Bhittani Range, North Pakistan: The Tectonic Evolution and Hydrocarbon Prospectivity – a Geological and Geophysical Approach

Abstract

The main topographic expression of the Bhittani Range is credited to the Pezu anticline which is compartmentalized by Pezu Fault into three distinct domains that are northwestern, central and southeastern. The limbs of all the three domains of the Pezu Anticline expose rocks belonging to the Siwaliks of Nagri, Dhok Pathan and Malagan Formations, whereas the Chinji Formation hosts its core. In the northwestern domain of the Pezu anticline, the Pezu Fault occupies the fore limb of the anticline which is asymmetric to the southwest with a prominent plunge to the southeast in the vicinity of Bain Darra. In contrast the Pezu Fault switches to back limb thrust in the central domain of the Pezu anticline which is a three way fold closure bounded by Pezu Fault in the northeast. In the southeastern domain, the Pezu Fault again becomes fore limb bounding fault of the Pezu anticline. The structural genesis of the Bhittani Range is mainly related to the Pezu Fault which has served as a lateral ramp for the southeast propagation of the coherent thrust slab underneath Bannu Basin, characterized by dextral wrenching concomitant with northeast-southwest directed contraction. The structural genesis of the Bhittani Range is well constrained by the available seismic data across the central domain of the Pezu anticline. The proposed geo-seismic model depicts that the Pezu Fault is steeply northeast dipping, southwest verging thrust fault whereas the Pezu anticline is developed on the hanging wall of a blind, southwest facing thrust fault within the Triassic and underlying older rocks which tips underneath its fore limb in the subsurface. Current investigations have revealed that the northwestern and southeastern compartments of the Pezu anticline are more prospective for the oil and gas accumulation as compared to its central compartment