Abstract:

Abstract:On the basis of sedimentary sequences, regional unconformities, lithological associations and distributions of the Paleogene and the Neogene in the Tuotuohe River Basin on the QinghaiTibet Plateau, four shallowingupward sequences consisting of, in an ascender order, the Tuotuohe Formation,Yaxicuo Formation, Wudaoliang Formation and Quguo Formation were recognized, which furthermore constructed two complete continental orogenic molasses successions. Current research indicates that Tuotuohe River Basin was involved in a successive evolution history, i.e., foreland basin (56.545.0Ma), strikeslip pullapart basin (45300 Ma), uplifted residual basin (235160Ma), foreland basinrestricted basinresidual basin(1636Ma) and foreland basin (3626Ma(?)). Combined with the basin evolution in the northern QinghaiTibet Plateau during the Cenozoic, this research suggests that an initial collision between the India and the Eurasian plates occurred at the turn of the Cretaceous and the Paleogene before the 56.5Ma, and further underwent three periods, i.e., the first collision (early than 565 Ma), then main collision (565450 Ma) and pulsation intracontinental convergence (4526 Ma ) finally. However, 450 Ma is the most important moment of tectonic transformation. Uplifting of the QinghaiTibet Plateau from the Paleogene to the Neogene was achieved in the successional periods. First, early than 565450 Ma; second, 3016 Ma; third,1636 Ma; and finally, 3626(?) Ma.The Qiangtang block had reached a considerable height as a result of sustained uplifting during the period from 30 to 16 Ma .

Key words: Tuotuohe River basin, basin analysis, initial collision, tectonic transformation, uplift