Tectonic evolution of the NW-Himalayan thrust front: The Trans-Indus Ranges, northern Pakistan

he results of structural, stratigraphic and paleomagnetic work in the Trans-Indus Ranges of northern Pakistan are presented. The Trans-Indus Ranges form the western part of the NW-Himalayan frontal thrust system, which comprises structural re-entrants and promontories with wave-lengths between 50 and 150 km. The structure of the Trans-Indus Ranges is characterized by abrupt lateral variations in tectonic style, between mainly compressive deformation along the central parts of re-entrants and promontories, and transpressive deformation along their lateral flanks. This complex geometry of the thrust front seems to be largely controlled by a system of frontal and lateral structural ramps, formed by north-dipping flexures and normal faults offsetting the basement. Balanced cross-sections, based on the integration of stratigraphic and structural mapping with seismic reflection data and well logs, show that the amount of convergence along the Trans-Indus Ranges is on the order of 10 km. The history of deformation along the Trans-Indus Ranges is constrained by sedimentological and magnetostratigraphic studies of synorogenic foreland basin deposits, which contain evidence for two main phases of tectonic activity. Locally derived conglomerates in...