Rockwall Slope Erosion in the Northwestern Himalaya

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 ± 0.04 × 104 to 260.0 ± 12.5 × 104 at/g SiO2, which yield erosion rates between 7.6 ± 1.0 and 0.02 ± 0.004 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 data set. 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.

Tectonic Control Over Shallow Crustal Exhumation Across the India‐Asia Convergent Margin

“…In comparison, these rates on the southern side of the Ladakh ranges vary between ∼0.020 and 0.039 mm yr −1 since 300 ka (Dortch et al., 2011). The regional study of bedrock slopes erosion rates suggests that these rates decrease from 7.60 ± 1.0 to 0.02 ± 0.004 mm a −1 from the north of MCT up to the Ladakh range (Orr et al., 2021). These magnitudes of erosional records can be correlated with the records of Himalayan denudation and rock uplift, which suggests that tectonics have major control on the rock uplift rather than climate (Orr et al., 2021).…”

Reconciling the Apparent Absence of a Last Glacial Maximum Alpine Glacial Advance, Yukon Territory, Canada, through Cosmogenic Beryllium-10 and Carbon-14 Measurements

“…The first scenario involves the plucking of a pre-exposed surface from a valley bottom, and englacial incorporation of the resulting boulder and transport to its final moraine resting place (Figure 7A). The second scenario envisions delivery of a pre-exposed paraglacial boulder to a supraglacial setting prior to burial and englacial transport to a moraine (i.e., Scherler and Egholm, 2020;Orr et al, 2021;Ward and Anderson, 2010; Figure 7B). We use characteristic elevations for the valley bottom, cliff, and moraine settings and assume that in both scenarios, the 14 C concentration is at production-decay secular equilibria and thus represents the maximum 14 C concentrations that could be observed prior to delivery to the glacier surface.…”

The influence of landslide morphology on erosion rate variability across western Himalayan catchments: Role of westerlies and summer monsoon interaction in the landscape characterization

“…The Lesser Himalayan Sequence (LHS) is constrained from north to south by the Main Boundary Thrust (MBT) and Main Frontal Thrust (MFT) (Miller et al, 2000;Vannay et al, 2004). From north to south, the initiation ages for these litho-tectonic divisions have decreased (Orr et al, 2019(Orr et al, , 2021. The western Himalayan terrain evolved through several tectonically active faults and thrust systems, and the steep topography along or near these discontinuities makes these regions highly susceptible and subject to hillslope failure (Kumar et al, 2019;Gupta et al, 2022).…”