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Patterns Within Centimeter-Scale Bedding in Carbonate Rocks in the Archean Transvaal Supergroup, South Africa

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Patterns Within Centimeter-Scale Bedding in Carbonate Rocks in the Archean Transvaal Supergroup, South Africa University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 8-2020 Patterns within centimeter-scale bedding in carbonate rocks in the Archean Transvaal Supergroup, South Africa James Harvey Alexander University of Tennessee Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Recommended Citation Alexander, James Harvey, "Patterns within centimeter-scale bedding in carbonate rocks in the Archean Transvaal Supergroup, South Africa. " Master's Thesis, University of Tennessee, 2020. https://trace.tennessee.edu/utk_gradthes/6060 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by James Harvey Alexander entitled "Patterns within centimeter-scale bedding in carbonate rocks in the Archean Transvaal Supergroup, South Africa." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Master of Science, with a major in Geology. Linda Kah, Major Professor We have read this thesis and recommend its acceptance: Robert Riding, Christopher Fedo Accepted for the Council: Dixie L. Thompson Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Patterns within centimeter-scale bedding in carbonate rocks in the Archean Transvaal Supergroup, South Africa A Thesis Presented for the Master of Science Degree The University of Tennessee, Knoxville James Harvey Alexander August 2020 Copyright © 2020 by James Harvey Alexander. All rights reserved. ii DEDICATION Mr. George “Larry” Ganley TMSCA/UIL Science Coach Flour Bluff Junior High School 12/17/1941 – 2/27/2009 Thank you iii ACKNOWLEDGEMENTS This project was supported by funding from the Geological Society of America (GSA), the Society for Sedimentary Geology (SEPM), the University of Tennessee (Graduate Teaching Assistantship), and the Kenneth R. Walker faculty endowment (to Linda Kah). Many individuals and groups contributed to this work including: Dr. Linda Kah for the opportunity to work, grow, and travel with unbridled support; Dr. Wladyslaw Altermann for his guidance and friendship in South Africa; Dr. Robert Riding, Dr. Chris Fedo, and Dr. Edmund Perfect for critical review; Agustin Kriscautzky for field assistance in South Africa; Jordan Romero for preparation of petrographic slides and geochemical work; Gert, Marti, Handre, and Archie for accommodations at Riverview Lodge Prieska; My family for their unconditional love. iv ABSTRACT The interpretation of Archean marine depositional environments relies on precise evaluation of facies that reflect shifts in sediment distribution and accumulation, which in turn are driven by changes in accommodation, in situ carbonate precipitation and detrital deposition, and hydrodynamic energy conditions. In the Griqualand West sub-basin of the Transvaal Supergroup, the Ghaap Plateau Facies (Reivilo Formation) and Prieska Facies (Upper Nauga Formation) represent distinct facies belts (250 km apart) that both consist of cm-scale bedding alternations within primarily carbonate strata. In this study, facies descriptions and stratigraphic analyses are combined with limited petrographic and geochemical investigation to compare bedding style and environments of deposition. Centimeter-scale bedding couplets are composed of a lower interval consisting of coarsely recrystallized calcite (A-type laminae) and an upper interval consisting of finely crystalline dolomite that can contain detrital sediment (B-type laminae). Couplets are inferred to represent changes in depositional conditions that potentially reflect eustatic sea level changes that resulted in variation in both detrital input and energy conditions of carbonate environments. Petrographic and geochemical analysis of facies within the Reivilo and Upper Nauga Formations reveal pervasive diagenesis that limits interpretation of microscale fabrics. However, the degree of diagenesis is similar in A- and B-type components in both of the two localities. Stratigraphic analysis of cm-scale couplets suggests similarity in response to oscillating parameters but with differing magnitudes. Modified Fischer plots, which v examine both the overall change in stacked couplet thickness through time, as well as changes in contributions from A- and B-components to couplet thickness, indicate that carbonate deposition was consistent within and between both facies belts, and that changes in detrital input played a primary role impacting couplet thickness. Strata of the Campbellrand Subgroup has previously been interpreted as a carbonate platform (Ghaap Plateau Facies) with a discrete, tectonically enhanced margin—reaching a penultimate relief of ~900 m—adjacent to deep slope and basinal (Prieska Facies) environments. This study, however, suggests that the Ghaap Plateau and Prieska facies accumulated carbonate in much more similar environments, which requires rethinking the current basin model. vi TABLE OF CONTENTS 1 Introduction .................................................................................................................. 1 1.1 Geologic Setting .................................................................................................... 6 1.1.1 The Transvaal Supergroup ................................................................... 6 1.1.2 The Campbellrand Subgroup ............................................................... 7 1.1.3 Locations of Study .............................................................................. 10 2 Methods ..................................................................................................................... 12 2.1 Field Methods ...................................................................................................... 12 2.1.1 Site Selection ..................................................................................... 12 2.1.2 Data Collection ................................................................................... 12 3 Data ............................................................................................................................ 13 3.1 Generalized Stratigraphy ..................................................................................... 13 3.1.2 Platform: Ghaap Plateau Facies......................................................... 13 3.1.2 Basin: Prieska Facies ......................................................................... 14 3.2 Facies Descriptions ............................................................................................. 15 3.2.1 Ghaap Plateau Facies ........................................................................ 15 3.2.2 Prieska Facies .................................................................................... 20 3.3 Interpretation........................................................................................................ 24 3.3.1 Lithofacies and Depositional Environment of Ghaap Plateau Facies . 24 3.3.2 Lithofacies and Depositional Environment of Prieska Facies ............. 29 4 Analysis ...................................................................................................................... 32 4.1 Petrographic and Geochemical Analysis ............................................................. 32 4.1.1 Methods ............................................................................................. 33 4.1.2 Results ............................................................................................... 35 4.1.3 Interpretation ...................................................................................... 38 4.2 Analysis of Stratigraphic Architecture .................................................................. 40 4.2.1 Fischer Plot Analysis of Bedding Alternations .................................... 40 4.2.2 Methods ............................................................................................. 41 4.2.3 Results ............................................................................................... 43 4.2.4 Interpretation ...................................................................................... 44 4.3.1 Statistical Analysis of Bedding Alternations ........................................ 52 4.3.2 Methods ............................................................................................. 54 4.3.3 Results ............................................................................................... 56 4.3.4 Interpretation ...................................................................................... 58 5 Discussion .................................................................................................................. 60 5.1 Implications for Basin Structure ........................................................................... 62 5.2 Implications for Basin Polarity .............................................................................. 64 5.3 Implications for Archean Environments ............................................................... 65 6 Conclusions ...............................................................................................................
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