Eucla Basin has both a slope and a large shallow neritic record. The elongate St. Vincent and Pirie basins contain mainly inner to mid neritic carbonates. The Otway Basin is somewhat different and consists of distinct embayments separated by bathymetric highs (Fig. 1.7). Successions in each of the Otway sub-basins consist of two major facies; (1) transgressive grainy, shallow water limestones in basinal locations and on highs and (2) fine-grained highstand limestones and marls that accumulated in deeper water mid- to outer neritic environments once sea level had flooded the highs (Holdgate and Gallagher 2003). As stressed above, stratigraphic nomenclature is complex because, (1) shallow neritic deposition was time transgressive since it took place first in depressions between structural highs but then, as sea level rose, similar deposition covered the highs, and (2) similar units have different names in the Otway Basin and in the Central Coast Basin.

4.2 SA3.1 Late Oligocene—Early Miocene 4.2.1 Inner Neritic Port Vincent Limestone: The late Oligocene to early Miocene comprises three informal members. The lower member is a series of bryozoan, miliolid, or bryozoan -bivalve floatstones to rudstones. The middle member of the formation in the St. Vincent Basin is distinctively cyclic. Some cycles have been interpreted as warming-upward because bryozoan biofragmental rudstone basal units pass upward into bryozoan grainstones and are capped by bryozoan-Amphistegina hardgrounds (Shubber et al. 1997). Other cycles lack the distinctive cap with warm-water foraminifers and are thought to have formed in cooler waters. The third capping early Miocene upper member is a non-cyclic unit of highly abraded bryozoan—Epinoides grainstones together with coralline algae and sponge spicules. Willunga Formation: The ~6 m-thick top (lower Miocene) of the formation, is poorly preserved but is present in the eastern part of St. Vincent Basin (Alley and Lindsay 1995). There it is a coarse, cross-bedded, fossiliferous calcarenite with silty sand units. The fossiliferous, marine, Mono Para Clay, represents coeval inboard strata beneath the Adelaide Plains. Port Campbell Limestone: Eastward in the Otway Basin the Port Campbell Limestone (Fig. 4.3) has various lithofacies with different member names (Abele et al. 1988) that occur both in outcrop and in the subsurface. In the subsurface, it is generally referred to as the Port Campbell Limestone ranging in age from Late Oligocene to Middle Miocene. It grades into the Gellibrand Marl and the Gambier Limestone. In the west, it is divided into a lower, Bochara Limestone Member and an upper Muddy Creek Member (see SA3.2).

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4 Succession SA3: Late Oligocene …

Fig. 4.3 a Sea stacks of Miocene Limestone (Pt. Campbell Limestone), Bay of Martyrs, Victoria, stacks ~15 m high; b Gellibrand Marl—Gibson Steps, Cliff section of burrowed bryozoan marl, cliff in foreground ~40 m high; c Gellibrand Marl, lower grey marl and upper burrowed bryozoan wackestone, cliff ~section 15 m thick; d Slumped marl, hammer 23 cm long

The Bochara Limestone Member (Upper Lower Miocene) is ~23 m of inboard, trough cross-bedded, coarse-grained bryozoan grainstone that contains abundant, large benthic foraminifers such as Lepidocyclina and Amphistegina (Abele et al. 1988). Other conspicuous components are epifaunal echinoids, pectens, limonite pellets, and nodules. Sections are punctuated by several Thalassinoides-burrowed, iron-encrusted hardgrounds. Maude Formation (Upper Oligocene- Lower Miocene): This coarse-grained limestone, also coeval with the lower part of the Gellibrand Marl, is located in marginal areas and consists of three members that grade landward into beach sands of the Sutherland Sand Creek Member (Abele et al. 1988). The lower member (upper Oligocene to lower Miocene), is ~10 m of mostly friable locally crossbedded, bryozoan grainstone with echinoids, bivalves, large benthic foraminifers, and coralline algae. It is interpreted as having accumulated in the lower shoreface. The middle member is a lower Miocene (22.0 Ma) pillow basalt. The upper member is ~12 m of rippled and cross-bedded grainstone to rudstone. Biofragments include bryozoans, echinoids, bivalves, large benthic foraminifers, and coralline algae, the latter of which decrease up-section. This lower to middle Miocene, shallow-water limestone is partly coeval with the Batesford Limestone.

4.2 SA3.1 Late Oligocene—Early Miocene

67

Batesford Limestone (Upper Lower Miocene): The quartzose carbonate (Fig. 4.4) is ~60 m of virtually uncemented bryozoan-foraminifer grainstone with two main lithologies and is transgressive onto isolated structural highs. The lower part is a foraminifer-bryozoan grainstone. The upper part is a bryozoan grainstone-packstone rich in large benthic protists (Lepidocyclina and Cycloclypeus), lesser bryozoans, epifaunal echinoid spines, numerous infaunal echinoids, and coralline algae. Other biota includes brachiopods, pectens, oysters, calcareous sponges, and prolific shark teeth. The strata are cross-bedded and burrowed. The postulated depositional environment is shallow inner shelf 10–20 mwd sand shoals (similar to the Point Addis but shallower) with seawater temperatures of 19–22 °C. The euphotic setting was an oligotrophic, normal marine environment. The deposits grade basinward into marls. Point Addis Limestone (Upper Oligocene): This ~25 m thick, friable quartzose cool-water limestone (Fig. 4.5) with numerous hardgrounds passes laterally into the Jan Juc Marl (Abele et al. 1988; Reekman 1988). It has two members separated by a prominent disconformity in the form of hardground and exposure surface. The lower member is a medium to coarse, cross-bedded bryozoan-echinoid grainstone with minor quartz. The upper member is a fine- to medium-grained, poorly cemented, bryozoan grainstone. Bryozoans are mostly flat but erect forms are commonly broken. The other main components are echinoids, brachiopods, pectin bivalves, gastropods, and corallines. Most echinoids are infaunal.

a

b

c

d

Fig. 4.4 a Batesford Limestone, Deakin Quarry, Victoria, walls ~15 m high; b Large benthic foraminifer (Lepidocyclina) grainstone, finger 1 cm wide; c Large, irregular infaunal echinoid, image 10 cm wide. d Echinoid spine floatstone with bioframental packestone—wackestone matrix; coin scale 1 cm diameter

68

4 Succession SA3: Late Oligocene …

Fig. 4.5 Point Addis Limestone, at Point Addis, Victoria. a Top of Pt. Addis lower unit a complex hardground-subaerial erosion surface (arrows); hammer scale 23 cm long. b Cross bedding in overlying limestone, hammer scale = 23 cm

4.2.2 Inner-Mid Neritic Melton Limestone: This carbonate (Figs. 4.6 and 4.7) in the St. Vincent Basin consists of five transgressive–regressive units (Lindsay 1970). The lower lithologies are early Miocene in age, the upper parts are middle Miocene. Lithologies consist of horizontally bedded to planar cross-bedded quartzose, bryozoan calcareous sandstone overlain by glauconitic limestone with bryozoans, echinoids, and brachiopods. Clifton Formation (Upper Oligocene): The ~5–60 m thick deposit in the Otway Basin ranges from a burrowed, coarse-grained, ferruginous, calcareous sandstone to a grainstone-packstone. Fossils include delicate branching bryozoans, gastropods, benthic foraminifers, octocoral spicules, scaphopod tubes and regular echinoid spines together with rare glauconite peloids, and limonite nodules. Small phosphate and limonite nodules are present in the quartzose layers. One particularly prominent phosphate layer is interpreted as a hardground (Baker 1945; Gallagher and Holdgate 2000; Holdgate and Gallagher 2003) (see Chapter 8, Fig. 8.10). The Clifton is interpreted as a high-energy unit that grades landward into paralic coastal deposits, grades

4.2 SA3.1 Late Oligocene—Early Miocene Fig. 4.6 Melton Limestone, Myponie Point, Yorke Peninsula South Australia; a Cliff section of Melton Limestone (M) overlying Precambrian crystalline rocks (Tickera Granite-P) cliff 14 m high; b Cross-bedded bryozoan grainstone—rudstone in basal beds, hammer scale 23 cm long; c Rhodolith rudstone in upper unit, image width ~12 cm

69

a M P

b

c

into the Port Campbell Limestone on highs and inland, and seaward the deeper water Gellibrand Marl. Fossils are similar to those in the Jan Juc Marl. Calder River Limestone (Upper Oligocene—Lower Miocene): This quartzose, bryozoan, calcarenite has several thin discontinuous beds of phosphate nodules. It is thought to be correlative with the Clifton Formation in the Pt. Campbell Embayment (Abele et al. 1988).

70 Fig. 4.7 Melton Limestone, Point Turton, Yorke Peninsula; a Varigated Permian sandstones and shales overlain by Melton Limestone, cm scale at center; b Cross-bedded Melton Limestone, cm scale at top, c Close view of bryozoan fragment grainstone-rudstone; image 4 cm wide

4 Succession SA3: Late Oligocene …

4.2 SA3.1 Late Oligocene—Early Miocene

71

4.2.3 Mid-Outer Neritic Abrakurrie Limestone: This is an unconformity-bound ~100 m-thick upper Oligocene to Lower Miocene unit (Fig. 4.8), of mostly a coarse-grained bryozoan calcarenite (Fig. 4.9) that onlaps the Wilson Bluff Limestone of SA2 in the Eucla Basin (James and Bone 1991; Li et al. 1996). Exposures are largely in sinkholes and caves beneath the Nullarbor Plain. Sediments accumulated ~200 m inboard from the shelf edge as mid-outer shelf deposits at interpreted water depths of ~100 m. The carbonates are composed of bryozoans, bivalves, benthic foraminifers and echinoids with lesser numbers of brachiopods, solitary corals and serpulids. Most bryozoan remains are from delicate-branching cyclostomes although delicatebranching, robust-branching, foliose, fenestrate, multilaminar-encrusting with freeliving cheilostomes are variably prominent in specific horizons. The sequence is cyclic and punctuated by numerous hardgrounds (Fig. 4.9). There are three main lithologies; (1) coarse bryozoan grainstones that are planar to trough cross-bedded, (2) fine skeletal grainstones composed of delicate branching bryozoans, benthic foraminifers and echinoids, and (3) rudstones that are conspicuously fossiliferous with numerous large bryozoans, bivalves, gastropods, infaunal echinoids, and local solitary corals. The limestone is divided into three informal members; (1) upper Oligocene— a thin-bedded and cross-bedded rhythmic rudstone lower member, (2) lower Miocene—a thin-bedded and burrowed grainstone middle member, and (3) upper Lower Miocene—a thick-bedded and heavily burrowed upper member, all with cycles of subtidal to deep-shelf origin (James and Bone 1992, 1994). Benthic

Fig. 4.8 Diagrammatic N-S cross-section of Eucla Basin carbonate stratigraphy (simplified from James and Bone 1994)

72

4 Succession SA3: Late Oligocene …

Fig. 4.9 Abrakurrie Limestone, Nullarbor Plain. a Abrakurrie Cave—Contact between Wilson Bluff Limestone below and Abrakurrie limestone above; a complex hardground—subaerial unconformity; ladder scale—30 cm wide; b Twilight Cove, cross-bedded bryozoan grainstone-rudstone; 10 cm scale; c Cliff exposure at Twilight Cove with three hardgrounds (arrows); person scale (circled); d Large infaunal echinoid in bryozoan grainstone, cm scale; e Close view of bryozoan grainstone, image 7 cm wide

foraminifers in the lower and middle members are largely infaunal and indicate cool, mesotrophic marine conditions. Those in the upper member are more epifaunal and suggest warmer, more oligotrophic waters (Li et al. 1996). The warm-water protist Amphistegina lessonii makes its first and episodic appearance in the lower member, but the species becomes abundant and widespread in the upper member. Likewise, such species as Elphidium spp. and Pararotalia mackayi, which prefer warmer water habitats, are more numerous in the upper member.

4.2 SA3.1 Late Oligocene—Early Miocene

73

Gambier Limestone (Upper Oligocene—Middle Miocene): The upper two members of the Limestone (Figs. 3.18 and 4.2) are generally fine-grained. Camelback Member: This middle member is upper Oligocene. Lithologies are cool-water bryozoan marl and limestone, locally dolomitized (James et al. 1991; Kyser et al. 2002), with poorly preserved microfossils but warm-water biofacies in the upper part. Conspicuous chert, along with numerous sponge spicules, is interpreted to signal deep or cold-water deposition (>100–200 mwd, 50% even though many have been in the meteoric diagenetic environment for over 30 My. This arresting situation is because, as stressed above, there was little or no aragonite in the sediment on the seafloor before being exposed to meteoric waters (cf. Reekman 1988). This phenomenon is dramatically illustrated when two of the carbonates in SA3, the Gambier and Naracoorte limestones are compared (Figs. 6.3, 6.4). The Oligocene—early Miocene Gambier Limestone, deposited in cool waters and composed of calcitic biofragments, lacks any evidence of former aragonite components and is barely lithified (Fig. 6.5), even if it has been exposed to meteoric waters since the early Pliocene. By contrast, the overlying middle Miocene Naracoorte Limestone, deposited in warmer waters and composed of numerous aragonitic gastropods and bivalves originally, is a hard, well-cemented limestone (James and Bone 1989). This observation implies, as illustrated on the modern seafloor, that the aragonite has been dissolved early (James et al. 2005; Rivers et al. 2008). Early cemented hardgrounds, however, do have aragonitic mollusk molds filled with synsedimentary cement, indicating that aragonite particles were present in the original sediment.

6.2.4 Dolomitization Dolomite replacing deposits in SA2 and SA3 is common, but not extensive, across the region. It is present in the Eucla Basin, St. Vincent Basin, Murray Basin, and Otway Basin. It has been studied in particular detail in the Oligocene Gambier Limestone

6.2 Pre-Uplift Diagenesis (Subsidence Diagenesis) Fig. 6.3 Sketch of Gambier Limestone petrographic attributes. a Typical lithology with cement lining most intraparticle pores as well as epitaxial cement on echinoid and planktic foraminifer particles b Slightly different sediments with minor particle contact pressure solution, epitaxial cement on echinoid and planktic foraminifer particle, and minor dentate calcite cement in intraparticle pores—grain surfaces are free. c Sediment that has undergone late-stage dissolution and formation of small vugs (modified from James and Bone 1989)

a

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Fig. 6.4 Petrographic attributes of the Naracoorte Limestone with aragonite particle dissolution and reprecipitation as calcite cement (modified from James and Bone 1989)

(James et al. 1991; Kyser et al. 2002). There, Ca-rich, medium crystalline, sucrosic, fabric destructive dolomite is widespread (Figs. 6.6, 6.7). The dolomite is present as scattered rhombs to whole units 10’s of meters thick and many km in extent. Replacement took place, on the basis of Sr-isotopes, in shallow-burial environments during the middle to late Miocene. Replacement was strongly facies-specific and focused in muddy units. The dolomite rhombs have cloudy cores and clear rims. The cores have bright CL, are nearly stoichiometric and interpreted to have formed in the mixing zone of brackish and seawater (Fig. 6.6). The clear rims, are non-stochiometric, have dark and bright zones under CL and are thought to have formed in seawater. The origin corresponds to transgressions wherein nucleation took pace in the mixing zone and growth in seawater as sea level rose and filled the pores (Fig. 6.8). Meteoric exposure during the subsequent sea level fall then resulted in local dedolomitization via leaching of the metastable cores and local filling of the voids by LMC (Figs. 6.6, 6.8).

6.2.5 Mesogenetic Diagenesis Most of the Cenozoic carbonates have never had more than several hundred meters of overburden and so burial diagenesis should not have been important. The lack

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Fig. 6.5 Meteoric Diagenesis, thin sections ppl. a Gambier Limestone bryozoan grainstone that has been exposed to meteoric fluids for at least 5 My and yet contains no calcite cement; b Pleistocene limestone from Gambier Coastal Plain (125 Ka) with meniscus LMC cement (arrows); image width 5 mm; c Pleistocene biofragmental grainstone (650 Ka) with isopachous LMC cement, image width 5 mm; d Completely cemented Pleistocene (750 Ka) biofragmental grainstone wherein the original aragonite particles are neomorphosed; image width 5 mm

of microscale meteoric alteration, especially cementation has, however, resulted in little structural resistance to burial change. This is dramatically demonstrated in the Clifton Limestone (SA 3.1-late Oligocene) in the Port Campbell Embayment of the Otway Basin (Nicolaides and Wallace 1997). Components there are dominated by calcite biofragments that were buried between 160 and 670 m and then uplifted to < 100 m. Shallow buried grainstones are weakly cemented with < 5% cement to burial depths of < 430m. Specifically, most grainstones buried shallower than 200m exhibit extensive evidence of mostly mechanical compaction in the form of grain interpenetration, fitted fabrics, dissolution seams and minor stylolites. By contrast, those that were more deeply buried below 550m are almost completely cemented with much evidence of chemical compaction. Clay-rich facies dissolution seams first appear at 190m but are best developed below 340m.

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a

b

c

d

0.1mm

Fig. 6.6 Gambier Limestone, thin sections. a Completely dolomitized porous carbonate, green background epoxy resin; ppl, b Enlarged area of A. illustrating rhombs with dirty cores and clear rims, ppl; c CL image of Gambier dolomite with viable luminescence; d Gambier dolomite wherein the cores of the crystals have been dissolved and filled with calcite (stained red by Alizarin red S), ppl, image 0.6 mm wide

6.3 Post-Uplift Diagenesis 6.3.1 Meteoric-Karst Late Miocene uplift brought SA2 and SA3 carbonates into the meteoric diagenetic realm late in their geohistory. Younger SA4 carbonates, by contrast, were in many cases altered by meteoric processes soon after deposition. The major processes that affected all carbonates, regardless of age, were karst and pedogenic calcrete formation (Fig. 6.1). Interparticle cementation affected only those SA4 deposits with original aragonite particles. The ubiquity of exposed limestone across southern Australia means that surface and subsurface karst is extensive. Such features are developed in and on both the Eocene to Miocene carbonates and the more recent Pleistocene aeolianites. The former mostly occur in two geomorphic regions, the Nullarbor Plain and the Gambier Coastal Plain. Karst is not extensive in the St. Vincent and Murray basins. Karst is a comparatively recent feature and was not a prominent landform in the Paleogene and early Neogene. This is because the hinterland was largely Precambrian and Paleozoic rocks or was covered by siliciclastic sediments. This

6.3 Post-Uplift Diagenesis Fig. 6.7 NW Bend Formation a Cliff section, 6 m high, Murray Basin, with limestones (L) below and above an intermediate unit of dolomitized carbonate, (D) cliff 6 m high; b Close view of dolomitized oysters, cm scale; c Thin section, ppl, of clear dolomite crystals from outcrop in B

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a

L D L

b

c

situation changed dramatically with late Miocene-Pliocene uplift that exposed the older, shelf carbonates to meteoric weathering. There are two types of karst; (1) Telogenetic Karst or hardrock karst, or paleokarst, consisting of those features developed in rocks after deposition and burial, and (2) Syngenetic Karst or softrock karst which forms at roughly the same time as the sediments are being consolidated and cemented in the meteoric diagenetic environment (Jennings 1968; Grimes 2006).

