Structural Transect of the Western Kohat Fold and Thrust Belt between Hangu and Basia Khel, N.W.F.P., Pakistan.

Abstract

 A structural transect of about 66km length has been constructed along the western Kohat Fold and Thrust Belt in order to understand the structural variations within the outcropping rocks. Along the transect from Hangu in the north to Kurma in the south, the belt is dominated by thin-skinned structures that includes south verging thrust faults, disharmonic shale-cored anticlines, shale-withdrawal synclines and pop-downs. The thin-skinned structures gives way to thick-skinned structures south of Kurma and is confined to a 12 km wide zone named as Zarwam Wrench Zone. This zone is defined by three, sub vertical wrench faults that involves crystalline basement as well. The genesis of these wrench faults is related to the westward under thrusting of Kohat Fold and Thrust Belt underneath the Sulaiman and Samana range along the transpressional boundary known as Kurrrum Fault. Orientation of both large and small-scale structures, within the Western Kohat Fold and Thrust Belt, indicate that it has undergone an earlier phase of compressional deformation over its major part, superimposed by a later phase of transpressional deformation in the south along ZarwamWrench Zone.