Stretching of the Eocene Kharan Limestone along the Strike-Slip Faults in the Southern Raskoh Range (Pakistan): An Example of the Time-Dependent Deformation

The series of strike-slip faults, dissecting the axes of folds and traces of thrusts, have created lateral off-sets ranging from a few to hundreds of meters in the southern part of the Raskoh Range in Pakistan. The Early Eocene Kharan Limestone stretches along the fault planes of these faults whereas the shale and interbedded sandstone/conglomerates of the underlying and overlying formations cut and truncate against the body of stretched limestone. The relationship of the structural elements reveals that the strike-slip faults represent the latest episode of structural deformation in the area, and these could have been developed when the Kharan Limestone was presented at a very shallower depth due to erosion of overlying formation during uplift. The major set of the strike-slip faults, having orientation of NNE‒SSW and along which Kharan limestone stretches, is parallel to the Chaman Fault—a tectonic plate scale transform fault, located to the east of the Raskoh Range. The movement along Chaman fault occurred slowly by displacing the Indian Plate to its east and creating strong continuous strain to its west where the study area is located. We believe that the stretching of Kharan Limestone along fault planes is likely the result of the slow and steady displacement along the strike-slip faults. The time-dependent deformation i.e., brittle creep is interpreted as the main phenomenon along with the minor role of plastic/ductile deformation that have created stretching of the Kharan Limestone.