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LOWSTAND & TRANSGRESSION

1 Sealevel

Migrating Mixing Zone

DOLOMITE NUCLEATION in MIGRATING MIXING ZONE

stochiometric, Mn-rich cores + nonstochiometric Mn & Fe zoned small crystals

2 HIGHSTAND

DOLOMITE GROWTH in INTERSTITIAL SEAWATER

nonstochiometric dolomite with low Mn, Fe & Marine Sr, C, O isotopes

REGRESSION & EXPOSURE DEDOLOMITIZATION metastable cores & parts of cortex are leached -some filled with LMC cement

Sealevel

3 Sealevel

Fig. 6.8 A sketch illustrating the interpreted formation and evolution of shallow burial dolomites in southern Australia that involved, (1) nucleation, (2) growth from seawater, and (3) meteoric alteration (modified from Kyser et al. 2002)

6.3.2 Telogenetic Karst 6.3.2.1

Eucla Basin

Middle Miocene limestones form most of the vast Nullarbor Plain surface (Figs. 6.9, 6.10), perhaps the largest areal karst on the globe (Jennings 1962). Overall, the Plain records ~ 14 my of subaerial exposure. The resultant karst is both surface and subsurface (Figs. 6.10, 6.11), with much of the exposed limestone also extensively altered by pedogenesis (see below). The Plain today is a gentle undulating deflation surface with karst features, such as uvalas, dolines, sinkholes, potholes and karren (surface

6.3 Post-Uplift Diagenesis

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8 6

7

1-3 NULLARBOR LIMESTONE

5 4

(50 -100 m)

Highest Paleo-water table 3m

MID-LATE MIOCENE 1. Fabric Selective Diagenesis 2. Microkarst 3. Post Karst Sedimentation

PLIOCENE 5. Shallow Caves & Precipitates 6. Subsoil Hollows

LATE MIOCENE 4. Deep Caves (below Nullarbor Lst.)

PLEISTOCENE 7. Dolines & Colluvium 8. Accretionary Calcrete

Fig. 6.9 Diagram summarizing the geohistory of karst development in the Eucla Basin (modified from Miller et al. 2012)

dissolution features) (Fig. 6.10). The exposed limestone, calcrete, or calcareous clay is locally vegetated by low bluebush and saltbush shrubs. The subsurface Nullarbor cave system is widespread and complex and has been extensively studied (Lowry 1970; Miller et al. 2012). Although there are caves in the northern part of the Plain, the majority are located within ~ 25 km of the coast. Most are subsurface passages, mazes, chambers, and lakes whose history can be resolved into several regional phases of alteration (Miller et al. 2012) (Fig. 6.9). Phases 1-3—Mid-Late Miocene: Exposure under a humid climate, mineralogical equilibration with minor fresh waters, cementation, extensive moldic porosity and subsequent widespread microkarst. Phase 4—late Miocene—early Pliocene:—A long period of alteration (~ 8m.y.) under a temperate to humid climate. Deep cave development (Fig. 6.11) coincided with the late Miocene sea-level lowstands and depressed water tables. A second shallow cave system formed during a short midPliocene sealevel highstand, humid climate, high water table, phreatic dissolution, and enlargement of deep caves. Phases 5-8—Pliocene—Pleistocene: Formation of stem drainage subsoil hollows, numerous collapse dolines followed by accretionary calcrete as the climate became increasingly arid (SA4.2) (Figs. 6.12, 6.13).

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Fig. 6.10 Surface karst. a Nullarbor Plain, the vast flat karst surface here truncated by seacliff erosoion, roads for scale; b Sinkhole and entrance to Koonalda Cave on Nullarbor Plain, automobile scale at right; c Areal view of sinkhole ~ 70 m across; d Ground view of Knoll Cave entrance, trucks for scale at left; e Sinkhole partially filled with water developed in Gambier Limestone near Mt. Gambier, SA; people scale; f Tarragal Caves, Cape Bridgewater, Victoria, cave entrance ~6 m high

There is, however, somewhat of a conundrum because, in spite of the numerous caves, there are few speleothems. The dearth of such features has been ascribed to the onset of aridity and a semi-arid climate (Dunkley and Wigley 1967; Lowry and Jennings 1974; Webb and James 2006). This explanation has to some extent been confirmed by recent dating of the speleothems in shallow caves. The geochronology reveals that most speleothems are comparatively old with growth between 5.0 and 3.0 Ma., and the main phase of precipitation during the early Pliocene (Woodhead et al. 2019). This corresponds to the warm and wet climatic period in southern Australia

6.3 Post-Uplift Diagenesis

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a

b

c

d

e

f

Fig. 6.11 Nullarbor Caves, courtesy Cave Exploration Group, South Australia; a Small sinkhole entrance ~ 15 m diameter, to Capstan Cave, Nullarbor Plain; b Abrakurrie Cave in Nullabor Limestone, person scale (circled), c Abrakurrie Cave, in Abrakurrie Limestone, persons scale (circled); d Massive speleothem developement in Sentinal Cave, person scale (circled); e Water table lake in Weebubbie Cave, image foreground 20 m across; f Divers in narrow passage, Pannikin Cave

and there has been little speleothem formation under the semi-arid climate since ~ 2.5 Ma. Alternatively, the cave systems must have been closed and deep, associated with the profoundly depressed water table. The low surface gradient that probably prevented much surface erosion also focused karst development underground (Webb and James 2006; Frisia and Borsato 2010).

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a

b

c

d

e

f

Fig. 6.12 Karst fills a Phase 3 coated grains and ooids filling dissolution voids in Nullarbor Limestone, Cook Quarry; cm scale; b Laminated Phase 5 cave precipitates in large Nullarbor Limestone voids, Watson Quarry cm scale; c Nullarbor Limestone with numerous gastropod molds, and dissolution voids filled with red clay; cm scale; d Dissolution voids in Nullarbor Limestone at Cook Quarry filled with phase 7 red clay and cave precipitates, cm scale, e Phase 7 red colluvium with white Nullarbor Limestone and black limestone clasts, cm scale, Watson Quarry; f Phase 7 blackened clasts in a mixed clay-carbonate matrix, cm scale Watson Quarry

6.3.2.2

Otway Basin

Karst is most extensively developed in the Gambier Embayment both in the SE part of South Australia and sporadically near the coast in Victoria west of the Otway Ranges (Fig. 6.10). The region has a more humid to sub-humid, seasonally wet climate compared to the Eucla Basin. Dissolution features are best developed on the Gambier limestone (Fig. 6.13) and most pronounced near Mt. Gambier. They

6.3 Post-Uplift Diagenesis

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a

b

c

d

e

f

Fig. 6.13 Surface karst. a Sharp surface karst on Gambier limestone; Y. Bone scale, Mt. Gambier SA; b Rounded surface karst developed on Pleistocene Bridgewater aeolianites under soil cover (10 cm scale increments). Robe S.A.; c Deep surface karst solution pipes developed on >450 ky old Pleistocene Bridgewater Fm. aeolianites and filled with terra rossa clay (red) and volcanic ash (grey) in Comaum Quarry, S.A., cliffs~10 m high; d Surface fracturing, dissolution, and phase 7 red clay colluvium infill on Nullarbor Limestone, outcrop 10 m high, Watson Quarry; e Melton Limestone, Yorke Peninsula, an outcrop where roughly 50% of the limestone has been dissolved and vuggy porosity filled with red clay; cliff ~6 m high; f Marte Quarry in Gambier Limestone with numerous surface dissolution pipes filled with brown clay and overlain by Holocene volcanic ash (black), quarry wall ~ 15 m high

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include pavements, uvalas, large cenotes (dolines) and joint-controlled cave systems (Murray-Wallace 2018). Solution pipes, locally filled with terra rossa, are common in the Gambier and Bridgewater limestones (Fig. 6.13), and in the latter case increase in size landward across the coastal plain. The caves, especially at Tantanoola, are rich in marsupial and bird fossils (> 15-18 ka). Speleothem growth in the caves took place over the last 400 ky, mostly during interglacials or interstadials.

6.3.3 Syngenetic Karst Pleistocene aeolianites virtually everywhere in the region exhibit exokarst (karren) with local neasurface caves (Fig. 6.13). This is particularly the case on western Eyre Peninsula (dry sinkholes, karren on calcrete surfaces, clints and grikes, potholes), southern Yorke Peninsula (minor karst, grikes and karren), southern Kangaroo Island (eroded sea caves) and Mt. Gambier coastal Plain (clay pots, karst pavements). Karst is not as extensive in the St. Vincent and Murray basins. The chronology of such karst is best displayed on the Gambier coastal plain where the series of prograding aeolianites developed over the last 900 ky (Murray-Wallace 2018).

6.3.4 Meteoric—Microscale Alteration In contrast to the absence of meteoric cementation in earlier SA2 and SA3 deposits, largely because of the lack of aragonite, SA4 aeolianites (Fig. 6.5) are progressively more lithified with increasing age (Reeckmann and Gill 1981; James et al. 2018). This is because beach-dune sediments are mainly derived from the shallow < 30 meters deep adjacent seafloor. They are mollusk-rich but with most bryozoan particles having been destroyed in the surf zone. The mollusks are dominantly aragonite. These nearshore sediments are swept onshore before any significant seafloor diagenesis can take place and so are compositionally different from the aragonite-poor openshelf sediments. Aragonite skeletal fragments in the dunes progressively dissolve with time under a semi-arid climate and produce diagenetic low-magnesium calcite meteoric cements, a well-known process common in tropical, aragonitic Pleistocene aeolianites (Bathurst 1975). Such alteration in this environment, however, seems to take longer than in tropical carbonates, with lithification herein not beginning until ~ 200 ka and complete cementation being achieved in ~ 450 Ky.

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135

6.3.5 Meteoric—Calcretes and Paleosols Pedogenic calcrete is a characteristic feature of meteoric diagenesis (Esteban and Klappa 1983; Wright and Tucker 1991; James 1997; Alonso-Zarza 2003; James and Jones 2016) but is dependent upon climate, specifically cool, rainy winters, and hot dry summers wherein there is a substantial moisture deficit. Such a climate is often referred to as ‘Mediterranean’ and calcrete is prevalent on rocks there as well as in the SW USA. Southern Australia has such a climate and calcrete (Fig. 6.14) is developed on many different lithologies from crystalline rocks to clays, to carbonates. They form via complex interactions between roots, physical processes, evaporation, and micro-organisms (Wright et al. 1988; Wright and Tucker 1991; Mack and James 1992; Wright 1994; Verrecchia et al. 1995; Alonso-Zarza et al. 1998; Zhou and Chafetz 2009). Such calcareous soils have a recurring set of features that include hard calcareous sheets, calcified roots (rhizoliths) (Fig. 6.15), soil ooids, and pisoids (called glaebules) (Fig. 6.16), blackened clasts, and calcified filaments. The texture ranges from laminar to massive to nodular. They are partly degradational and partly accretionary such that a profile usually passes down from the surface calcrete to a basal zone of altered

Fig. 6.14 Calcretes a Seacliff exposure of Pleistocene aeolinaite ~8 m high with well-lithified calcrete cap at top and poorly lithified calcarenite below, Cape Dombey Victoria; b Pleistocene 5 m high aeolianite exposure with several calcretes (at arrows) between aeolianite; c Multigeneration calcrete developed in aeolianite section 1.5 m thick; Cable Bay, S.A.; d Laminar calcite at the top of aeolianites, Marion Bay, S.A., image 5 cm wide

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Fig. 6.15 Rhizoliths and roots. a Numerous rhizoliths in Pleistocene aeolianite, Cape Spencer; cm scale; b Laminar calcrete developed around a tree root that has now vanished, pen scale 12 cm long

a

b

c

d

Fig. 6.16 Nodular calcrete along River Murray bank. a Hard laminar calcrete, with extensive nodular calcrete below, outcrop 4 m high; b Close view of nodular calcrete, cm scale; c Nodular calcrete where nodules have been broken to reveal laminar character, cm scale. d Broken nodules to reveal blackened calcrete core, Cape Spencer image width 8 cm

bedrock and eventually into bedrock. Each area has a slightly different profile that is climate and parent lithology dependent. Carbonate in the calcrete can be derived from the underlying lithology, from air-borne dust or from sea spray (James 1972; Warren 1983). Calcretes across southern Australia are mostly a product of the mid-

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137

and late Pleistocene and Holocene climate and are developed on both exposed preuplift limestones (telogenetic calcretes) and post-uplift mostly aeolianites (eogenetic calcretes) soon after formation.

6.3.6 Telogenetic Calcretes The most extensive such calcareous soils occur on the Nullarbor Plain where they are developed in the top of the middle Miocene Nullarbor Limestone (Lowry 1970). The calcrete profile can be up to 7 m in thickness where it is fully preserved to non-existent where it has been removed by erosion. The lower part usually consists of elongate plates of Nullarbor Limestone coated by several generations of thin laminated micrite. The platy nature of the profile grades into a more nodular fabric up section where there is little to no parent material preserved. This upper part is well-lithified calcrete pisoids (Fig. 6.16) with micrite laminations in a dense micrite matrix. Pisoids or glaebules can be cemented into boulder-size clasts (20–50 cm) with a marked decrease in such lithification upwards wherein large boulders gradually becoming smaller and finally gravel size at the top of the section. The very top of the profile is characterized by individual calcrete pisoids and loose, fine-grained colluvium.

6.3.7 Eogenetic Calcretes The Pleistocene aeolianites as stressed above, are either stacked or progradational. The calcretes formed during glacial lowstands when the source of marine carbonate was removed from the nearshore source and the calcareous soil developed. The paleosols range from classic calcretes (Fig. 6.14) to a mixture of calcrete and terra rossa. The latter soils are soft and argillaceous (illite) with conspicuous rhizoliths and black pebbles commonly with a laminar calcrete cap. Soils are mostly terra rossas on Bridgewater Formation sediments (especially Woakwine ranges - MIS 5e), and redzinas on the lagoonal and estuarine deposits between ridges and podzols on the tops of ranges (Murray-Wallace 2018). Australia’s premier wine-growing region in the southeast is situated on such terra rossa soils. Calcretes appear to have extensively developed since the LGM and are especially prominent in the northern part of the Coorong Coastal Plain. The prograding calcretes contain micrite envelopes, rhizoconcretions (Fig. 6.15), nodules (Fig. 6.16), blackened clasts zones of fractured sediment and intraclast breccias. On the mesoscale, many contain intraclast horizons that show ‘clast-within-clast’ fabrics, and some of the clasts have an unusual stellate form.

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6.4 Summary The Cenozoic succession in southern Australia can be likened to a natural laboratory for the study of temperate carbonate diagenesis. The well-dated rocks superbly illustrate the suite of now well-documented alteration processes that take place in all coolwater systems, many of which were discovered here. The well-known complexity of diagenesis is a function of the suite of original mineralogies and the changes that take pace in a series of eogenetic, mesogenetic, and telogenetic environments (cf. Choquette and Pray 1970; James and Choquette 1990; Tucker and Wright 1990). The question is what processes were there here that set these rocks apart from those in the wider photozoan realm?

6.4.1 Synsedimentary Seafloor diagenetic processes are, as noted above, somewhat puzzling because results seem to be contradictory. On the one hand, synsedimentary cement precipitation was present in the form of hardgrounds, on the other hand there is clear evidence of seafloor aragonite dissolution. Such dissolution is not confined to heterozoan systems but is also documented in photozoan systems (Burton and Walter 1987; Walter and Burton 1990; Patterson and Walter 1994; Ku et al. 1999) in tropical carbonate sediments from Florida and the Bahamas, where seawater is oversaturated with respect to aragonite yet pore waters are saturated or undersaturated, approximately 50% of the sediment has undergone dissolution. Hardgrounds throughout the Cenozoic succession speak to cementation on the seafloor, likely largely driven by microbial chemical interactions (Nelson and James 2000). This process could also be related to vertical seawater movement. Carbonaterich waters capable of cementation, for example, characterize upwelling periods and regions. By contrast, downwelling times are typified by carbonate-depleted waters likely incapable of such processes (James et al. 2001; Middleton et al. 2014), but possible mineral-specific dissolution. This system, apparently not present or yet to be recognized in photozoan carbonates, illustrates the clear linkage between synsedimentary seafloor diagenesis and subsequent meteoric alteration. The Cenozoic carbonates also clearly demonstrate the effects of phosphatization during upwelling. The processes are clearly diagenetic because both preexisting carbonates and siliciclastic particles are incorporated into the newly formed phosphate layers and nodules.

6.4 Summary

139

6.4.2 Meteoric 6.4.2.1

Mineralogy

The presence of, or more important the lack of, aragonite in the original sediment particle milieu was critical in the subsequent diagenesis of these Cenozoic carbonates. Simply put, no aragonite, no cementation in the meteoric diagenetic realm (Reekman 1988; James and Bone 1989). This is beautifully illustrated throughout by the lack of such meteoric diagenesis in most deposits wherein most aragonite was dissolved on the seafloor before the sediments were flushed with fresh water. The importance of aragonite is dramatically highlighted in the modern nearshore zone where the presence of innumerable aragonitic mollusk particles thrown up into the dunes results in subsequent quick and extensive meteoric lithification of the aeolianites. This is so unlike their offshore cousins without aragonite that can remain uncemented for millions of years (James and Bone 1989; James and Jones 2016). Otherwise, as stressed above, most of the Cenozoic carbonates are soft and uncemented, except for those few that were deeply buried before pre-Pliocene uplift. The processes discovered here help explain why so many Phanerozoic carbonates formed in ‘calcite seas’ exhibit extensive burial but little meteoric alteration (Bathurst 1975; James et al. 2020).

