The formation and evolution of the Qiangtang Basin during the Late Triassic-Middle Jurassic period in northern Tibet

Abstract：The major marine sedimentary facies basin formed during the Late Triassic and Middle Jurassic period is very important in studying the genetic process and type of Qiangtan Mesozoic basin. Based on lots of stratigraphic secting data, this paper made an analysis of regional tectonics, basin-filling sequences, lithofacies palaeogeography and thickness of the ore deposits formed during this period and, on such a basis, suggests that, instead of a foreland basin or a back-arc basin formed in Late Triassic and Jurassic period, the basin was an epicontinental basin formed in early Late Triassic (called Xiaochaka Phase) and also a depression-rifting basin formed in an extensional background from Norian Age to Middle Jurassic (called Nadigangri-Quemocuo Phase). During the Xiaochaka Phase, the basin was impacted by the Hoh Xil-Jinshajiang active belt, and the regression event in the early stage of this period might have resulted form the collision between the Eurasian continent and the Gondwana land. During the Nadigangri-Quemocuo Phase, the strong extension and rifting event occurred, which probably reflects the extensional background of the margin of the Gondwana land.