Regional Geology Reviews

Regional Geology Reviews Series editors Roland Oberhänsli Maarten J. de Wit François M. Roure More information about this series at http://www.springer.com/series/8643 Ode to Fieldwork Arthur Fuller with his field equipment exploring the Cape-Karoo on his motorcycle in 1960. Today young geo-scientists are less attracted by such basic fieldwork (and freedom), yet the Cape Mountains and Karoo hinterland is a unique natural laboratory to observe, discover, learn and preserve Bastien Linol • Maarten J. de Wit Editors Origin and Evolution of the Cape Mountains and Karoo Basin 123 Editors Bastien Linol Maarten J. de Wit AEON-ESSRI AEON-ESSRI Nelson Mandela Metropolitan University Nelson Mandela Metropolitan University Port Elizabeth Port Elizabeth South Africa South Africa ISSN 2364-6438 ISSN 2364-6446 (electronic) Regional Geology Reviews ISBN 978-3-319-40858-3 ISBN 978-3-319-40859-0 (eBook) DOI 10.1007/978-3-319-40859-0 Library of Congress Control Number: 2016943862 © Springer International Publishing Switzerland 2016 This work is subject to copyright. All rights are reserved 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, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. Cover illustration: View through a window of columnar joints of a Karoo sill at the top of the Great Escarpment looking south, through Desolation Valley, towards the distant Cape Mountain ranges, all features reported on in this book Printed on acid-free paper This Springer imprint is published by Springer Nature The registered company is Springer International Publishing AG Switzerland This book is dedicated to three extraordinary lovers of nature and of the geology across Cape-Karoo routes—and advocates of “do your own thing” Arthur O. Fuller, Samuel O. Bowing and David L. Roberts For years during his early career, Arthur Fuller traversed the Cape and the Karoo on his motorcycle. He seldom documented his observations in writing, but he photographed every nook and cranny, and freely shared his vast knowledge and understanding of the stratigraphy, sedimentology and geomorphology of iconic Cape-Karoo landscapes that he mem- orized and knows by hard. During one of these ‘motorcycle maintenance’ trips, Arthur discovered a dilapidated farmhouse near Laingsburg, and per- suaded the farmer Colenso van Wyk to long-lease it as a field-work station. Since that day, literally hundreds and possibly thousands of students have tasted their first exposure to and mapping of ‘Cape-Karoo’ rocks from there; and listened to some legendary Arthur Fuller stories around campfires. Today, Arthur still has vivid geological and motorcycle memories of Cape-Karoo challenges that he loves to share. On and off, over 20 odd years, Sam Bowring traversed Cape-Karoo routes with numerous South African geologists. He recognized early on that his high-precision chronology tools would prove to be of immense value to record the paleo-history of the Karoo. And so it has. In 1996 Sam was the first person to date zircons collected from the Collingham Formation, establishing ‘proof of concept’ that the age of Karoo tuff beds could be measured at 100 Kyr levels using the time-consuming mechanical and chemical abrasion systems with the TIMS that he developed at MIT, and which are even now well established by several of his graduate students at leading universities in the USA. Sam continued to work unselfishly with South African paleontologists, under his motto ‘no dates, no rates’, to track the evolutionary paths of Karoo fossils. Sam had an unrivalled memory of thousands of outcrops he visited throughout his career. Sadly, Sam recently suffered brain damage; and whilst his long-term knowledge appears intact, his unique short-term memory is locked away. Thankfully his deep empathy remains as ever. Dave Roberts was the ultimate field geologist. He walked the mountains and the beaches of southern Africa, and made stunning observations that he analysed in detail. He had deep first-hand knowledge of paleo-sea levels and erosion surfaces from scrambling across them, and interpreting their histories based on his interdisciplinary connections with sedimentology, stratigraphy, paleontology and archeology—and contributed widely to appreciation of our relatively recent geological history. Dave found the oldest fossilized Homo sapiens footprints (‘Eve’s Footprints’ near Langebaan in the West Coast National Park in 1995 along both the east and south coasts of South Africa, and was protective of these ‘global heritages’). Whilst a ‘loner’—and what good field geologist is not—he shared his enthusiasm of his new discoveries and interpretations with anyone who showed