6.4.2.2

Climate & Karst

The importance of climate was paramount! Eocene through Miocene humid climates and attendant forests promoted the formation of numerous silcrete and laterite (ferricrete) horizons (Benbow et al. 1995). Semi-arid climates of the later Pleistocene resulted instead in extensive and intense calcareous soil (calcrete) formation on and in Miocene through Pleistocene limestones, The distribution of karst is baffling. Although surface and subsurface forms are common in Miocene and later carbonates their absence, or only local development, in Eocene and Oligocene rocks is puzzling, especially with clear evidence of humid climates in older periods. It could be a problem of exposure time, type of soil, or water table disposition?

6.4.2.3

Dolomite

Dolomites, other than the Holocene synsedimentary Coorong dolomites, although present, are comparatively rare in the thick Cenozoic succession. Some of the minor dolomites have been attributed to mixed marine and freshwater chemical interactions, but if correct such situations should also have been present at numerous times in the past?

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References Alexandersson ET (1978) Destructive diagenesis of carbonate sediments in the eastern Skagerrak, North Sea. Geo 6:324–327 Alexandersson ET (1979) Marine maceration of skeletal carbonates in the Skagerrak, North Sea. Sedimentol 26:845–852 Alonso-Zarza A, Esther Sanz M, Calvo JP, Estevez P (1998) Calcified root cells in Miocene pedogenic carbonates of the Madrid Basin; evidence for the origin of Microcodium b. Sed Geol 116:81–97 Alonso-Zarza AM (2003) Palaeoenvironmental significance of palustrine carbonates and calcretes in the geological record. Earth Sci Rev 60:261–298 Bathurst RGC (1975) Carbonate sediments and their diagenesis, Developments in Sedimentology. Elsevier Science, Amsterdam, pp. 658 Benbow MC, Lindsay JM, Alley NF (1995) Eucla Basin and palaeodrainage. In: Drexel JF, Preiss VP (eds) The Geology of South Australia, vol 2 The Phanerozoic. Geological Survey of South Australia Bulletin, pp. 178–186 Bone Y, James NP, Kyser TK (1992) Synsedimentary detrital dolomite in quaternary cool-water carbonate sediments, Lacepede shelf, South Australia. Geol 20:109–112 Burton EA, Walter LM (1987) Relative precipitation rates of aragonite and Mg calcite from seawater: temperature or carbonate ion control? Geol 15: 111–114 Choquette PW, Pray LC (1970) Geologic nomenclature and classification of porosity in sedimentary carbonates. Am Asso Petrol Geol Bull 54:207–250 Dunkley JR, Wigley TML (1967) Caves of the Nullarbor; a review of speleological investigations in the Nullarbor plain, southern Australia. Speleological Research Council, Sydney, Australia Esteban M, Klappa CF (1983) Subaerial exposure environment. In: Scholle PA, Bebout DG, Moore CH (eds) Carbonate depositional environments. American Association of Petroleum Geologists Memoir 33, Tulsa, OK, pp. 1–54 Freiwald A (1995) Bacteria-induced carbonate degradation; a taphonomic case study of Cibicides lobatulus from a high-boreal carbonate setting. Palaios 10:337–346 Frisia S, Borsato A (2010) Karst. In: Alonso-Zarza A, Tanner LH (eds) Carbonates in continental settings: facies, environments and processes: developments in Sedimentology. Elsevier, Oxford, pp 269–318 Golubic S, Perkins RD, Lukas KJ (1975) Boring microorganisms and microborings in carbonate substrates. In: Frey RW (ed) The study of trace fossils. Springer-Verlag, New York, pp 229–259 Grimes KG (2006) Syngenetic karst in Australia: a review. Helectite 39:27–38 James NP (1972) Holocene and Pleistocene calcareous crust (caliche) profiles: criteria for subaerial exposure. J Sediment Petrol 42:817–836 James NP (1997) The cool-water carbonate depositional realm. In: James NP, Clarke MJ (eds) Cool-water carbonates. SEPM Special Publication, pp. 1–20 James NP, Bone Y (1989) Petrogenesis of Cenozoic, temperate water calcarenites, South Australia: a model for meteoric/shallow burial diagenesis of shallow water calcite sediments. J Sediment Petrol 59:191–203 James NP, Bone Y (1991) Sediment dynamics of an Oligo-Miocene cool water shelf limestone, Eucla Platform, southern Australia. Sedimentol 38:323–342 James NP, Bone Y (1992) Synsedimentary cemented calcarenite layers in Oligo-Miocene cool-water shelf limestones, Eucla Platform, southern Australia. J Sediment Petrol 62:860–872 James NP, Bone Y (2011) Neritic carbonate sediments in a temperate realm, Southern Australia. Springer, Dordrecht Heidelberg London New York, p 254 James NP, Bone Y, Collins LB, Kyser TK (2001) Surficial sediments of the Great Australian Bight; facies dynamics and oceanography on a vast cool-water carbonate shelf. J Sediment Res 71:549–567

References

141

James NP, Bone Y, Joury M, Malcolm I, Kyser TK (2018) Diagenesis and compositional partitioning of quaternary cool-water carbonate aeolianites, Southeastern Australia. J Sediment Res 88:431– 448 James NP, Bone Y, Kyser TK (1991) Shallow burial dolomitization of mid-Cenozoic, cool-water, calcitic, deep-shelf limestones, southern Australia. AAPG Bull 75:602 James NP, Bone Y, Kyser TK (2005) Where has all the aragonite gone? Mineralogy of Holocene neritic cool-water carbonates, Southern Australia. J Sediment Res 75:454–463 James NP, Choquette PW (1990) Limestone—the meteoric diagenetic environment. In: McIlreath I, Morrow D (eds, Diagenesis. Geological Association of Canada Reprint Series 4, St. John’s, ND, Canada, pp. 35–74 James NP, Jones B (2016) Origin of carbonate sedimentary rocks. Wiley, Chicester, UK, p 446 James NP, Narbonne GM, Armstrong AKR (2020) Aragonite depositional facies in a Late Ordovician Calcite Sea, Eastern Laurentia. Sedimentol 67. doi.org/10.1111/sed.12753 Jennings JN (1962) The limestone geomorphology of the Nullarbor Plains (Australia). In: International Congress of Speleology. Bari. pp. 371–386 Jennings (1968) Syngenetic Karst in Australi. In: Williams PW, Jennins (eds) Contributions to the study of karst; Australian National University, Research School of Pacific Studies. Department of Geography, Publication G/5 Ku TCW, Walter LM, Coleman ML, Blake RE, Martini AM (1999) Coupling between sulfur recycling and syndepositional carbonate dissolution; evidence from oxygen and sulfur isotope composition of pore water sulfate, South Florida Platform, USA. Geochim Cosmochim Acta 63:2529–2546 Kyser TK, James NP, Bone Y (1998) Alteration of Cenozoic cool-water carbonates to low-Mg calcite in marine waters; Gambier Embayment, southern Australia. J Sediment Res 68:947–955 Kyser TK, James NP, Bone Y (2002) Shallow burial dolomitization and dedolomitization of Cenozoic cool-water limestones, southern Australia; geochemistry and origin. J Sediment Res 72:146–157 Lowry DC (1970) Geology of the Western Australian part of the Eucla Basin. Geol Surv W Aus Bull 122:201 Lowry DC, Jennings JN (1974) The Nullarbor karst Australia. Z fuer Geomorphol 18:35–81 Mack GH, James WC (1992) Calcic Paleosols of the Plio-Pleistocene camp rice and Palomas formations, Southern Rio Grande Rift, USA. Sed Geol 77:89–109 Middleton JF, James NP, James C, Bone Y (2014) Cross-shelf seawater exchange controls the distribution of temperature, salinity, and neritic carbonate sediments in the Great Australian Bight. J Geophys Rese Ocean 119. doi:https://doi.org/10.1002/2013JC009420 Miller CR, James NP, Bone Y (2012) Prolonged carbonate diagenesis under an evolving late cenozoic climate; Nullarbor Plain, southern Australia. Sed Geol 261–262:33–49 Murray-Wallace CV (2018) Quaternary history of the Coorong Coastal Plain, Southern Australia. Springer International Publishing, Cham, Switzerland, p 229 Nelson CS, James NP (2000) Marine cements in mid-tertiary cool-water shelf limestones of New Zealand and Southern Australia. Sedimentol 47:609–629 Nicolaides S, Wallace MW (1997) Pressure dissolution and cementation in an Oligio-Miocene nontropical limestone (Clifton Formation), Otway Basin, Australia. In: James NP, Clarke JDA (eds) Cool-water carbonates. SEPM, pp. 249–262 Patterson WP, Walter LM (1994) Depletion of 13C in seawater  C02 on modern carbonate platforms: significance for the carbon isotopic record of carbonates. Geolo 22:885–888 Reeckmann SA, Gill ED (1981) Rates of vadose diagenesis in quaternary dune and shallow marine calcarenites, Warnambool, Victoria, Australia. Sed Geol 30:157–172 Reekman S (1988) Diagenetic alterations in temperate shelf carbonates from southeastern Australia. Sed Geol 60:209–219 Rivers JM, James NP, Kyser TK (2008) Early diagenesis of carbonates on a cool-water carbonate shelf, Southern Australia. J Sediment Res 78:784–802

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Smith AM, Nelson, CS (2003) Effects of early sea-floor processes on the taphonomy of temperate shelf skeletal carbonate deposits. Earth-Sci Rev 63: 1–31 Tucker ME, Wright VP (1990) Carbonate sedimentology. Blackwell Scientific Publications, Oxford, p 482 Verrecchia EP, Freytet P, Verrecchia KE, Dumont J-L (1995) Spherulites in calcrete laminar crusts; biogenic CaCO3 precipitation as a major contributor to crust formation. J Sediment Res, Sect A: Sediment Petrol Process 65:690–700 Walter LM, Burton EA (1990) Dissolution of recent platform carbonate sediments in marine pore fluids. Am J Sci 290:601–643 Warren JK (1983) Pedogenic calcrete as it occurs in quaternary calcareous dunes in Coastal South Australia. J Sediment Petrol 53:787–796 Webb JA, James JM (2006) Karst evolution of the Nullarbor Plain, Australia. In: Harmon RS, Wicks CM (eds) Perspectives on Karst Geomorphology, Hydrology, and Geochemistry—a tribute volume to Derek C Ford and William B. White. Geological Society of America, Boulder, Colorado, pp 65–78 Woodhead JD, Sniderman JM, Hellstrom J, Drysdale RN, Maaas R, White N, White S, Devine P (2019) The antiquity of Nullarbor speleothems and implications for karst paleoclimate archives. Sci Rep 9:603–611 Wright VP (1994) Paleosols in shallow marine carbonate sequences. Earth Sci Rev 35:367–395 Wright VP, Platt NH, Wimbledon WA (1988) Biogenic laminar calcretes: evidence of calcified root-mat horizons in paleosols. Sedimentol 35:603–620 Wright VP, Tucker ME (eds) (1991) Calcretes. International Association of Sedimentologists, Reprint Series Vol 2. Blackwell Scientific Publications, pp 352 Zhou J, Chafetz HS (2009) Biogenic caliches in Texas; the role of organisms and effect of climate. Sed Geol 222:207–225

Part III

Analysis

Chapter 7

Integration and Interpretation

Abstract The Cenozoic successions are integrated and analyzed here with respect to the dominant controlling factors present during deposition, namely tectonics, oceanography, climate, and influence of Antarctica. Middle Eocene–early Oligocene SA2 biogenic shelf sediments accumulated during a time of at first warm, but then gradually cooling ocean waters under a relative quiescent tectonic regimen. The climate was mostly humid subtropical with extensive temperate rainforests and fluvial activity that gradually waned in the post-Eocene. It is interpreted that the prolific nutrient elements delivered from land during the Eocene promoted extensive neritic biosiliceous deposition. The Oligocene -Miocene SA3 carbonate shelf was similar to that of today under a progressively warming climate and ocean waters such that in the mid-Miocene sedimentation was nearly photozoan. The comparatively quiet AAG had evolved into the Southern Ocean by the Oligocene resulting in a much more active hydrodynamic marine system. Antarctica had become ice covered and glacioeustacy promoted extensive m-scale carbonate cyclicity. The Plio-Pleistocene SA4 shaved shelf developed because of active tectonism that is continuing today and resulted in a different sedimentary system dominated by marginal marine and slope carbonate deposition. Keywords Controlling factors · Passive margin · Tectonic uplift · Carbonate · Trophic resources · Southern ocean

7.1 Introduction As emphasized throughout, interpreted deposition of these Cenozoic rocks is largely actualistic and their attributes can be framed by a series of well-understood local controls. Their cousins are accumulating offshore today; one can stand on a bryozoanrich limestone outcrop and look to sea knowing that similar sediments are accumulating on the ocean floor in front of you. This aspect not only demands that the deposits be interpreted in a rigorous fashion but also permits new analysis of puzzling aspects that have recurred throughout much of geological history. These latter problems are discussed in the following chapters, but this section concentrates on specific aspects of the sedimentology. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 N. P. James and Y. Bone, Biogenic Sedimentary Rocks in a Cold, Cenozoic Ocean, https://doi.org/10.1007/978-3-030-63982-2_7

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Our philosophy, that combined intrinsic and extrinsic factors govern sedimentation (Fig. 2.1), has resulted in the synthesis of sedimentary rock descriptions and interpretations against these factors. Although such influences have changed through time, our interpretations utilize as much as possible the modern offshore depositional system as an actualistic template (James and Bone 2011b). The main intrinsic influences were geomorphology, climate, tectonics, oceanography (illumination, temperature, hydrodynamics, oxygenation, salinity) and nutrient resources. Today the southern Australian shelf is mostly zonal (latitude-parallel) and has undergone recent uplift. Whereas the climate is largely Mediterranean, the ocean is cold, stormy, and extremely energetic. Trophic resource levels are moderate throughout. The most important extrinsic influence was by far glacioeustasy as determined largely by the vicissitudes of Antarctic glaciation. These various controls, by acting in concert, produced a suite of diverse biogenic deposits against the background of an unfriendly, cold ocean. These controls are enumerated under the headings of tectonics, oceanography, climate, and Antarctic glaciation. Each of the three successions is analyzed against the controls in play when they accumulated.

7.2 SA2—Mid-Eocene to Early Oligocene—‘The Biogenic Shelf’ 7.2.1 Tectonics Australia-Antarctica separation began in the Middle Eocene when spreading rates increased abruptly to ~ 45 mm year −1 and the spreading direction changed from NW-SE to N-S (Veevers 2000). This west-to-east, scissors-like opening resulted in a gradually widening, elongate marine embayment, the Australia-Antarctica Gulf (AAG, Exon et al. 2004), open in the west and closed in the east (Fig. 1.3). Ultimate continental disconnection was protracted, with final detachment of Tasmania from Antarctica at the end of the early Oligocene (~ 28.5 Ma.). Otherwise southern Australia was relatively quiescent.

7.2.2 Oceanography Equitable warm-temperatures in the Eocene were characterized by prolonged sluggish global circulation with pronounced stratification, halohaline circulation, and oxygen-poor deep waters. The Tasman Gateway is reasoned to have first opened the Middle Eocene (47–38 Ma.) with shallow water flow across a partially submerged isthmus (Bijl et al. 2013). Recent studies and modeling suggest that cold-water flow was initially from the east to the west, largely driven by weak Polar Easterlies (Huber

7.2 SA2—Mid-Eocene to Early Oligocene—’The Biogenic Shelf’

147

et al. 2004; Huber 2006; Sijp et al. 2011). By contrast, the presence of large benthic foraminifers in Eocene strata in southern Australia suggest the incursion of warm, Proto-Leeuwin Current surface waters from the Indian Ocean (McGowran et al., 1997) into the Australia-Antarctica Gulf. Surface winds over the ocean, were mostly westerly (Benbow 1990; Hou et al. 2008) and as such should have induced mostly downwelling along the southern margin with seasonal upwelling, much like today (Kämpf et al. 2004; McClatchie et al. 2006; Middleton and Bye 2007; van Ruth et al. 2018; Richardson et al. 2019). Continued opening of the Tasman Gateway in the late Eocene is thought to have deepened the strait with accompanying strong water flow, but now from the west. The deep Tasman gateway was fully open by the Eocene/Oligocene boundary (Sijp et al., 2011; Scher et al. 2015). Global sea level was relatively high (150–200 m above present) during the late Eocene except for a short fall to ~ 125 m in the latest Eocene (Fig. 7.1). Sea surface temperatures at the Terminal Eocene Event (TEE) were estimated to have been ~ 7°C (McGowran et al. 1997; Bohaty and Zachos 2003). Sea ice formation off Antarctica in the latest Eocene further injected cold, oxygen-rich surface waters into the deep ocean thus resulting in pronounced invigorated vertical circulation, and generation of the modern ocean thermohaline circulation.

Fig. 7.1 Depositional succession SA2 placed against global sea level, general sediment composition and major events (modified from Quilty 1977; and McGowran et al. 2004)

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7.2.3 Climate and Vegetation The overall Eocene setting was one of a subdued, low relief landscape with extensive erosion under a humid climate. Marshes, bogs, and sluggish rivers were the norm. Extensive beaches and dunes of the Ooldea Range along the northern margin of the Eucla Basin were formed by persistent winds from the west-northwest (Benbow 1990; Hou et al. 2008) (Fig. 3.4). Land was covered by a widespread temperate rainforest with no modern analog, containing abundant Nothophagus (southern beech conifer), a frost-intolerant tree indicative of high rainfall. The diverse flora, including palm trees, was typical of a mesothermal to megathermal rainforest. Temperatures are thought to have ranged from an average of ~ 21°C in the north to ~ 18°C in the south. There was a gradual change in the latest Eocene to a cool-temperate subtropical forest with sclerophylls, broad-leafed angiosperms, together with Nothofagus (White 1994; Benbow et al. 1995a). Whereas the early Eocene was a period of deep weathering and formation of ferricretes under comparatively high temperatures and rainfall, the late Eocene, was a time of silcrete formation under interpreted cooler and somewhat more arid conditions (Benbow et al. 1995b; Taylor and Eggleton 2017). Non-seasonal, peri-humid conditions prevailed in the subsequent early Oligocene but with a flora that preferred cooler climates and one that could tolerate some seasonal dryness (White 1994; Benbow et al. 1995a).

