Geomorphic imprints of neotectonic activity along the frontal part of eastern Himalaya, Pasighat, east Siang district, Arunachal Pradesh

Abstract

Geomorphology in relation with tectonics has been studied along the Himalayan frontal part around Pasighat, Eastern Himalaya Arunachal Pradesh Squeezed between Main Boundary Thrust and Himalayan Frontal Thrust (HFT), the morphology of the area indicates significant influence by tectonic processes. The streams including the Siang River show anomalous drainage patterns whenever they cross the lineaments. Mountain front sinuosity index, and development of deeply incised narrow valleys along the front zone indicate recent tectonic movement along the HFT. Four levels of terraces are observed In the Pasighat area. Terraces show crude stratification of their constituents. Three levels of unpaired terraces are observed in Roing-Balek area. Paleochannel reconstruction suggests a gradual eastward migration of the Siang River, which shows a swing in its flow direction from N-S to present NW-SE. Drainage basin asymmetry vectors, calculated from transverse topographic profiles of two segments, suggest preferred stream migration towards northeast and southeast direction in response to northeastward and southwestward ground tilting.