Tectonic forcing of drainages and geomorphic features developed across Himalayan mountain frontal part of western limb of Siang Antiform, Arunachal Himalaya

Drainages display tectonic forcing of their channels on the frontal region of the Arunachal Himalaya due to structural control. Dikari, a transverse river flowing along the N–S trending western limb of the major Siang Antiform, exhibits structurally controlled nature of its drainage on its downstream flow towards south, through a network of NE–SW and NW–SE trending conjugate faults. The river shows compressed meandering as the regional structural trend of ENE–WSW seems to be reactivated by the transverse NW–SE trend of neotectonic fault activity. The Himalayan frontal thrust (HFT) tracing along the Himalaya mountain front has been displaced sinisterly for a distance of ~7 km by a WNW–ESE trending fault running along the Sileng stream. Development of parallel drainages in the southern part of the Sub-Himalaya is interpreted to have formed as a result of uplifting related to the above-mentioned strike-slip movement. Along the HFT zone, the frontal streams and rivers exhibit deflection of their channels from NE–SW to ENE–WSW directions. Channel of the transverse Siang river has been deflected for a length of 3 km along the NNE–SSW direction across the Himalayan frontal part. In this part of the Himalaya, previous workers did not give much emphasis on the role of Siang Antiform as far as neotectonic with respect to the tectonics related to the HFT is concerned. There is a syntectonic relationship between the active NE–SW-oriented compression direction and the tectonic forcing of the drainages including development of the tectonic geomorphology.