7.2.4 Antarctic Glaciation Deciduous, temperate forests covered pre-glacial Antarctica in the early Eocene but began to disappear thereafter. Actual glaciation began at ~ 37–34 Ma. (late Eocene) with local mountain glaciers expanding into a major east Antarctica ice sheet with adjacent sea ice by ~ 35 Ma (latest Eocene) (Pagani et al. 2011). Francis et al. (2008) have succinctly reviewed recent thinking about Paleogene Antarctic glaciation. The Eocene-Oligocene boundary with increased sea ice development caused a drop in deep ocean water temperature of ~ 5–6°C coincident with opening of the Tasman Gateway and full flow of the Circum-Antarctic Current. At ~ 32.8 Ma (early Oligocene) there was a continental ice sheet with shoreline calving and by ~ 33.8 Ma the ice sheet had peaked (DeConto and Pollard 2003). The largest episode of pre-Miocene glaciation occurred at ~ 30 Ma at the end of the Early Oligocene and resulted in a large global sea level fall and numerous unconformities worldwide (Hill and Exon 2004).

7.2 SA2—Mid-Eocene to Early Oligocene—’The Biogenic Shelf’

149

7.2.5 Stratigraphic Sedimentology The neritic facies in southern Australia (Fig. 7.2) changed from diverse lithologies deposited in a warm, generally poorly ventilated ocean with numerous greensands, opaline silicas, and organic-rich marls, containing a high infauna to calcareous sediments with an active epifauna that accumulated in a cool ocean with vigorous circulation. This change that took place at the Eocene-Oligocene boundary (SA2.3–SA2.4) is termed the ‘Auversian Faces Shift’ (Berger and Wefer 1996; McGowran 2009). Carbonate deposition began first in the west, in the Eucla Basin (Middle Eocene), then with time spread into the St. Vincent Basin (late Eocene) and finally into parts of the Otway Basin (Early Oligocene). At any given time, deposits passed from biogenic in the west into siliciclastic sediments in the east. Formation names in the following sections are in regular font with member names in italics.

Terrestrial

Marginal Marine

Port Julia

SA2.4

Chinaman Gully

Inner Neritic

Mid Neritic

Upper Ooldea

Slope

Glen Aire Gambier (Greenways)

Port Vincent Rogue Upper Kingscote Aldinga

SE2.3

Outer Neritic

Throoka Lower Kingscote Kasta Princess Royal Fitzgerald

ODP

Ruarung Castle Cove Narrawaturk Brown’s Creek

ODP

Blanche Point Wilson Bluff

Pallinup

SA2.2

SA 2.1

South Maslins Lower Ooldea Clinton Werrilup Paling Maralinga North Maslins

Mulloowurtie Tortachilla

Wilson Bluff

ODP

Wilson Bluff

ODP

Norseman

Hampton

AUSTRALIA -ANTARCTICA GULF Runoff Forests Coal Swamps

Sea Level Inner

Mid

Outer ~ 200 mwd Slope

Fig. 7.2 Sketch summarizing facies interpretation for all neritic deposits in Succession SA2. Formations are in regular font, members in italics

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7.2.5.1

7 Integration and Interpretation

SA2.1 Middle Eocene (8 My.)

This largely buried carbonate succession (Hampton, Wilson Bluff) is composed of outboard warm-water slope and deeper water marls with shelf edge bryozoan reef mounds. Coeval inboard terrestrial deposits to the east are siliciclastic sands (North Maslins) rich in carbonaceous fragments that accumulated in deltaic, braided-river, and fluvio-lacustrine settings.

7.2.5.2

SA2.2 Middle to Late Eocene (6My.)

These carbonate strata occur in the Eucla and St. Vincent basins (Fig. 7.2). Slope facies are calcareous ooze and wackestone with warm-water planktic foraminifers but shelf facies are poorly known. Terrestrial: Inboard sediments (Werrilup, Maralinga, South Maslin Sands) are siliciclastic sands rich in leaf and wood fragments that accumulated in interpreted coastal- estuarine plains and paludal environments adjacent to the open shelf. These quartzose sands contain scarce marine fossils. They grade landward into true coal deposits (Clinton) again reflecting the warm, rainy climate. Marginal Marine—Inner Neritic: These carbonates in the Eucla Basin are lagoonal limestones (Paling) deposited behind quartzose sand barrier islands (Ooldea Sands). Extensive marine heterozoan limestones (Norseman, Muloowurtie) accumulated in the landward, flooded paleovalleys (Hou et al. 2003). The Norseman in particular contains large benthic foraminifers at the top as well as possible aragonitic green algae signaling warm-temperate, potentially oligotrophic marine conditions. The system in the St. Vincent Basin is the lower part of a thin, intensively burrowed, condensed, glauconitic, bryozoan–mollusk grainstone with several hardgrounds (Tortachilla) that is thought to have formed in and out of the zone of wave abrasion (see Figs. 8.1, 8.4). Sediments in both basins are interpreted to have accumulated across an extended period of time as broad subaqueous dunes in overall warm-temperate marine environments. The setting is generally interpreted as well-oxygenated, photic, and low mesotrophic to oligotrophic.

7.2.5.3

SA2.3 Late Eocene (3My.)

Exposed again mainly in the Eucla and St. Vincent basins, parts of these Upper Eocene rocks are significantly different from those beneath. Slope facies are fine-grained wackestone ooze with clay-rich interbeds that record increased trophic resources (high mesotrophic) and ocean cooling. Terrestrial-Marginal Marine: These deposits are like underlying inner-shelf and strandline SA2.3 facies in the Eucla Basin and St. Vincent basins. Marginal marine deposits are represented by barrier island sands (Ooldea) and leeward lignitic sands, silts and clays, with but locally abundant bryozoans and echinoids (Werrilup).

7.2 SA2—Mid-Eocene to Early Oligocene—’The Biogenic Shelf’

151

Inner Neritic: These different facies in the Eucla Basin are thick and spectacular spiculites and spongolites (Pallinup, Princess Royal, and Kasta) that accumulated in shallow, warm, oligotrophic waters. Initial inner neritic deposition in the St. Vincent Basin was a thin, intensively burrowed, bryozoan grainstone with a hardground cap (upper Tortachilla) again thought to have accumulated in the zone of wave abrasion. Mid-Neritic: Western facies in the Eucla basin are marls or bryozoan marls to floatstones (Wilson Bluff). These mesotrophic sediments are warm-water near the top. St. Vincent Basin deposits (Blanche Point marls) fluctuate between high C/U values with turitellids (low mesotrophic) to low C/U values (high mesotrophic). Marine straits between islands on the inner-shelf (Kangaroo Island— lower Kingscote) were sites of biofragmental floatstones and grainstones with small and large benthic foraminifers as well as basal rhodoliths thought to be overall warm, oligotrophic deposits. Finally, mid to outer neritic clays, marls and minor limestones (Brown’s Creek) accumulated in the Aire District of the Otway Basin, SW of Melbourne (Fig. 1.7).

7.2.5.4

SA2.4 Early Oligocene (6My.)

The Lower Oligocene is only present in the St. Vincent and the Otway basins and the top is commonly eroded. Eocene-Oligocene boundary erosion also removed many 10’s of meters of underlying SA2.3. Terrestrial—Marginal Marine: Deposits are carbonaceous, quartzose sands, silts, and clays with beds of lignite inland (Chinaman Gully). Depositional environments are interpreted as freshwater bogs and coastal marshes. Inner Neritic: Strata in the St. Vincent Basin are coarse-grained, bimodal crossbedded quartzose, locally glauconitic sands (Pt. Julia) or sands with abundant bryozoans, large benthic foraminifers and corallines (Aldinga) signaling euphotic, low mesotrophic to oligotrophic conditions. Coeval strata in the Otway Basin (basal Narrawaturk) are bryozoan packstones and grainstones grading up to microbioclastic wackestones with cyclostome bryozoans (low mesotrophic). Overlying strata in the Otway Basin are a suite of cyclic, clay floatstones, quartzose floatstones, and bryozoan grainstones (Ruarung, upper Rogue, Port Vincent). Mid-Neritic: Outboard in mid-shelf interisland straits the limestones (upper Kingscote) are high-energy m-scale, cyclic, cross-bedded or intensively burrowed bryozoan-mollusk grainstones indicating low mesotrophic conditions. These deposits do not contain large benthic foraminifers confirming cooler water outboard conditions compared to the underlying Eocene. Eastward, in the Gambier Embayment of the Otway Basin (Gambier Greenways, upper Narrawaturk) the mid-outer shelf carbonates are a series of a cyclostome wackestones to packstones, with conspicuous chert nodules reflecting mesotrophic environments. M-scale cyclicity was prevalent throughout for the first time. Mid—outer neritic deposits in the Otway Basin (Castle Cove, Glen Aire) are clays and quartzose limestones.

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7.2.6 Synopsis Most rocks exposed range from terrestrial to marginal marine to inner neritic with carbonates only present in the west. 1. Terrestrial deposits are mostly siliciclastic sands, commonly lignitic, or with leaf and wood fragments. They accumulated in interpreted paludal settings, bogs, swamps and coastal marshes. 2. Marginal marine sediments were generally siliciclastic sand barrier islands with leeward muddy lagoonal limestones. 3. Inner neritic seafloors were either flooded paleovalleys or in the lee of offshore islands in the widening Australian-Antarctica Gulf. Middle Eocene deposits were high-energy cross-bedded quartzose calcarenites with coralline algae, large benthic foraminifers and local green algae or condensed bryozoan mollusk grainstones in the zone of fluctuating wave abrasion. Late Eocene and early Oligocene sediments were by contrast either spiculites, spongolites, coccolith and spiculitic marls or cyclic quartzose, bryozoan floatstones and grainstone rich in benthic foraminifers, echinoids and corallines with up to 50% sponge spicules. These pass laterally unto pure spongolites and spiculites in the inner neritic zone. 4. Middle neritic deposits were lower energy bryozoan (cyclostome) marls or floatstones with coccolith or sponge spicule matrix, whole echinoids, brachiopods, chert nodules, turitellid gastropods with local higher-energy bryozoan grainstones with benthic foraminifers and again up to 50% sponge spicules. A series of straits between mid-shelf islands were sites of m-scale cyclic bryozoan-mollusk grainstones with small and large benthic foraminifers in the Eocene. Overlying early Oligocene deposits were cross-bedded, bryozoan-mollusk grainstones with only small benthic foraminifers recording a cooling ocean.

7.3 SA 3 Late Oligocene to Middle Miocene—‘The Carbonate Shelf’ 7.3.1 Tectonics This was overall a time of comparative tectonic quiescence wherein sea level fluctuations were principally driven by glacioeustacy with minor contributions from local tectonics.

7.3.2 Oceanography The modern oceanographic system south of Australia was established at this time. Sedimentation took place facing the open Southern Ocean with attendant large seas

7.3 SA 3 Late Oligocene to Middle Miocene—’The Carbonate Shelf’

153

SUCCESSION 3 EUSTATIC CURVES +200

MIOCENE

20

25

OLIGO

SA 3.1

STAGES

DEPOSITIONAL SUCCESSION

+100

0

Sea level - Meters

-100

Open Shelf Southern Ocean

TORTONIAN SERRAVALIAN

W W

LANGHIAN

SA 3

Miocene Climatic Optimum (MCO)

BURDIGALIAN LOWER

15

Ma.

SA 3.2

UPPER

10

MIDDLE UP

SERIES

W AQUITANIAN

W

SECOND ORDER

CHATTIAN

Late Oligocene Warming (LOWE)

30

Depositional Succession

W

Warm Period

Chert

Abundant Carbonate

Fig. 7.3 Depositional succession SA3 placed against global sea level, general sediment composition and major events (modified from Quilty 1977; and McGowran et al. 2004)

and swells. The Circum-Antarctic Current was strong and persists to the present day. On the other hand, SA3.1 was also a period of gradual warming of these ocean waters. This monotonic heating was nonetheless punctuated by shorter warm highstands and cool lowstands driven by Antarctic glaciation perturbations. Sea level was at its highest and warmest during SA3.2, the mid-Miocene Climatic Optimum (MCO— 17.5–14.5 Ma) (Fig. 7.3). The widespread appearance and subsequent disappearance of subtropical to tropical Indo-Pacific molluscan genera (Darragh 1985) and large, subtropical, benthic foraminifers, such as Lepidocyclina (e.g., Chaproniere 1975; McGowran 1979; Chaproniere 1984; McGowran and Li 1994), signal this Miocene seawater warming. The temperature increase was likely aided somewhat by the equatorward movement of southern Australia from ~ 50°S in the Oligocene to ~ 42°S in the Middle Miocene (Veevers et al. 1991; Feary et al. 2000).

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7.3.3 Climate and Vegetation Late Oligocene and Early Miocene (SA3.1). Although there was gradual stepwise warming in the Late Oligocene, overall it was still cool. There was a decrease in rainfall and temperate forest growth, together with an increase in seasonal aridity and savannah development throughout the Late Oligocene with accompanying sluggish drainage. Silcrete (Cordillo Surface) and ferricrete was common. Nothofagus beech and casuarinas became more dominant with time and there was a decrease in flowering plants, ferns and mosses (i.e., drier forests) (White 1994). Climatic variability was low. Margins of the Murray Basin were the sites of extensive swamps (Benbow et al. 1995a). Air temperatures gradually continued to increase through the Early Miocene. Middle Miocene (SA3.2). This was a comparatively short period of profound climate warming (MCO) with temperatures higher than at any time since the Eocene. Rainforests were again widespread and characterized by abundant Nothofagus, gymnosperms, and broadleaf trees. Coal swamps developed far to the east in the Pt. Philip Embayment of the Otway Basin (Gallagher et al. 1999). Late Middle Miocene (14.5 Ma–11.6 Ma). This time of rapid cooling began toward the end of the Middle Miocene (~ 12 Ma). There was an accompanying drastic decrease in Nothophagus forests, again confirming an accompanying increasing dryness. All neritic deposition across the southern Australian margin ceased because rapid growth of the Antarctic Polar Ice Sheet resulted in a significant global sea level fall and total withdrawal of the ocean from the shelf at ~ 14.5 Ma (Flower and Kennett 1994; Abreu and Anderson 1998). In short, the Late Miocene was largely a period of non-deposition.

7.3.4 Glaciation Significant cooling and continental glaciation that began in the early Oligocene (30.1– 28.0 Ma) peaked in the ‘mid’ Oligocene (28.0–26.3 Ma) with expansion of the east Antarctic ice sheet and dramatic sea level fall. Antarctic climate ameliorated continuously during the Late Oligocene Warming Event (LOWE) (26.3–23.7 Ma) in a stepwise fashion with low-amplitude climate variability as the southern polar ice cap gradually melted. The Oligocene–Miocene transition and earliest Miocene (23.7– 20.4 Ma), however, was a short period of cooling, re-expansion of the East Antarctic Ice sheet, and high amplitude climate variability and m-scale carbonate depositional cyclicity. Eventually, the Miocene Climatic Optimum (MCO) was accompanied by major melting of ice sheets, sea level rise, and little m-scale cyclicity. The late Middle Miocene by contrast was a period of rapid east Antarctic ice sheet expansion (Flower and Kennett 1994), initiation of the west Antarctic ice sheet and sea level fall, and as stressed above, with very little stratigraphic record.

7.3 SA 3 Late Oligocene to Middle Miocene—’The Carbonate Shelf’

155

7.3.5 Depositional Summary Deposition (Fig. 7.4) during this time (SA 3.1) must be placed against a gradual increase in seawater temperature (as discussed above) and sea level rise, punctuated by short episodes of cooling, just prior to the MCO (SA3.2). Integrating deposition styles across the different basins and subbasins (Figs. 7.4, 7.5) reveals a recurring theme of deposition.

7.3.5.1

SA 3.1 Late Oliogocene–Early Miocene

Inner-Mid-Neritic: Late Oligocene and early Miocene sediments (Fig. 7.4) in the Eucla and St. Vincent basins are mostly inner to mid-neritic (Pt. Vincent, Willunga) heterozoan deposits. Late Oligocene–early Miocene limestones are cool-temperate and mesotrophic whereas late, early Miocene carbonates are warm-temperate and low mesotrophic to oligotrophic.

