Evaluation of neotectonic variability along major Himalayan thrusts within the Kali River basin using geomorphic markers, Central Kumaun Himalaya, India

Abstract

We have analysed the geomorphic signatures in aggregation with the geomorphic indices with respect to hinterland and foreland neotectonic variability across the major Himalayan thrust system along the Kali River valley of eastern Kumaun Himalaya. The valley floor morphology in the vicinity of the major thrust gave rise to the accommodation space for the aggradation of the recent fluvial sediments. For a longitudinal distance of 212 km between the South Tibet Detachment (STD)and Himalayan Frontal Thrust (HFT), the valley has preserved significant aggradational landforms. These landforms have been physically examined to explain the spatial and temporal variability in phases of aggradation/incision in response to the tectonic activity during the late Quaternary. Fossil valleys and associated epigenetic gorges, cut-and-fill terraces with thick alluvial cover, debris-flow terraces, bedrock strath terraces, and alluvial fan terraces are the significant aggradational landforms observed within the valley. They provide signatures of tectonic activity and past climatic records. We have analysed various geomorphic indices, namely, stream-gradient index (SL), steepness index (Ks), hypsometric curve and index (HI), and asymmetric factor (AF) to map the spatial variability in tectonic processes across the major thrusts. The channel morphology (depth and width) of a river becomes adjusted in geological time because of long-term tectonic and erosional processes. However, the channel geometry and deviations can be highly adjustable in a tectonically disturbed mountainous region. The deviations along the river course can be attributed to active tectonic movement along thrusts/faults or because of erosion/sedimentation processes. We applied a novel method called the river Gradient Length Anomaly (GLA) for 37 subbasins of the Kali River to deduce active deformation (uplift/subsidence) corresponding to the increased sedimentation and erosional rates, both from the upstream and downstream parts of the thrusted blocks, from where river flows through. The results of basin-wise morphometric indices were corroborated with GLA anomaly and field observations, which suggests that the area has undergone active deformation between the Main Central Thrust (MCT) and Himalayan Frontal Thrust (HFT), which is attributed to the regional compression. The results of geomorphic and morphometric data are validated with the focal mechanisms of moderate earthquakes. The geomorphic analysis suggests that the hinterland part of eastern Kumaun is more active than the foreland region.

Evidences of neotectonic activity along Goriganga River, Higher Central Kumaun Himalaya, India

“…In order to ascertain tectonic deformation (uplift) and erosion/or subsidence, we used Žibret and Žibret () for river GLA and followed Talukdar, Kothyari, and Pant () for the Kali River basin. GLA anomaly precisely detects uncertainties occurring along the river channel within the intersection points of thrusts/faults and river courses (Žibret & Žibret, , ) and can be expressed by the following equation (Žibret & Žibret, , ) where h is the altitude, l is the distance from the river source measured in the direction of river flow, and k and n are specific coefficients of the river derived from the best‐fit exponent regression curve to the measured data.…”

Landscape evolution of Rivers in the Ganga Plain and Himalaya

“…In the Kumaun sub-Himalaya a ~9.5 km long splay of the MBT is mapped offsetting an alluvial fan at >20 ka that remained active until atleast 8.7 ka (Philip et al, 2017). Similarly, a study using geomorphic indices and Interferometric Synthetic Aperture Radar (In-SAR) mapped active deformation between the MBT and the Himalayan Frontal Thrust (HFT) in Soan Dun area and several river basins in the Kumaun and Garhwal Himalaya were evaluated to understand the neotectonic deformation in the region (Talukdar et al, 2019;Luirei et al, 2015Luirei et al, , 2016Luirei et al, , 2018Kothyari and Luirei, 2016;Bhakuni et al, 2017;Kothyari et al, 2017aKothyari et al, , b, 2019Joshi et al, 2018;Asthana et al, 2018).…”

Small-scale regional engineering geological study of the Czech Republic evaluating the relationship between slope gradients and engineering geological zones

“…One of the most critical tasks of engineering geology is the description of geological engineering conditions for building structures within the civil engineering industry. The slope gradient is affected by a number of factors, such as erosion 6 – 8 , landslides 9 – 11 , neotectonic processes 12 – 14 and others.…”