Thermochronometric evidence for Miocene tectonic reactivation of the Sevan-Akera suture zone (Lesser Caucasus): a far-field tectonic effect of the Arabia-Eurasia collision?

Low-temperature thermochronological data for the Eurasian foreland north of the Bitlis-Zagros suture zone suggest that the tectonic stresses related to the Arabian collision during mid-Miocene time were transmitted efficiently over large distances, focusing preferentially at rheological discontinuities. Since the late Middle Miocene a new tectonic regime is active as the westward translation of Anatolia is accommodating most of the Arabia-Eurasia convergence, thus precluding efficient northward stress transfer. Apatite fission-track data from the central Lesser Caucasus show that a portion of such orogen underwent a discrete phase of cooling/exhumation at 18-12 Ma (late Early - early Middle Miocene) as a result of structural reactivation of a segment of the Late Cretaceous - Paleogene Sevan-Akera suture zone. This inference contradicts the notion that the post-collisional history of the study area was dominated by strike-slip tectonics with relatively minor dip-slip components. Reactivation and exhumation focused along those segments of the suture zone at high angle with the inferred collisional stress field; the remaining areas were not exhumed enough to expose a new apatite partial annealing zone and thus retained the thermochronologic record of a phase of Late Cretaceous cooling/exhumation associated with ophiolite obduction and the following continental collision along the suture zone.