Terrestrial

Marginal Marine

Coleville

SA3.2

Mono Para

SA 3.1

Inner Nektic

Mid Nektic

Deep Nektic

Melton Fynasford Peubla Port Campbell (Zeally) (Muddy Creek) Peubla Narracoorte (Yellow Bluff) Nullarbor

ODP

Peubla Port Addis (Celleporaria) Batesford Peubla Clay Port Campbell (Bochara) Jan Juc Fishing Point Calder River Port Campbell Maude Clifton Gellibrand Willinga Gambier (Camelback-Greenways) Melton Port Vincent Abrakurrie

SOUTHERN OCEAN Forests

Slope

Inner

ODP

Sea Level

Mid

Upwelling

Outer ~ 200 mwd Slope

Fig. 7.4 Summary sketch of SA 3 formations and their interpreted neritic depositional environments. Formations are in regular font, members in italics

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Coeval deposits in the Otway Basin are temporally partitioned; Upper Oligocene (Clifton, Calder River, Point Addis); Upper Oligocene–early Lower Miocene (Maude); Upper Lower Miocene (Bochara, Batesford, Zeally). They are variably quartzose heterozoan (Gallagher et al. 1999),with a variety of largely cool-water components in the form of cycles separated by hardgrounds. Local phosphate nodules or phosphatic hardgrounds in upper Oligocene rocks point to periodic upwelling of nutrient-rich waters into otherwise oligotrophic environments (Chapter 8—Fig. 8.10). Lower Miocene deposits contain variable numbers of large benthic foraminifers and coralline algae confirming euphotic, warm-water environments, whereas ubiquitous cross-bedding and grainy sediments point to high-energy seafloor conditions. Mid-Outer Neritic: Such deposits, mostly in the Eucla (Abrakurrie) and Otway Basins, accumulated in the upper Oligocene–lower Miocene (Gambier, Gellibrand, Fishing Point), and Middle Miocene shallowing (Port Campbell, Jan Juc, Puebla Clay). Sediments are mainly marls, chalks, and microbioclastic calcisiltites, locally punctuated by storm reworked grainstone and packstone layers. Upper Oligocene deposits are mainly cool-water marls that pass upward with shallowing into warmer-water grainstones with bryozoans and biosiliceous chert. The lower Miocene typically has large benthic foraminifers in upper strata and the units are interrupted by phosphate-glauconite hardgrounds implying local upwelling of mesotrophic-eutrophic waters. Many have chert nodules especially in the warmer early Miocene. Epicratonic Murray Basin: Basal carbonate strata (Fig. 7.5) (Mannum) are a warm-temperate heterozoan assemblage that accumulated on a mesotrophic ramp in this shallow intracratonic basin under a humid, rainy climate. Nutrients were derived from the surrounding land (Lukasik et al. 2000; Lukasik and James 2006). Facies in the basin comprise large-scale, transgressive-regressive packages with transgressive sediments mainly echinoid-bryozoan grainstones and regressive facies composed of nearshore clays or limestones comparable to those in modern nearshore seagrass environments. The Padthaway Ridge was capped by two units (Riordan et al. 2012). The lower Upper Oligocene–lower Miocene unit is mostly echinoid–coralline algae (rhodolith) facies interpreted to have accumulated in cool-temperate, nutrient-rich, poorly illuminated environments. The upper lower to Middle Miocene unit of bryozoan grainstones containing small and large benthic foraminifers is thought to have accumulated in euphotic, quiet water, low mesotrophic settings atop the ridge. Large and small benthic foraminifers are present in both units.

7.3.5.2

SA3.2 Middle Miocene

Neritic: These strata are only present locally because in most places they were removed by erosion associated with late Miocene uplift. Lacustrine muddy carbonates (Garford) accumulated in the inner perimeter of the Eucla Basin whereas

7.3 SA 3 Late Oligocene to Middle Miocene—’The Carbonate Shelf’

157

MANNUM FORMATION - SA3.1 wet climate,low energy,mesotrophic-eutrophic Tidal Flats

Muddy, MolluskLBF Facies

wave winnowing

Muddy Echinoid-Bryozoan Grainy, Facies EchinoidBryozoan Facies

0 FWWB Muddy, Echinoid-Bryozoan Facies

m 50

MORGAN GROUP - SA 3.2 (Glenforcelan, Cadell, Bryant Ck., Pata) dry climate, low energy, low mesotrophic

Tidal Flats

Muddy, MolluskLBF Facies

wave winnowing

Muddy Bryozoan LBF Facies

Grainy Bryozoan LBF Facies

0 FWWB FWWB Muddy, Bryozoan LBF Facies

m 50

Fig. 7.5 Summary sketch of Murray Basin SA3.1 and SA3.2 formations and their interpreted depositional environments on a centripital, epeiric ramp (from Lukasik et al. 2000)

marginal marine deposits were mainly peritidal sands (Colville). Neritic facies indicate that warmest ocean waters were in the west and gradually cooled eastward. Inner to mid-neritic, grainy, high-energy carbonates everywhere (Nullarbor, Melton, Morgan, Naracoorte, Muddy Creek) contain large benthic foraminifers, rhodoliths, and large tropical to subtropical molluscs. Inner to mid-shelf deposits in the Eucla Basin also include low diversity reef-building zooxanthellate corals (Lowry 1970; O’Connell et al. 2012). On the basis of seismic evidence, a coral barrier reef has been proposed to have developed at the shelf edge at this time (Feary and James 1995). Mid-outer Otway Basin neritic deposits (Fynnesford) also contain large benthic foraminifers attesting to both warm and clear waters (Chaproniere 1975, 1984). Deeper mid-outer neritic clays, marls and minor limestones (Puebla, Yellow Bluff ), however, record cooler waters. Epicratonic Murray Basin: The Glenforselan, Cadell, Bryant Creek and Pata sediments accumulated under a seasonal temperate climate of temporally increasing aridity, lowered terrestrial input, low-energy, low mesotrophic conditions, and higher carbonate productivity compared to the underlying Mannum Formation. Many of the facies have clear photozoan characteristics.

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7.3.6 Synopsis This period (Fig. 7.3) of tectonic quiescence, gradual growth of the AAG into an active Southern Ocean with a strong Circum-Antarctic Current all led to development of neritic facies characteristic of heterozoan neritic carbonates everywhere (cf. Nelson 1988; James 1997; James and Lukasik 2010; Michel et al. 2018); a truly carbonate shelf. It was the reverse of SA2 with the AGG giving way to the full Southern Ocean and cool ocean waters that gradually warmed into the Middle Miocene thermal maximum. 1. Marginal marine depositional environments were largely strandline quartzose sands and lacustrine carbonates. 2. Inner neritic carbonates were mostly quartzose, bryozoan-echinoid grainstones in the Oligocene and similar Middle Miocene facies but with large benthic foraminifers, rhodoliths, tropical mollusk and even zooxanthellate corals in the west. Miocene rocks are most comparable to modern carbonates in southern, warm, elongate gulfs (James and Bone 2011a, 2011b) or northward in subtropical to tropical photozoan Australia (Pandolfi and Kelley 2008) or MIS 5e highstand Pleistocene deposits (Murray-Wallace and Woodroffe 2014). 3. Mid-neritic facies were either delicate bryozoan–bivalve, benthic foraminifer, echinoid grainstones with accessory brachiopods, corals and serpulids or marls and chalks and microbioclastic calcisiltites punctuated by storm beds. 4. Outer neritic sediments everywhere were clays, marls, and minor limestones with cool-water benthic foraminifers. 5. The epicratonic Murray Basin was the site of inner ramp clays and limestones that passed outboard into echinoid-bryozoan grainstones. The confining Padthaway Ridge was the site of high-energy echinoid-coralline grainstone deposition. Sedimentation during the warm mid-Miocene was similar with the exception of numerous large benthic foraminifers and local photozoan elements.

7.4 SA4—Pliocene-Pleistocene—‘The Shaved Shelf’ 7.4.1 Controls on Sedimentation Rocks represent sedimentation during the climatic transition into the icehouse world of today against a background of tectonic instability (Murray-Wallace and Woodroffe 2014), a setting so altogether different from the preceding passive continental margin. Pleistocene deposition was strikingly bipolar! Impressive marginal marine and inland basin, shallow marine, and aeolianite sediments together with extraordinary thick slope deposits separated by an essentially barren, non-depositional, sediment starved shelf (James et al. 1994) (Figs. 7.6, 7.7).

7.4 SA4—Pliocene-Pleistocene—’The Shaved Shelf’

159

SUCCESSION 4 OPEN SHELF EUSTATIC CURVES SOUTHERN OCEAN SERIES

U

0

Ma. SA 4.2

5

Pliocene Pleist

SA 4.1

STAGES

DEPOSITIONAL+200 SUCCESSION

+100

0

-100

Sea level - Meters

M

L

CALABRIAN

U

PLACENZIAN

L

ZANCLEAN

GELASIAN

SA 4

W W

MESSINIAN

PRE - PLIOCENE UNCONFORMITY

Depositional Succession

W

Warm Period

Abundant Carbonate

Fig. 7.6 Depositional succession SA4 placed against global sea level, general sediment composition and major events (modified from Quilty 1977; and McGowran et al. 2004)

7.4.2 Tectonics Uplift and Deformation: The southern Australian Mesozoic-Paleogene long-lived passive, subsiding continental margin was dramatically altered in the Late Miocene via tectonic inversion, wrenching compression, and associated tectonics (Flottmann and James 1997; Sandiford 2003a; Sandiford 2003b; Hill and Exon 2004). Importantly, large segments of the inner continental margin and most epicratonic basins described herein were uplifted, variably deformed, and exposed. Current interpretations are that the Otway Ranges were raised by late Miocene tectonism ~ 8–6 Ma (Dickinson et al. 2002; Sandiford 2003a). All of southern Australia is still undergoing strong E-W and SE-NW compression with ongoing evidence of tectonic activity through the Pliocene, Pleistocene, and Holocene (Greenhalgh et al. 1994). Pliocene strandlines, for example, are displaced upward 200–250 m on the west side of the Otway Ranges (Wallace et al. 2005). Specifically, during this time the Eucla Basin was more or less tectonically stable whereas the gulfs and peninsulas of the St. Vincent Basin were a series of active horsts and grabens. The Murray Basin underwent gradual subsidence whereas the Gambier coastal plain was and is today undergoing epirogenic uplift. Volcanism: Basin inversion was accompanied by Plio-Pleistocene volcanism (Price et al., 2003) largely restricted to the Otway Basin. Volcanism is, however, continuing in South Australia (the Newer Volcanics) with eruptions as recently as 1500 BP (aboriginal oral tradition—Sheard 1986).

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SA 4 THE SHAVED SHELF Pliocene-Pleistocene Terrestrial

Marginal Marine

Inner Neritic

Mid Neritic

Glanville Padthaway Bridgewater

SA4.2

SA 4.1

Bungunnia

Outer Neritic

Slope Extremely Thick Slope Wedge

Little Deposition

Moorabool Doorondong Grange Burn Whalers Bluff North West Bend Nelson Bay Bookpunong LoxtonPoint Ellen Parilla Burnham Hallet Cove Roe

Little Deposition

Narrow Slope

SOUTHERN OCEAN Sea Level Semi-arid Aeolianites

Inner

Mid Outer

upwelling

~ 200 mwd Slope

Fig. 7.7 Summary sketch of SA 4 formations and their interpreted neritic depositional environments. Formations are in regular font, members in italics

7.4.3 Oceanography The seaway between Antarctica and southern Australia progressively, if slowly, widened during this time. The West Wind Drift was well established and the deeper water bodies were somewhat stable (Stickley et al. 2004; Bijl et al. 2013). Glacial fluctuations, however, affected near-surface circulation. The Leeuwin Current (LC) source of warm-water from Indonesia was dramatically reduced during glacial lowstands (McGowran et al. 1997). By contrast, during interglacial highstands the LC, like today, flowed unimpeded across the southern margin. It was, however, focused along the shelf edge, and not inboard. On the other hand, the warmer interglacial climate (similar to today) could have resulted in inboard warming and inner neritic subtropical, warm-temperate, carbonate deposition (cf. Betzler et al. 1997; James et al. 2001). In short, the ocean was still a cool-temperate system and seafloor carbonate deposition was mainly heterozoan.

7.4 SA4—Pliocene-Pleistocene—’The Shaved Shelf’

161

7.4.4 Glaciation Regionally, as stressed above, very late Middle and Late Miocene time was a period of rapid expansion of the east Antarctic ice sheet and initiation of the west Antarctic ice cap. These events resulted in a profound sea level fall and initiation of the modern icehouse world. The Middle Pleistocene Transition (MPT) was further a time of significant modification in the spectral character of sea level change from low-amplitude highfrequency 41 ka glacial cycles to higher amplitude, lower frequency events (Shackleton et al. 1990; Clark et al. 2006). It is thought to have occurred between 1.5 and 0.6 Ma (MIS 22, ~ 880–870 ka) and is generally considered the first major cold event with a sea level fall similar to that following the last glacial maximum (MIS 2). Sea level highstands during the 41 ky-dominated cycles of the early Pleistocene were only a few thousand years in length. By comparison, they were ~ 10 ky for the middle and late Pleistocene. Thus, there was much less time for marginal marine deposition during highstands and the stratigraphic record reflects this.

7.4.5 Climate and Vegetation Pliocene: Pliocene climate was capricious, beginning with cold, escalating to warm, but ending with cold. Late Miocene temperatures across southern Australia cooled and sea level fell to below the shelf edge. On land the terminal Miocene was arid, forests shrank markedly, and there was an overall significant increase in dryland vegetation. This situation quickly reversed in the early Pliocene as sea level rose to perhaps + 20 m compared to today, temperatures increased, and vegetation changed (Sniderman et al. 2016). The climate became warm and wet, saw the local resurgence of Nothofagus forests, abundant eucalypts and cassurinas, together with grasslands and woody shrublands. Temperature fluctuations were rapid with short warm and wet periods alternating with cool and dry times. It is postulated (White 1994) that this upsurge in precipitation and intensified weathering combined with uplift, caused increased siliciclastic sedimentation. Deep weathering also coincided with episodes of ferricrete and silcrete formation (Zheng et al. 1998). This resulted in the Dundas Surface and the Karoonda surface-two widespread iron-enriched and silica-cemented horizons (Benbow et al. 1995c). Temperatures peaked at ~ 3 Ma, the Mid Pliocene Warm Period (MPWP) and are estimated to have been 3–4°C warmer than today. By contrast, they plunged globally in the late Pliocene such that by ~ 2.4 Ma the modern icehouse world had begun. The effect of widespread Antarctic ice was to increase the polar anticyclone, increase westerlies, decrease air temperatures, and produce modern style climatic zones. This change also brought about increased dryness everywhere with the dominance of sclerophyllous vegetation to southern Australia.

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Pleistocene: It is generally considered that widespread aridity in southern Australia began relatively quickly at ~ 0.7 Ma (Bowler 1976; Williams 2001). Recent studies in paleo Lake Bungunnia, however, reveal that the climate change was likely more stepped and started much earlier at ~ 1.4–1.5 Ma, just prior to the MPT (McLaren and Wallace 2010). The 100 ky glacial-interglacial cycle was established at ~ 700 ky, with warm interglacial periods forming 10–15% of the cycles and 85% of the cycles overall being cooler, drier, and windier. Temperatures in southern Australia during glacials are estimated to have been ~ 8–10°C lower than today, with much reduced rainfall. Furthermore, on a smaller scale, change in regimens caused by the bipolar control of global weather patterns, brought winter-rain and summer-dry conditions to southern Australia. These attributes progressively turned more and more of the continent permanently arid. The flora also changed. By the end of the Pliocene rainforests had contracted to the eastern fringe of the continent only to expand and contract slightly during Pleistocene climatic fluctuations. Eucalypts still occupied only the marginally harsh and seasonally dry environments but there was a dramatic and rapid speciation of acacias throughout the continent (White 1994). Since then large areas of Australia have been covered with wind-blown, quartzose sand dunes; the red center!

7.4.6 Stratigraphic Sedimentology These post-tectonic strata (Fig. 7.7) are unlike any that came before! Late Miocene and ongoing uplift had two major effects; (1) it reduced Pliocene-early Pleistocene deposition to patchy inner neritic, marginal marine (aeolianites) or estuarine environments and (2) it diminished shelf accommodation such that little neritic Pleistocene deposition took place.

7.4.6.1

SA4.1 Early Pliocene—Mid-Pleistocene (5.33 to 1.8 Ma)

As stressed above, accommodation was low throughout because of late Miocene ongoing uplift and thus much of the shelf was within swell and storm wave base resulting in little neritic sediment accumulation. There are, however, minor inner neritic strata, but they are in somewhat isolated locations. Such deposits are mostly quartzose sands with calcareous bioclasts, typically mollusk (oysters, pectens) and benthic foraminifers. The sediments are interpreted to have accumulated in nearshore grass meadows, coastal sand barriers, shallow embayments, and estuaries (Roe, Hallett Cove, Burnham, Pt. Ellen, Bookpronong, Whalers Bluff, Grange Burn Dorodong, Moorabool Viaduct). Large benthic foraminifers, especially Marginopora vertebralis are present in the western basins (Eucla and St. Vincent) signaling warm, subtropical marine waters there. Bryozoans are also present in the west. These Neogene shallow marine marls and strandline molluscan quartzose beach sands today

7.4 SA4—Pliocene-Pleistocene—’The Shaved Shelf’

163

cover much of the modern coastal plain, especially in the Otway Basin. The high sea level resulted in little off-shelf transport and a thin slope succession (Fig. 7.6). Pliocene deposition in the Murray Basin was estuarine to lacustrine with early and middle Pliocene bivalve-rich quartzose sands passing upward into oyster-rich buildups (NW Bend). The basin was wholly lacustrine during the early Pleistocene in the form of the large Lake Bungunnia whose deposits consist of basal clays (Blanchetown) overlain by limestone (Bungunnia). This limestone becomes progressively more ‘saline’ with evaporite minerals upward.

7.4.6.2

SA4.2 Middle—Late Pleistocene (1.8 Ma- 10.4 Ka)

Neritic: Once again because of reduced accommodation, neritic sediments were swept either seaward or landward. Thus, a true ‘shaved shelf’ developed and was characterized by extensive marginal marine aeolianites and associated lagoons together with spectacularly thick slope deposits. The shaved shelf is a function of the shallow abrasion zone and glacioeustasy (James et al. 1994). Although sediment was deposited during each highstand and largely unaffected during lowstand, it was eroded via ravinement during subsequent sea level rises. The sediments are partly moved shoreward but mostly shifted seaward to accumulate on the slope. The impressive slope sediment wedge is in fact composed almost entirely of material shed from the outer shelf edge. This imposing structure is equal to or larger than equivalent sediment wedges in photozoan systems. Internal structure is cyclic in both middle and late Pleistocene deposits reflecting the numerous, glacially driven, sea level oscillations. Most sediments are a mixture of allochthonous neritic components and allochthonous slope particles. Transgression was marked by mobilization of sandy shelf sediments generating slope sandy debrites and fining upward sequences. Lowstands and transgressions saw active basinward transport via canyons with overspill turbidites derived from shelf dunes and older Tertiary deposits. A series of bryozoan-sponge buildups are embedded within the Plio-Pleistocene slope wedge. They are comparatively deep-water structures that grew during sea level lowstands. They do not exhibit internal growth stages but are conspicuously rhythmically bedded (see Chapter 8). Marginal Marine: Aeolianites (Bridgewater), as marginal marine prograding and stacked successions (Figs. 5.9, 5.10, 5.11), are a hallmark of this depositional phase. They are a mixture of nearshore, inner neritic components and intertidal bivalve fragments. Progradational systems are best exposed where there has been gradual tectonic uplift whereas stacked systems characterize shorelines in regions of relative tectonic stability. The former are a series of aeolianite ridges and intervening lagoonal facies (Padthaway, Glanville). The latter are interbedded aeolianites and paleosols that are locally eroded into spectacular sea cliffs. The superbly exposed suite of relatively recent aeolianites has received exceptional scientific attention (Sprigg 1952; Boutakoff 1963; Murray-Wallace and Belperio 1991; Murray-Wallace et al. 1999; Abegg et al. 2001) especially recently (James and Bone 2015; James and Bone 2017; Murray-Wallace 2018). These recent

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studies have built on such research, reemphasizing the role of tectonics in their different preservation styles (Murray-Wallace 2002). Interestingly it is now clear that most sediment in the marginal marine aeolianites comes from adjacent shallow neritic sources and is somewhat different in composition compared to mid- and outer shelf sediments (James et al. 1991; James and Bone 2017; Joury et al. 2018). They are only partly a record of the vanished offshore marine. The semi-arid climate had other consequences for terrestrial, non-marine deposition. The Paleogene and early Neogene humid to semi-humid climates with attendant forests and rivers resulted in ferricrete formation. By contrast, the change to a more semi-arid climate has led to extensive calcrete development. Murray Basin: Early Pleistocene lacustrine sediments in the Murray Basin reflect the Pleistocene climate change with progressively younger deposits becoming more calcareous and evaporitic with increasing aridity.

