Georgia State University ScholarWorks @ Georgia State University Geosciences Theses Department of Geosciences 8-8-2017 Geochemical Signatures of Stream Capture in the Retreating Blue Ridge Escarpment, Southern Appalachian Mountains David DuBose Follow this and additional works at: https://scholarworks.gsu.edu/geosciences_theses Recommended Citation DuBose, David, "Geochemical Signatures of Stream Capture in the Retreating Blue Ridge Escarpment, Southern Appalachian Mountains." Thesis, Georgia State University, 2017. https://scholarworks.gsu.edu/geosciences_theses/108 This Thesis is brought to you for free and open access by the Department of Geosciences at ScholarWorks @ Georgia State University. It has been accepted for inclusion in Geosciences Theses by an authorized administrator of ScholarWorks @ Georgia State University. For more information, please contact [email protected]. GEOCHEMICAL SIGNATURES OF STREAM CAPTURE IN THE RETREATING BLUE RIDGE ESCARPMENT, SOUTHERN APPALACHIAN MOUNTAINS by DAVID DuBOSE Under the Direction of Katie Price, PhD ABSTRACT Stream capture is a major driver of the retreat of the Blue Ridge Escarpment, but timescales of capture are not well understood. This study examines stream sediment geochemistry to establish a set of sediment source fingerprints which can be used to identify and date the capture of the Tallulah River. Statistical analyses show significant differences in U, Th, and certain REE enrichment. These differences result from variations in bedrock along the lengths of each river and a shift in relative stream powers after capture to favor mobilization or deposition of heavy elements. The observed differences should be sufficient to identify where Tallulah sediment appears in floodplains of the capturing Tugaloo River, facilitating future dating of the capture event. Understanding the timing of river capture will provide insight into the ongoing reshaping and redistribution of river systems and interactions of geomorphic processes in the continuing evolution of the southern Appalachian Mountains. INDEX WORDS: Stream capture, Blue Ridge Escarpment, Geochemistry, Tallulah River, Southern Appalachians, Sediment, Geomorphology GEOCHEMICAL SIGNATURES OF STREAM CAPTURE IN THE RETREATING BLUE RIDGE ESCARPMENT, SOUTHERN APPALACHIAN MOUNTAINS by DAVID DuBOSE A Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science in the College of Arts and Sciences Georgia State University 2017 Copyright by David Benjamin DuBose 2017 GEOCHEMICAL SIGNATURES OF STREAM CAPTURE IN THE RETREATING BLUE RIDGE ESCARPMENT, SOUTHERN APPALACHIAN MOUNTAINS by DAVID DuBOSE Committee Chair: Katie Price Committee: Katie Price Daniel Deocampo David S. Leigh Electronic Version Approved: Office of Graduate Studies College of Arts and Sciences Georgia State University August 2017 iv DEDICATION This thesis is dedicated to my awesome wife Natalie, who stood by me from the start of my career with love and patience through all the long days in the field, all the time on the road, then picking up and moving to go back to school with our little one in tow, and even longer days of research and writing. Through everything and more. For Pop Pop Charlie, always a hard-working, hard-playing family man, and for Grandma Betty, an educator, a nature lover, always quiet, always strong. Though they didn’t get to see me finish, they never had any doubt. Most of all for little Elliot. At the beginning, she could barely roll over, then she walked, then she ran, then she kept running and started jumping and climbing. Through all of our adventures in the back yard, in the car, playing with rocks, playing with sand and trucks and dinosaurs, watching the birds, reading books and doing puzzles, every day is full of amazement and wonder, and she faces it with fascinated determination and an unquenchable thirst for knowledge like nothing I’ve ever seen. Look out world, she’s coming. v ACKNOWLEDGEMENTS I want to offer a special thanks to Dr. Katie Price for taking me on as a student when I was new to the department and my tentative area of research interest was basically “Rivers and what they do to mountains.” She was very forthcoming with ideas from small to large scales and helped me narrow down a topic by inciting an interest in stream capture, which I did not previously know I had. After digging into the literature, I discovered how surprisingly complex and poorly understood the Appalachian Mountains actually are, and I jumped at the opportunity to fill a knowledge gap related to Tallulah Gorge, a favorite hiking spot of mine. Our meetings and discussions always helped me to refocus when the workload and dataset seemed cumbersome. I always came away with more questions to find answers to and a new determination to find them. Through many plans and iterations and proposals and setbacks and alternate ideas, we finally came away with a good question to answer and a good set of data with which to answer it. Drs. Dan Deocampo and David Leigh were also instrumental in the formation of this thesis, from our initial meeting to kick around ideas for study areas and methods to later committee discussions about which directions to take the research. I had a top-notch team of researchers to work with and mine for wisdom, and I always came away feeling a little smarter (though even more aware of just how much I don’t know). I also must thank all my GSU professors because this thesis truly encompasses the breadth of my graduate school experience. In every class, there has been some topic, assignment, or discussion vi that flicked on the lightbulb over my head and eventually made its way into influencing the finished thesis. They made me work, and I came out better on the other end for it. Finally, I would like to thank the numerous U.S. Geological Survey and Department of Energy personnel, whoever and wherever they are, who have collected thousands of samples in the field and analyzed thousands of samples in the lab and compiled all the data to be made available for me to dig through from the relative comfort of my office chair. vii TABLE OF CONTENTS ACKNOWLEDGEMENTS ............................................................................................. V LIST OF TABLES ............................................................................................................ X LIST OF ABBREVIATIONS ..................................................................................... XIII 1 INTRODUCTION AND BACKGROUND .............................................................. 1 1.1 Fluvial Processes and Stream Capture.............................................................. 2 1.1.1 Stream Power and Erosion ............................................................................. 2 1.1.2 Stream Capture ............................................................................................... 4 1.2 Study Area and Geologic Setting ..................................................................... 10 1.2.1 Southern Appalachian Geomorphology ....................................................... 10 1.2.2 Northeast Georgia, Northwest South Carolina River Systems .................... 14 1.2.3 Tallulah Gorge and Tallulah River Capture ............................................... 20 1.3 Research Objectives .......................................................................................... 24 2 METHODS ................................................................................................................ 25 2.1 Data Collection and Analyses ........................................................................... 25 2.1.1 Stream Sediment Samples ............................................................................. 25 2.1.2 Bedrock Samples ........................................................................................... 27 2.2 Statistical Analyses ............................................................................................ 28 2.3 Weathering Assessment .................................................................................... 29 2.4 Stream Power Assessment ................................................................................ 30 viii 3 RESULTS .................................................................................................................. 32 3.1 Data Collection and Analyses ........................................................................... 32 3.1.1 Stream Sediment Samples ............................................................................. 32 3.1.2 Bedrock Samples ........................................................................................... 34 3.2 Statistical Analyses ............................................................................................ 36 3.3 Weathering Assessment .................................................................................... 53 3.4 Stream Power Assessment ................................................................................ 56 4 DISCUSSION ............................................................................................................ 61 4.1 Sediment Geochemistry Statistics .................................................................... 61 4.2 Weathering Assessment .................................................................................... 62 4.3 Stream Power Assessment ................................................................................ 63 4.4 Sediment Source Fingerprints.........................................................................