Structural modeling of the southern Kohat Basin and Frontal Ranges; implications for tectonic evolution and hydrocarbon play

Abstract

More recently Kohat's fold-thrust belt, including the Karak area has emerged as an important hydrocarbon fertile region of the western Himalayan orogenic system. The Eocene and Paleocene strata, including mechanical weak Eocene units representing a shallow decollement have a noticeable contribution to the deformation style and petroleum system of the area. In the present study, surface mapping is integrated with seismic information to elucidate the structural style of the Karak area, the data reveal that there are two different structural entities, separated by Karak Fault Zone. The northern domain portrays salt diapiric structures representing doubly plunging and complexity overturned, and fault bounded folds' geometries. However, in the subsurface below the Eocene sequence, the deformation is characterized by south-directed imbricate thrust system. In contrast, because of the absence of Eocene salt horizon, the southern domain of the Karak area illustrates a brittle style of deformation, mimicking fault propagation folding. In addition, an array of south-verging imbricate system from a regional basal decollement translates rock as old as Permian along the Surghar range frontal thrust. It can be observed that fault geometry and fold styles in the north and south of Karak Fault Zone are entirely different. Restored cross-sections across the area indicate 35% of shortening has been accommodated in the area. Moreover, from the present study it has been concluded that in the purlieu of Karak Fault Zone, possibly occupy auspicious structural traps at top Paleocene Lockhart level.