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Breakup Unconformity SEDIMENTOLOGICAL AND STRATIGRAPHICAL ASPECTS OF THE SYN- TO POST-RIFT TRANSITION ON FULLY SEPARATED CONJUGATE MARGINS Duarte Miguel Paulinha Soares A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Cardiff University September 2014 DECLARATION This work has not been submitted in substance for any other degree or award at this or any other university or place of learning, nor is being submitted concurrently in candidature for any degree or other award. Signed ………………………………………… (candidate) Date ………………………… STATEMENT 1 This thesis is being submitted in partial fulfilment of the requirements for the degree of PhD Signed ………………………………………… (candidate) Date ………………………… STATEMENT 2 This thesis is the result of my own independent work/investigation, except where otherwise stated. Other sources are acknowledged by explicit references. The views expressed are my own. Signed ………………………………………… (candidate) Date ………………………… STATEMENT 3 I hereby give consent for my thesis, if accepted, to be available online in the University’s Open Access repository and for inter-library loan, and for the title and summary to be made available to outside organisations. Signed ………………………………………… (candidate) Date ………………………… To my mother and father. In memory of Avô Zé and Avó Vidade. Abstract The integration of several industry and scientific 2D seismic surveys with various well data allowed for the first time a detailed analysis of the sedimentological, stratigraphic and architectural changes recorded during syn- to post-rift transitions on passive margins. The Northwest Iberia margin and its conjugate margin of Newfoundland formed the basis for an interpretive model. Comparison with the South Australia–East Antarctica conjugate margins enabled hypothesis testing and premise refinement. The breakup unconformity concept is revised and a more comprehensive term is proposed for the stratigraphic surface recording the transition between syn- and post-rift: the lithospheric breakup surface. This new term: a) discriminates between continental crust breakup and complete lithospheric breakup as verified in several magma-poor margins, and b) takes into account the different character this surface can show according to its position on the margin. The concept of a breakup sequence is proposed as a sedimentary sequence showing a distinct architecture to strata deposited prior to the lithospheric breakup event. The breakup sequence records the depositional changes occurring across the lithospheric breakup surface due to lithospheric adjustments triggered by lithospheric breakup. Contourites were identified for the first time as being associated with lithospheric breakup, supposedly being triggered by the lithospheric plate in-plane stress release occurring at the time of lithospheric breakup. Consequently, it is proposed that contourites can be used as an indicator for established lithospheric breakup. On the East Antarctica margin, a surface usually dated as mid Eocene to early Oligocene by comparison with the conjugate South Australia margin, is dated as latest Maastrichtian–earliest Palaeocene using data from IODP Site 1356. This new date suggests that the surface is a lithospheric breakup surface, which can explain its generation and the overlying strong contouritic deposition. I Author’s note Chapters 4 and 5 of this thesis were published as two papers in an international publication: Chapter 4 has been published as: The breakup sequence and associated lithospheric breakup surface: Their significance in the context of rifted continental margins (West Iberia and Newfoundland margins, North Atlantic) . Soares, D.M., Alves, T.M., Terrinha, P., (2012), Earth and Planetary Science Letters 355–356, p. 311-326. Chapter 5 has been published as: Contourite drifts on early passive margins as indicators of established lithospheric breakup . Soares, D., Alves T., Terrinha, P. (2014), Earth and Planetary Science Letters, 401, p. 116-131. II Acknowledgments My parents should be thanked in first place, as this thesis came to existence due to them, not only because they are my parents but as well because it was them who instilled in me the love for science/questioning in general (my mother) and rocks in particular (my father). Thanks go to my three supervisors, Tiago Alves, Pedro Terrinha and Joe Cartwright, for their support during this project. Tiago Alves, as my first supervisor I want to thank for his crucial editorial work and being there when needed. Pedro Terrinha and Joe Cartwright are thanked for their help on key moments of this project. Fundação para a Ciência e a Tecnologia (FCT) is thanked for the SFRH/BD/64127/2009 PhD scholarship which allowed me to undertake this project. I must thank DGEG/DPEP (Direcção Geral de Energia e Geologia/Divisão para