Tectonic history, microtopography and bottom water circulation of the Natal Valley and Mozambique Ridge, southwest Indian Ocean. By: Errol Avern Wiles Submitted in fulfilment of the degree Doctor of Philosophy In the Discipline of Geological Sciences School of Agricultural, Earth and Environmental Sciences College of Agriculture, Engineering and Science University of KwaZulu Natal, Durban South Africa 2014 i Preface The experimental work described in this thesis was carried out in the Discipline of Geological Sciences, University of KwaZulu-Natal, Westville, from July 2010 to November 2014, under the supervision of Prof. Watkeys, Dr. Green and Prof. Jokat. These studies represent original work by the author and have not otherwise been submitted in any form for any degree or diploma to any tertiary institution. Where use has been made of the work of others it is duly acknowledged in the text. Signed:_____________________ Name:________________________ Date:_____________ ii Declaration 1 – Plagiarism I, Errol Avern Wiles, declare that: 1. The research reported in this thesis, except where otherwise indicated, is my original research. 2. This thesis has not been submitted for any degree or examination at any other university. 3. This thesis does not contain other persons’ data, graphs or other information, unless specifically acknowledged as being sourced from other persons. 4. This thesis does not contain any other persons writing, unless specifically acknowledged as being sourced from other researchers. Where other written sources have been quoted then: a. Their words have been re-written but the general information attributed to them has been referenced b. Where their exact words have been used, then their writing has been placed in italics and inside quotation marks, and referenced. 5. This thesis does not contain text, graphics or tables copied from the Internet, unless specifically acknowledged, and the source being detailed in the thesis and in the References section. Signed:_____________________ Name:________________________ Date:_____________ iii Declaration 2 – Publications A detailed account of the contributions by the authors of published work is given in section 1.4 Structure and layout of Thesis (page 5). Published, peer reviewed papers comprise the following: • Article I, Chapter 3: Anomalous seafloor mounds in the northern Natal Valley, southwest Indian Ocean: Implications for the East African Rift System. Tectonophysics, 630:300–312. dx.doi.org/10.1016/j.tecto.2014.05.030. Errol Wiles a, Andrew Green a, Mike Watkeys a, Wilfried Jokat b, Ralf Krocker b a Geological Sciences, School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, Private Bag X 54001, Durban 4000, South Africa. b Alfred-Wegener-Institute for Polar and Marine Research, Am Alten Hafen 26, D-27568 Bremerhaven, Germany. • Article II, Chapter 4: The evolution of the Tugela Canyon and submarine fan: A complex interaction between margin erosion and bottom current sweeping, southwest Indian Ocean, South Africa. Marine and Petroleum Geology 44 (2013) 60 – 70. Errol Wiles a, Andrew Green a, Mike Watkeys a, Wilfried Jokat b, Ralph Krocker b a Geological Sciences, School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, Private Bag X 54001, Durban 4000, South Africa. b Alfred-Wegener-Institute for Polar and Marine Research, Am Alten Hafen 26, D-27568 Bremerhaven, Germany. • Article III, Chapter 5: A new pathway for Deep water exchange between the Natal Valley and Mozambique Basin. Accepted by Geo-Marine Letters (JrnlID 367_ArtID 383). Errol Wiles a, Andrew Green a, Mike Watkeys a, Wilfried Jokat b, Ralf Krocker b a Geological Sciences, School of Agricultural, Earth and Environmental Sciences, University of KwaZulu-Natal, Private Bag X 54001, Durban 4000, South Africa. b Alfred-Wegener-Institute for Polar and Marine Research, Am Alten Hafen 26, D-27568 Bremerhaven, Germany. In each case E. A. Wiles drafted the manuscripts and figures/tables for submission as the primary and corresponding author based on research carried out by the first author (E.A. Wiles). Subsequent authors (Prof. Mike Watkeys, Dr. Green, Prof. Dr. Wilfried Jokat and Ralph Krocker) represent advisory and editorial roles played by the Supervisor, Co- supervisors, and technical personnel. Signed:_____________________ Name:________________________ Date:_____________ iv Acknowledgements This thesis is the culmination of a journey which began in 2005 when I enrolled as an undergraduate at the University of KwaZulu-Natal. I never imagined it would come this far. The thought of going beyond Honours was daunting, and anyway, who in their right mind wants to study for that long?? However, after beginning this study in 2011 time seems to have flown. Many people and institutions have been involved is this work and I thank them all. In particular I must thank the Alfred Wegner Institute for marine and polar research. The data used in this study were made available by the Alfred Wegner Institute, without which this study would not have been possible. The National Research Foundation is acknowledged