Glaciation-tectonic coupling: Stabilizing the southeastern Tibetan Plateau

Why rivers have not deeply incised the interior of the Tibetan Plateau over geologic time scales remains an open question. Resolving this issue requires clarifying and quantifying the respective influences of different geological factors on headward river erosion. Focusing on the Eastern Himalayan syntaxis, we reveal that glacial damming occurred frequently along an ∼70 km reach of the Yarlung Tsangpo River, based on 10Be exposure dating and paleoglacial modeling. Glacial-damming episodes limited headward erosion via a cycle in which prolonged damming inhibited erosion during glacial periods and short-lived damming delayed it during interglacial periods. Moreover, these damming processes triggered extensive aggradation upstream and protected bedrock from erosion over long time scales, while they enhanced downstream incision, reshaping the longitudinal profile of the Yarlung Tsangpo River. Repeated glacial-damming processes cumulatively raised the effective local base level by ∼300 m since the middle Pleistocene. Overall, we show that the coupling of glaciation and tectonics is the key factor maintaining the long-term stability of the southeastern Tibetan Plateau margin.