Systematic Variations in the Deformation Intensity in the Zagros Hinterland Fold-and-Thrust Belt, Iran

The Zagros Orogen is one of the most important collisional belts in the central part of the Alpine-Himalayan orogenic chain. One of the main controversies about this belt is the location of the suture zone between the Iranian and Arabian continental plates. Since the suture zones are often the most deformed parts of the collisional belts, in this study, variations in the deformation intensity in a region which is located between the probable traces of the suture zone (i.e. the outer and inner ophiolitic belts of Zagros Orogen) were investigated. The study area is located in the NE of the Main Deep Fault in the Zagros Hinterland Fold-and-Thrust Belt. In order to investigate the deformation intensity variation, some properties of several structures were studied. Toward SW, the fault density, the displacements created by map-scale thrusts, thickness, and degree of development of the shear zones, and plunge of the mesoscopic fold axes increase, and spacing of shear zones and various scale faults, fold interlimb angles, and dip of the mesoscopic fold axial planes decrease. Therefore, the results of this study reveal that in the studied part of the Zagros Hinterland Fold-and-Thrust Belt, deformation intensity increases systematically towards SW. This evidence confirms the presence of the main suture zone in the SW of the Zagros Hinterland Fold-and-Thrust Belt and they are more compatible with the hypothesis that considers the Sanandaj-Sirjan Zone as the southern margin of the Iranian Plate before the collision.