Nonmarine stratigraphic successions in the Yidun Terrane: a record of Mesozoic and early Cenozoic deformation and deposition in the Eastern Tibetan Plateau

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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 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.

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