Abstract
Rockwall slope erosion is an important component of alpine landscape
evolution, yet the role of climate and tectonics in driving this erosion
remains unclear. We define the distribution and magnitude of periglacial
rockwall slope erosion across 12 catchments in Himachal Pradesh and
Jammu and Kashmir in the Himalaya of northern India using cosmogenic
10Be concentrations in sediment from medial moraines. Beryllium-10
concentrations range from 0.5±0.04x104 to 260.0±12.5x104 at/g SiO2,
which yield erosion rates between 7.6±1.0 and 0.02±0.04 mm/a. Between
~0.02 and ~8 m of rockwall slope erosion
would be possible in this setting across a single millennium, and
>2 km when extrapolated for the Quaternary period. This
erosion affects catchment sediment flux and glacier dynamics, and helps
to establish the pace of topographic change at the headwaters of
catchments. We combine rockwall erosion records from the Himalaya of
Himachal Pradesh, Jammu and Kashmir and Uttarakhand in India and
Baltistan in Pakistan to create a regional erosion dataset. Rockwall
slope erosion rates progressively decrease with distance north from the
Main Central Thrust and into the interior of the orogen. The
distribution and magnitude of this erosion is most closely associated
with records of Himalayan denudation and rock uplift, where the highest
rates of change are recorded in the Greater Himalaya sequences. This
suggests that tectonically driven uplift, rather than climate, is a
first order control on patterns of rockwall slope erosion in the
northwestern Himalaya. Precipitation and temperature would therefore
come as secondary controls.