Rapid Pliocene exhumation of the central Greater Caucasus constrained by low‐temperature thermochronometry

Abstract

Constraining the timing of onset and rates of deformation within the Greater Caucasus mountains is key to understanding their role in accommodating deformation across the Arabia‐Eurasia orogen. We present new low‐temperature thermochronometric constraints on the Cenozoic thermal evolution of the central Greater Caucasus that elucidate a three‐phase cooling history. Between 50 and 30 Ma, cooling within the range was negligible. In Oligocene time, cooling rates throughout the range increased to ∼4°C/Myr. These rates remained constant until the early Pliocene time, when they increased again, reaching ∼25°C/Myr along the axial part of the range. Rates and timing of Oligocene exhumation are consistent with previous results from the western Greater Caucasus and are proposed to result from onset of subduction of the Greater Caucasus back‐arc basin. Rapid exhumation of the Greater Caucasus, beginning in Pliocene time, contrasts with previously reported thermal histories for other portions of the range. Pliocene exhumation of the central Greater Caucasus appears to be tectonically driven and coincides with widespread evidence for a major reorganization of the Arabia‐Eurasia plate boundary. We hypothesize that this exhumation, and regionally observed plate reorganization, results from the collision of the Lesser Caucasus with Eurasia, completing the subduction of oceanic lithosphere across this segment of the Arabia‐Eurasia plate boundary.