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Title:
Rates and patterns of short-term erosion on the eastern margin of the Tibetan Plateau, a transient landscape
Authors:
Ouimet, W.; Whipple, K.; Granger, D.
Affiliation:
AA(Department of Earth, Atmospheric and Planetary Science, MIT, Cambridge, MA 02139 ; ), AB(School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 ; ), AC(Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN 47907 ; )
Publication:
American Geophysical Union, Fall Meeting 2006, abstract #H21H-01
Publication Date:
12/2006
Origin:
AGU
AGU Keywords:
1150 Cosmogenic-nuclide exposure dating (4918), 1815 Erosion, 1824 Geomorphology: general (1625), 9320 Asia
Abstract Copyright:
(c) 2006: American Geophysical Union
Bibliographic Code:
2006AGUFM.H21H..01O

Abstract

Measuring 10Be concentrations in quartz extracted from river sediment has been shown to yield reliable mean, short-term (103-105 yr) basin-wide erosion rates in many different tectonic and climatic settings. Here, we present erosion rates for 70 small river basins (<100 km2) located on the eastern margin of the Tibetan Plateau, one of the world's broadest and most dramatic transient landscapes, where preliminary data has shown that erosion rates range by nearly two orders of magnitude, from ~0.025 mm/yr to >1 mm/yr. Basins were carefully selected to cover a regional distribution and to be representative of specific areas of transient adjustment. Our sample basins cover a range of elevations, channel steepness indices, and mean hillslope angles. They drain relatively uniform, quartz-rich bedrock lithologies (either granite or sandstone flysch) and have adjusted, smooth river profiles without significant knickpoints or changes in profile convexity that are suggestive of non-uniform rates of erosion within individual basins. Major rivers on the eastern margin start at high elevations over 4000m where they are slightly incised into a low-relief relict landscape and transition into rapidly incised, high-relief, dissected gorges with steep hillslopes. Our data allow us to characterize in detail the differential rates of erosion associated with the relict landscape and incised gorges, as well as to describe fundamental aspects of the regional transient response of rivers on the eastern margin to rapid incision on trunk streams as waves of landscape adjustment propagate upstream and up hillslopes. In addition to using erosion rates to analyze regional transient river response, we also use them to: (1) address long standing question of the quantitative relationship between topography and erosion rate by exploring relationships between hillslope angle, channel steepness and erosion rate; (2) solidify our quantitative understanding of river response to tectonic forcing that can be ported into other landscapes as a refined tool; and (3) provide an important shorter-term complement to the long-term exhumation rate estimates from low- temperature thermochronometers.
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