Active fault study along foothill zone of Kumaun sub-Himalaya: Influence on landscape shaping and drainage evolution

Abstract

The Kumaun Sub-Himalaya region is one of the most active regions falling into Seismic Zone V along the Himalaya. The geomorphology and drainage patterns in the area of active faulting and related growing fold provide significant information on the ongoing tectonic activity. The Kaladungi Fault (KF), an imbricated thrust fault of the Himalayan Frontal Thrust system provides an excellent example of forward and lateral propagation of fault and related folding in both directions along the strike of the fault. The KF has displaced the distal part of the Kaladungi fan surface resulting into formation of south-facing active fault scarp with variable heights along the front. In the east, the uplifted fan surface is ~ 60 m, is comparatively higher in the central part with height of ~ 200 m and ~ 80 m high in the west. The variation in heights along the fault is attributed to lateral propagation of fault and associated fold in both directions (i.e. east and west) from the centre. These clearly testify displacement starting at nucleation in the centre and propagating laterally in an elliptical manner. The northwest and southeast propagation of KF has resulted into diversion of the Dabka and Baur rivers respectively. A marked diversion of the modern Dabka river along its present course from east to west can be traced between Shivlalpur and Karampurtowns, covering a distance of about 10–12 km. Similarly, the Baur river is shifted from west to east by about 5–6 km between Kamola and Kaladungi towns. The diversion of Dabka and Baur rivers can well be justified by the existence of palaeo-wind-gaps through which these rivers flowed earlier during the recent past. The wind-gaps are characterized by about 0.5–1.0 km wide incised valley extending in NE–SWdirection between Kaladungi and Karampur along the frontal zone.