Characterizing two basement strike-slip faults in the Zagros Mountains; Razak and West Mand faults

The north-south trending strike-slip faults within the basement of the Zagros fold and thrust belt, which are inherited from the Pan-African construction phase, were reactivated during the suturing and convergence of Arabia and Central Iran since the Late Cretaceous and influenced the NW-SE trending structures of the Zagros belt. Among most of these transverse faults, the Kazerun fault which delineates the western boundary of the salt plugs in the Zagros belt near longitude 51.5°E is described in detail as the most significant transverse strike-slip fault recognized in the belt. Here, during the course of our investigations we found new evidence indicating that the north-south trending Kazerun fault system can be extended southwards to the coast of the Persian Gulf as evidenced by a prominent escarpment marking the west side of the Mand anticline as well as the observations of surface faulting associated with the right-lateral motion of recent geomorphic features. However, the north-south trending Razak fault has also been recognized as one of the major transverse faults in the Zagros basement. Right-lateral strike-slip motion along the Razak fault strands can be inferred from the associated lateral offset of stream beds observed on satellite images, aerial photos and on the field. Unlike what have been previously suggested, this study concludes that the southern ends of some of the north-south trending strike-slip faults which cross the NW-SE structures of the Zagros belt are not turned into thrusts striking ESE, sub-parallel to the fold axes, but instead the southern continuation of the north-south trending faults can be extended southwards to the coast of the Persian Gulf and Saudi Arabia.