Cenozoic uplift of the Tibetan Plateau: Evidence from the tectonic-sedimentary evolution of the western Qaidam Basin |
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Authors: | Yadong Wang Jianjing Zheng Weilin Zhang Shiyuan Li Xingwang Liu Xin Yang Yuhu Liu |
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Institution: | 1. Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Donggang West Road No. 382, Lanzhou 730000, China 2. Center for Basin Resource and Environment, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Post Box 2871, Beilin North Street 18, Beijing 100085, China 3. Research Institute of Petroleum Exploration and Development, PetroChina Qinghai Oilfield Company, Dunhuang 736202, China 4. Exploration and Development Academy of Northeast Petroleum Branch, China Petroleum & Chemical Corporation, Changchun 130061,China |
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Abstract: | Geologists agree that the collision of the Indian and Asian plates caused uplift of the Tibet
Plateau. However, controversy still exists regarding the modes and mechanisms of the Tibetan Plateau
uplift. Geology has recorded this uplift well in the Qaidam Basin. This paper analyzes the tectonic
and sedimentary evolution of the western Qaidam Basin using sub-surface seismic and drill data.
The Cenozoic intensity and history of deformation in the Qaidam Basin have been reconstructed based
on the tectonic developments, faults growth index, sedimentary facies variations, and the migration of the
depositional depressions. The changes in the sedimentary facies show that lakes in the western Qaidam
Basin had gone from inflow to still water deposition to withdrawal. Tectonic movements controlled deposition in various depressions, and the depressions gradually shifted southeastward. In addition, the
morphology of the surface structures in the western Qaidam Basin shows that the Cenozoic tectonic
movements controlled the evolution of the Basin and divided it into (a) the southern fault terrace zone,
(b) a central Yingxiongling orogenic belt, and (c) the northern fold-thrust belt; divided by the XI fault
(Youshi fault) and Youbei fault, respectively. The field data indicate that the western Qaidam Basin
formed in a Cenozoic compressive tectonic environment caused by the IndiaeAsia plate collision.
Further, the Basin experienced two phases of intensive tectonic deformation. The first phase occurred
during the Middle EoceneeEarly Miocene (Xia Ganchaigou Fm. and Shang Ganchaigou Fm., 43.8e
22 Ma), and peaked in the Early Oligocene (Upper Xia Ganchaigou Fm., 31.5 Ma). The second phase
occurred between the Middle Miocene and the Present (Shang Youshashan Fm. and Qigequan Fm.,
14.9e0 Ma), and was stronger than the first phase. The tectonicesedimentary evolution and the orientation
of surface structures in the western Qaidam Basin resulted from the Tibetan Plateau uplift, and
recorded the periodic northward growth of the Plateau. Recognizing this early tectonicesedimentary
evolution supports the previous conclusion that northern Tibet responded to the collision between India
and Asia shortly after its initiation. However, the current results reveal that northern Tibet also experienced
another phase of uplift during the late Neogene. The effects of these two stages of tectonic activity
combined to produce the current Tibetan Plateau. |
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Keywords: | Western Qaidam Basin Sedimentary facies Depositional depression Tectonic evolution Tibetan Plateau uplift |
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