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Rates of rockwall slope erosion in the upper Bhagirathi catchment, Garhwal Himalaya
Author(s) -
Orr Elizabeth N.,
Owen Lewis A.,
Saha Sourav,
Caffee Marc W.
Publication year - 2019
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.4720
Subject(s) - moraine , geology , glacier , erosion , drainage basin , rockfall , sediment , glacial period , hydrology (agriculture) , landslide , weathering , geomorphology , physical geography , denudation , snowmelt , debris , snow , tectonics , paleontology , geography , oceanography , cartography , geotechnical engineering
Rockwall slope erosion is defined for the upper Bhagirathi catchment using cosmogenic Beryllium‐10 ( 10 Be) concentrations in sediment from medial moraines on Gangotri glacier. Beryllium‐10 concentrations range from 1.1 ± 0.2 to 2.7 ± 0.3 × 10 4 at/g SiO 2 , yielding rockwall slope erosion rates from 2.4 ± 0.4 to 6.9 ± 1.9 mm/a. Slope erosion rates are likely to have varied over space and time and responded to shifts in climate, geomorphic and/or tectonic regime throughout the late Quaternary. Geomorphic and sedimentological analyses confirm that the moraines are predominately composed of rockfall and avalanche debris mobilized from steep relief rockwall slopes via periglacial weathering processes. The glacial rockwall slope erosion affects sediment flux and storage of snow and ice at the catchment head on diurnal to millennial timescales, and more broadly influences catchment configuration and relief, glacier dynamics and microclimates. The slope erosion rates exceed the averaged catchment‐wide and exhumation rates of Bhagirathi and the Garhwal region on geomorphic timescales (10 3 −10 5 years), supporting the view that erosion at the headwaters can outpace the wider catchment. The 10 Be concentrations of medial moraine sediment for the upper Bhagirathi catchment and the catchments of Chhota Shigri in Lahul, northern India and Baltoro glacier in Central Karakoram, Pakistan show a tentative relationship between 10 Be concentration and precipitation. As such there is more rapid glacial rockwall slope erosion in the monsoon‐influenced Lesser and Greater Himalaya compared to the semi‐arid interior of the orogen. Rockwall slope erosion in the three study areas, and more broadly across the northwest Himalaya is likely governed by individual catchment dynamics that vary across space and time. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons, Ltd.