Implications of the ongoing rock uplift in NW Himalayan interiors

Saptarshi Dey,Rasmus C. Thiede,Arindam Biswas,Pritha Chakravarti,Naveen Chauhan,Vikrant Jain

doi:10.5194/esurf-9-463-2021

Abstract

Abstract. The Lesser Himalaya exposed in the Kishtwar Window (KW) of the Kashmir Himalaya exhibits rapid rock uplift and exhumation (∼3 mm yr−1) at least since the late Miocene. However, it has remained unclear if it is still actively deforming. Here, we combine new field, morphometric and structural analyses with dating of geomorphic markers to discuss the spatial pattern of deformation across the window. We found two steep stream segments, one at the core and the other along the western margin of the KW, which strongly suggest ongoing differential uplift and may possibly be linked to either crustal ramps on the Main Himalayan Thrust (MHT) or active surface-breaking faults. High bedrock incision rates (>3 mm yr−1) on Holocene–Pleistocene timescales are deduced from dated strath terraces along the deeply incised Chenab River valley. In contrast, farther downstream on the hanging wall of the MCT, fluvial bedrock incision rates are lower (<0.8 mm yr−1) and are in the range of long-term exhumation rates. Bedrock incision rates largely correlate with previously published thermochronologic data. In summary, our study highlights a structural and tectonic control on landscape evolution over millennial timescales in the Himalaya.

Highlights

Protracted convergence between the Indian and the Eurasian Plate resulted in the growth and evolution of the Himalayan orogen and temporal in-sequence formation of the Southern Tibetan Detachment System (STDS), the Main Central Thrust (MCT), the Main Boundary Thrust (MBT) and the Himalayan Frontal Thrust (HFT) towards the south (e.g., Yin and Harrison, 2000; DiPietro and Pogue, 2004)
A large body of literature in the eastern, central and western Himalaya favors the idea that the majority of the late Pleistocene–Holocene shortening is rather partitioned throughout the sub-Himalayan domain and not solely accommodated by the HFT (e.g., Wesnousky et al, 1999; Burgess et al, 2012; Thakur et al, 2014; Mukherjee, 2015; Vassallo et al, 2015; Dey et al, 2016a, 2018)
The Lesser Himalayan sequence (LHS) rock units exposed within the Kishtwar Window (KW) are mainly composed of fine-grained quartzites and phyllites with occasional schists in between (Steck, 2003; Gavillot et al 2018)

Summary

Introduction

Protracted convergence between the Indian and the Eurasian Plate resulted in the growth and evolution of the Himalayan orogen and temporal in-sequence formation of the Southern Tibetan Detachment System (STDS), the Main Central Thrust (MCT), the Main Boundary Thrust (MBT) and the Himalayan Frontal Thrust (HFT) towards the south (e.g., Yin and Harrison, 2000; DiPietro and Pogue, 2004) Seismic reflection profiles reveal that all these fault zones emerge from a low-angle basal decollement, the Main Himalayan Thrust (MHT), forming the base of the Himalayan orogenic wedge (e.g., Ni and Barazangi, 1984; Nábelek et al, 2009) that was established in the late. A large body of literature in the eastern, central and western Himalaya favors the idea that the majority of the late Pleistocene–Holocene shortening is rather partitioned throughout the sub-Himalayan domain (morphotectonic segment between the MBT and the MFT) and not solely accommodated by the HFT (e.g., Wesnousky et al, 1999; Burgess et al, 2012; Thakur et al, 2014; Mukherjee, 2015; Vassallo et al, 2015; Dey et al, 2016a, 2018).

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