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Thesis Sci 2016 Sciscio Lara.Pdf Position of the Triassic-Jurassic boundary in South Africa and Lesotho: A multidisciplinary approach aimed at improving the chronostratigraphy and biostratigraphy of the Elliot Formation, Stormberg Group Lara Sciscio THESIS presented in fulfilment of the requirements for the degree of PHILOSOPHIAE DOCTOR in GEOLOGY University iofn the Cape Town FACULTY OF SCIENCE of the Supervisor Dr. E. M. Bordy Co-supervisor: Dr. M. O. de Kock December 2015 The copyright of this thesis vests in the author. No quotation from it or information derived from it is to be published without full acknowledgement of the source. The thesis is to be used for private study or non- commercial research purposes only. Published by the University of Cape Town (UCT) in terms of the non-exclusive license granted to UCT by the author. University of Cape Town DECLARATION I declare that this thesis is my own original work, conducted under the supervision of Dr. E.M. Bordy. It is submitted for the degree of Doctor of Philosophy at the Faculty of Science at the University of Cape Town, Cape Town. No part of this research has been submitted in the past, or is being submitted, for a degat any other University. Lara Sciscio December 2015 "Nothing, my friends, is so sobering as an outcrop. And many a fine theory has been punctured by a drill hole." Francis John Pettijohn (1956) i Table of Contents Declaration ..................................................................................................................................................... i Acknowledgments ....................................................................................................................................... vii Abstract ...................................................................................................................................................... viii 1 General introduction ........................................................................................................................... 10 1.1 Thesis rationale ........................................................................................................................... 11 1.2 Statement of research problem .................................................................................................... 12 1.3 Literature review (general) .......................................................................................................... 14 1.3.1 End Triassic extinction event (ETE) ................................................................................... 14 1.3.2 Position of the Triassic-Jurassic boundary .......................................................................... 15 1.4 The structure of the dissertation .................................................................................................. 17 2 Geological background ....................................................................................................................... 19 2.1 Cape Orogeny and the main Karoo Basin ................................................................................... 19 2.2 The Stormberg Group (Upper Karoo Supergroup) ..................................................................... 21 2.3 Elliot Formation .......................................................................................................................... 23 2.3.1 Historical background ......................................................................................................... 24 2.3.2 Lithostratigraphy ................................................................................................................. 25 2.3.3 Age the Elliot Formation ..................................................................................................... 28 3 Triassic-Jurassic fossil groups and biostratigraphic dating of the Elliot Formation ........................... 30 3.1 Biostratigraphy of the Elliot Formation, Karoo Basin ................................................................ 31 3.2 “Euskelosaurus” Range Zone ..................................................................................................... 33 3.2.1 Global correlatives of the lower Elliot Formation .............................................................. 35 3.3 Massospondylus Range Zone ...................................................................................................... 42 3.3.1 Global correlatives of the upper Elliot Formation .............................................................. 43 4 Magnetostratigraphy: a general introduction ...................................................................................... 49 4.1 Late Triassic- Early Jurassic magnetostratigraphic work in South Africa .................................. 49 4.1.1 The ‘Van Zijl reversal’ and palaeomagnetic data from the overlying Drakensberg Group 52 4.2 Global perspectives ..................................................................................................................... 53 4.2.1 Triassic-Jurassic magnetostratigraphy problems and perspectives ..................................... 54 4.2.2 Time resolution of magnetostratigraphic correlation .......................................................... 54 4.3 Late Triassic-Early Jurassic Tethyan marine magneto- and bio-stratigraphy, in brief ............... 55 4.3.1 Norian - Rhaetian transition ................................................................................................ 55 ii 4.3.2 Rhaetian – Hettangian transition ......................................................................................... 58 4.4 Continental record ....................................................................................................................... 59 4.4.1 Non-marine and marine TJB section comparisons ............................................................. 59 4.4.2 Newark and its importance ................................................................................................. 60 4.4.3 Continental Carnian - Norian boundary .............................................................................. 67 4.4.4 Continental Norian-Rhaetian Boundary and the duration of the Rhaetian ......................... 68 4.5 Early Jurassic magnetostratigraphy ............................................................................................ 71 5 Sampling and methodology ................................................................................................................ 73 5.1 Palaeomagnetic sampling ............................................................................................................ 73 5.2 Demagnetization ......................................................................................................................... 73 5.3 XRD, XRF and ICP-MS analyses ............................................................................................... 74 5.3.1 XRD .................................................................................................................................... 74 5.3.2 XRF & ICP-MS .................................................................................................................. 75 Result chapters for southern-most sections ................................................................................................. 76 6 New palaeomagnetic constraints for the Elliot Formation at the type locality at Barkly Pass, Eastern Cape, South Africa ...................................................................................................................................... 77 6.1 Introduction ................................................................................................................................. 77 6.1.1 Previous mineralogy/geochemistry ..................................................................................... 79 6.1.2 Previous magnetostratigraphy ............................................................................................. 79 6.1.3 Biostratigraphy: Palaeontological information from BP ..................................................... 80 6.1.4 Sampling ............................................................................................................................. 81 6.2 Results ......................................................................................................................................... 81 6.2.1 Sedimentology .................................................................................................................... 81 6.2.2 Demagnetization results ...................................................................................................... 85 6.2.3 Reversals test ...................................................................................................................... 88 6.3 Conclusion .................................................................................................................................. 91 7 Newly constructed southern magnetostratigraphic section for a LEF-UEF site within the Quthing district, Lesotho ........................................................................................................................................... 94 7.1 Introduction ................................................................................................................................. 94 7.1.1 Previous palaeontological work in the Quthing district ...................................................... 94 7.1.2 Sampling ............................................................................................................................
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