Evolution of sedimentary basins in Qiangtang-Sanjiang from Paleozoic to Mesozoic

The structure and evolution of Qiangtang-Sanjiang during Paleozoic-Mesozoic sedimentary basins were controlled by the Tethys. On the basis of the exploration of previous studies on lithostratigraphy, fossil assemblages, isotopic geochronology and tectonics of the study area, this paper classifies the sedimentary basins of Qiangtang-Sanjiang region, and analyzes the formation and evolution of each sedimentary basin. During the Early Paleozoic, Qiangtang-Sanjiang basins were mostly ocean environment; with the subduction of the Tethys Ocean to the northeastward and southeastward in Late Paleozoic, the active margin sedimentary basins developed in this area, forming Jinshajiang back arc-ocean, Lancangjiang back arc-ocean and Ganzi-Litang back arc-ocean and then the multiple island arc-basin systems of eastern Tethys system gradually formed. During the Mesozoic, with the subduction of the Tethys in Late Triassic in Qiangtang-Sanjiang, three arc-basins gradually closed, then large-scale arc-arc collision and arc-continent collision occurred in this area. This area eventually entered intracontinental evolution stage from the active margin sedimentary basins, Due to the close of Tethys in Cretaceous, the Indian plate and western China collided, inland basins developed in Qiangtang-Sanjiang.