University of Arkansas, Fayetteville ScholarWorks@UARK Theses and Dissertations 5-2017 Depositional Dynamics of the Upper Eagle Ford (Upper Cretaceous): Karnes and Gonzales Counties, South Texas Josie Brunick University of Arkansas, Fayetteville Follow this and additional works at: http://scholarworks.uark.edu/etd Part of the Geochemistry Commons, and the Geology Commons Recommended Citation Brunick, Josie, "Depositional Dynamics of the Upper Eagle Ford (Upper Cretaceous): Karnes and Gonzales Counties, South Texas" (2017). Theses and Dissertations. 1889. http://scholarworks.uark.edu/etd/1889 This Thesis is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of ScholarWorks@UARK. For more information, please contact [email protected], [email protected]. Depositional Dynamics of the Upper Eagle Ford (Upper Cretaceous): Karnes and Gonzales Counties, South Texas A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geology by Josie Brunick University of Arkansas Bachelor of Science in Geology, 2015 May 2017 University of Arkansas This thesis is approved for recommendation to the Graduate Council. Dr. Walter Manger Thesis Director Dr. Thomas McGilvery Dr. Adriana Potra Committee Member Committee Member Abstract The mixed siliciclastic/carbonate late Cretaceous Eagle Ford Formation is commonly divided into the lower Eagle Ford and the upper Eagle Ford. The lower Eagle Ford is arguably the most obvious organic rich interval highlighted with wireline log data; however, the upper Eagle Ford may have just as much potential for hydrocarbon production success as the lower Eagle Ford has had. A better understanding of the upper Eagle Ford will allow a more thorough and educated assessment into its full potential as an unconventional reservoir, and allow its sweet spots for oil or gas to be found and exploited. This study is based on the description and interpretation of four cores of the upper Eagle Ford located within Karnes and Gonzales counties, Texas, thin sections, and key XRF data in an effort to better understand its sediment sources and depositional regime. Seven lithofacies were identified in the upper Eagle Ford are as follows: 1) Bioturbated Wackestone/Packstone; 2) Deformed Wackestone/Packstone; 3) Wavy Laminated Wackestone/Packstone; 4) Massive Mudstone/Wackestone; 5) Coarsely to Finely Laminated Wackestone/Packstone; 6) Massive packstone/grainstone; 7) Volcanic Ash. The highest Total Organic Carbon (TOC) percent relative to each core always occurred within the base of the upper Eagle Ford. In fact, the highest TOC percentage recorded was 4.5% within the base of the upper Eagle Ford in the most distally located core. Thorium to Uranium ratios of the upper Eagle Ford were on average less than 1 indicating that the upper Eagle Ford contains very little terrigenous sourced material. Nickel, copper, vanadium, molybdenum, and uranium concentrations were also analyzed and correlated to relative organic matter influx and Paleoredox levels within the upper Eagle Ford in each core. ©2017 by Josie Brunick All Rights Reserved Acknowledgements Much appreciation and gratitude goes out to the San Antonio division of EOG Resources (Eddie Valek and Nestor Phillips) for giving me this dataset for my thesis, and to my thesis committee (Dr. Walter Manger, Dr. Thomas McGilvery, and Dr. Adriana Potra) for their patience with working with me. Dedication To my husband, who no matter how stressed and irritable I was during my college career, was always willing to put up with my neglect and never lost faith in me. Table of Contents I. Introduction ..............................................................................................................................1 A. Geologic Background ............................................................................................................... 3 B. Previous Investigations ............................................................................................................. 8 C. Statement of the Problem ........................................................................................................ 12 II. Data and Methods ..................................................................................................................13 A. Data Limitations...................................................................................................................... 16 III. Lithofacies Descriptions ........................................................................................................17 A. Bioturbated Wackestone/Packstone ........................................................................................ 19 B. Deformed Wackestone/Packstone .......................................................................................... 21 C. Wavy Laminated Wackestone/Packstone ............................................................................... 23 D. Massive Mudstone/Wackestone .............................................................................................. 25 E. Coarsely to Finely Laminated Wackestone/Packstone ........................................................... 27 F. Massive Packstone/Grainstone ............................................................................................... 30 G. Volcanic Ash ........................................................................................................................... 32 IV. Depositional Processes Evaluation .......................................................................................35 A. Finely to Coarsely Laminated Wackestone/Packstone: Suspension Settling ......................... 35 B. Wavy Laminated Wackestone/Packstone: Bottom Water Currents ....................................... 37 C. Deformed Wackestone/Packstone: Post-Deposition Soft-Sediment Deformation Processes 39 D. Bioturbated Wackestone/Packstone: Higher Oxygenation and Thriving Organisms ............. 42 E. Massive Mudstone/Wackestone: Mass Wasting Events ......................................................... 42 F. Massive Packstone/Grainstone: Turbidites and Diagenetic Recrystallization ........................ 45 V. Geochemistry ..........................................................................................................................51 A. Introduction ............................................................................................................................. 51 B. Thorium to Uranium Ratio...................................................................................................... 52 C. Thorium to Uranium Ratio Method ........................................................................................ 56 D. Thorium to Uranium Ratio Results ......................................................................................... 56 E. Nickel and Copper Enrichments as Organic Matter Flux Indicators ...................................... 62 F. Nickel and Copper Analysis Results....................................................................................... 62 G. Molybdenum, Vanadium, and Uranium Enrichments as Paleoredox Conditions .................. 66 H. Molybdenum, Vanadium, and Uranium Analysis Results...................................................... 67 VI. Summary and Conclusions ...................................................................................................77 A. Lithological and Sedimentological Conclusions .................................................................... 77 B. Geochemistry Conclusions ..................................................................................................... 81 VII. References ...............................................................................................................................84 VIII. Appendices ..............................................................................................................................91 A. Appendix A: Core 1 TOC Data .............................................................................................. 91 B. Appendix B: Core 2 TOC Data ............................................................................................... 92 C. Appendix C: Core 3 TOC Data ............................................................................................... 93 D. Appendix D: Core 4 TOC Data .............................................................................................. 94 E. Appendix E: Core 1 XRF Data ............................................................................................... 95 F. Appendix F: Core 2 XRF Data ............................................................................................. 100 G. Appendix G: Core 3 XRF Data ............................................................................................. 112 H. Appendix H: Core 4 XRF Data ............................................................................................. 133 List of Figures Figure 1: EIA map of Eagle Ford Hydrocarbons ............................................................................ 2 Figure 2: Simplified stratigraphic column ...................................................................................... 3 Figure 3: Paleogeographic maps of the late Cretaceous ................................................................. 5 Figure 4: Structural and Geologic Features ...................................................................................