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Northward migration of the eastern Himalayan syntaxis revealed by OSL thermochronometry

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Science  19 Aug 2016:
Vol. 353, Issue 6301, pp. 800-804
DOI: 10.1126/science.aaf2637

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Unlinking erosion from uplift in Tibet

Conventional wisdom suggests that the locations of gorges or “knickpoints” along the edges of large plateaus remain fixed because erosion drives tectonic uplift. Nowhere should this be more evident than the rapidly uplifting and eroding Tibetan plateau. However, King et al. found evidence for slow migration of a major knickpoint along the Parlung River in eastern Tibet. They used a new method with exceptional time resolution for determining regional cooling rates called multi–OSL (optically stimulated luminescence) thermochronology. It appears that the Parlung knickpoint is steadily moving upstream as a response to tectonic uplift that is unrelated to the local erosion rates.

Science, this issue p. 800

Abstract

Erosion influences the dynamical evolution of mountains. However, evidence for the impact of surface processes on tectonics mostly relies on the circumstantial coincidence of rugged topography, high stream power, erosion, and rock uplift. Using the optically stimulated luminescence (OSL) thermochronometry technique, we quantified the spatial and temporal exhumation of the eastern Himalayan syntaxis. We found increasing exhumation rates within the past million years at the northeast end of the Namche Barwa–Gyala Peri dome. These observations imply headward propagation of erosion in the Parlung River, suggesting that the locus of high exhumation has migrated northward. Although surface processes influence exhumation rates, they do not necessarily engage in a feedback that sets the location of tectonic deformation.

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