Geomorphic Evolution of the Nushki Segment of the Chaman Fault in Western Pakistan
Abubakar, Yahaya 1983-
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The Chaman strike-slip fault marks the western boundary of the collision zone between the Indian and Eurasian plates. It accommodates both lateral translation and convergence of the Indian plate beneath the Eurasian plate and connects the Makran subduction zone to the Himalayan convergence zone. The geomorphic evolution of this very important tectonic feature is relatively unknown compared to other tectonically important faults in the Himalayas such as the Altyn-Tagh and Karakoram faults. The Nushki Basin marks the southern portion of the of the Chaman fault where strike-slip and thrust faults interaction predominates. This work utilizes a morphometric approach towards understanding the geomorphic evolution of the southern segment of the Chaman fault. Fifteen meter Digital Elevation Models (DEM), Advanced Spaceborne Thermal Emission and Reflection (ASTER), and GeoEye-1 satellite images were all integrated to measure three geomorphic indices; stream-length gradient index (SL), mountain-front sinuosity (Smf), and valley-floor width to height ratio (Vf). Analysis of results obtained from the measured indices shows that evolution of landforms in the area is tectonically controlled with propagation of thrust towards the northern flanks of the basin. This is further supported by the results of topographic analysis carried out on a ridge which shows two wind gaps in the north and a corresponding water gap further south. Measured offsets on Quaternary landforms also vary from the northern to southern flanks of the basin, generally showing a larger total displacement in the northern portion relative to the south.