Quaternary block-tilting in southern Himalayan ranges of eastern Uttarakhand, India

摘要

The Himalaya is traversed by numerous criss-crossing faults and thrusts that ultimately subdivide it into several distinct tectonic blocks. Geomorphic features such as paired and unpaired river terraces, triangular fault facets, escarpments, train of landslides, entrenched rivers, anomalies along the river courses and drainage patterns indicate active tectonic movements along the block defining faults/thrust and, thus, tectonic unrest in the three tectonic blocks of Lesser Himalaya and the tectonic block of the Siwalik in Uttarakhand state of India. Basin Asymmetry Factor (AF) and Transverse Topography Symmetry Factor (T) of the 44 drainage basins indicate gentle to steep tilting of these tectonic blocks due to Quaternary tectonic movements. The Lesser Himalayan tectonic blocks are generally up-tilted in SE to NW directions due to uplift along the block defining thrusts, whereas the Siwalik tectonic block is up-tilted in NE to SE directions due to its differential uplift along the range-bounding Himalayan Frontal Thrust (HFT). Deflections along the antecedent Gola River course also suggest gradual, east to west progression of the Siwalik tectonic block.