a Pesquisa e Exploração de Petróleo), in particular Teresinha Abecassis, Carlos Moita, José Miguel Martins and Maria José Trindade for granting me access to their archives and use of their facilities. Cristina Roque is thanked for her help, discussions and confirmation of some of my interpretations. Carlos Kullberg is thanked for his support for my field work in Portugal. Gwenn Péron-Pinvidic and Tim Reston are thanked for providing the CAM survey. A big thank you goes to those persons behind the extremely useful projects and respective websites Academic Seismic Portal (ASP) at UTIG, the Antarctic Seismic Data Library System (SDLS), the International Ocean Discovery Program (IODP) database and the General Bathymetric Chart of the Oceans (GEBCO) from which so much data is available for researchers and without it this project would not be possible. Rafael Moura and Blueback Reservoirs are thanked for providing access to the Blueback Geophysics Toolbox plug-in for Petrel. University Centre in Svalbard (UNIS) is thanked for offering me a place on their ‘Sequence Stratigraphy–A tool for basin analysis’ course, one of the most enjoyable things I have done during this project. The Halifax 2008 Legacy Bursary 2008 (a big thanks to David Brown) and the organization of the Atlantic Conjugate Margins Conference 2014–St. John's are thanked for their generous financial support, which allowed me to attend this conference. I thank the reviewers of my papers, Javier Hernández-Molina, Adriano Viana and three anonymous reviewers, for their very useful comments who greatly helped improve III the quality of my work. The staff from Cardiff University is thanked, especially Gwen Pettigrew for her computer expertise and humour. These years spent at the 3D Lab group in Cardiff University allowed me to meet many people that were important for several reasons during the completion of this project. With them, I had many scientific discussions, they helped me with my work, they provided moments of good fun, and in general they helped preserve my mental sanity intact while writing. They are Martino, Davide & Ana, Aldina (plus thanks for your house while doing work in Lisbon to avoid commuting–part 2), Bledd, Ricardo, Iqbal, Cristina, Chris, Kamal, and all the other colleagues from the 3D Lab. The above mentioned extends to people from other groups as well: Paola, Laura, Maggi, Anabel, Scott and Katie. Lesley Cherns is thanked for her friendship, her teachings while in the field in the Cantabria Mountains (I will miss that!) and her love for Palaeontology, which helped maintain mine on. Of course, not only those associated with Geology are to be thanked, other people played an important role in my life at Cardiff to who I need to thank: Treena Huang (thank you very much! :), Adam & Ana, Katia (& Martino), Mafalda & Zé, Rita & Jon (plus Sarah & Sophie), Bei-Shan (Mei-mei), Hung-Chang, Jia-Hau, Hélio, Sara, Padmasimha (I will miss your great Yoga classes a lot). During the completion of this thesis I went back to Portugal, not only on holidays but for work as well. Some friends should be thanked for hearing me complaining about the Welsh weather and the project in general: Alcobia, Paulo & Ana, Pedro & Karina, Alvaro, André, Gabi (thanks for your house while working in Lisbon to avoid commuting–part 1), Pastor and many others. At last but most importantly, is the giant thank you I owe to my wife. Huiyu helped me through these years, while she was doing a PhD as well. She fed me (I have many meals to cook to pay you back!), supported me, wisely advised me on many things and gave me her love even during the many days I arrived home long after she was in bed and many weekends without resting. I could not have done this without her. Thank you, very much :) IV Table of Contents Summary ........................................................................................................................ ............... I Author’s note ............................................................................................................................... II Acknowledgments .................................................................................................................... III Table of Contents......................................................................................................................... V Table of abbreviations .............................................................................................................. XI Chapter One Introduction.................................................................................................................... ................. 1 1.1. Project rationale and objectives .........................................................................................
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