Enhanced Quaternary exhumation in the Namche Barwa syntaxis, eastern Himalaya

Abstract

The Namche Barwa syntaxis in the eastern Himalaya is rapidly evolving in terms of its tectonics and topography. Here we constrain the exhumation history of the Yigong River to the immediate north of the syntaxis across different time scales using a multidisciplinary approach. Our new thermochronometric data reveal an acceleration of exhumation rates since 2 Ma in the downstream of the Yigong. Cosmogenic nuclides and thermoluminescence thermochronometry analyses confirm persistent rapid exhumation in the lower Yigong over the Quaternary with further increased exhumation in the last 100 ka. Together with the analysis of the morphology of the Yigong River profile, we interpret that northward expansion of the syntaxis together with capture of the Yigong by the Yarlung Tsangpo River during this expansion is responsible for the exhumation history of the Yigong River in the Quaternary.