Impact of long term uplift on stream networks in tectonically active Northern Hill Range, Kachchh palaeo-rift basin, western India

The study deals with stream response to sustained tectonic during the Cenozoic and development of two parallel scarps in the western Kachchh. The study encompasses fluvial networks developed over the Jara and Jumara domes, which are a part of the laterally extensive belt of flexures bounded by the Kachchh Mainland Fault (KMF) to their north and called as Northern Hill Range (NHR). Parameters such as longitudinal profile, Hack profile, stream length gradient index (SL), hypsometric curve, hypsometric integral (HI), valley floor width to height ratio (Vf), elongation ratio (Re) and escarpment sinuosity (ES) were analysed. Hack profiles of the major rivers draining through the area show similar convex up nature suggesting primary influence of the tectonics in controlling and shaping the landscape of the region. Elongation ratio < 6 and undergone higher degree of fluvial erosion indicated by the low values of hypsometric integral suggest the tendency of river systems to increase the basin area longitudinally rather than laterally. The study suggests that higher net uplift in the eastern half (Jumara dome) caused the rivers to overcome the structural control and to carve out generally straight north oriented channels. The rivers of western part (Jara dome) show more prominent structural control of cuesta girdles formed in compact lithologies and attributed to the domal structure. The ~10 km long Jaramara scarp believed to the remnant of older KMF scarp, is a product of headward erosion of the fluvial channels through different hard and soft litho-units of the area. The similar orientation of Jaramara scarp and morphology of the Ukra intrusive body suggests that the Ukra intrusive played a significant role in controlling the formation and morphology of the Jaramara scarp.