Palinspastic Reconstruction Around a Thrust Belt Recess: an Example from the Appalachian Thrust Belt in Northwestern Georgia
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University of Kentucky UKnowledge University of Kentucky Doctoral Dissertations Graduate School 2010 PALINSPASTIC RECONSTRUCTION AROUND A THRUST BELT RECESS: AN EXAMPLE FROM THE APPALACHIAN THRUST BELT IN NORTHWESTERN GEORGIA Brian Stephen Cook University of kentucky, [email protected] Right click to open a feedback form in a new tab to let us know how this document benefits ou.y Recommended Citation Cook, Brian Stephen, "PALINSPASTIC RECONSTRUCTION AROUND A THRUST BELT RECESS: AN EXAMPLE FROM THE APPALACHIAN THRUST BELT IN NORTHWESTERN GEORGIA" (2010). University of Kentucky Doctoral Dissertations. 5. https://uknowledge.uky.edu/gradschool_diss/5 This Dissertation is brought to you for free and open access by the Graduate School at UKnowledge. It has been accepted for inclusion in University of Kentucky Doctoral Dissertations by an authorized administrator of UKnowledge. For more information, please contact [email protected]. ABSTRACT OF DISSERTATION Brian Stephen Cook The Graduate School University of Kentucky 2010 PALINSPASTIC RECONSTRUCTION AROUND A THRUST BELT RECESS: AN EXAMPLE FROM THE APPALACHIAN THRUST BELT IN NORTHWESTERN GEORGIA _____________________________________ ABSTRACT OF DISSERTATION _____________________________________ A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College Arts and Sciences at the University of Kentucky By Brian Stephen Cook Lexington, Kentucky Director: Dr. William A. Thomas, Hudnall Professor of Geological Sciences Lexington, Kentucky 2010 Copyright © Brian Stephen Cook 2010 ABSTRACT OF DISSERTATION PALINSPASTIC RECONSTRUCTION AROUND A THRUST BELT RECESS: AN EXAMPLE FROM THE APPALACHIAN THRUST BELT IN NORTHWESTERN GEORGIA In a well-defined subrecess in the Appalachian thrust belt in northwestern Georgia, two distinct regional strike directions intersect at approximately 50°. Fault intersections and interference folds enable tracing of both structural strikes. Around the subrecess, tectonically thickened weak stratigraphic layers—shales of the Cambrian Conasauga Formation—accommodated ductile deformation associated with the folding and faulting of the overlying Cambrian–Ordovician regional competent layer. The structures in the competent layer are analogous to those over ductile duplexes (mushwads) documented along strike to the southwest in Alabama. The intersection and fold interference exemplify a long-standing problem in volume balancing of palinspastic reconstructions of sinuous thrust belts. Cross sections generally are constructed perpendicular to structural strike, parallel to the assumed slip direction. An array of cross sections around a structural bend may be restored and balanced individually; however, restorations perpendicular to strike across intersecting thrust faults yield an imbalance in the along-strike lengths of frontal ramps. The restoration leads to a similar imbalance in the surface area of a stratigraphic horizon, reflecting volume imbalance in three dimensions. The tectonic thickening of the weak-layer shales is evident in palinspastically restored cross sections, which demonstrate as much as 100% increase in volume over the restored-state cross sections. The cause of the surplus shale volume is likely pre- thrusting deposition of thick shale in a basement graben that was later inverted. The volume balance of the ductile duplex is critical for palinspastic reconstruction of the recess, and for the kinematic history and mechanics of the ductile duplex. KEYWORDS: Appalachian thrust belt, geology of Georgia, recess, palinspastic restoration, ductile duplex Brian Stephen Cook Student’s signature July 21st, 2010 Date PALINSPASTIC RECONSTRUCTION AROUND A THRUST BELT RECESS: AN EXAMPLE FROM THE APPALACHIAN THRUST BELT IN NORTHWESTERN GEORGIA By Brian Stephen Cook Dr. William A. Thomas Director of Dissertation Dr. Alan E. Fryar Director of Graduate Studies July 21st, 2010 RULES FOR THE USE OF DISSERTATIONS Unpublished dissertations submitted for the Doctor's degree and deposited in the University of Kentucky Library are as a rule open for inspection, but are to be used only with due regard to the rights of the authors. Bibliographical references may be noted, but quotations or summaries of parts may be published only with the permission of the author, and with the usual scholarly