7.5 Synopsis This succession, especially the mid and late Pleistocene, is so different in all aspects that it hardly seems part of the same preceding, large-scale continental margin system. The only thing that unites the deposits is that they are heterozoan carbonates. Yet these comparatively young strata are easiest to understand and categorize because they are essentially modern with the same general depositional pattern having prevailed since the Pliocene 1. The Pliocene record of deposition during the warm highstand is one of quartzose sands with warm-temperate molluscs and benthic foraminifers that accumulated in very inner neritic, estuarine, or lacustrine settings. Murray Basin deposition was similar but with local conspicuous oyster accumulations. Lacustrine carbonate and especially oyster accumulations are unknown in earlier successions. 2. The mid-Late Pleistocene, marginal marine prograding or stacked aeolianite and interdune lacustrine and estuarine deposits are truly unique and characterize the semi-arid climatic system. 3. The shaved shelf motif is present today with active slope and marginal marine deposition a shelf of mostly indurated older carbonates and local Precambrian and Paleozoic bedrock veneered by a ragged blanket of latest Pleistocene and Holocene carbonates.

7.6 Summary As stressed at the outset, sedimentation in this region was determined by an integration of tectonic, oceanographic, climatic, and glaciation controls. Nevertheless, each aspect influenced sedimentation in several ways.

7.6 Summary

165

1. As with all things geological, tectonics was the principal control. Tectonics (1) drove the separation that changed the Paleogene AAG into the post-Eocene Southern Ocean, which in turn altered oceanography, (2) moved Australia continuously equatorward, thus keeping the ocean waters temperate instead of becoming polar, and (3) led to late Miocene uplift that changed the whole depositional system and promoted significant meteoric diagenesis. 2. This is not to say that oceanography was unimportant as the transformation from a wide gulf to a polar southern ocean, with attendant changing currents, nutrients, hydrodynamic energy, were profound. Fluvial outflow, current patterns and upwelling delivered nutrient elements to the shelf through time thus affecting the siliceous and calcareous biota and promoting development of local phosphate hardgrounds. This control is also manifest by the change from relatively low–energy deposits along the margins of the AGG to the later, higher-energy sediments along the northern perimeter of the Southern Ocean. Fluctuating seawater temperatures resulted in a seafloor calcareous biota that varied from cool-temperate to subtropical in character. 3. Climate evolved through time from warm, rainy, subtropical Eocene weather systems that fostered the growth of steamy rainforests and fetid coal swamps to semi-arid, Pleistocene, Mediterranean-like seasonal cool weather fronts that promoted formation of strandline aeolian carbonates together with marginal synsedimentary marine dolomites. The Eocene–Oligocene humid climate resulted in significant delivery of both terrestrial sediments and nutrient elements to the ocean. The latter is interpreted to have promoted significant biosiliceous sedimentation. At the same time important silcrete and ferricrete surfaces developed on land in contrast to the calcrete surfaces that formed during comparatively dry Plio-Pleistocene. 4. Antarctica is the repository of one of the largest glaciated landscapes on the planet. The Cenozoic depositional geohistory of southern Australia cannot be interpreted without acknowledging the continued presence of nearby Antarctica. Initially connected and then drifting apart, the first controls were nearby tectonic, but then changed to far-field as the continent moved away, became glaciated and drove global glacioeustacy. Post-Eocene fluctuations in glaciation in turn powered eustatic changes in sea level and thus produced cyclicity in the neritic carbonates. 5. Finally again, to reemphasize, the sediments were heterozoan, the principles discovered here apply to only such cool-water deposits worldwide, a completely different scheme from the more extensively studied tropical, photozoan systems.

References Abegg FE, Harris PM, Loope DB (eds) (2001) Modern and ancient carbonate eolianites: Sedimentology, sequence stratigraphy, and diagenesis. SEPM Special Publication 71. SEPM, Tulsa, OK, USA, p 207

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Abreu VS, Anderson JB (1998) Glacial eustasy during the Cenozoic; sequence stratigraphic implications. AAPG Bulletin 82:1385–1400 Benbow MC (1990) Tertiary coastal dunes of the Eucla Basin. Australia Geomorphology 3:9–29 Benbow MC, Alley NF, Callen RA, Greenwood DR (1995a) Geologic History and Paleoclimate In: Drexel JF, Preiss VP (eds) The Geology of South Australia, The Phanerozoic. geological survey of South Australia, Bulletin 54, vol. 2, pp 208–217 Benbow MC, Callen RA, Bourman RP, Alley NF (1995b) Deep weathering, ferricrete and silcrete. In: Drexel JF, Preiss VP (eds) The geology of South Australia, The phanerozoic geological survey of South Australia, Bulletin 54 vol. 2, pp 201–207 Benbow MC, Lindsay JM, Alley NF (1995c) Eucla Basin and palaeodrainage. In: Drexel JF, Preiss VP (eds) The geology of South Australia, Volume 2 The Phanerozoic. Geological Survey of South Australia Bulletin, pp 178-186 Berger WH, Wefer G (1996) Expeditions into the past: Paleoceanographic studies in the South Atlantic. In: Wefer G, Berger WH, Siedler G, Webb DJ (eds) The South Atlantic: Present and Past Circulation. Springer-Verlag, Berlin, pp 363–410 Betzler C, Brachert TC, Nebelsick J (1997) The warm temperate carbonate province: A review of facies, zonations and delineations. Courier Forschungsinstitut Senckenberg 201:83–99 Bijl PK, Bendle JAP, Bohaty S, Pross J, Schouten S, Tauxe L, Stickey CE, McKay RM, Rohl U, Olney M, Sluijs A, Escutia C, Brinkhuis H, Scientists E (2013) Eocene cooling linked to early flow across the Tasmanian Gateway. PNAS 110:9645–9650 Bohaty S, Zachos JC (2003) Significant Southern Ocean warming event in the late middle Eocene. Geology 31:1017–1020 Boutakoff N (1963) The geology and geomorphology of the Portland area. Memoirs—Geological Survey of Victoria, Memoirs—Geological Survey of Victoria, Melbourne, p 171 Bowler JM (1976) Aridity in Australia; age, origins and expression in aeolian landforms and sediments. Earth Sci Rev 12:279–310 Chaproniere GCH (1975) Palaeoecology of oligo-miocene larger foraminiferidas, Australia. Alcheringa 1:37–58 Chaproniere GCH (1984) Oligocene and miocene larger foraminiferida from Australia and New Zealand. Bureau of Mineral Resources Bulletin 188:1–98 Clark PU, Archer D, Pollard D, Blum JD, Rial JA, Brovkin V, Mix AC, Pisias NG, Roy M (2006) The middle Pleistocene transition: characteristics, mechanisms, and implications for long-term changes in atmospheric pCO2. Quatern Sci Rev 23:3150–3184 Darragh TA (1985) Molluscan biogeography and biostratigraphy of the Tertiary of southern Australia. Alcheringa 9:83–116 DeConto R, Pollard D (2003) A coupled climate-ice sheet modeling approach to the Early Cenozoic history of the Antarctic ice sheet. Palaeogeogr Palaeoclimatol Palaeoecol 198:39–52 Dickinson JA, Wallace MW, Holdgate GR, Gallagher SJ, Thomas L (2002) Origin and Timing of the Miocene-Pliocene Unconformity in Southeast Australia. J Sediment Res 72:288–303 Exon NF, Kennett JP, Malone MJ, Exon NF, Kennett JP, Malone MJ, Brinkhuis H., Chaproniere GCH, Ennyu A, Fothergill P, Fuller MD, Grauert M, Hill PJ, Janecek TR, Kelly DC, Latimer JC, Nees S, Ninnemann US, Nuernberg D, Pekar SF, Pellaton CC, Pfuhl HA, Robert CM, Roessig KLM, Roehl U, Schellenberg SA, Shevenell AE, Stickley CE, Suzuki N, Touchard Y, Wei W, White TS, Ocean Drilling Program LSSPCSTXUS (2004) Leg 189 synthesis; CretaceousHolocene history of the Tasmanian gateway; Proceedings of the Ocean Drilling Program; scientific results; the Tasmanian gateway; Cenozoic climatic and oceanographic development; covering Leg 189 of the cruises of the drilling vessel JOIDES Resolution; Hobart, Tasmania, to Sydney, Australia; Sites 1168–1172; 11 March-6 May 2000. Proceedings of the Ocean Drilling Program, Scientific Results (CD-ROM) 189: 38 Feary D, Hine AC, Malone M, et al (2000) Great Australian Bight: Cenozoic cool-water carbonates. Proceedings of the ocean drilling program, initial reports, 182. Proceedings of the Ocean Drilling Program, Initial Reports, College Station, Texas, pp 58

References

167

Feary DA, James NP (1995) Cenozoic biogenic mounds and buried Miocene (?) barrier reef on a predominantly cool-water carbonate continental margin—Eucla Basin, western Great Australian Bight. Geology 23:427–431 Flottmann T, James P (1997) Influence of basin architecture on the style of inversion and foldthrust belt tectonics–the southern Adelaide Fold-Thrust Belt, South Australia. J Struct Geol 19:1093–1110 Flower BP, Kennett JP (1994) The middle Miocene climatic transition: East Antarctic ice sheet development, deep ocean circulation and global carbon cycling. Palaeogeogr Palaeoclimatol Palaeoecol 108:537–555 Francis JE, Marensi S, Levy R, Hambrey M, Thorn VC, Mohr B, Brinkhuis H, Warnaar J, Zachos JC, Bohaty S, DeConto R (2008) Chapter 8 From Greenhouse to Icehouse—The Eocene/Oligocene in Antarctica. Developments in Earth and Environmental Sciences. Elsevier, Amsterdam, pp 309–368 Gallagher SJ, Jonasson K, Holdgate G (1999) Foraminiferal biofacies and paleoenvironmental evolution of an Oligo-Miocene cool-water carbonate succession in the Otway basin, Southeast Australia. Journal of Micropaleontology 18:143–168 Greenhalgh SA, Love D, Malpas K, McDougall R (1994) South Australian earthquakes, 1980-92. Aust J Earth Sci 41:483–495 Hill PJ, Exon NF (2004) Tectonics and Basin Development of the Offshore Tasmanian Area Incorporating Results from Deep Ocean Drilling. In: Exon NF, Kennett JP, Malone MJ (eds) The Cenozoic Southern Ocean: Tectonics, sedimentation, and climate change between Australia and Antarctica. American Geophysical Union, pp 19–42 Hou B, Frakes LA, Alley NF, Gammon P, Clarke JDA (2003) Facies and Sequence stratigraphy of Eocene valley fills in Eocene palaeovalleys, the eastern Eucla Basin, South Australia. Sed Geol 163:111–130 Hou B, Frakes LA, Sandiford M, Worrall L, Keeling J, Alley NF (2008) Cenozoic Eucla Basin and associated palaeovalleys, southern Australia—climatic and tectonic influences on landscape evolution, sedimentation and heavy mineral accumulation. Sed Geol 203:112–130 Huber M (2006) The ocean circulation in the Southern Hemisphere and its climatic impacts in the Eocene. Palaeogeogr Palaeoclimatol Palaeoecol 231:9–28 Huber M, Brinkhuis H, Stickey CE, Doos K, Sluijs A, Warnaar J, Schellenberg SA, Williams GL (2004) Eocene circulation of the Southern Ocean: Was Antarctica kept warm by subtropical waters? Paleoceanography and Paleoclimatology 19:4–26 James NP (1997) The cool-water carbonate depositional realm. In: James NP, Clarke MJ (eds) Cool-water carbonates. SEPM Special Publication, pp 1–20 James NP, Bone Y (2011a) Carbonate sedimentation in a warm-temperate carbonate macroalgal depositional system, South Australia. Sed Geol 240:41–53 James NP, Bone Y (2011b) Neritic carbonate sediments in a temperate realm. Southern Australia, Springer, Dordrecht Heidelberg London New York, p 254 James NP, Bone Y (2015) Pleistocene aeolianites at Cape Spencer, South Australia; record of a vanished inner neritic cool-water carbonate factory. Sedimentology 62:2038–2059 James NP, Bone Y (2017) Provenance of Holocene calcareous beach-dune sediments, western Eyre Peninsula, Australia. Sed Geol 357:83–98 James NP, Bone Y, Collins LB, Kyser TK (2001) Surficial sediments of the Great Australian Bight; facies dynamics and oceanography on a vast cool-water carbonate shelf. J Sediment Res 71:549–567 James NP, Bone Y, Kyser TK (1991) Shallow burial dolomitization of mid-Cenozoic, cool-water, calcitic, deep-shelf limestones, southern Australia. AAPG Bulletin 75:602 James NP, Boreen TD, Bone Y, Feary DA (1994) Holocene carbonate sedimentation on the West Eucla Shelf, Great Australian Bight; a shaved shelf. Sed Geol 90:161–177 James NP, Lukasik J (2010) Cool- and cold-water neritic carbonates. In: James NP, Dalrymple RW (eds) Facies Models 4. Geological Association of Canada GEOtext 6, pp 369–398

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7 Integration and Interpretation

Joury M, James NP, James C (2018) Nearshore cool-water carbonate sedimentation and provenance of Holocene calcareous dunes eastern South Australia. Aust J Earth Sci 65:221–242 Kämpf J, Doubell M, Griffin D, Matthews RL, Ward TM (2004) Evidence of a large seasonal coastal upwelling system along the southern shelf of Australia. Geophys Res Lett 31(L09310):09311– 09314 Lowry DC (1970) Geology of the Western Australian part of the Eucla Basin. Geological Survey of Western Australia Bulletin 122:201 Lukasik J, James NP (2006) Carbonate sedimentation, climate change and stratigraphic completeness on a Miocene cool-water epeiric ramp, Murray Basin, South Australia. Geological Society Special Publications 255:217–244 Lukasik JJ, James NP, McGowran B, Bone Y (2000) An epeiric ramp; low-energy, cool-water carbonate facies in a Tertiary inland sea, Murray Basin, South Australia. Sedimentology 47:851– 881 McClatchie S, Middleton JF, Ward TM (2006) Water mass analysis and alongshore variation in upwelling intensity in the eastern Great Australian Bight. J. Geophys. Res. 111 McGowran B (1979) The Tertiary of Australia: Foraminiferal overview. Mar Micropaleontol 4:235– 264 McGowran B (2009) The Australo-Antarctic Gulf and the Auversian facies shift. In: Koeberl C, Montanari A (eds) The late eocene Earth—Hothouse, Icehouse, and impacts. geological society of america special paper, pp 215–240 McGowran B, Holdgate GR, Li Q, Gallagher SJ (2004) Cenozoic stratigraphic succession in southeastern Australia. Aust J Earth Sci 51:459–496 McGowran B, Li Q (1994) The Miocene oscillation in southern Australia. In: Pledge N S (ed) Australian vertebrate evolution. Palaeontology and systematics records of the South Australian Museum 27: 197–212 McGowran B, Li Q, Moss G (1997) The Cenozoic neritic record in southern Australia: The biogeohistorical framework. In: James NP, Clarke JAD (eds) Cool-Water Carbonates. Special Publication—SEPM, pp 185–203 McLaren S, Wallace MW (2010) Plio-Pleistocene climatic change and the onset of aridity in southeastern Australia. Global Planet Change 127:81–91 Michel J, Borgomanoa J, Reijmer JJG (2018) Heterozoan carbonates: when, where and why? A synthesis on parameters controlling carbonate production and occurrences. Earth Sci Rev 182:50–67 Middleton JF, Bye JAT (2007) A review of the shelf-slope circulation along Australia’s Southern Shelves: Cape Leeuwin to Portland. Prog Oceanogr 75:1–41 Murray-Wallace CV (2002) Pleistocene coastal stratigraphy, sea-level highstands and neotectonism of the southern Australian passive continental margin; a review; Sea-level changes and neotectonics. JQS. Journal of Quaternary Science 17: 469–489 Murray-Wallace CV (2018) Quaternary History of the Coorong Coastal Plain. Springer international publishing, Cham, Switzerland, Southern Australia, p 229 Murray-Wallace CV, Belperio AP (1991) The last interglacial shoreline in Australia; a review. Quatern Sci Rev 10:441–461 Murray-Wallace CV, Belperio AP, Bourman RP, Cann JH, Price DM (1999) Facies architecture of a last interglacial barrier; a model for Quaternary barrier development from the Coorong to Mount Gambier coastal plain, southeastern Australia. Mar Geol 158:177–195 Murray-Wallace CV, Woodroffe CD (2014) Quaternary Sea Level Changes. Cambridge University Press, Cambridge, U.K, A Global Perspective, p 484 Nelson CS (Ed.), (1988) Non-tropical shelf carbonates-modern and ancient., 60. Sedimentary Geology, pp 367 O’Connell LG, James NP, Bone Y (2012) The Nullarbor Limestone, Southern Australia: A vast subtropical Miocene carbonate Platform. Sed Geol 253–254:1–16

