Tertiary crustal shortening and peneplanation in the Hoh Xil region: implications for the tectonic history of the northern Tibetan Plateau |
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| Institution: | 1. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, China;2. School of Geography Science, Nanjing Normal University, Nanjing 210046, China;3. Institute of Soil and Water Conservation, Northwest A&F University, Yangling 712100, China;4. Department of Geosciences and Geography, University of Helsinki, Helsinki 00014, Finland;5. Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China;1. State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, PR China;2. CAS Center for Excellence in Tibetan Plateau Earth Sciences, PR China |
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| Abstract: | The Hoh Xil Basin is the largest Cenozoic sedimentary basin in the hinterland of the Tibetan Plateau. Tertiary sedimentary strata 5.8 km thick, comprising the Fenghuoshan, Yaxicuo and Wudaoliang groups, provide compelling evidence concerning the crustal shortening, erosion and peneplanation of the northern Tibetan Plateau. The basal Fenghuoshan and overlying Yaxicuo groups span the Eocene-Early Oligocene stratigraphically, and have been dated by magnetostratigraphy as 56–30 Ma old. Both groups are composed of terrigenous rocks. Provenance analysis of sandstones and conglomerates demonstrates that Permian and Triassic strata in the Tanggula Orogenic Zone in the south were the source for the Fenghuoshan Group. In contrast, the Carboniferous–Triassic strata in the Tanggula, Bairizhajia, and Heishishan-Gaoshan orogenic zones in the north, were the source for the Yaxicuo Group.During the Late Oligocene, northern Tibet underwent strong north–south crustal shortening (～43%) and thickening. Extensive erosion, which occurred over the entire plateau surface near the end of the Oligocene, resulted in development of a peneplain surface. The latter is overlain by the Early Miocene Wudaoliang Group, composed of fresh water limestones. These are exposed both on summit surfaces, as well as on the valley floors, showing that a phase of differential uplift occurred after the deposition of the Wudaoliang Group. This post-Miocene differential uplift was due to regional extension, in a region of overall shortening. Even though we have not succeeded in obtaining conclusive data about the exact timing of phases of rapid uplift of the Tibetan Plateau, it is most likely that the major phase of uplift occurred during the Late Oligocene. |
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