Structural Evolution of South Eastern Kohat Deciphered Through 3D Geoseismic Model, Shakardarra Area, KP Pakistan

Abstract

Geologically the Shakardarra area has evolved through multiple episodes of deformation. In the current research structural evolution of southeastern Kohat is deciphered and shown through a 3D geoseismic model. The model is generated by integrating surface structural geological data and subsurface seismic reflection data. At the surface doubly plunging anticlines and synelines are truncated by thrust faults along their limbs. The tight anticlinal and broad synclinal folded structures evolved on evaporites as detachment folds which are later truncated by thrust faults. In the subsurface, stratigraphic packages are marked on seismic sections based on regional stratigraphic studies and dominant reflections. The seismic sections show that the thrust faults emanate from basal detachment located at the sedimentary crystalline interface cutting up upsection to the surface or losing their displacement by originating back thrusts. The cross-section shows that these back thrusts are emanating from fore-thrusts at much shallower depths as compared to fore thrusts. At the surface, the Shakardarra fault Tolabangi fault, Chorlaki fault, and axial trend of fold change their strike from EW te NS which narrate that thrusts and axial trend of folds are rotated along vertical axis b influence of Kalabagh strike-slip fault. The current research suggests that Shakardarr is sequentially evolved in three episodes of deformation. In the first phase, detachment folds are on Eocene evaporites which are truncated by thrust faults emanating from basal detachment in the second phase. In the third phase early formed folds and faul are rotated along the vertical axis by the influence of the Kalabagh strike-slip fault.