Tectonics of the Greater Caucasus and the Arabia-Eurasia Orogen.

The new thermochronometric dataset presented in this dissertation unequivocally shows a 5 Ma onset of rapid exhumation throughout the Greater Caucasus. Patterns of exhumation rule out the possibility of climate being a major cause of the accelerated erosion and point to a tectonic forcing. Asymmetric exhumation with higher rates on the southern front of the Greater Caucasus agrees with the south-verging structure of the orogen and suggests that the uplift is the result of thrusting of Eurasia over the Transcaucasus that, thus, began in Pliocene time. Sedimentologic observations, in combination with thermochronometric data, led to the conclusion that the onset of thrusting in the Greater Caucasus resulted from collision between Transcaucasus and Eurasia, following closure of the Greater Caucasus back-arc basin. Subduction of the Greater Caucasus basin, therefore, provided a mechanism for a previously puzzling fact of the existence of a high mountain range far away from the Neotethyan suture. The paradox of the western Greater Caucasus, where high elevations and deep levels of exhumation are associated with low seismicity and little active shortening is resolved. An estimate for a long-term (Ma) rate of overthrusting on the Main Caucasus fault derived from a thermokinematic model constrained by thermochronometric and seismic data agrees with the active rate of convergence derived from geodetic observations. The rapid exhumation is a result of highly focused deformation occurring on a steeply dipping fault. Such kinematics is likely dictated by a competent rheology of the ancient crust of the western Transcaucasus and Eurasia. The final chapter provides a development of the detrital thermochronometric methodology with a new method for estimating erosion models describing short-term spatial patterns of erosion and long-term history of denudation. This approach allows thermochronometric studies of terrains inaccessible for bedrock sampling and is useful in the Greater Caucasus, where the axis of the range coincides with three international borders.PhDGeologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/86342/1/borya_1.pd