Two and Three-Dimensional Structural Modelling of Central Kohat Plateau, Northwestern Himalaya, Pakistan

The Kohat Fold and Thrust Belt (KFTB) lies in the north western margin of Himalayan arc in the Pakistan. It covers a part of outer Himalayan Foreland Basin where 800 m thick Eocene package is predominantly exposed at the surface forming different structures. Current research describes the structural geometry and kinematics of the central KFTB and identifies the role ofmechanical heterogeneity in defining the surface structuration as well as its impacts on the deeper horizons. The east west trending, open to tight and overturned folds having curvilinear axes associated with thrust fault system dominates the exposed structural geometry of the area. Three mechanically different stratigraphic packages have been identified in the research area. The thick middle (Late Paleocene to Middle Eocene) clayey and mechanically soft package is sandwiched between upper and lower mechanically competent packages. The upper package comprises of Middle Eocene to Late Miocene rocks while the lower package consists of Paleozoic up to Paleocene rocks. Our structural modelling suggests that the deformation within the exposed upper competent stratigraphic package is disharmonic in structural relation to the lower stratigraphic package, which is comprised of south verging, ramp-related fore-folds. The middle, soft and plastic stratigraphic package is acting as surface of fault-fold decoupling between the lower and upper competent packages. The structural balancing reveals that the area has undergone 42.35% shortening. The mode of deformation is thinskinned, while the facing of structures show southward propagation of deformation as a result of the Indo-Eurasian plates collision.