The role of climate and tectonics in aggradation and incision of the Indus River in the Ladakh Himalaya during the late Quaternary

Abstract

The geomorphic evolution of the upper Indus River that traverses across the southwest (SW) edge of Tibet, and the Ladakh and Zanskar ranges, was examined along a ~350-km-long stretch of its reaches. Based on the longitudinal river profile, stream length gradient index, and river/strath terraces, this stretch of the river is divided into four segments. Valley fill river terraces are ubiquitous, and strath terraces occur in the lower reaches where the Indus River cuts through deformed Indus Molasse. Optically stimulated luminescence ages of river/strath terraces suggest that valley aggradation occurred in three pulses, at ~52, ~28, and ~16 ka, and that these broadly coincide with periods of stronger SW Indian summer monsoon. Reconstructed longitudinal river profiles using strath terraces provide an upper limit on the bedrock and provide incision rates ranging from 1.0±0.3 to 2.2±0.9 mm/a. These results suggested that rapid uplift of the western syntaxes aided by uplift along the local faults led to the formation of strath terraces and increased fluvial incision rates along this stretch of the river.

Chronology and climate sensitivity of the post‐LGMglaciation in the Dunagiri valley, Dhauliganga basin, Central Himalaya, India

“…Standard chemical pretreatment was given to all samples to separate a fraction of 90–150 μm clean quartz (Aitken ; Srivastava et al . ; Kumar & Srivastava ). To remove the alpha affected outer layer, the quartz grains were etched using 40% HF for 80 min followed by 40 min of treatment with 35% HCl.…”

“…Establishing the chronology of the Dunagiri Glacier valley moraines using optically stimulated luminescence (OSL) dating was extremely challenging because of the scarcity of datable material, low luminescence signal, and feldspar contamination. The Himalayan glaciers’ moraine sediments may generally present two complications: (i) sediment deposited in high‐energy environments may experience inhomogeneous and/or incomplete zeroing, and (ii) quartz in the Himalayan region with poor OSL sensitivity may also have some contamination from feldspars (Ray & Srivastava ; Kumar & Srivastava ).…”

Chronology and sediment provenance of extreme floods of Siang River (Tsangpo‐Brahmaputra River valley), northeast Himalaya

“…Samples having higher photon counts were further treated, once or twice as needed, with 40% HF for 10 minutes followed by 10 minutes 35% HCl treatment (Figure 3A). Samples that continue to have higher IRSL counts were analyzed using a Double SAR Protocol method (Jain and Singhvi, 2001; Jain et al, 2005; Kumar and Srivastava , 2017). The single aliquot regeneration (SAR) technique of Murray and Wintle (2000) was used to determine D E values.…”

“…The initial 100‐km of the gorge has a steep river gradient of around 30 m/km (Burg et al, 1998); and it is highly susceptible to slope failures and landslides. This gorge region has yielded river incision rates that are approximately 1.4–3.7 times higher than the Indus gorge in the northwest Himalayan syntaxis (Finlayson et al, 2002; Garzanti et al, 2004; Kumar and Srivastava, 2017). It has also experienced a high rock exhumation rate (10 mm/yr at 3.5‐3.2 Ma to 3‐5 mm/yr since 2.2 Ma) that has exhumed migmatitic gneises at the core of Paleozoic to Mesozoic quartzites, phylites and marbles of the calc‐alkaline pluton of the Trans Himalaya (Burg et al, 1998).…”

Active tectonics of Himalaya, rift basins in Central India and those related to crustal deformation at different time scales

“…The procedures were also applied to document the multi-bending configuration of the blind thrust of the Dehradun reentrant. Kumar and Srivastava (2017) studied the role of tectonic-climate interaction in the incision and aggradation of the Indus River in the Ladakh Himalaya during the late Quaternary. Examining about ~350 km long stretch of the Indus River and its upper reaches, the geomorphometry was estimated.…”