The surface and subsurface structural delineation with the integration of geological seismic and well bore data of Shakardarra area, District Kohat (P-0887) (MFN 3229)

Abstract

Geologically Shakardarra is a suite of complex deformational structure related to different origins in their evolution. Detachment folding, thrust faulting, and strike slip faulting are responsible for the complex structural frame built up for this area. An integrated structural model based on seismic line 865-NK-15, well data of Chanda-l and surface orientation data is prepared to understand the structure style at the surface and subsurface. The model shows that the disharmonic detachment folds containing Eocene evaporites in the core are transected by high angle thrust faults in the north and an echelon folds in the Siwalik group rocks at the surface transected by reverse faults originates from strike slip fault in the central and southern part of the study area. The research suggests that the area is subjected to three episodes of deformation i) detachment folding ii) thrust faulting and iii) strike slip related reverse slip faulting. The disharmony in the orientation of bedding at the hanging wall of the faults clearly suggest that the different parts of the disharmonic folds cored by Eocene evaporites (Jatta Gypsum) are later on transected by thrust faults. In the subsurface a blind reverse fault facing north is present in the central part of the area. Reverse faults facing south originates from the blind thrust in the subsurface transecting Nagri Formation at the surface with less vertical throw up section forming a positive flower structure in the subsurface. The en echelon nature of folds change in the trend of the structure at the surface and the presence of flower structure at subsurface narrates dominant transpressional related deformation in the central and southern part of the study area.