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Structural and Metamorphic Evolution of the West-Central Newton Window, Eastern Inner Piedmont, Burke, Catawba, and Lincoln Counties, North Carolina

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Structural and Metamorphic Evolution of the West-Central Newton Window, Eastern Inner Piedmont, Burke, Catawba, and Lincoln Counties, North Carolina University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 8-2010 Structural and metamorphic evolution of the west-central Newton window, eastern Inner Piedmont, Burke, Catawba, and Lincoln Counties, North Carolina William George Gilliam [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Part of the Tectonics and Structure Commons Recommended Citation Gilliam, William George, "Structural and metamorphic evolution of the west-central Newton window, eastern Inner Piedmont, Burke, Catawba, and Lincoln Counties, North Carolina. " Master's Thesis, University of Tennessee, 2010. https://trace.tennessee.edu/utk_gradthes/798 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 William George Gilliam entitled "Structural and metamorphic evolution of the west-central Newton window, eastern Inner Piedmont, Burke, Catawba, and Lincoln Counties, North Carolina." 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 requirements for the degree of Master of Science, with a major in Geology. Robert D. Hatcher, Jr., Major Professor We have read this thesis and recommend its acceptance: Christopher Fedo, Theodore Labotka Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) To the Graduate Council: I am submitting herewith a thesis written by William George Gilliam entitled “Structural and metamorphic evolution of the west‐central Newton window, eastern Inner Piedmont, Burke, Catawba, and Lincoln Counties, North Carolina.” 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 requirements for the degree of Master of Science, with a major in Geology. Robert D. Hatcher, Jr. Major Professor We have read this thesis and recommend its acceptance: Christopher Fedo Committee member Theodore Labotka Committee member Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School STRUCTURAL AND METAMORPHIC EVOLUTION OF THE WEST- CENTRAL NEWTON WINDOW, EASTERN INNER PIEDMONT, BURKE, CATAWBA, AND LINCOLN COUNTIES, NORTH CAROLINA A Thesis Presented for the Masters of Science Degree The University of Tennessee, Knoxville William G. Gilliam August 2010 DEDICATION This thesis is dedicated to my grandfather, William Frank Gilliam. ii ACKNOWLEDGMENTS Completion of this thesis would not have been possible without the patience and support of many people. First and foremost I would like to thank my adviser Dr. Robert D. Hatcher, Jr. for the mentorship and financial support to complete this thesis. I am very grateful to have had the opportunity to work and map alongside such a passionate geologist. I would also like to thank my committee members, Drs. Theodore Labotka and Christopher Fedo, for their support and assistance in finishing this thesis. I would also like to thank Dr. Larry Taylor and Allen Patchen in the University of Tennessee Electron Microprobe Facility. Additional thanks are extended to Carl Merschat and Bart Cattanach for their insightful field review and feedback on my geologic map. I would also like to thank my field partner and fellow Kentuckian, Heather Byars, for her insightful conversations about our field areas and her wonderful home cooking. I was a pleasure to map and learn with you. A special thanks is extended to Arthur Merschat for willingness to discuss Inner Piedmont geology with me. Additionally I would like to thank my former and current office mates, Brittany Davis, Phillip Derryberry, Chris Howard, Matt Huebner, and Mary (Varnell) Jubb for putting up with me. Nancy “Damama” Meadows, thank you for your patience, positivity, and for making me feel at home. I am forever grateful for your positive encouragement, thorough proofreading, and birthday celebrations. My graduate experience would not have been possible without the patience, love, and support from my family. Special thanks to my wife Lyndci for all the love and support she has provided me while I finish my thesis. This would not have been possible without you. Thanks to my mom, Evelyn for the positive encouragement, love, and support throughout my academic career. Thank you all for believing in me. Last but not least I would like to thank my grandfather, William Frank Gilliam, for introducing me to geology through our many walks up the creek. Who knew it would manifest into this. iii ABSTRACT Rocks of the western and eastern