and thanked for granting scholarships (Innovation Scholarship) throughout this Doctoral study. Without this financial support this study would not have been sustainable. My supervisors, Professor Michael Watkeys, Doctor Andrew Green and Professor Wilfried Jokat are thanked for their valued guidance, support and input (academic and in general) throughout this study, as well as during my time at the University of KwaZulu Natal, on research cruises, at conferences and abroad. I have learnt a lot more from these people than this thesis can possibly show. Prof. Watkeys inspired an interest in Geology from the first lecture I took in the subject and ignited a passion for rocks and the stories they tell. Dr. Green exposed me to the world of marine geology and set me on this marine course early in my undergraduate degree, and has continued to expose me to new facets of marine geoscience. Prof. Watkeys introduced me to Prof. Jokat and the AWI in 2009. I have not looked back since. Prof. Jokat has generously allowed me access to the data used in this study, as well as providing me with fantastic practical experience through two research cruises in the southwest Indian Ocean (although both these cruises involved several weeks of seasickness). To the post-grad team from Geology Alex Metz, Carlos Loreio, Lauren Hoyer, Lauren Pretoriuos, Shannon Dixon, Leslee Salzmann, Nku Dladla, Jannie Weitz, Riaan Botha and Warwick Hastie, you all have had an impact on this thesis in one way or another, be it practical advice, as a sounding board, or a much needed distraction when my mind went AWOL. Warwick Hastie, in particular, set the tone of post-graduate research for me as a Masters student (although he likely does not realise this). His work ethic and focus is something I have tried to emulate throughout this study, and it has done me well. v To my non-varsity friends and family, in particular Craig Howie, Miguel Rodriges, Allen Foster, and my brothers Graham Wiles and Bryan Paynter, who have hiked, fished, cycled and surfed (and eaten junk-food when there was no surf) with me, I cannot thank you enough. You guys all helped me keep on track. On a professional note I must also thank Doug Slograve, Michael MacHutchon, Hayley Cawthra, Rio Lueci and Zane Thakerey for offering me the opportunity to gain practical experience associated with the marine geology/survey industry. I learnt a hell of a lot from you all, and I appreciate the time spent in this regard. It has left me with a far more well-rounded understanding than what purely academic work would have afforded me. To my family Wendy Wiles, Laura Jaggard and Matt Jaggard, thank you for standing by me through these years of study (it has been a good few years…), stressful times (there were many…), and for celebrating the good times (including, but not limited to, the submission of this thesis). Without this support life would have been a lot more difficult. We thank the BMBF (Bundesministerium fur Bildung und Forschung) for funding the scientific projects (contract number 03G0183A, 03G0730A). The crews of RV Sonne (AISTEK II) and RV Pelagia (AISTEK III) are acknowledged for their excellent support and expertise in the data acquisition phases. The financial assistance of the National Research Foundation (DAAD-NRF) towards this research is hereby acknowledged (Innovation Scholarship: 83799). Opinions expressed and conclusions arrived at, are those of the author and are not necessarily to be attributed to the DAAD-NRF. The Petroleum Agency of South Africa are thanked for allowing us access to multichannel seismic data. Lastly I thank my mind for always coming back and not disintegrating during the course of this research. vi Abstract This thesis focuses on aspects of the tectonic history, sediment delivery and subsequent sediment redistribution within the Natal Valley and Mozambique Basin of the southwest Indian Ocean. It aims to 1) better constrain the tectonic history of these basins based on anomalous seafloor features, 2) understand the timing, evolution and formative processes of sediment delivery systems within the Natal Valley and Mozambique Basin, 3) account for the redistribution of seafloor sediments within the southwest Indian Ocean. The southwest Indian Ocean opened during the Gondwana breakup event giving rise to two north/south orientated rectangular basins separated by the Mozambique ridge. Early research (1980’s) within these basins discussed basin features in terms of the available data at the time. By modern standards these data sets are relatively low resolution, and did not allow early researchers to fully account for the existence, development or evolution of many morphological features within the southwest Indian Ocean. This study uses recently acquired multibeam bathymetry and PARASOUND/3.5 kHz seismic data sets to describe and account for the geomorphology of the southwest Indian Ocean. Antecedent geology is discussed with respect to its development, in association with regional regimes, and role in provision of accommodation space and sediment redistribution within the study area.