Spatial controls on erosion in the Three Rivers Region, southeastern Tibet and southwestern China

Global data suggest that erosion rates variously scale with steepness or climate forcing (precipitation or glacial excavation), but the relative influence of these factors has proven difficult to assess without comparisons from a single location. A new suite of detrital 10Be data from the Three Rivers Region, SE Tibet is used to examine the relative importance of rainfall and relief in predicting patterns of erosion rates across a region with a strong gradient in exhumation. The data reveal millennial erosion rates vary by two orders of magnitude, from 0.01 to 8 mm/yr across a regional gradient in exhumation rates inferred from previous thermochronology and cosmogenic nuclide data to the west and east of the study region. The new millennial erosion rates mirror the pattern of decreasing exhumation rates from west to east across the region, with the highest rates in the lower Salween River drainage and the lowest rates in the Yangtze River drainage. Erosion rates in the Mekong and Salween River drainages are correlated with mean local relief whereas in the Yangtze River drainage they are correlated most strongly with mean annual rainfall. The tectonic setting of this region, with a strong west to east gradient in exhumation rates which we infer to mirror a gradient in rock uplift, seems to exert a stronger control on erosion rate patterns than rainfall or relief.

Research Highlights
► Detrital 10Be erosion rates in eastern Tibet show a strong north to south increase.
► Erosion increases 2-fold from east to west in the southern part of the region.
► Erosion rates track well with a gradient in uplift inferred from exhumation rates.
► In west, with high uplift rates, relief correlates best with erosion rates.
► In east, with low uplift rates, rainfall correlates best with erosion rates.