Onset of Mid-Pleistocene glaciation in the Eastern Himalayan syntaxis

The Tibetan Plateau contains the largest numbers of glaciers outside the polar regions, yet the initiation times of glacial advances remain unclear. The potential relics of original moraines might be preserved in the sedimentary basins. Here, we present sedimentological and geochronological data from five boreholes located upstream of the Tsangpo Gorge, Eastern Himalayan Syntaxis. Our findings reveal that fluvial sediment accumulation began over 2.5 million of years ago due to enhanced rock uplift downstream, and extensive glacial advances occurred after ~0.75 million of years. 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. The onset of Himalayan glaciation took place ~0.75 million years ago enhancing the average erosion and mountain exhumation of the Eastern Himalayan syntaxis, based on borehole sedimentological and geochronological data.