References

169

Pagani M, Huber M, Liu Z, Bohaty S, Henderiks J, Sijp WP, Krishnan S, DeConto R (2011) The Role of Carbon Dioxide During the Onset of Antarctic Glaciation. Science 334: http://DOI10.1126.12390%2c12328p Pandolfi JM, Kelley R (2008) The Great Barrier Reef in time and Space: Geology and Paleontology. In: Hutchings PA, Kingsford MJ, Hoegh-Guldberg O (eds) The Great Barrier Reef: Biology, Environment and Management. CSIRO Publishing, Collingwood, Victoria, Australia, pp 17–27 Price RC, Nicholls IA, Gray CM (2003) Cainozoic igneous activity. In: Birch WD (ed) Geology of Victoria. Geological Society of Australia, Special Publication 23, pp 362–375 Quilty PG (1977) Cenozoic sedimentation cycles in Western Australia. Geology 5:336–340 Richardson LE, Middleton JF, James NP, Kyser TK, Opdyke BN (2019) Upwelling characteristics and nutrient enrichment of the Kangaroo Island upwelling region, South Australia. Continental Shelf Research 200: doi.org/10.1016/j.csr.2020.104111 Riordan NK, James NP, Bone Y (2012) Oligo-Miocene seagrass-influenced carbonate sedimentation along a temperate marine paleoarchipelago, Padthaway Ridge, South Australia. Sedimentology 59:393–418 Sandiford M (2003a) Geomorphic constraints on the late Neogene tectonics of the Otway Range, Victoria. Aust J Earth Sci 50:69–80 Sandiford M (2003b) Neotectonics of southeastern Australia; linking Quaternary faulting record with seismicity and in situ stress. In: Hillis RR, Muller RD (eds) Evolution and dynamics of the Australian Plate. Geological Society of Australia, Special Publication 22, pp 101–113 Scher HD, Whittaker JM, Williams SE, Latimer JC, Kordesch WE, Delaney ML (2015) Onset of Antarctic circumpolar current 30 million years ago as Tasmanian Gateway aligned with westerlies. Nature Research Letters 523:580–583 Shackleton NJ, van Andel TH, Boyle EA, Jansen E, Labeyrie L, Leinen M, McKenzie J, Mayer L, Sundquist E (1990) Contributions from the oceanic record to the study of global change on three time scales; Report of Working Group I, Interlaken workshop for Past global changes. Global Planet Change 2:5–37 Sheard MJ (1986) Some volcanological observations at Mount Schank, southeast South Australia. Geological Survey of South Australia, Quarterly Geological Notes 100:14–20 Sijp WP, England MH, Huber M (2011) Effect of the deepening of the Tasman Gateway on the global ocean. Paleoceanography and Paleoclimatology 26: doi.org/10.1029/2011PA002143 Sniderman JM, Woodhead JD, Hellstrom J, Jordan GJ, Drysdale RN, Tyler J, Porch N (2016) Pliocene reversal of late Neogene aridification. PNAS 113:1999–2004 Sprigg RC (1952) The geology of the South-East Province, South Australia, with special reference to Quaternary coast-line migrations and modern beach developments. Bulletin—Geological Survey of South Australia, 29. Geological Survey of South Australia, Adelaide, South Aust., 120 pp Stickley CE, Brinkhuis H, Schellenberg SA, Sluijs A, Rohl U, Fuller MK, Grauert M, Huber M, Warnaar J, Williams G. (2004) Timing and nature of the deepening of the Tasmanian Gateway Paleoceanography and Paleoclimatology 19: https://doi.org/10.1029/2004pa001022 Taylor G, Eggleton RA (2017) Silcrete: an Australian perspective. Aust J Earth Sci 64:987–1016 van Ruth PD, Patten NL, Doubell MJ, Chapman P, Rodriguez AR, Middleton JF (2018) Seasonaland event-scale variations in upwelling, enrichment and primary productivity in the eastern Great Australian Bight. In: Begg G (ed) Great Australian Bight Research Program—a whole of system investigation. Elsevier, pp 36–45 Veevers JJ (2000) Billion-year earth history of Australia and neighbours in Gondwanaland. Gemoc Press, Sydney, p 388 Veevers JJ, Powell M, Roots SR (1991) Review of seafloor spreading around Australia, 1. Synthesis of patterns of spreading. Austalian Journal of Earth Sciences 38 Wallace WW, Dickinson DJA, Moore DH, Sandiford M (2005) Late Neogene strandlines of southern Victoria: A unique record of eustasy and tectonics in southeast Australia. Aust J Earth Sci 52:279– 297 White ME (1994) After The Greening. The Browning Of Australia. Kangaroo Press Pty, Ltd, Kentworth, NSW, Australia, p 288

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Williams MAJ (2001) Quaternary climatic changes in Australia and their environmental effects. In: Gostin VA(ed) Gondwana to greenhouse: Australian environmental geoscience. Geological society of Australia Inc., Special Publication No. 21, pp 3–11 Zheng H, Wyrwoll K-H, Li Z, Powell CM (1998) Onset of aridity in southern Western Australia—a preliminary palaeomagnetic appraisal. Global Planet Change 18:175–187

Part IV

Discussion

Chapter 8

Sedimentary Attributes

Abstract Several aspects in the preceding narrative such as m-scale cyclicity, reef mounds, biosiliceous sedimentation, and trophic resources are scientifically contentious and so are discussed herein. M-scale cyclicity is clearly driven by glacioeustacy, principally via waxing and waning of Antarctic ice sheets. A series of five different cycle styles are recognized, largely dependent on specific neritic environments and each with a distinct motif. Deep-water bryozoan reef mounds are present in the Eocene and Pleistocene but are not good analogs for similar Paleozoic structures. Trophic resources were critical not only for biosiliceous deposition but also development of phosphatic hardgrounds related to interpreted upwelling. Reasons for biosiliceous sedimentation are controversial but seem to be related to terrestrially derived nutrient elements controlled by climate and again a modern equivalent is not a good geohistorical analog. Carbonate deposition in the epicratonic Murray Basin was closely tied to climate and trophic resources. Keywords Cyclicity · Reef mounds · Biosiliceous · Trophic resources · Phosphate

8.1 Introduction Interpretation of carbonate rocks through the depth of time has always been a multiphasic task because of the many variables that control deposition and diagenesis. Our ability to interpret new rock successions utilizes the combination of comparative sedimentology, using both modern systems and the library of studied ancient examples, placed against aspects of the rocks under study. It has been stated many times that each succession is unique and yet at the same time has aspects that are universal. Comparative aspects of the Cenozoic cool-water carbonates described and interpreted herein are clear and when collectively explained could add significantly to the library of examples that are used to understand similar rocks sequences throughout geological history. Several pertinent aspects that might be added stand out and are discussed below, namely; (1) m-scale cyclicity, (2) reef mounds, (3) trophic resources, (4) biosiliceous sedimentation, and (5) epicratonic, cool-water carbonate shallow basinal sedimentation. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2021 N. P. James and Y. Bone, Biogenic Sedimentary Rocks in a Cold, Cenozoic Ocean, https://doi.org/10.1007/978-3-030-63982-2_8

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8.2 Subtidal, Meter-Scale Cyclicity 8.2.1 Overview M-scale cyclicity is a hallmark of neritic carbonates throughout geologic history (Tucker and Wright 1990; James and Jones 2016). These are 4th and 5th order parasequences in sequence stratigraphic terminology (Plint et al. 1992). Cycles in this study are defined as those packages with three or more repeatable elements, including hardgrounds. By contrast, rhythms are delineated as those units with only two recurring different lithologies. There has long been an ongoing discussion as to the relative importance of allogenic versus autogenic controls on such sedimentation (Pratt 2010; James and Jones 2016). Autogenic controls, such as the accretion of sediments to sea level that then acts as a critical bounding surface is important in warm-water carbonate systems (Ginsburg, in Hardie and Shinn 1986). The much slower accretion rates of coolwater carbonates dictate that the sea surface is not per se as important. Instead, there is a consensus that allogenic controls are more significant in these open platform depositional systems, especially in cool-water carbonates where seafloor carbonate sediment accretion rarely builds to sea level (James and Lukasik 2010). The major allogenic regulator is glacial eustasy and this factor is augmented by hydrodynamics, and seawater temperature.

8.2.2 Glacial Eustasy 8.2.2.1

Phase 1—SA1 and Early SA2

With exception of the Middle Eocene Tortachilla Limestone, cyclicity is not obvious in SA2 strata until the late Eocene (at the top of the Wilson Bluff, and PallinupFitzgerald Member) but is common in early Oligocene strata. This latter time is when the first Antarctic ice sheets became continental and began to influence global eustasy.

8.2.2.2

Phase 2—SA2.3–SA4.1

Carbonates were strongly cyclic throughout SA2.4 and SA3.1 with short-term, 4th order fluctuations in continental glaciation resulting in short-term transgressions and longer-term regressions. Sea level fluctuations on the order of 10s of meters are known to characterize this time (Kennett and Barker 1990). Deposits during the MCO (SA3.2), however, do not seem to be cyclic, probably because the driver, Antarctic ice sheets, were dramatically reduced during this warm period.

8.2 Subtidal, Meter-Scale Cyclicity

8.2.2.3

175

Phase 3—SA4.2 Mid–Late Pleistocene

As stressed in Chapter 6, the Middle Pleistocene Transition (MPT) represents a significant time of adjustment in the spectral character of sea level change. The modification was from low-amplitude, high-frequency 41 ky obliquity-driven glacial cycles to higher amplitude, to lower frequency 100 ky eccentricity-driven events (Shackleton et al. 1990). The change is generally thought to have occurred ~1.4–1.5 Ma (McLaren and Wallace 2010).

8.2.3 Hydrodynamics Hydrodynamics is also critical for the type of cycle or rhythm. By and large heterozoan accumulation only takes place below the ‘zone of wave abrasion’ (Collins 1988; James and Bone 1994, 2011) because, as noted earlier, loose sediment in shallower water is swept away before it can accumulate. The base of wave abrasion results in what has been called a ‘shaved shelf’ (Boreen and James 1993) and the seafloor is characteristically a firmground or hardground (Fig. 8.1). Sediment in deeper water environments remains in place but bedding contacts are planar or slightly burrowed,

ORIGIN OF NERITIC LIMESTONE CYCLES HARDGROUND

a

c

b

HARDGROUND

ZONE OF WAVE ABRASION NEW CYCLE

EROSION & CEMENTATION

EPIFAUNAL SEDIMENTATION

Bryozoans Sponges

INFAUNAL & EPIFAUNAL SEDIMENTATION

Echinoids Brachiopods

INFAUNAL & EPIFAUNAL SEDIMENTATION

EROSION & CEMENTATION

Bivalves Gastropods

Fig. 8.1 A generalized sketch illustrating sequential development of a neritic, cool-water carbonate subtidal cycle. Letters correspond to the different parts of a given cycle that formed as the base of wave abrasion rose and fell (modified from James and Bone 1994)

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ABRAKURRIE LIMESTONE CYCLE BRYOZOANS

A H

OMISSION SURFACE Well Cemented

Shallow

C

Deep

B

Poorly Cemented

Nodular/Arborescent Erect Rigid,Fenestrate, Foliose & Flat Robust Branching MOLLUSCS Epifaunal bivalves mainly Pecten type Infaunal bivalve molds & gastropods ECHINOIDS Epifaunal, Regular spines Infaunal, Irregular tests BRACHIOPODS Mainly, Magadinelia

A H C

Shallow Well Cemented

OMISSION SURFACE

TRACE FOSSILS Scolicia Thalassinoides

Fig. 8.2 A sketch showing the characteristics of an Abrakurrie Limestone subtidal cycle as in A above (modified from James and Bone 1994)

whereas below storm wave base, beds are normally rhythmic. An interpreted example (James and Bone 1991) is from the Abrakurrie Limestone (Fig. 8.2), but the concept has been used in other studies of these rocks (Riordan et al. 2012).

8.2.4 Seawater Temperature Cool-temperate Cenozoic carbonate strata are characteristically cyclic with prominent hardground and firmground omission, but not exposure, surfaces (James and Lukasik 2010). By contrast, as stressed above, warm-temperate heterozoan deposits are not generally cyclic in this Cenozoic succession, probably because of more rapid sedimentation that does not promote cycle completeness. There is also likely a climate effect wherein storms are less numerous but individually more intense during warm climate times.

8.2 Subtidal, Meter-Scale Cyclicity

177

8.2.5 Cenozoic Rhythms and Cycles 8.2.5.1

Overview

As stressed above, subtidal, m-scale cycles and rhythms are a hallmark of parts of this succession. Such cycles were clearly related to fluctuating Antarctic climate and glaciation, conditions that were not present until the late stages of preceding SA2. Eustatic sea level fluctuations during this time were of short duration and low amplitude, 10s of meters are known to characterize Oligo-Miocene time (Kennett and Barker 1990). Although present throughout, they have been studied most in the Eucla, St. Vincent, and Murray basins and the Torquay Embayment of the Otway Basin. Their location and style can be divided into (1) open neritic and (2) enclosed basin types.

8.2.5.2

Open Neritic Rhythms and Cycles

There are five different but recurring types of open shelf, neritic cycles or rhythms in SA3 (Fig. 8.3). These units (Boreen and James 1995) can, in a general way be linked to the modern shelf sedimentology as outlined by James and Bone (2011). In all instances, bounding surfaces are marine hydrodynamic and not subaerial, principally the base of wave abrasion. These are quite different from the cycles in the intracratonic Murray Basin (see below). (1)–Cross-bedded grainstone cycles: Hardground-capped, trough cross-bedded, bryozoan-echinoid grainstones. These are similar to open shelf sands deposited during high-energy storms and waves at ~60–130 mwd on the modern shelf. Coralline algae, or large benthic foraminifers with photosymbionts when present, confirm the photic zone. Such cycles are common in the Abrakurrie, Port Vincent, Tortachilla (Fig. 8.4), Aldinga, Upper Kingscote, Bochera, Maude, Calder River, Batesford, and Pt. Addis units. (2)–Burrowed grainstone, packstone and clay floatstone cycles: These cycles consist of a thin basal, locally trough cross-bedded grainstone that passes upward into fine burrowed skeletal grainstone with whole echinoids local HCS, ripple crosslaminations or a mottled burrowed texture. Main components are foliose, erect and fenestrate bryozoans, echinoid tests and spines, mollusks, especially pectens, a diverse benthic foraminifer assemblage with a matrix of locally numerous sponge spicules, calcispheres, glauconite pellets and quartz silt. The cap is a coarse skeletal lag, with local phosphate granules, a Thalassinoides-burrowed firmground with chert, or a burrowed, encrusted hardground. These cycles occur in the Abrakurrie Limestone, Willunga Formation, Port Campbell Formation, Clifton Formation, part of the Gellibrand Marl and the Zeally Limestone. They are thought to have formed on the mid-shelf in water depths of ~100–180 m, below fairweather wave base but above swell wave base.

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NERITIC M- SCALE CYCLES 1. CROSS-BEDDED GNST.

bioturbated wackestone

Abrasion

INNER-MID SHELF

Swell-Dom HST LST

bioturbated packstone

OUTER SHELF UPPER SLOPE

Storm-Dom Swell-Dom

HSC grainstone burrowed wkst.

x-bedded grainstone

4. BRYOZOAN MARL & CLAY RHYTHMS

3. INTERBEDDED GNST.-WKST. x-bedded grainstone

burrowed packstone

MID - OUTER SHELF

Abrasion

coarse qtz. gnst

INNER-MID SHELF

Swell

x-bedded grainstone

burrowed grainstone

OUTER SHELF - MID - OUTER SHELF UPPER SLOPE

burrowed grainstone

firmground

MID - OUTER SHELF

2. BURROWED GNST. - PKST.

hardground

burrowed wackestone & clay

Legend Echinoderms Cross-beds

Molluscs HCS

Bryozoans

Bioturbation

Cycle - shallowing upward

Fig. 8.3 Characteristics and interpretations of meter-scale subtidal cycles and rhythms in Cenozoic strata from southern Australia (based on Boreen and James 1995)

(3)–Interbedded grainstone and wackestone cycles: Such packages are coarsening- and thickening-upward successions of sharp-based grainstone-packstone beds. The scoured base with rip-up clasts passes upward into foraminifer-rich skeletal wackestone that is locally laminated, has layers of mollusc lags, with normally or inverse graded grainstones. Coarse grains become more numerous and clays less common upwards together with more phosphate granules, quartz, erect rigid bryozoans, echinoids, serpulids, brachiopods, and poorly preserved HCS. Cycle tops are either plain bedding, or simple, burrowed bedding planes veneered with phosphate granules and quartz. Such cycles are found in the Gambier Limestone, the Castle Cove Limestone, parts of the Geillibrand Marl, and Port Campbell Limestone. They are interpreted as storm beds or fairweather beds close to swell wave base. These conditions occur today on the modern shelf at ~130–250 mwd. (4)–Bryozoan marl and calcareous clay rhythms: These packstoneswackestones and calcareous clays form uniform bedded successions tens of meters

8.2 Subtidal, Meter-Scale Cyclicity

179

Fig. 8.4 Stratigraphic column illustrating different parts of the Tortachilla Limestone and lower part of the Blanche Point Formation. Thickness of hardground-bound cycle units is shown at right (modified from James and Bone 2000)

thick. Bedding is defined by thin continuous skeletal layers or burrowed horizons. All sediments are extensively burrowed or bioturbated. Delicate bryozoans are ubiquitous as are whole large turitellids, thin-walled brachiopods, azooxanthellate corals, glauconitized pellets, and the bivalve Glycymeris. The matrix is a suite of benthic and planktic foraminifers, nannofossils, and sponge spicules. These are the quietest and deepest environments on the Cenozoic shelf. They are present in the modern ocean between ~130 and 350 mwd; but most were likely ~200 mwd in the Oligo-Miocene, i.e., a wide range of environments from mid to outer neritic. The rhythms are thought

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to reflect variations in fine siliciclastic input—and carbonate productivity. These rhythms are part of Gambier Limestone, Muddy Creek Marl, Browns Creek Clay, Fishing Point Marl, Jan Juc Marl, and Puebla Marl. (5)–Rhythmically bedded bryozoan bioherm: These rhythms are restricted to one unit the Puebla Celleporaria Beds. They are interpreted to be a bryozoan-sponge bioherm like the Plio-Pleistocene ones (see Chapter 4) on the modern slope (see Sect. 8.3).

