Summary of the Late Triassic tectonic paleogeography in the Qinghai-Tibetan Plateau， China

Based on the systematic analytical stratigraphic framework and tectonic unit division, following the guiding ideology of "tectonic controlled basin and basin controlled sedimentary facies" suggested by Liu Baojun academician, it is determined that the late Triassic tectonic paleogeography of the Qinghai-Tibetan Plateau giant orogenic belt developed the Qiangtang-Sanjiang multi-island sea, the Bangonghu-Shuanghu-Nujiang ocean, the Gangdis-Himalaya multi-island sea and several secondary tectonic-paleogeographic units from the north to the south. The Bangonghu -Shuanghu-Nujiang ocean is the Tethys ocean separating the Gondwana and the Eurasia continents, and the southern Qiangtang is a floating block in the Tethys ocean. This paper focuses on the sedimentary facies distribution and paleogeography of the northern Qiangtang foreland basin and the northern Himalayan passive continental margin basin. Tectonic events determined the nature of the basin, which in turn controls the spatial distribution of sedimentary facies belts. The northern Himalayan basin was located in the Gangwana tectonic domain, and the basement of the late Triassic basin deepened from the south to the north, inheriting the Paleozoic tectonic discrete passive continental margin deposits, and the Indosinian orogeny didn't develop at that time. The northern Qiangtang basin located in the Cathaysian tectonic domain, developed the Indosinian extrusion orogeny and foreland basin sedimentary records during the late Triassic. The basinal analysis shows that the bottom of the lower Triassic Kanglu formation in Jiangaidarina Mt. and Rejuechaka lake in the southern part of North Qiangtang Basin, occurred upward thinning and finning transgressive stratigraphic structures composed of gray-purple medium-thick bedding polymictic conglomerates, gravel-bearing coarse sandstones and fine sandstones, and the sedimentary facies was shore-delta. The sedimentary facies of the upper Triassic Tumengera Group were coal-bearing basin marginal delta. Analysis of NE direction paleocurrent and sedimentary facies distribution pattern indicates the material sources of the Triassic northern Qiangtang basin were mainly from the Shuanghu orogenic denuded zone at the middle of Qiangtang or "Qiangtang central uplift belt".