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Nonmarine Stratigraphic Successions in the Yidun Terrane

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Nonmarine Stratigraphic Successions in the Yidun Terrane NONMARINE STRATIGRAPHIC SUCCESSIONS IN THE YIDUN TERRANE: A RECORD OF MESOZOIC AND EARLY CENOZOIC DEFORMATION AND DEPOSITION IN THE EASTERN TIBETAN PLATEAU by WILLIAM T. JACKSON, JR. DELORES M. ROBINSON, COMMITTEE CHAIR AMY L. WEISLOGEL SAMANTHA E. HANSEN REZENE MAHATSENTE MATTHEW M. WIELICKI A DISSERTATION Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Geological Sciences in the Graduate School of The University of Alabama TUSCALOOSA, ALABAMA 2017 Copyright William T. Jackson, Jr. 2017 ALL RIGHTS RESERVED ABSTRACT The Tibetan Plateau is the largest and highest plateau on Earth, covering > 2,500,000 km2 with an average elevation > 4,500 m. The plateau’s present crustal configuration is a product of the Early Cenozoic India-Asia collision as well as similar Mesozoic collisions along the southern margin of Eurasia. The spatial and temporal relationship of Mesozoic and Early Cenozoic deformation resulting from collisions are required parameters to advance understanding of the plateau’s rise and outgrowth evolution. Nonmarine strata in interior parts of the plateau provide records of this deformation; however, in the eastern Tibetan Plateau these strata remain unexplored. This dissertation presents structural and sedimentological field data, detrital zircon U-Pb geochronology and Hf isotope geochemistry, as well as petrology data from the Mula basin, west Ganzi basin, east Ganzi basin, and Ganzi-Litang suture to determine the stratigraphic age, sedimentary provenance, and tectonic setting of the nonmarine strata in the Yidun terrane, eastern Tibetan Plateau. Weighted mean averages from the youngest detrital zircon age populations suggest that the Mula basin and nonmarine strata in the Ganzi-Litang suture are Early Cenozoic, while the west Ganzi basin and east Ganzi basin are Mesozoic. Sedimentary provenance analyses show that Early Cenozoic strata were sourced locally, whereas Mesozoic strata indicate regional sourcing. Basin-bounding fault characteristics demonstrate that deformation and nonmarine deposition were associated with compressional tectonic settings for both the Mesozoic and Cenozoic basins. Integration of data from this dissertation illustrates that a fold-thrust belt developed in Mesozoic and Early Cenozoic time near the Late Triassic Ganzi-Litang suture ii throughout the eastern Yidun terrane. The Late Triassic Ganzi-Litang suture was structurally reactivated by subsequent Mesozoic and Cenozoic collisions along the southern margin of Eurasia, suggesting that the spatial evolution of deformation in the eastern Tibetan Plateau was controlled by the presence of crustal weaknesses. In addition, this dissertation establishes the stratigraphic architecture for nonmarine strata in the Yidun terrane, providing the stimulus for regional correlations that further clarify the timing and style of deformation throughout the eastern Tibetan Plateau. iii DEDICATION To Mary Claire and Foster. iv LIST OF ABBREVIATIONS AND SYMBOLS BSE back-scattered electron cm centimeter(s) EGB east Ganzi basin GLS Ganzi-Litang suture GSA Geological Society of America Hf hafnium km kilometer(s) LA-ICP-MS Laser Ablation Inductively Coupled Plasma Mass Spectrometry m meter(s) Ma million years ago µm micrometer(s) MSWD mean sum of weighted deviations Pb lead ppm parts per million U uranium WGB west Ganzi basin % percentage ° degrees σ sigma v > greater than < less than ≥ greater than or equal to ≤ less than or equal to ~ approximately ± plus or minus vi ACKNOWLEDGMENTS I would like to thank the many individuals and organizations who provided support and guidance during this dissertation. I would especially like to thank my advisor, Delores M. Robinson. Over the past five years, “D” offered motivation, encouragement, and friendship at all times. Without her mentorship this dissertation would not have been possible. Amy L. Weislogel provided support in the field, at professional conferences as well as through editorial critiques. Committee members Samantha E. Hansen, Rezene Mahatsente, and Matthew M. Wielicki provided valuable feedback. Alison Duvall and Alberto Perez-Huerta contributed from the infancy of this dissertation to the final products. Fei Shang and Xing Jian provided assistance in the field and discussions on the geology of East Tibet. Work permits were arranged by Chunmiao Zheng. This research was funded by National Science Foundation grants awarded to Delores M. Robinson (EAR-1119266) and Amy L. Weislogel (EAR-1119219). Additional funding was provided by the Geological Society of America, The University of Alabama’s Graduate School, Department of Geological Sciences, and the Geological Science Advisory Board. Analytical support was provided by the Central Analytical Facility at The University of Alabama and the LaserChron Center at University of Arizona. I would also like to extend my gratitude towards the staff at the Geological Survey of Alabama for supporting the completion of this dissertation, especially G. Daniel Irvin and B. H. (Nick) Tew, Jr. vii CONTENTS ABSTRACT ………………………………………………………………………………. ii DEDICATION ……………………………………………………………………………. iv LIST OF ABBREVIATIONS AND SYMBOLS………………………………………….. v ACKNOWLEDGMENTS ………………………………………………………………… vii LIST OF TABLES ………………………………………………………………………... xiii LIST OF FIGURES ……………………………………………………………………….. xiv CHAPTER 1: INTRODUCTION ………………………………………………………… 1 1.1. Mesozoic Tectonic History of the Tibetan Plateau …………………………………... 2 1.2. Cenozoic Tectonic History of the Tibetan Plateau …………………………………… 4 1.3. Objective ……………………………………………………………………………… 5 1.4. Outline ………………………………………………………………………………... 8 References ………………………………………………………………………………… 10 CHAPTER 2: EARLY CENOZOIC DEVELOPMENT OF THE NONMARINE MULA BASIN, SOUTHERN YIDUN TERRANE: DEPOSITION AND DEFORMATION IN THE EASTERN TIBETAN PLATEAU RESULTING FROM THE INDIA-ASIA COLLISION ……………………………………………………………………………… 16 2.1. Abstract ………………………………………………………………………………. 16 2.2. Introduction …………………………………………………………………………... 17 2.3. Geologic Setting ……………………………………………………………………… 21 2.4. Previous Work ………………………………………………………………………... 22 2.4.1. Southern Tibetan Plateau …………………………………………………… 23 viii 2.4.2. Central Tibetan Plateau …………………………………………………...... 23 2.4.3. North-Central Tibetan Plateau ……………………………………………… 24 2.4.4. East-Central Tibetan Plateau ……………………………………………….. 24 2.4.4. Eastern Tibetan Plateau …………………………………………………….. 25 2.4.5. Northeastern Tibetan Plateau ……………………………………………….. 25 2.5. Methods ………………………………………………………………………………. 25 2.5.1. Field Procedures ……………………………………………………………. 25 2.5.2. Detrital Zircon Geochronology …………………………………………….. 26 2.5.3. Detrital Zircon Hf Isotopes …………………………………………………. 27 2.5.4. Petrology ……………………………………………………………………. 28 2.6. Results ………………………………………………………………………………... 28 2.6.1. Mula Basin Stratigraphy …………………………………………………..... 28 2.6.2. Detrital Zircon Geochronology …………………………………………….. 29 2.6.3. Detrital Zircon Hf Analysis ………………………………………………… 30 2.6.4. Petrology ……………………………………………………………………. 31 2.6.5. Structure ……………………………………………………………………. 31 2.7. Interpretations ………………………………………………………………………… 38 2.7.1. Depositional Environments ………………………………………………… 38 2.7.2. Age of Strata ………………………………………………………………... 38 2.7.3. Sedimentary Provenance …………………………………………………… 38 2.7.4. Tectonic Setting …………………………………………………………….. 43 2.8. Discussion …………………………………………………………………………….. 43 2.8.1. Sediment Provenance, Stratigraphic Age, and Regional Correlation ………. 43 ix 2.8.2. Tectonic Model ……………………………………………………………... 44 2.8.3. Broader Implications ……………………………………………………….. 44 2.9. Conclusions …………………………………………………………………………... 45 Acknowledgments ………………………………………………………………………… 46 References ………………………………………………………………………………… 47 CHAPTER 3: MESOZOIC DEVELOPMENT OF NONMARINE BASINS IN THE NORTHERN YIDUN TERRANE: DEPOSITION AND DEFORMATION IN THE EASTERN TIBTENA PLATEAU PRIOR TO THE INDIA-ASIA COLLISION ……….. 56 3.1. Abstract ……………………………………………………………………………….. 56 3.2. Introduction ………………………………………………………………………....... 56 3.3. Geologic Setting ……………………………………………………………………… 59 3.3.1. Yidun Terrane ………………………………………………………………. 59 3.3.2. Songpan-Ganzi Terrane …………………………………………………….. 61 3.4. Methods ………………………………………………………………………………. 61 3.4.1. Field Procedures ……………………………………………………………. 61 3.4.2. Detrital Zircon Geochronology …………………………………………….. 62 3.4.3. Thin Section Petrology ……………………………………………………... 63 3.5. Results ………………………………………………………………………………... 63 3.5.1. Stratigraphy ………………………………………………………………… 63 3.5.2. Basin Boundaries and Structure ……………………………………………. 66 3.5.3. Detrital Zircon Geochronology …………………………………………….. 68 3.5.4. Petrology Analysis …………………………………………………………. 76 3.6. Interpretations ………………………………………………………………………… 76 3.6.1. Depositional Environments ………………………………………………… 76 x 3.6.2. Age of Strata ………………………………………………………………... 77 3.6.3. Sediment Provenance ………………………………………………………. 79 3.6.4. Tectonic Setting …………………………………………………………….. 82 3.7. Discussion …………………………………………………………………………….. 83 3.7.1. Tectonic Model ……………………………………………………………... 83 3.7.2. Mesozoic vs Cenozoic Yidun Terrane Nonmarine Basins …………………. 87 3.7.3. Broader Implications ……………………………………………………….. 88 3.8. Conclusions …………………………………………………………………………... 88 Acknowledgments ………………………………………………………………………… 89 References ………………………………………………………………………………… 90 CHAPTER 4: EARLY CENOZOIC REACTIVATION OF THE TRIASSIC GANZI- LITANG SUTURE RECORDED BY DETRITAL ZIRCON GEOCHRONOLOGY: IMPLICATIONS FOR STRAIN PARTITIONING IN THE EASTERN TIBETAN PLATEAU ………………………………………………………………………………… 95 4.1. Abstract ……………………………………………………………………………….
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