LATE CENOZOIC TECTONIC EVOLUTION OF THE GEORGIA (SW CAUCASUS)

The tectonic evolution of Caucasus is largely determined by its position between the still converging Eurasian and Arabian plates, within the wide zone of a continent-continent collision. Within convergence zone there existed a system of island arc and back-arc basins etc. characteristic of pre-collisional stage of evolution of the region. The evolution of Mesozoic Greater Caucasus back-arc basin is related to the extensional processes resulting from northward subduction zone. During collisional stage, at the place of back-arc basins were inverted and formed fold-thrust belts of Greater and Lesser Caucasus separated by foreland fold and thrust belt (FFTB). The FFTB which developed formerly as a foreland basin (Oligocene-U. Neogene), is incorporated to the both thrust and fold belts. Georgia as a part of the Caucasus region consists of two major thrust and fold belts: the Greater Caucasus (GC) and Achara-Trialeti (AT). Between GC and AT thrust and fold belts, Paleozoic basement outcrops in the Dzirula massif separates the FFTB into the Rioni and the Kura. Integration of the present-day topography, structural features and section balancing, together with seismic reflection profiles, was used to develop a new tectonic model for the region. Balanced sections suggest that formation of Dzirula basement tectonic wedge structure is related to the southward thrusting of GC accretionary wedge and the presence of basement nappes. These structures were formed during late Alpain time, and characterized by a thick-skinned style of shortening. The amount of displacement of the Dzirula tectonic wedge indicating large horizontal crustal shortening and is accommodated by back thrusting of the Jurassic and Cretaceous strata of the overlying above Paleozoic basement rock. Thrust front of tectonic wedge is linked by backthrust and is structural boundary between AT and GC fold and thrust belts. Seismic reflection profiles show that north and east from Dzirula masiff the Rioni and Kura FFTB of Caucasus are an active thin-skinned fold and thrust belt and they preserve growth strata that record the tectonic and stratigraphic evolution. Analysis of synorogenic (or growth strata) deposits in seismic section documents that evolution of deformation has been continuing during the last ~5-4.5 Ma together with the thrust system kinematics.