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

Abstract

The Himalayan mountains are dissected by some of the deepest and most impressive gorges on Earth. Constraining the interplay between river incision 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 and dating sediments at the base of the valley fill, we show that steepening of the Tsangpo Gorge started at about 2 million to 2.5 million years ago as a consequence of an increase in rock uplift rates. The high erosion rates within the gorge are therefore a direct consequence of rapid rock uplift.

Uplift-driven diversification in the Hengduan Mountains, a temperate biodiversity hotspot

“…We expected regional differences to reflect contrasting times of orogeny, in particular the prediction of the uplift-driven diversification hypothesis that in situ speciation increases with mountain-building activity. In this context, the late Miocene emerges as an important reference point, because previous studies of geology and paleontology indicate that the Hengduan Mountains achieved their current height only after this time, whereas the Himalayas and central QTP did so before (4,13,15,17,21). Here, our phylogenetic inferences, which make no prior assumptions about the timing of geological events, show that after about 8 Ma the rate of in situ diversification increased in the Hengduan Mountains (Fig.…”

“…Rapid Himalayan orogeny during the early to middle Miocene (15,21,28) would predict a similar pulse of uplift-driven diversification, but none is evident whether the Himalayas are treated as part of the QTP (Fig. 3) or separately (SI Appendix, Fig.…”

“…By contrast, uplift of the Hengduan Mountains region, at the southeastern margin ( Fig. 1), is generally believed to have been rapid and recent, occurring mainly between the late Miocene and late Pliocene (18)(19)(20)(21)(22)(23).…”

<sup>10</sup>Be systematics in the Tsangpo-Brahmaputra catchment: the cosmogenic nuclide legacy of the eastern Himalayan syntaxis

“…This is supported by the valley infill upstream of the gorges being dominated by sands over the upper 100 to 200 m (Wang et al, 2014). Equation (5) simplifies to…”

“…The eastern Himalayan syntaxis has been proposed as a typical example of how active tectonic deformation, thermal weakening of the crust, and steep topography could be selfsustained by intense erosion and rapid exhumation of crustal material within the framework of the tectonic aneurysm model (Zeitler et al, 2001). Although the extent and nature of this coupling has recently been challenged (Bendick and Ehlers, 2014;Wang et al, 2014;King et al, 2016), there is ample evidence for superimposed rapid exhumation (Burg et al, 1998;Seward and Burg, 2008;Zeitler et al, 2014;Bracciali et al, 2016) and active erosion (Finlayson et al, 2002;Finnegan et al, 2008;Stewart et al, 2008;Enkelmann et al, 2011;Larsen and Montgomery, 2012;Lang et al, 2013) in a focused area around the Namche Barwa-Gyala Peri massif (NBGPm), where the course of the Tsangpo-Brahmaputra is marked by a sharp bend to the south-west (Fig. 1).…”