Physical modeling of block rotation and the role of ductile sediments in the structural evolution of Kopeh Dagh and Zagros

Anticline axes in both orogenic belts of the Zagros and Kopeh Dagh are offset by NW-SE trending transvers faults. These faults are rotating anticlockwise due to their oblique orientation relative to maximum stress vector, causing shortening across the belt and elongation along the strike. The transverse faults move right laterally and known as prominent faults of Bajgiran, Quchan, Shokranlou, Baghan in central Kopeh Dagh; and Kazerun, Karehbas, Sabzpushan, Sarvestan in central Zagros. Faults in two regions, however, show different pattern of offset. We proposed two different physical models, consist of rotating blocks at the base overlaid by sand with and without silicon layers, resembling variation of stratigraphy in two belts. In the Zagros model, where we have more incompetent layers, offset on the basement faults causes bending of the fold axes at the surface prior to any offset. While in the Kopeh Dagh, where we have less incompetent layers, the fold axes are offset with no major change in their orientation.