Inner Piedmont, along with the eastern Blue Ridge, comprise the Neoacadian metamorphic core of the southern Appalachians. The composite Inner Piedmont consists of the eastern Tugaloo (western Inner Piedmont) and Cat Square (eastern Inner Piedmont) terranes, which are separated by the Brindle Creek fault. Geochronologic evidence established the Brindle Creek fault as a terrane boundary within the Inner Piedmont, separating terranes of Laurentian and mixed Laurentian/Avalonian (peri-Gondwanan) zircon suites. The Newton window exposes Tugaloo terrane rocks of the Tallulah Falls Formation in the footwall of the Brindle Creek thrust sheet. Detailed geologic mapping in the western Newton window revealed structural and metamorphic similarities between rocks across the Brindle Creek fault. Peak metamorphism occurred contemporaneously with peak deformation, reaching upper amphibolite facies across both terranes. Peak Neoacadian metamorphism occurred between 360 and 345 Ma. Electron microprobe analyses of Cat Square terrane core and rim garnet-biotite and garnet-plagioclase pairs indicate an average temperature and pressure of 620 C, 3.6 kbar and 710 C, 6.1 kbar, respectively. Temperature and pressure estimates from the lower Tallulah Falls Formation core and rim analyses yield conditions of 570 C, 4.1 kbar and 690 C, 5.9 kbar, respectively. The maximum burial depth for both Cat Square and Tugaloo terrane rocks is ~20 km. The range in metamorphic ages suggests subduction and accretion occurred at a rate of 1 kilometer per 1.75 million years. Six deformational events shaped the western Newton window. D1 features are limited to amphibolite boudins of the Tugaloo terrane. D2 regional penetrative structures such as high- temperature foliations, mineral stretching lineations, and curved fold axes are the product of Neoacadian tectonism. The dominant S2 foliation trends north-northwest and dips moderately to the west-southwest. North-northwest-trending L2 mineral lineations parallel F2 fold axes, creating a curved map pattern recording crustal flow in an ancient orogenic channel. D3 resulted in open folding. The D4 event produced regional open folds. D5 and D6 features occur as joints, cataclasis, and diabase intrusion. iv TABLE OF CONTENTS CHAPTER 1 INTRODUCTION……………………………………………………….…...1 Geologic Setting………………………………………………………………………..….4 The Newton window/antiform………………………………………...………………..…8 Regional structural framework and tectonics models……………………..........................9 Metamorphism…………………………………………………………………………...11 Objectives………………………………………………………………………………..11 Methodology……………………………………………………………………………..11 CHAPTER 2 LITHOLOGIC UNITS…………………………………………………..…13 Introduction…………………………………………………………………………..….13 Eastern Inner Piedmont Ashe-Tallulah Falls…………………………….........................17 Eastern Inner Piedmont Cat Square terrane……………………………………………...26 Cat Square sillimanite schist……………………………………..........................26 Cat Square biotite gneiss………………………………………………………...28 Walker Top Granite………………………………………………..………….…31 Mesozoic features…………………………………………………………………….….35 Diabase dikes………………………………………………………………….…35 Cataclasite……………………………………………………………………..…35 CHAPTER 3 P–T ESTIMATES NEAR THE WESTERN NEWTON WINDOW……………………………………………………………………………………...41 Introduction……………………………………………………………………………....41 Timing of Metamorphism………………………………………………………………..46 Field and Petrographic Observations………………………………………………….…47 Migmatite………………………………………………………………………………...50 Pegmatite…………………………………………………………………………………52 Pressure and Temperature Conditions………………………………………………..….52 Analytical Methods…………………………………………………………………..…..52 Survey of Geothermometers and Barometers………………………………………..…..55 v H3 Lower Tallulah Falls biotite gneiss/metagraywacke…………………………….….56 LV284 Cat Square terrane biotite gneiss/metagraywacke……………………………….61 Results and Discussion……………………………………………………………….…67 Summary………………………………………………………………………..……….69 CHAPTER 4 STRUCTURAL EVOLUTION OF THE WESTER NEWTON WINDOW BASED ON MAP PATTERNS AND GEOLOGIC STRUCTURES……………………………………………………………...74 Introduction………………………………………………………………………….….74 Deformational Events……………………………………………………………….…..78 D1 Deformation…………………………………………………………….……78 D2 Deformation……………………………………………………………….…78 Foliations………………………………………………………………..78 Lineations……………………………………………………………….81 Folds……………………………………………………………….……90 Faults……………………………………………………………….…...90 D3 and D4 Deformation……………………………………………………….…93 D5 and D6 Deformation………………………………………………………..…95 Map Patterns…………………………………………………………………………..…95 Cross Section Interpretation……………………………………………………………..98 Western Newton
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