acknowledgments. Extensive copying or publication of the dissertation in whole or in part also requires the consent of the Dean of the Graduate School of the University of Kentucky. A library that borrows this dissertation for use by its patrons is expected to secure the signature of each user. Name Date ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ DISSERTATION Brian Stephen Cook The Graduate School University of Kentucky 2010 PALINSPASTIC RECONSTRUCTION AROUND A THRUST BELT RECESS: AN EXAMPLE FROM THE APPALACHIAN THRUST BELT IN NORTHWESTERN GEORGIA _____________________________________ DISSERTATION _____________________________________ A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the College Arts and Sciences at the University of Kentucky By Brian Stephen Cook Lexington, Kentucky Director: Dr. William A. Thomas, Hudnall Professor of Geological Sciences Lexington, Kentucky 2010 Copyright © Brian Stephen Cook 2010 This dissertation is dedicated to God, who has blessed me with a wonderful family ACKNOWLEDGMENTS First, I would first like to thank my advisor, Dr. William A. Thomas, for his insight and guidance during the course of this research project. Also, I would like to thank my committee: Dr. James Drahovzal, Dr. Michael Kalinski, Dr. Kieran O’Hara, and Dr. Edward Woolery. I would also like to thank my outside examiner Dr. Richard Sweigard, who agreed to help at my defense on very short notice. Every one of the above improved this dissertation tremendously with their suggestions. I wish to also thank all the sources of funding that helped to get this project off and running. A considerable part of this research project was funded by the EDMAP component of the National Cooperative Geologic Mapping Program of the United States Geological Survey. The University of Kentucky Department of Earth and Environmental Sciences provided funding through the Brown-McFarlan and Ferm Funds. The University of Kentucky Graduate School provided funding through the student support program. Funding was also provided by the American Association of Petroleum Geologists and the Geological Society of America. Many other faculty members here have helped me through the years, especially those for whom I taught as an assistant. I wish to thank Dr. Rick Bowersox, Dr. Alan Fryar, and Dr. David Moecher. You taught me so much! I wish to also thank my colleagues through the years, and especially my friends and officemates. Mike Solis took the raw contour lines for my models and transformed them into the finished product included in this dissertation. Liz Dodson and Carrie Kidd helped to keep me sane. Most of all, I wish to thank Dr. Matt Surles for his help and friendship, and for knowing the words to “Georgia on a Fast Train.” It would take pages upon pages for me to thank all the people who helped me get to this place in my life. I wish I could name them all. I have been blessed with a wonderful family, and I want to thank all of them for their love and support. Many of my closest family members are no longer here. I wish I could share this time in my life with my mother, Martha Melton, and her parents, Calvin and Lois, who will always be such an important part of the person I am (at least the good parts!). Words cannot express how I miss you all. I also want to thank my father, Gary Cook, his mother, Irene Cook, and my aunt, Linda Melton. Finally, I wish to thank Lois Yoksoulian for her love and friendship over the last few years. Thank you for the laughs and the quality time with the cats. iii TABLE OF CONTENTS Acknowledgments.............................................................................................................. iii List of Tables .................................................................................................................... vii List of Figures.................................................................................................................. viii List of Files ........................................................................................................................ xi CHAPTER I: INTRODUCTION........................................................................................1 CHAPTER II: BACKGROUND STRUCTURAL GEOLOGY.........................................7 2.1 ALONG-STRIKE BENDS IN THRUST BELTS .............................................7 2.1.1 Controls on formation and development of salients ...........................7 2.1.1.1 Mechanisms