the slightest interest, and even those who didn’t. Sadly whilst still in his geologic prime and with lots of ideas and goals, he passed away late in 2015; his vast geologic memory suddenly disappeared like a ‘burnt library’. Those who read his published work will gain deep insights in how to excel as an outstanding field-observer and, following his footsteps, will appreciate his astuteness as a guide towards further unravelling Cape-Karoo geo-bio narratives. Preface 1 Introduction What Is in This Book and Why? This book has 18 chapters that summarize advances made over the last 25 odd years towards better understanding the wealth and value of the geological heritage of southernmost Africa, and in particular its Phanerozoic history across the Cape-Karoo landscapes. This region is a unique natural laboratory from which to reconstruct, predominantly, the terrestrial evolution of our southern hemisphere continents over the last 500 million years or so. We have tried to summarize this history in Fig. 1.1. This book, a follow-up of an earlier book (de Wit and Ransome 1992), is an outcome of the 2015 Cape-Karoo ‘Imbizo’ (=South African meeting or dialogue, especially a gathering of the Zulu people called by the king or a traditional leader to exchange ideas) with a focus to stimulate cross-disciplinarity in future research of the Cape-Karoo archives. We asked contributors to be brief in summarizing their recent work within limited space, and to address their findings without jargon, so that both students and professionals could easily understand their aims and analyses, and to stimulate young researchers to identify new challenges and to get involved. What Is Not in This Book? Inevitably not all ongoing work is represented in this book, and some classic missing segments are major shortcomings. For example, the history of the Cape Mountains along the west coast of South Africa (e.g. Cedarberg/Piketberg) are barely mentioned, nor is its flanking Karoo stratigraphy, or their (Gariep) basement and Cape Granites. This (Saldanian) region has unique narratives to tell, particularly about the early Cape Supergroup sequences, such as the Ordovician glaciation and related fossil record, especially so because these Cape-Karoo sections are less affected by the Cape Orogeny, since the western part of the Cape Fold Belt is linked to tectonic strike-slip rather than “head-on” convergence (we expand on this a little in this Preface). Similarly, the structural history of ‘syntaxis’ linking the two Cape tectonic domains, and the related foreland depositional environment in the delta-turbidite sequences of the Tanqua Karoo that best record this tectonic history, are not documented here (the interested reader might consult Fildani et al. 2007 and references therein). Similarly, a detailed examination of the Karoo and related magmatism is wanted. However, Chaps. 6 and 12 explore some outstanding Karoo volcanic problems that have been neglected for some time, and highlight the need for more careful geochemical and geochronological data to separate those sequences that are related to Karoo magmatism and those with affinities to South American sources. The lack of coastal marine and off-shore continental margin work, as well as the details related to geomorphology and landscaping, is also obvious. To highlight these ‘black holes’ we have added some relevant sections in this Preface. Not because we understand them well, but precisely because there is severe lack of knowledge and cross-disciplinary communication; and thus to highlight where there is a real need for transformation in Cape-Karoo research in the future. Additionally the reference lists of the preface and the chapters provide ample opportunities to explore further. vii viii Preface Preface ix b Fig. 1.1 Graphic summary of the generalized Cape-Karoo stratigraphy linked to the chapters of this book. The oldest sequences (e.g. the Kango, Kaaimans and Gamtoos complexes—pale purple) comprise deformed carbonates, black phyllites with voluminous polyphase quartz veins, and dacite-granitoids (pink) that are dated between 550 and 510 Ma. These are overlain by conglomerates (the Sardinia Bay Formation in eastern Cape; the Klipheuvel Formation in western Cape) containing youngest detrital zircons dates of 521–510 Ma, and thick sequences of cross-bedded quartzites with interbedded micaceous mudrocks of the Cape Supergroup (the Table Mountain, Bokkeveld and Witteberg Groups; blues). Major décollement zones are rooted in the black phyllites, and from there propagate upward as thrusts, duplicating overlying siliclastic sequences (Chap.

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