Himalayan Geology, Vol. 43 (1B), 2022, pp. 303-318, Printed in India
Non-emergent thrust front along the northwest Jammu Sub-Himalaya: Evidence from channel profile analysis across the Surin Mastgarh Anticline
A. ARAVIND1,2, RAHUL DEVRANI1,3*, R. JAYANGONDAPERUMAL1#, C.C. PANT2
1Wadia Institute of Himalayan Geology, Dehradun - 248001, India
2Department of Geology, Kumaun University, Nainital, India
3Delhi School of Climate & Sustainability, Institution of Eminence, University of Delhi, Delhi - 110007, India
Email (Corresponding authors): * rahuldevrani18@gmail.com; # ramperu.jayan@gmail.com
Abstract: The Himalayan Frontal Thrust (HFT) is emergent throughout the central and NE Himalayas. The emergent thrust creates an anticline structure in its hanging wall, and they are either fault-bend or fault-propagation-fold. However, the Jammu NW Sub-Himalaya (between Beas and Munvar Tawi Rivers) is different from the adjacent mountain fronts. The HFT remains blind or non-emergent and developed a ~200km long Surin Mastgarh Anticline (SMA). We divided the SMA into six zones from NW to SE based on transverse rivers flowing across the SMA. To understand the along-strike variation of stream morphology, lithology, and tectonics, we investigate 106 river channels developed across the SMA. The Lower Siwalik rock at the core of SMA shows the highest channel concavity index (θ = 0.95) and normalized channel steepness index (Ksn=7.225). Quaternary deposits dominated zone in the forelimb of SMA showed a lower channel concavity index (θ = 0.1) and normalized channel steepness index (Ksn = 4.44 x 10-05). There is a slight variation in the channel concavity index (θ) and high Ksn values at SMA core with high resistance lower Siwalik bedrocks. The variable channel concavity index (θ) with high normalized channel steepness (Ksn) of stream profiles suggests tectonic and lithologic controls on the morphology of rivers. We observed a high channel steepness index (Ksn ) around the crest of the SMA. The morphometric studies and the field evidence suggest the SMA is a detachment fold rather than a fault-bend or fault-propagation fold with an emergent thrust front.
Keywords: Emergent and non-emergent, thrust front, Stream profile, Surin Mastgarh anticline, Channel steepness index, lithology, and tectonic uplift
