摘要：The Kirthar Fold Belt is part of the transpressive transfer zone in Pakistanlinking the Makran accretionary wedge with the Himalaya orogeny. The regionis deforming very obliquely, nearly parallel to the regional S–N platemotion vector, indicating strong strain partitioning. In the central KirtharFold Belt, folds trend roughly N–S and their structural control is poorlyunderstood. In this study, we use newly acquired 2-D seismic data withpre-stack depth migration, published focal mechanisms, surface andsubsurface geological data, and structural modelling with restorationand balancing to constrain the structural architecture and kinematics of theKirthar Fold Belt.The central Kirthar Fold Belt is controlled by Pliocene to recent linkedthick-skinned to thin-skinned deformation. The thick-skinned faults are mostlikely partially inverting rift-related normal faults. Focal mechanismsindicate dip-slip faulting on roughly N–S-trending faults with some dipangles exceeding 40∘, which are considered too steep for newlyinitiated thrust faults. The hinterland of the study area is primarilydominated by strike-slip faulting. The inverting faults do not breakstraight through the thick sedimentary column of the post-rift and flexuralforeland; rather, the inversion movements link with a series of detachmenthorizons in the sedimentary cover. Large-scale folding and layer-parallelshortening has been observed in the northern study area. In the southernstudy area progressive imbrication of the former footwall of the normalfault is inferred. Due to the presence of a thick incompetent upper unit(Eocene Ghazij shales) these imbricates develop as passive roof duplexes. Inboth sectors the youngest footwall shortcut links with a major detachmentand the deformation propagates to the deformation front, forming a largefault-propagation fold. Shortening within the studied sections is calculatedto be 18 %–20 %.The central Kirthar Fold Belt is a genuine example of a hybrid thick- andthin-skinned system in which the paleogeography controls the deformation.The locations and sizes of the former rift faults control the location andorientation of the major folds. The complex tectonostratigraphy (rift, post-rift, flexural foreland) and strong E–W gradients define themechanical stratigraphy, which in turn controls the complex thin-skinneddeformation.
