Structural Geometry of Taleqan Mountains; an Evidence for Structural Evolution of South Central Alborz Range from Inversion to Transpression Tectonics

Taleqan Mountains located in South-Central Alborz range accommodate one of the best stratigraphic sequences of the range. The area bounded by the Taleqan fault in the north and the Mosha fault in the south. These faults separate Paleozoic-Mesozoic rocks from southern and northern Tertiary rocks. In this paper structural geometry of these faults is analyzed to unravel structural evolution of the range which interpreted to be initiated as inversion tectonics then followed by transpression tectonics. The Mosha fault in the eastern part of the Mountains has high angle and thrusts Precambrian rocks, cored a large Hangingwall anticline, over the Tertiary rocks accommodate footwall synclines. This geometry constrains the fault as a deep-seated basement fault which has been developed through inversion of an initial normal fault. The Taleqan fault consequently is analyzed as a back thrust to the Mosha fault and the mountain as a pop up zone between them. Detail kinematic analysis of the Taleqan fault show two different reverse movement with right and left lateral components. Given that the fault located on the Mosha fault hangingwall, it has been analyzed that the former movement direction to be related to the Mosha fault inversion from Late Cretaceous while the latter movement direction is the consequence of left lateral transpression tectonics in the range since late Pliocene.