Graduate Theses, Dissertations, and Problem Reports 2016 Influence of the Gondwanide Magmatic Arc and Cape Fold Belt on the Karoo Basin - South Africa Clyde Pitt Findlay III Follow this and additional works at: https://researchrepository.wvu.edu/etd Recommended Citation Findlay III, Clyde Pitt, "Influence of the Gondwanide Magmatic Arc and Cape Fold Belt on the Karoo Basin - South Africa" (2016). Graduate Theses, Dissertations, and Problem Reports. 5597. https://researchrepository.wvu.edu/etd/5597 This Thesis is protected by copyright and/or related rights. It has been brought to you by the The Research Repository @ WVU with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you must obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. 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Influence of the Gondwanide Magmatic Arc and Cape Fold Belt on the Karoo Basin – South Africa Clyde Pitt Findlay III Thesis submitted to the Eberly College of Arts and Sciences at West Virginia University In partial fulfillment of the requirements for the degree of Masters of Science In Geology Amy Weislogel, Ph.D., Chair Tim Carr, Ph.D. Jaime Toro, Ph.D. Department of Geology and Geography Morgantown, West Virginia 2016 Keywords: Karoo Basin, Gondwana, Permian, Triassic, Shale, Mudstone, Provenance, Geochemistry, Major Elements, Trace Elements, Rare Earth Elements, Sm-Nd, Subsidence Model, Foreland Basin Copyright 2016 Clyde Pitt Findlay III ABSTRACT Influence of the Gondwanide Magmatic Arc and Cape Fold Belt on the Karoo Basin – South Africa Clyde Pitt Findlay III The Permian Ecca Group in South Africa preserves a thick succession of clastic basin fill, including mud-rich turbidite sequences and hemipelagic mudstone units. Provenance of mud influx into the basin is an important constraint for understanding the tectonic processes influencing regional basin development and distribution of organic-rich Lower Ecca Group mudstone and subsequent depositional style of the Upper Ecca Group turbidite systems. In this study, we interpret the Ecca Group mudstones were sourced by the Cape Fold Belt and Gondwanide Magmatic Arc based on geochemistry and mineralogy of 38 mudstone samples. Muscovite and high quartz content (average 32.9%) indicate metamorphic and recycled sedimentary sources. Chemical index of alteration (CIA) values are greatest (CIA = 76 – 82) and Index of Compositional Variability (ICV) is depressed (ICV = 0.5 – 0.8) at the base of the Ecca Group, and indicate less weathering upsection. Rare earth element abundances display LREE enrichment and a negative Eu anomaly, and various trace element plots are consistent with mixing of sediment derived from Old Upper Continental Crust (OUC) and Young Differentiated Arc (YDA) terranes, such as the Cape Fold Belt and Gondwanide Magmatic Arc, respectively. Epsilon Nd and chondritic model ages are consistent with mixing of OUC and YDA sources. These results indicate that the southern Gondwanide Magmatic Arc and the Cape Fold Belt affected subsidence and sedimentation during early development of the Karoo Basin, and that the basin is a retroarc foreland basin. Acknowledgments First and foremost I thank my wife, Jenny, for helping me through my master’s degree. She not only kept me on track to finish writing this thesis, but supported me financially as well. I would also like to thank my advisor, Amy Weislogel, for introducing me to the Karoo project and guiding me through my research. I also thank my graduate committee, Tim Carr and Jaime Toro, for their support. This project would not have been possible without the help of my fellow classmates Matt McKay and Ben Johnson. Finally I would like to thank Harold Stowell and Liz Bollen at the University of Alabama, the GeoAnalytical lab at Washington State University, Actlabs, and the Shared Resource Facilities at West Virginia University for the use of their analytical facilities. iii Table of Contents ABSTRACT ................................................................................................................................................. ii Acknowledgments ...................................................................................................................................... iii List of Tables ............................................................................................................................................ viii Chapter 1: Introduction ............................................................................................................................. 1 1.1 Research Problem ............................................................................................................................. 1 1.2 Geologic Background ........................................................................................................................ 3 1.2.1 Tectonic setting ........................................................................................................................ 3 1.2.2 Karoo Basin Stratigraphy ........................................................................................................ 4 1.2.2.1 Laingsburg Subbasin ............................................................................................................. 6 1.2.2.2 Ripon Subbasin ...................................................................................................................... 6 1.2.3 Previous Provenance Studies .................................................................................................. 6 1.3. Provenance Terranes ....................................................................................................................... 7 1.3.1 Kalahari Craton and Namaqua-Natal Metamorphic Province ............................................. 8 1.3.2 Pan-African Orogenic belts ..................................................................................................... 8 1.3.3 North Patagonian and Deseado Massifs ................................................................................ 8 1.3.4 Cape Fold Belt ......................................................................................................................... 8 2.1 Sampling .......................................................................................................................................... 10 2.2 Petrography ..................................................................................................................................... 13 2.3 X-ray Diffraction Analysis ............................................................................................................. 13 2.4 X-ray Fluorescence analysis ........................................................................................................... 13 2.5 ICP-MS Analysis ............................................................................................................................. 14 2.7 Samarium and Neodymium Isotopes ............................................................................................ 15 Chapter 3: Results ..................................................................................................................................... 15 3.1 Petrography Results ........................................................................................................................ 15 3.2 Mineralogy Results ......................................................................................................................... 19 3.2.1 Laingsburg Subbasin ............................................................................................................. 19 3.2.2 Ripon Subbasin ...................................................................................................................... 20 3.3 Major Element Results ................................................................................................................... 21 3.3.1 Laingsburg Subbasin ............................................................................................................. 21 iv 3.3.2 Ripon Subbasin ...................................................................................................................... 23 3.3.3 Comparison of Major Element Composition ........................................................................ 25 3.4 Trace Element Results .................................................................................................................... 28 3.5 Rare Earth Element Results........................................................................................................... 30 Chapter 4: Discussion ............................................................................................................................... 37 4.1 Provenance of mudstone units in the Ecca and Beaufort groups ............................................... 37 4.1.1 Lithology and Composition of the source terranes ............................................................... 37 4.1.2 Weathering of the source terranes .......................................................................................