Stephen F. Austin State University SFA ScholarWorks Electronic Theses and Dissertations Fall 12-17-2016 Geologic and Geochemical Characterization of Cross- Communication Potential within the Northern Edwards Aquifer System, Texas Ingrid J. Eckhoff Stephen F. Austin State University, [email protected] Follow this and additional works at: https://scholarworks.sfasu.edu/etds Part of the Geology Commons Tell us how this article helped you. Repository Citation Eckhoff, Ingrid J., "Geologic and Geochemical Characterization of Cross-Communication Potential within the Northern Edwards Aquifer System, Texas" (2016). Electronic Theses and Dissertations. 59. https://scholarworks.sfasu.edu/etds/59 This Thesis is brought to you for free and open access by SFA ScholarWorks. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of SFA ScholarWorks. For more information, please contact [email protected]. Geologic and Geochemical Characterization of Cross-Communication Potential within the Northern Edwards Aquifer System, Texas Creative Commons License This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License. This thesis is available at SFA ScholarWorks: https://scholarworks.sfasu.edu/etds/59 Geologic and Geochemical Characterization of Cross-Communication Potential within the Northern Edwards Aquifer System, Texas By Ingrid Jenssen Eckhoff, Bachelor of Science Presented to the Faculty of the Graduate School of Stephen F. Austin State University in Partial Fulfillment of the Requirements for the Degree of Masters of Science STEPHEN F. AUSTIN STATE UNIVERSITY December 2016 Geologic and Geochemical Characterization of Cross-Communication Potential within the Northern Edwards Aquifer System, Texas By Ingrid Jenssen Eckhoff, B.S. APPROVED: ___________________________________ Dr. Kevin Stafford, Thesis Director ___________________________________ Dr. Wesley Brown, Committee Member ___________________________________ Dr. Melinda S. Faulkner, Committee Member ___________________________________ Dr. I-Kuai Hung, Committee Member ______________________________________ Richard Berry, D.M.A. Dean of the Graduate School ABSTRACT The Edwards Aquifer is a large, complex groundwater system located throughout Central Texas in association with the Balcones Fault Zone. The San Antonio and Barton Spring segments of the Edwards Aquifer have been extensively studied in the past because they provide groundwater resources to the largely urbanized areas of San Antonio and Austin, respectively, and smaller communities along the Interstate 35 corridor. Previous research has been conducted on these southern and central portions of the Edwards Aquifer system, which have characterized the structural, hydrogeological and geochemical variations within the highly karsted region. However, the Northern Segment of the Edwards Aquifer primarily consists of undeveloped rural land, and is therefore lacking sufficient studies to fully understand the structural, hydrogeological, and geochemical systems in this region. LIDAR (Light Detection and Ranging) and remote sensing analyses have enabled identification and delineation of spatial distribution of fractures and karstic features visible at the surface, and provided valuable information regarding the understanding of potential cross-communication between aquifer systems. Water quality data from water wells of the Edwards and Trinity aquifers were extracted from the Groundwater Database of the Texas Water Development Board. ArcGIS was utilized to generate geochemical maps for spatial distribution and correlation purposes. Evidence for probable cross-communication between aquifer systems is discernable when examining the directional trend of constituents and comparing them to highly dense i areas of lineaments and sinkhole features. Results from this study provide essential data that can be used in the refinement of groundwater characterization for the northern extent of the Edwards Aquifer System. ii ACKNOWLEDGEMENTS First and foremost, I would like to thank my thesis advisor Dr. Kevin Stafford who truly went above and beyond to help me complete my master’s thesis here at Stephen F. Austin State University. Without Stafford’s helpfulness and with his door always open and ready to answer questions, I would not be where I am today. I also want to thank Dr. I-Kuai Hung, Dr. Wesley Brown, and Dr. Melinda Faulkner who are on my thesis committee, and assisted me in completing this thesis. I would like to acknowledge my mother, Unni Jenssen, and my father, Jan Eckhoff, who have been there every step of the way. This thesis and everything I have accomplished could not have been done without their support and motivation from day one. In addition to my parents, my sister, Liv, has always been a stellar role model and has always encouraged me to work hard. I would also like to thank Dr. Amy Luther, my field camp supervisor, who has always pushed me to be a better geologist and to never give up regardless of what life throws at you. Lastly, I would thank all of my friends, and especially my fellow graduate students who have shared deadlines and kept me sane during those late nights. Thank you! iii TABLE OF CONTENTS ABSTRACT ........................................................................................................................ i ACKNOWLEDGEMENTS ............................................................................................... iii TABLE OF CONTENTS .................................................................................................. iv LIST OF FIGURES........................................................................................................... vi APPENDIX FIGURES ..................................................................................................... ix LIST OF TABLES ............................................................................................................. xi LIST OF ACRONYMS .................................................................................................... xii INTRODUCTION .............................................................................................................. 1 STUDY AREA ................................................................................................................... 3 Geologic Setting ................................................................................................... 9 Stratigraphy ......................................................................................................... 18 Balcones Fault Zone .......................................................................................... 24 Hydrogeology ...................................................................................................... 27 Karst ..................................................................................................................... 33 METHODOLOGY ........................................................................................................... 35 GIS ........................................................................................................................ 35 LiDAR ................................................................................................................... 35 Lineaments .......................................................................................................... 42 Depressions ........................................................................................................ 44 Hydrochemistry ................................................................................................... 50 RESULTS ........................................................................................................................ 53 Lineament Analyses .......................................................................................... 53 Karst Feature Analyses ..................................................................................... 56 Hydrochemistry ................................................................................................... 58 DISCUSSION .................................................................................................................. 73 iv Geochemical Spatial Correlations between Aquifers ................................... 74 Sinkhole Spatial Correlation to Geochemistry ............................................... 78 Lineament Spatial Correlation to Geochemistry ............................................ 82 Composite Spatial Correlations ....................................................................... 84 Geochemistry - Piper Diagrams ....................................................................... 85 CONCLUSION ................................................................................................................ 87 Future studies ..................................................................................................... 94 BIBLIOGRAPHY ............................................................................................................. 95 APPENDIX .................................................................................................................... 100 VITA ............................................................................................................................. 115 v LIST OF FIGURES Figure 1. The study area, seen in green, is located at the boundary of Bell and Williamson