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Durham University

Institute of Medieval and Early Modern Studies (IMEMS)

Members

The list below shows Durham University research staff who are members of IMEMS. Click the member's name to see a more detailed biography and department.

We also welcome anyone from outside the University with an interest in our work to join. Membership is free of charge. You will receive invitations to our programme of events, with a weekly emails digest about what is happening in the Insitute and further afield. To join IMEMS contact: admin.imems@durham.ac.uk

Publication details for Prof Mark Allen

Allen, M.B., Kheirkhah, M., Emami, M.H. & Jones, S.J. (2011). Right-lateral shear across Iran and kinematic change in the Arabia–Eurasia collision zone. Geophysical Journal International 184(2): 555-574.

Author(s) from Durham

Abstract

New offset determinations for right-lateral strike-slip faults in Iran revise the kinematics of the Arabia–Eurasia collision, by indicating along-strike lengthening of the collision zone before a change to the present kinematic regime at ∼5 Ma. A series of right-lateral strike-slip faults is present across the Turkish—Iranian plateau between 48°E and 57°E. Fault strikes vary between NW—SE and NNW—SSE. Several of the faults are seismically active and/or have geomorphic evidence for Holocene slip. None of the faults affects the GPS-derived regional velocity field, indicating active slip rates are ≤2 mm yr−1. We estimate total offsets for these faults from displaced geological and geomorphic markers, based on observations from satellite imagery, digital topography, geology maps and our own fieldwork observations, and combine these results with published estimates for fault displacement. Total right-lateral offset of the Dehu, Anar, Deh Shir, Kashan, Ab-Shirin-Shurab, Kousht Nousrat, Qom, Bid Hand, Indes, Soltanieh and Takab faults is ∼250 km. Other faults (North Zanjan, Saveh, Jorjafk, Rafsanjan, Kuh Banan and Behabad) have unknown or highly uncertain amounts of slip. Collectively, these faults are inferred to have accommodated part of the Arabia–Eurasia convergence. Three roles are possible, which are not mutually exclusive: (1) shortening via anticlockwise, vertical axis rotations; (2) northward movement of Iranian crust with respect to stable Afghanistan to the east; (3) combination with coeval NW—SE thrusts in the Turkish–Iranian plateau, to produce north–south plate convergence (‘strain partitioning’). This strike-slip faulting across Iran requires along-strike lengthening of the collision zone. This was possible until the Pliocene (≤ 5 Ma), when the Afghan crust collided with the western margin of the Indian plate, thereby sealing off a free face at the eastern side of the Arabia–Eurasia collision zone. Continuing Arabia–Eurasia plate convergence had to be accommodated in new ways and new areas, leading to the present pattern of faulting from eastern Iran to western Turkey, and involving the westward transport (‘escape’) of Anatolia and the concentration of thrusting in the Zagros and Alborz mountains.