The Binalud Mountains: A key piece for the geodynamic puzzle of NE Iran

International audienceWe applied a combined approach of morphotectonic analyzes of SPOT-5 satellite images and field surveys complemented by in situ-produced Be-10 exposure dating to determine the kinematics and rate of active faulting in the Binalud Mountains bounded by the Neyshabur Fault System to the southwest and the Mashhad Fault Zone to the northeast. Three regional episodes of alluvial surface abandonment were dated at similar to 4.8 ka (Q(1)), similar to 105 ka (Q(3)), and similar to 255 ka (S-3). Along the Neyshabur Fault System, cumulative offsets recorded by Q(3) fan surfaces yield slip rates of 2.4 +/- 0.5 and 2.8 +/- 0.6 mm/yr for right-lateral and reverse components of active faulting (corresponding to an oblique slip rate of 3.6 +/- 1.0 mm/yr), respectively. Reconstructing the cumulative right-lateral offset recorded by S-3 surfaces, a maximum slip rate of 1.3 +/- 0.1 mm/yr is suggested for the Mashhad Fault Zone. These imply an overall rate of 3.7 +/- 0.6 mm/yr for the range-parallel displacement and an uplift rate of similar to 2.8 mm/yr due to the range-normal shortening (1.6-2.2 mm/yr) during late Quaternary. The Binalud Mountains are deformed as a soft-linked restraining relay zone, taking up the motion between central Iran and Eurasia at a rate of 4.0 +/- 1.3 mm/yr; this translates central Iran in the similar to N340 degrees E direction. Our data favor localized faulting, instead of distributed deformation, at the northeastern boundary of the Arabia-Eurasia collision zone