Early tectonic uplift affecting sedimentary filling and evolution of Paleogene basins in the central- eastern Tibetan Plateau
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    Abstract:

    Many medium- and small- sized Paleogene graben and strike- slip basins are distributed in the central- eastern Tibetan Plateau. The Indo- Asia plate collision has already resulted in the responses to the geological events including tectonic, deposition, and magmatism in the basins, such as the formation of hugely thick coarse clastic rock widely distributed in the Paleogene basins, the disappearance of the New Tethys Bay, the large- scale fold and thrust due to crustal compression, high- potassium magmatism, formation of the peripheral foreland basins. Field geological mapping and the studies of basin tectonic- sedimentology, biostratigraphy and isotope chronology for magmatic rocks show that the large- scale compression tilt and thrust occurred in the Yushu- Nangqian graben basins, formation of high- angle strata and expression syncline at the basin margin, and obvious development of fold deformation in the strata in the basins. The Paleogene basins are filled with hugely thick basal conglomerate, purple- red terrigenous clastic rocks interbedded volcanic clastic rocks, carbonate rocks and gypsum layers, and were cut by late magmatic rocks. Strike- slip and pull- apart basins were formed in the Batang- Lijiang area. The studies of regional stratigraphic correlation, sporo- pollen and paleoflora in fine clastic rocks, and U- Pb and 40Ar/39Ar dating of volcanoclastic and intrusive rocks revealed that the sediments in these basins were formed in Eocene(56~32 Ma). The appearance of the Paleogene crimson fine- grained sediments, carbonate rocks and gypsum layers indicates that the basins were in a dry- hot paleoclimate environment in their closure period. The period of 38~32Ma is a transitional stage from transgression to the transtension in the east- central Tibet after the Indo- Asia plate collision, as shown by the occurrence of a large- scale high- K volcanic eruption followed by magmatic intrusion and the closure and cracking of the Paleogene basins in east- central Tibet. The closure (~37 Ma) of the northern basins is earlier than the cracking of the southern basins (~32~28 Ma). The closure and cracking of the Paleogene basins in east- central Tibet was mainly caused by the compression, deformation and shortening of the continental crust, and the thrust compression, strike- slip and pull- apart due to the early tectonic uplift of the plateau after the collision of the Indo- Asian plate at about 38Ma.

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ZHOU Jiangyu, WANG Jianghai.2019. Early tectonic uplift affecting sedimentary filling and evolution of Paleogene basins in the central- eastern Tibetan Plateau[J]. Acta Geologica Sinica,93(8):1793-1813

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History
  • Received:August 21,2018
  • Revised:December 19,2018
  • Adopted:April 01,2019
  • Online: April 01,2019
  • Published: