Publikationsdatum:
2013-11-30
Beschreibung:
[1] Erosion in the Himalaya is responsible for one of the greatest mass redistributions on Earth, and has fueled models of feedback loops between climate and tectonics. Although the general trends of erosion across the Himalaya are reasonably well known, the relative importance of factors controlling erosion is less well constrained. Here, we present 25 10 Be-derived catchment-average erosion rates from the Yamuna catchment in the Garhwal Himalaya, northern India. Tributary erosion rates range between ~0.1-0.5 mm yr -1 in the Lesser Himalaya and ~1-2 mm yr -1 in the High Himalaya, despite uniform hillslope angles. The erosion-rate data correlate with catchment-average values of 5-km radius relief, channel steepness indices, and specific stream power, but to varying degrees of non-linearity. Similar non-linear relationships and coefficients of determination suggest that topographic steepness is the major control on the spatial variability of erosion, and that 2-3-fold differences in annual runoff have only minor effects in this area. Instead, the spatial distribution of erosion in the study area is consistent with a tectonic model in which the rock-uplift pattern is largely controlled by the shortening rate and the geometry of the Main Himalayan Thrust fault (MHT). Our data support a shallow dip of the MHT underneath the Lesser Himalaya, followed by a mid-crustal ramp underneath the High Himalaya, as indicated by geophysical data. Finally, analysis of sample results from larger main-stem rivers indicates significant variability of 10 Be-derived erosion rates, possibly related to non-proportional sediment supply from different tributaries and incomplete mixing in main-stem channels.
Print ISSN:
0148-0227
Thema:
Geologie und Paläontologie
,
Physik
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