Impact of Sedimentation on Convergent Margin Tectonics: Example of the Makran Accretionary Prism (Pakistan)

This paper discusses the geodynamic evolution of the Makran accretionary prism from a new field investigation in the Pakistani area and from the interpretation of reprocessed seismic lines in the offshore area. The field reconnaissance has provided new structural data about the general structure of the prism and a rejuvenated stratigraphic chart based on new datings. This work outlines that the sediment input in the Makran originated from various origins during Cenozoic times: (1) direct influx from the Indus River conveying eroded series from the Indian shield or Himalayas, (2) strong erosion of the growing inner prism. En-echelon elongated anticlines which are cross-cut by strike-slip faults developed along the eastern Makran Range. Recent out-of-sequence thrust propagation has been evidenced in the onshore area in relation to recent erosion. A large un-deformed platform responsible for a huge trap for sedimentation developed during Miocene and Pliocene times between the emerged part of the Makran and the offshore active compressive front. The internal architecture of the prism is also strongly influenced by the propagation of the deformation with in secondary decollement levels. These upper detachments are hosted with in the Miocene slope-to-basin prograding wedges, upon which a recent normal growth fault system developed in the near offshore area, at the same time when compression occurred at the front of the prism.