Multistage Exhumation in the Catchment of the Anninghe River in the SE Tibetan Plateau: Insights From Both Detrital Thermochronology and Topographic Analysis.

The roles of lower-crustal flow and upper-crustal shortening on the growth of the SE Tibetan Plateau remain under debate, which calls for a knowledge about regional exhumation history. We analyzed apatite fission track ages of modern sediments from both the east and west sub-catchments along the Anninghe River, in the SE plateau. We obtained four age components, with peaks a bit younger in the east than in the west. Combing the asymmetric topography with higher relief in the east, we concluded a non-uniform exhumation pattern. The components are at the Oligocene, late-Miocene, Pliocene, and Pleistocene, mostly consistent with the timing for changes in catchment-wide erosion rates as indicated by the inverse erosion history. We concluded that, in addition to the late-Miocene lowercrustal flow and Oligocene upper-crustal shortening, the landscape in the SE plateau might also be under influences of fault strike-slip transfer and drainage network reorganization. Plain Language Summary Different models that have been proposed to explain how the topography in the SE Tibetan Plateau grows predict different histories for regional uplift and/or erosion. Lower-crust flow was suggested to drive rapid surface uplift since 10-15 Ma, while findings of earlier fault thrusting implies the effects of upper-crust shortening. To test these models, we analyzed detrital ages of sediments from both the east and west sub-catchments along the modern Anninghe River, in the SE plateau. We obtained the Oligocene, late-Miocene, Pliocene, and Pleistocene age components, all of which are with peaks a bit younger in the east than in the west. Considering that the topography is also somewhat steeper in the east, we concluded a spatially non-uniform erosion pattern since the middle Cenozoic. The four age components reveal multistage erosion processes in the Anninghe catchment and thus indicate multiple forces to drive topographic growth in the SE plateau. [ABSTRACT FROM AUTHOR]