A. Naeimi; Gh. Heidarzadeh; M. R. Sheikholeslami
Abstract
The ~100km-long NE-SW Cheshmeh nay fault zone is located in Alborz-Allah Dagh Mountains. This fault zone is composed of several faults with dips between 40 to 85° toward NW or SE. The Cheshmeh nay fault zone belongs to the Shahrud fault system and has a left-lateral motion. Geomorphic evidence such ...
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The ~100km-long NE-SW Cheshmeh nay fault zone is located in Alborz-Allah Dagh Mountains. This fault zone is composed of several faults with dips between 40 to 85° toward NW or SE. The Cheshmeh nay fault zone belongs to the Shahrud fault system and has a left-lateral motion. Geomorphic evidence such as deflected streams, bisected alluvial fans and cut Quaternary deposits shows that this fault zone has been active during Quaternary. Exposure of Paleozoic and Mesozoic formations over or in contact with younger units as well as abundant thrust fault planes present in the fault zone indicate that there seems to have been a thrust faulting along the fault zone sometime during its evolution. In addition, the Cheshmeh nay fault zone coincides with the F-431 aeromagnetic lineament, indicating that the fault zone is supposed to be an old basement fault. Making part of the boundary between the Alborz and Kopeh Dagh basins, this fault zone was a basin-bounding normal fault zone which changed the kinematics into a thrust fault zone. This kinematics change resulted likely from the Iran Block moving toward the Turan and Kopeh Dagh regions and/or in Late Cretaceous. Following the regional reorganization in the Arabia-Eurasia collision zone between 3-7 Ma and/or in Quaternary, the Cheshmeh nay fault zone became a fault zone with a dominant left-lateral movement.
