Field observations and satellite geodesy indicate that little crustal shortening has occurred along the central to southern margin of the eastern Tibetan plateau since about 4 million years ago. Instead, central eastern Tibet has been nearly stationary relative to southeastern China, southeastern Tibet has rotated clockwise without major crustal shortening, and the crust along portions of the eastern plateau margin has been extended. Modeling suggests that these phenomena are the result of continental convergence where the lower crust is so weak that upper crustal deformation is decoupled from the motion of the underlying mantle. This model also predicts east-west extension on the high plateau without convective removal of Tibetan lithosphere and without eastward movement of the crust east of the plateau.

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Whether strike‐slip fault systems in Eurasia accomplish eastward extrusion of Tibetan crust and lithosphere depends largely on the kinematics of deformation at the fault tip. Here we present new slip rate determinations using millennial‐scale geomorphic markers from sites along the easternmost segment of the Kunlun fault in north central Tibet. This fault system represents one of the major strike‐slip faults within the Indo‐Asian collision zone, has been argued to exhibit uniform slip rates along much of its length, and plays a central role in models for eastward extrusion of Tibetan lithosphere. Displaced fluvial terrace risers along tributaries of the Yellow River, coupled with 14C ages of terrace material, provide constraints on slip rates over late Pleistocene to Holocene time. Results indicate that slip rates decrease systematically along the eastern ∼150 km of the fault from >10 to <2 mm/yr. These data challenge the view that slip along the Kunlun fault remains uniform along the entire length of the fault and instead reveal gradients in displacement similar to those expected at fault tips. Moreover, slip along the fault appears to terminate within the thickened crust of the plateau, and therefore any extrusion of Tibetan lithosphere accomplished by slip along the Kunlun fault must be absorbed by internal deformation of the plateau surrounding the fault tip.

We present new sedimentary data integrated into a regional Mesozoic stratigraphic framework to provide a detailed picture of spatio-temporal variations in deposition and depocenter migration of the northwest Sichuan basin. The Mesozoic sedimentary evolution is utilized to interpret basin subsidence history and to unravel coeval basin-margin tectonics. The northwest Sichuan basin, together with the Songpan-Ganzi terrane, behaved as a passive margin south of the Qinling Paleo-Tethys from late Paleozoic to early Middle Triassic times and then evolved into a peripheral foreland basin in response to collision of the North and South China blocks since the late Middle Triassic. Coeval with strong north-south contraction of the Songpan-Ganzi terrane in the Late Triassic, sinistral transpressional deformation of the Longmen Shan belt led to fl exural subsidence of the adjacent western Sichuan basin. Renewed basin-margin fold-thrust activity triggered recurrence of fl exural subsidence of the northwest Sichuan basin since the Middle Jurassic, with the depocenter eventually shifting to the northwestern corner of the basin in the Early Cretaceous. Sedimentary evolution of the northwest Sichuan basin and the basin-margin deformation imply that the South China block had been rotating clockwise relative to the North China block throughout the Mesozoic with an interim period of Early Jurassic tectonic quiescence. A model is advanced that invokes clockwise rotation of the South China block as a driver for tectonic evolution of both the basin and adjoining structural belts and provides an explanation for several salient features that are otherwise puzzling.