HR: 1330h
AN: T42B-0293    [PDF]
TI: Preliminary results of 10Be analyses from the eastern Himalayan syntaxis: evidence for unsteady erosion on two spatial scales.
AU: * Finnegan, N J
EM: noahf@u.washington.edu
AF: University of Washington Department of Earth and Space Scences, Box 351310, Seattle, WA 98195-1310
AB: In-situ 10Be concentrations in quartz sediments sands collected from the beds of seven small (10-100 km2), unglaciated tributaries of the Parlung River, a tributary of the Tsangpo River in southeastern Tibet, indicate suggest basin-wide erosion rates between 0.40 +/- .02 and 2.99 +/- .45 mm/yr. This six-fold variation in erosion rate is not explained by differences in climate, morphology, or lithology among the basins. We interpret the variation in 10Be concentrations, instead, to be a reflection of the extremely stochastic nature of sediment delivery in these steep, high relief catchments. Two fluvially polished quartzite surfaces above the Po Tsangpo River near the town of Parlung exhibit nearly identical 10Be ages of 3105 +/- 415 yr (30 m above modern river level) and 3155 +/- 275 yr (15 m above modern river level), despite a 15 m vertical difference in elevation above the river level. This apparent absence of an age elevation trend suggests that incision on this river is not steady and incremental, but rather is characterized by infrequent, large erosive events. Large floods have occurred at least twice in the last century on the Parlung river, with a 35 meter increase in stage during the most recent flood in 2000, and may contribute to punctuated erosion.
DE: 1625 Geomorphology and weathering (1824, 1886)
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1860 Runoff and streamflow
SC: Tectonophysics [T]
MN: 2003 Fall Meeting