Marine sedimentary evidence for monsoon strengthening, Tibetan uplift and drainage evolution in East Asia
Uplift of the Tibetan Plateau has caused an increased flux of clastic material from Asia into the surrounding marginal seas. This flux reflects increased regional erosion, partially caused by topographic uplift of Tibet, but dominantly by higher precipitation linked to monsoon intensification. Using regional seismic profiles from East Asia as proxies for the Cenozoic accumulation history we constrain the timing of enhanced erosion and thus climate change and plateau uplift. Most of the seas show sedimentation increasing after ̃45 Ma following India-Asia collision. Rates rose sharply at ̃33 Ma, and again around 18 Ma, possibly caused by stages in monsoon strengthening enhancing regional erosion. Erosion of gorges in eastern Tibet is a modest source of sediment to the marginal seas. The late Miocene (5-11 Ma) is a time of reduced sedimentation in all basins except in the Mekong area, which alone is influenced by exhumation of the Vietnamese Central Highlands. The slower regional erosion reflects a drier climate and strong winter monsoon during the late Miocene, while the Plio-Pleistocene (<5 Ma) sees a return to fast accumulation rates, possibly triggered by global climatic deterioration. Single grain Pb and bulk sediment Nd isotopic characteristics of modern river and Eocene sediments from the Gulf of Tonkin support models of drainage capture in the Red River system since the Eocene. This drainage has lost flux from sources similar to the Yangtze Block, possibly reflecting capture of flow from the middle and lower Yangtze from the Red River linked to Tibetan uplift.