Paleogene thrust system in southern Qiangtang basin, central Tibetan Plateau

A large-scale thrust system was formed in Paleogene, which included Xiaochaka-Shuanghu thrust, Duoma-Qixiang Co thrust and Saibu Co-Zagya thrust in southern Qiangtang basin. Permian marbleized limestone and dolomite, Triassic sandstone and shale, Jurassic clastic rocks and carbonate rocks and Triassic-Jurassic ophiolite were thrusted southward over Paleogene red-beds along frontier faults of each thrust, forming tectonic slices, outliers and nappes of Permian-Jurassic rocks overlying Paleogene red-beds in north, central and south Qiangtang basin. Miocene lacustrine deposits of weak deformation lying unconformably over major thrust faults indicate that major thrust faults have stopped activity since Miocene in southern Qiangtang basin. Minimal estimation of southward thrust displacement in Paleogene is ~90km, corresponding to ~47% upper crust shortening of southern Qiangtang block. The Paleogene thrust system played an important role in the formation and preservation of oil-gas in southern Qiangtang basin.