8.2.5.3

Murray Basin Epicratonic Basin Cycles

Carbonates of the Murray Supergroup, comprising both fossiliferous-heterozoan and foraminifer-photozoan facies, accumulated on a low-energy, marine, mesotrophic epeiric ramp in a broad, shallow, epicratonic basin. Depositional conditions ranged from temperate-water with abundant nutrients supplied from the surrounding hinterland under a cool, moist climate regime in the Late Oligocene and early Miocene (SA3.1), to warm-temperate and subtropical seas with reduced levels of trophic resources associated with an increasingly arid regional climate in the Middle Miocene (SA3.2). These cycles are more complex than the neritic ones described above and have a ‘deepening-upward’ motif that reflects gradual flooding of the basin and progressively more open marine conditions (Fig. 8.5). More specifically their lithologies record a continuum from inner restricted locales to outer, open marine, bryozoan-colonized environments (Lukasik and James 2003). Such deepening-upward cycles consist of five discrete parts that are from the base upward; (1) Part A is a faunally poor or molluscan clay-rich shallow water horizon, with the highest trophic resource levels, consisting of shallow water, variably restricted, variably stressed euryhaline to stenohaline, high mesotrophic environments; (2) Part B forms the bulk of most cycles, is bioturbated deepening, but coarsening-upward with progressively decreasing trophic resources, increasing faunal diversity, and multiple ichnofaunal overprinting, (3) OM1 is a firmground or hardground interpreted as a time of low sedimentation associated with increased wave and storm energy in a widening sea with maximum fetch; (4) Part C is a thin (1–20 cm) biotically diverse, epifaunal-dominated, condensed grainy unit deposited in the deepest and most open marine setting, (5) OM2 is a more subdued omission surface reflecting the sea level stillstand from maximum transgression to early regression. It is generally a Fe-stained, or oyster encrusted weakly convoluted hardground.

8.2.5.4

Plio-Pleistocene Slope Cyclicity

Cyclicity is also prominent in Upper Pliocene–Pleistocene upper slope deposits on the large prograding wedge (Fig. 5.8) penetrated by Leg 182 drilling (Feary et al. 2004). They are of two styles, cycles, and rhythms. The cycles (Feary et al. 2000; Saxena and

8.2 Subtidal, Meter-Scale Cyclicity

INTRACONTINENTAL MURRAY BASIN Epeiric Ramp Cycle OM2 OM1 C

181

OPEN OCEAN SHELF Neritic Shelf Cycle

R

deepest

shallowest

C

R

B

T A

shallowest

“deepening-upward’ deepening

C

B

deepest

A

T

“shallowing-upward’ deepening

B

B C

A A

RSL

RSL

Fig. 8.5 A comparison between interpreted epeiric ramp subtidal cycles in the Murray Basin (left) and subtidal cycles in neritic, open-shelf settings (right) on the Cenozoic continental margin (after, Lukasik and James 2003); T = transgression, R = regression, RSL = relative sea level

Betzler 2003), most prominent in the eastern transect, are ~10 m thick, coarseningupward from wackestone to packstone. Cycles can be correlated with isotope curves and suggest obliquity (41ky) forcing. Sediments shed to the slope during sea level rise comprise tunicate spicules, bryozoan fragments, coralline particles and relict grains (mostly aragonite and HMC) whereas mostly sponge spicules and mud characterize sediments during sea level falls. Siliciclastics in the form of clays are abundant during highstands, and interpreted to reflect rainfall and runoff whereas dolomite rhombs are highest during periods of sea level rise, and thought to signify transport of detrital grains (cf. Bone et al. 1992). The most rapid accumulation occurred during initial shelf inundation with a pulse of sediment production and exports that decreased toward peak flooding. The somewhat younger rhythms (Simo and Slatter 2004) are more prominent in the western transect and comprise alternating coarse, aragonite-HMC-rich, lowstand packstones and LMC-rich highstand, wackestones. These seem to reflect 100 ky precession-forced deposition.

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8.2.6 Summary M-scale, subtidal, cyclicity was best developed in cool-water carbonates deposited during the time of Antarctic glaciation (Early Oligocene to Early Miocene). The cycles and rhythms formed both on the open shelf and in the partially restricted Murray Basin, but the motif in each environment was different. Although water temperature and trophic resources were important influences, hydrodynamics was the primary control on cycle development. The principal interfaces were the depth of swell wave base and the depth of wave abrasion. Cyclicity is also prominent in Plio-Pleistocene slope successions and clearly driven by fluctuations in glacioeustasy.

8.3 Reef Mounds 8.3.1 Overview The presence of interpreted bryozoan reef mounds has important implications for the rock record. There were two periods of interpreted mound growth, the early Eocene (SA1) and the Plio-Pleistocene (SA4) with a suspected mound in the early Miocene Puebla Formation (SA3.1) of the Otway Basin. Origin of the younger structures is, however, somewhat controversial.

8.3.2 SA2 Paleogene Bryozoan Mounds The Mid-Eocene reef mounds (Sharples et al. 2014), originally interpreted as volcanic structures, are a suite of convex-upward seismic reflectors with clear overlapping strata, comprising a central core, with basinward and landward flanks. They are locally up to 200 m thick but mostly ~75 m thick. The elongate buildups are oriented normal to slope, generally 5 km wide 60–150 km in length. The internal geometry is one of multicrested mound geometries with flank angles from 5–15° (Fig. 8.6). Bryozoans are a mix of both cyclostomes (Porina, Cellaria, Puellina, Chondriovelum, Foveolaria, ?Reteporella, Nudicella, and Exechonella) and cheilostomes (Patinella, Nevianipora, Hornera, ‘Entalophora,’ Idmidronea, Crisia, Platonea, and Diaperoecia). Water depth is speculative but postulated to have been near the shelf edge.

8.3 Reef Mounds S

183 N

Seafloor TWT 0.8s

Bryozoan Mound Complex

Unconformity

Mid-Eocene -Present Cool-Water Carbonates Early-Mid Eocene Siliciclastics

1.0s

1.2s 3 km

Fig. 8.6 Seismic cross-section showing a bryozoan reef mound complex on the final clinoform breakpoint of an underlying siliciclastic delta complex in the Eucla Basin, Great Australian Bight; TWTB = two way travel time (modified from Sharples et al. 2014)

8.3.3 SA4 Plio-Pleistocene Bryozoan Mounds 8.3.3.1

Original Interpretation

The Plio-Pleistocene mounds embedded in slope faces and cored by ODP Leg 182 (Fig. 5.8) were originally interpreted (Bone and James 1993; James et al. 2000, 2004) to have grown during sea level lowstands (Fig. 8.7). An integrated model begins with delicate branching bryozoan floatstone that increases in bryozoan abundance and diversity upward over a thickness of 5–10 m, culminating in thin intervals of grainstone characterized by reduced diversity and locally abraded fossils. Mound accumulation was relatively rapid (30–67 cm ky-1 ) and locally punctuated by rudstones and firmgrounds. Intermound highstand deposition was comparatively slow (17–25 cm ky-1 ) and typified by meter-scale, fining upward packages of packstone and grainstone or burrowed packstone, with local firmgrounds overlain by characteristically abraded particles. Mound growth during glacial periods is interpreted to have resulted from increased nutrient supply and enhanced primary productivity. Such elevated trophic resources were both regional and local, and thought to be focused in this area by cessation of Leeuwin Current flow, together with northward movement of the subtropical convergence and related dynamic mixing.

8.3.3.2

Alternative Interpretation

Anderskouv et al. (2010) have reinvestigated the structures using multichannel reflection seismic profiles and a short 5-m-long gravity core. In their study, they immediately interpret the structures as sediment waves and correlate them with similar Danian structures which several of the co-authors have described from Denmark (Surlyk 1997). The seismic is spectacular, clearly showing the structures to be elongate features parallel to the regional bathymetric contours. They are asymmetric with the shorter flank dipping northward upslope and the longer flank dipping southward

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Fig. 8.7 A sketch depicting interpreted Pleistocene bryozoan mound growth during a single glacial cycle from interglacial highstand to interglacial lowstand (modified from James et al. 2000)

downslope. Flanks dip at up to 11°. They can be as high as 40 m and more than 1 km wide and can extend more than 10 km along strike. The most landward structures are the largest. The structures accreted by aggradation and migration or combinations of both. Internal reflections that were interpreted as sediment waves with complex internal structure by (Anderskouv et al. 2010; Figs. 7 and 8) could equally be interpreted as variable growth features in response to changing environmental conditions as many

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reef mounds are (Monty et al. 1995). Stratigraphic correlations do not agree with earlier interpretations (James et al. 2000). The sediment waves are not thought to have any clear correlation with glacial-interglacial cycles. Regardless, the bryozoans are interpreted to have thrived on elevated and current-affected topography during glacial lowstands, in agreement with earlier studies.

8.3.4 Models for Older Phanerozoic Reef Mounds These Cenozoic structures are attractive younger analogs for some past, especially Paleozoic, reef mounds. Older reef mounds are in general a group of buildups unified by their construction via small skeletal elements (Lees and Miller 1985; James and Bourque 1992; James and Wood 2010). In the Paleozoic they are also rich in carbonate mud, interpreted microbes, growth cavities, and synsedimentary cements (Lees and Miller 1985). Such structures occurred, although not universally so, in PaleozoicMesozoic upper slope/mid-ramp settings. There are, however, not many modern, subneritic examples with most being deep-water azooxanthellate coral-rich structures that grow to bathyl depths (Roberts et al. 2006). When compared to those described here and elsewhere there are significant differences. These southern Australian mounds, drilled on ODP leg 182’, do not contain significant mud, Stromatactis cavities, pervasive synsedimentary cements, or calcimicrobes. They do however, have similar shapes, occupy similar environments, and are rich in bryozoans. Lack of carbonate mud and lack of pervasive cementation could be because of the cold waters. Any cavities could have been collapsed during drilling. Hardgrounds do, however, attest to episodic seafloor lithification.

8.3.5 Summary Bryozoan reef mounds are present in Paleogene and Pleistocene slope strata. The Paleogene structures are well documented, display good mound geometry, and are composed of a community of diverse bryozoans. The Pleistocene examples are also well documented, have a diverse bryozoan biota, and grew during periods of increased nutrient supply, mainly in times of sea level lowstand. The structures are alternatively interpreted as sediment waves. Both examples are good but not perfect analogs to Paleozoic reef mounds because the environment is cool-water, had lower carbonate saturation, different bryozoans, and a lack of early synsedimentary cements.

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8.4 Trophic Resources 8.4.1 Introduction Nutrient elements such as P, N, Si and Fe are critical to the existence of any marine ecosystem (e.g., Lees and Buller 1972; Hallock and Schlager 1986; Hallock 1987; Hallock et al. 1991; Brasier 1995a, b; Halfar et al. 2006; Pufahl 2010) (Fig. 8.8). The sources of these elements, collectively called the ‘trophic resources continuum’ (TRC—Fig. 8.9), are multifold, via fluvial runoff from land, via airborne dust from an adjacent continent, or via upwelling of deep marine waters (Mutti and Hallock 2003; Lukasik and James 2006). Thus, the primary determinants are climate and oceanography. In southern Australia these controls have varied both through time and in two different depositional systems, open shelf, and epicontinental basin.

Fig. 8.8 A cross-plot of sea surface temperature and seawater chlorophyll content with appropriate environments wherein the different carbonate sediment associations are plotted; conditions present during southern Australian Cenozoic carbonate deposition is highlighted by a box (modified from Halfar et al. 2006; James and Lukasik 2010; James and Bone 2011)

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Fig. 8.9 The trophic resource continuum and correlative biotic, ecologic, and sedimentological information used to define trophic resources in the rock record (simplified from James and Lukasik 2010)

8.4.2 Neritic Paleoenvironments The character of the open shelf, as stressed in earlier chapters, changed through time. During the Eocene it faced the gradually widening Australia-Antarctica Gulf. With the opening of the Tasman Gateway in the early Oligocene and establishment of the east-flowing Circum-Antarctic Current, the margin thereafter faced the gradually widening Southern Ocean. When viewed at the large-scale, deposition along the Eocene-Miocene passive margin was temperate, cool-water to subtropical under largely mesotropic conditions (Fig. 8.8). The mostly SA2, middle Eocene to early Oligocene, inner neritic deposits record conditions that changed from warm to cool-temperate with time whereas trophic resources were mostly mesotrophic to locally oligotrophic throughout. Late Oligocene to early Miocene SA3 inner neritic conditions also gradually evolved with time but from cool-temperate and mesotrophic to warm-temperate and oligotrophic in the west. They remained cool-temperate and mesotropic in the Otway Basin. By contrast, all middle Miocene neritic waters were warm-temperate to

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subtropical with low mesotrophic to oligotrophic conditions. The epicratonic Murray Basin was warm-temperate and mesotropic except for local oligotrophic conditions during the Middle Miocene.

8.4.3 Phosphates Increased nutrients along the continental margin are usually marked by increased precipitation of bioelemental sediments, particularly manganese and phosphate, via upwelling (Pufahl 2010). Phosphates are not conspicuous in neritic sediments along the margin of the Eocene Australia-Antarctica Gulf. Such deposits are, however, present in late Paleogene and early Neogene sediments that faced the open Southern Ocean. Phosphate is particularly noticeable as nodules and layers of nodules in late Oligocene to early Miocene deposits of the Otway Basin; specifically in the upper Jan Juc Marl, the Calder River Limestone, and the upper part of the Clifton Limestone. It is also prominent along the upper Miocene unconformity that postdated initial uplift. Interestingly phosphate is not common in either the Eucla or St. Vincent basins. The layer of phosphate nodules in the late Oligocene Clifton Formation near Princetown Victoria is typical (Fig. 8.10). The Clifton is a ~12-m-thick unit there and comprises a limonitic, calcareous sandstone at the base, the 0.3–1.0-m-thick phosphate bed, an interpreted hiatus (Baker 1945), and an overlying 4.5–6.0 m of quartzose richly fossiliferous limestone at the top. The succession is capped by a thin Gellibrand Marl and thick overlying Pleistocene Bridgewater Formation aeolianites. The nodules contain quartz that is common in the beds below and fossils that occur in the limestone above. The fossils in particular are octocorals, bivalves, gastropods, bryozoans, echinoid spines, benthic foraminifers, brachiopods, sharks teeth, and whalebones together with Fe-stained pebbles. These attributes suggest that phosphogenesis took place in an upwelling situation via replacement of existing sediments (cf. Pufahl 2010). There are two major areas of upwelling along the southern margin today, the Bonney Coast off southwestern Victoria and the Lincoln Shelf off southern Eyre Peninsula (Kämpf et al. 2004; McClatchie et al. 2006; Richardson et al. 2018). Both are regions of seasonal summer upwelling and whereas nutrient elements support a vibrant seafood industry there is no record of bioelemental deposition. It does suggest, however, that conditions could have been present in the past to periodically promote upwelling and phosphate deposition.

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189

Fig. 8.10 Princetown Nodule Bed in the Upper Oligocene Clifton Formation, near Princetown, Victoria. a Outcrop view of the nodule bed at base overlain by limestone, hammer scale 23 cm long; b Close view of the contact illustrating the nodules and overlying floatstone rich in pectenid bivalves and crinoid stems, cm scale at base; c Bedding plane view of nodules and intervening buff limestone, cm scale at left; d Cross-section of broken nodules showing the partially replaced core and intensely altered rim, cm scale; e Bedding plane of nodule bed with replaced pectinid bivalves (arrows) close view of C above, cm scale; f Bedding plane view illustrating replaced fenestrate (upper right) and robust columnar (lower left) bryozoans (arrows), cm scale

8.4.4 Summary Trophic resources were essential in determining Cenozoic facies along the Southern Margin. Delivered as dissolved silica and nutrients via runoff they resulted in Eocene neritic spiculites and possibly Oligo-Miocene chert. Delivered via upwelling they led

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to sporadic late Oligocene–early Miocene neritic phosphate. There is little evidence of extensive bioelemental precipitation in more recent Plio-Pleistocene strata even though there is seasonal upwelling onto the shelf today.

8.5 Biosiliceous Sedimentation 8.5.1 Overview Succession SA2 (Middle Eocene to early Oligocene; 43–28 Ma) is strikingly different from most of the younger strata in southern Australia because it is composed of a variable mix of carbonate and biosiliceous sedimentary deposits. Such strata are not common in the Phanerozoic rock record (Ritterbush 2019) and it is unclear under what specific oceanographic conditions they formed. Any interpretation of such strata, because they are so poorly understood elsewhere, must consider all attributes of the depositional setting including tectonics, climate, oceanography, and paleobiology.

8.5.2 Deposits The spicule-rich deposits (Fig. 8.11) outlined in Chapter 5 (especially PallinupFitzgerald Member, Princess Royal, Kasta, and Blanche Point), stretch from the western Eucla Basin to the St. Vincent Basin and into the western part of the Otway Basin where they pass eastward into siliciclastic deposits. As noted above, the succession comprises three sedimentological associations; (1) SA2.1 and 2.2 middle Eocene carbonates, (2) SA2.3 late Eocene biosiliceous strata with minor carbonates, and (3)

Fig. 8.11 Blanche Point Formation. a Opal A sponge spicules, image width 25µm; b Close view of sponge spicule almost completely transformed to Opal CT lepispheres, image view, 15µm

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191

Fig. 8.12 A sketch illustrating the relationship between inboard biosiliceous facies and outboard carbonate facies in late Eocene and early Oligocene neritic deposits of southern Australia (modified from James et al. 2016)

SA 2.4 early Oligocene carbonates with accessory biosiliceous sediments. It is the late Eocene that has the most biosiliceous deposits, largely in the form of true spongolites and spiculites that accumulated mostly in flooded paleovalleys and inner neritic, shallow marine environments. These deposits pass outboard into relatively pure carbonate (Gammon and James 2001) (Fig. 8.12).

8.5.3 Late Eocene Setting The large Eocene Gulf (Fig. 1.3) was filled by warm seawater, with a pronounced halocline and oxygen-poor deep water (McGowran et al. 1997). The first opening of the Tasman Gateway is now thought to be in the mid-Eocene (Stickley et al. 2004) with the seafloor during initial stages being