Quaternary foreland tectonics and landscape changes - a case study of Himalayan piedmont zone of Jaldhaka river system, eastern Himalaya, India

The Jiti–Khuji Diana interfluve of the Himalayan piedmont zone has been considered to reanalyse the tectonic character of the Main Boundary Thrust (MBT) and Main Frontal Thrust (MFT), which are two major east–west trending structural units of the Himalayan orogen. The MBT marks a tectonic boundary between the Lesser and sub-Himalayan sequences (Gansser, Geology of Himalayas, Wiley Interscience, New York, 1964), while the MFT is the youngest deforming front that carries the Siwalik Group of rocks over the Quaternary deposits (Yin, Earth Sci Rev 76:1–131, https://doi.org/10.1016/j.earscirev.2005.05.004, 2006). This area is dissected by three main steams of the Jaldhaka system, i.e. rivers Jiti, Khuji Diana, and Thaljhora; amongst which the Thalhjora flows from east to west and the other two rivers flow roughly from NNE to SSW. Thaljhora and Chalsa fault scarps are observed, respectively, at and near the MBT and MFT. The present research focuses on significance of active Thaljhora and Chalsa fault scarps, which represent the monocline faults that deformed the geomorphic landscape. The displacement along these faults have formed a synform that uplifted over time and formed river terraces by incision processes of rivers. The analysis of morphometric indices confirms the recent neotectonic activities going on in the region. The deformed landforms, emerged as terrace and Doon-shaped valley, are observed between the Jiti fault (MBT) and Chalsa scarp (MFT). The doon-shaped valley is developed as a flat-lying surface situated between the Jiti fault and Thaljhora scarp. This study has deciphered the application of morphometric indices to study the active neotectonics.