Application of geomorphic indices to Address the foreland Himalayan tectonics and landform deformation- Matiali-Chalsa- Baradighi recess, West Bengal, India

Abstract

In the Himalayan foreland basin of the Tista-Jaldhaka system of North Bengal, the presence of Main Boundary Thrust (MBT) and Himalayan Frontal Thrust (HFT) along an E-W direction has been reanalysed in the context of tectonic instability especially along the 17.93 km stretch of the Kurti River. It is a small rain-fed stream that originated in the piedmont zone near the Samsing scarp (lineament trending E-W). This work discusses in detail the control of active Matiali, Chalsa, and Baradighi faults that has been determined by the river morphometric aspects, deformed landform as terraces, and the valley incision mechanism over time. We document not only the fault scarps as MBT near Matiali and HFT near Chalsa, but also decipher the Baradighi fault as a local manifestation of tectonism with well-exposed scarps. A ramp anticline (Synformal zone I) exists between the northernmost part of the Matiali scarp (MBT) and towards the south near the Chalsa scarp (HFT). However, to the south of Chalsa, lies another depression zone (Synformal zone II) that extends up to the Baradighi scarp, exposed in the left (eastern) side of Kurti River. Changes in geomorphic indices such as long profile analysis, drainage basin asymmetry, hypsometric curve, valley floor width to height ratio (Vfwh), concavity index, transverse topographic symmetry factor, and sinuosity index along the Kurti River have been evaluated. Uplift-erosion cycle with valley incision between the MBT-HFT and HFT-Baradighi fault scarp connotes that the foreland tectonics emerged to be the recent evolutionary phases in the tecto-morphological study.