Block Rotations in NW Iran in Response to the Arabia-Eurasia Collision Constrained by Paleomagnetism

Abstract

Northwest Iran is a seismically active region dominated by NW-SE trending strike-slip faults, such as the North Tabriz and Qosha Dagh faults, and smaller NNE-SSW striking faults. The Bozgush Mountains are shaped by these faults and divided into two domains that show a difference in strike. To quantify rotational tectonic deformation in NW Iran, we performed a paleomagnetic study along three transects of the Bozgush and Qosha Dagh Mountains with 127 sites. Our large new paleomagnetic data set shows that the Bozgush Mountains did not rotate as a single rigid block. In the western domain of the Bozgush Mountains, we find evidence for clockwise vertical axis rotations of ∼40°, while the eastern domain has rotated up to ∼80° clockwise. Declinations of the western Bozgush domain fit well with observed declinations in the Qosha Dagh Mountains. Fault patterns show that the eastern domain of the Bozgush Mountains is divided by a set of NNE-SSW striking sinistral strike-slip faults, which created domino-style blocks that accommodated the additional 40° of rotation. We estimate that these extra rotations have resulted in around 4 km of N-S shortening and more than 1.5 km of differential uplift.