Late Quaternary tectono-geomorphic forcing vis-a-vis topographic evolution of Indus catchment, Ladakh, India

Abstract

The Indus River valley has frequently reorganized itself to attain geomorphic equilibrium during the Late Quaternary. In this regard, significant advances have been made towards the understanding of the response of landform/ landscape to climate (exogenic) forcings. However, advancements in geomorphic studies on the upper Indus basin focusing on recent tectonics (endogenic) are lacking, thus implementing a partial picture of landscape evolution. This article attempts to synthesize geomorphic indices of active tectonics to understand the prevalence of neotectonic activity in the Ladakh area. A combination of geomorphic field data, morphometric analysis and previously published incision rates, denudation rates, the chronology of landform features and soft-sediment deformation structures are used to suggest the region is undergoing differential tectonic activity. Based on morphometric parameters and landform characteristics, the region is divided into three differentially uplifted morphotectonic segments. The neotectonic activity is inferred to be the response to the thrusting of Indus Molasse over the rigid Ladakh Batholith along with oblique convergence of the Indian plate in the study area. This led to the development of a system of back thrust (Stok Thrust) and cross-cutting minor strike-slip faults. Recurrent tectonic activity largely responding to the differential movement along this system of thrust fault is recorded at 50 ka, 35 ka and 21 ka (Last Glacial Maxima) through lower Greenlandian (~11 ka) to middle Northgrippian (~6 ka), while the climatically induced topographic changes are marked between ~13 and 12 ka.