Sedimentation in related to thrust tectonics of Binalud Mountains

Binaloud Mountains formed during collision of Iran and Turan plate in the Late Triassic time and caused shortening of the sedimentary cover because of Cimmerian and Alpine orogeny. The thrust sheets with different generations formed as a results of the Binalood and Alborz fold- thrust belts. Northeast of Iran that was already south coast of the divergent margin of the Paleothetys Ocean at this time، has become a marine foreland basin as a result of this colliding and bending of lithosphere. Stratigraphical column of foreland basin usually is made up of a few upward coarsening and shallowing sequences that each of them represents a step loading and removal times of the lithosphere beneath the basin. The first generation of thrust faults began with thrusting of Mashhad sheet (Paleothetys remnants) over the Shemshak Formation that is syn-orogenic with Cimmerian orogeny. As a result of erosion of mountains، large amounts of siliciclastic deposits transported to foreland basin in southern parts and the Middle Jurassic conglomerate and sandstone layers of Aghonj formation and siliciclastic beds of Ferizee are deposited. These sequences show upward coarsening and thickening with flow direction to the south. Alpine movements began during the Mid-Cretaceous time، and caused the formation of the second generation thrusts of Binalud fold-thrust belt، uplift، erosion and transport of siliciclastic material with upward coarsening and thickening (Foreland basin) of Paleogene. These sequences represent depositions in different parts of the alluvial fans with movement towards the south. Third generation thrusting related to Late Alpine movements caused regression of sea water to the south and creation of lagoon in foreland basin. Evaporate sediments at the base of Neogene clastic sequence is the result of such a process. Uplift of the foreland basin deposits due to new thrusting activity and erosion of them caused transportation of large amounts of siliciclastic sediments into the foreland basin and creating upward coarsening and thickening sequence of Neogene to the present.