Tectonic and climatic control of Yarlung Tsangpo Gorge revealed by a buried canyon in Southern Tibet

The Himalayan mountains are dissected by some of the deepest and most impressive gorges on Earth. Constraining the interplay among river incision, glacial movement and rock uplift is important for understanding tectonic deformation in this region. We report here the discovery of a deeply incised canyon of the Yarlung Tsangpo River, at the eastern end of the Himalaya, which is now buried under more than 500 meters of sediments. By reconstructing the former valley bottom, analyzing sedimentary phase and dating sediments at the base of the valley fill, we show that fluvial sediment accumulation started at about 2 million 2.5 million of years ago, and extensive glacial advances occurred after ~0.75 million of years. Our findings reveal that rapid rock uplift is the direct cause of the high erosion rates within the gorge, which began to steepen about 2-2.5 million years ago. Notably, the earliest extensive glacial advance (~0.75 million of years) is considerably younger than the formation of the Tsangpo Gorge (>2.5 million of years). Following the initiation of this glacial advance, the Eastern Himalayan Syntaxis experienced rapid exhumation of approximately 1.3-1.6 kilometers. Such geomorphological processes and exhumation history suggest that rock uplift, rather than glacial damming, played a pivotal role in maintaining the stability of the knickpoints on the southeastern margins of the Tibetan Plateau.