Himalayan Geology, Vol. 44 (1), 2023, pp. 117-129, Printed in India
Gravity survey to delineate the subsurface extension of the Khair-i-Murat Thrust under the Sub-Himalayas, Kohat-Potwar region, Pakistan
AAMIR ALI1*, ASAM FARID2, UMER FAROOQ AWAN1, YAWAR AMIN1, WAQAR ALI ZAFAR3,
ANEES AHMED BANGASH1, SAIF ULLAH4
1Department of Earth Sciences, Quaid-i-Azam University, 45320, Islamabad, Pakistan
2Department of Geophysics, Arab Company for Laboratories and Soil, 31952, Al Khobar, Kingdom of Saudi Arabia
3DNE, Pakistan Institute of Engineering and Applied Sciences, 45650, Islamabad, Pakistan
4Department of Earth Sciences, Khalif University of Science and Technology, 127788, Abu Dhabi, United Arab Emirates
*Email (Corresponding author): aamirali.geo@gmail.com, aakgeo82@qau.edu.pk
Abstract: A gravity survey was designed and performed on local geological aspects to delineate the subsurface extension of the Khair-i-Murat Thrust (KMT) within the Sub-Himalayas, Kohat-Potwar region, Pakistan. A temporary station was established and the gravity data were acquired in loops. We applied all the necessary reduction techniques to correct the acquired gravity data within the context of the subsurface extension of KMT. Regional and residual maps were segregated from the Bouguer anomaly map with the application of an upward continuation technique. Furthermore, a tilt derivative was applied to the residual gravity field in order to highlight distinct structures. The tilt derivative of the residual gravity field successfully delineates the subsurface extension of the KMT (≈ 4 km based on this survey data) and also distinguishes secondary structures. These include two transform faults, splays associated with the KMT, and depressions with low gravity anomalies representing the accumulation of alluvium deposits over time. A present-day stream channel follows these depressions and cuts through the KMT via a transform fault. It was also observed that most of the Pliocene strata in the Siwaliks Group have been eroded from the study area, exposing the thicker Miocene sediments (Rawalpindi Group) deposited in the Indus foreland basin. Moreover, the interpretation of our gravity models suggests that the basement at an approximate depth of 7-8 km was not involved in the deformation, revealing a thin-skinned tectonics style in the study area.
Keywords : Gravity anomaly, Tilt Derivative, Sub-Himalaya, Bouguer gravity anomaly
