TECTONIC EVOLUTION AND STRUCTURAL MODELING OF BANDA DAUD SHAH-SURGHAR AND MARDAN KHEL-SOOR DAG TRANSECTS, KOHAT BASIN, PAKISTAN

Abstract The Kohat basin in the northwestern Pakistan is a sedimentary basin and a Fold and Thrust belt bounded by the Main Boundary Thrust in the north and the Surghar ranges in the south. Geological mapping, structural modelling and restoration have been conducted in central and southern Kohat basin to understand the evolution of the Fold and Thrust belt and its hydrocarbon potential. Surface geology of the area reveals the dominancy of thrust tectonics. Manzalai Anticlinorium, Karak fault zone and Surghar ranges are the prominent structural features of the area under discussion. Synclines are generally wide while anticlines are sharp, possibly due to the isostatic adjustment of ductile and incompetent Eocene evaporites, under the post Eocene stratigraphic column. This part of the Kohat basin is in the stage of initial deformation of the presently developed tectonic model in the northern Kohat basin, where it is believed to have formed by double decollement. The subsurface contour on top of the Paleocene shows promising traps in Manzalai anticline, Karak anticline, and Karak fault zone for the well-developed and proven petroleum system of the Kohat basin. The eastern and western structural transects (A-B and C-D) show crustal shortening of 15.19% and 6.63% respectively. Major crustal shortening and stress release is concentrated in the uplift of Manzalai structure and Karak fault zone. The un-mapable intra-formational en-echelon folding at the western part of the basin, toward the Kurram fault, represents transpressional tectonics.