Late Cenozoic Tectonic Development of the Eastern Achara-Trialeti Fold and Thrust Belt, South-East Georgia

Victor Alania, Tbilisi state University, Institute of Geophysics

The Achara-Trialeti fold and thrust belt is located in the northern part of active collisional Lesser Caucasus orogen associated with Arabia-Eurasia convergence and are represent best example of mountain building processes in late Alpine time. The collision between the Arabian and Eurasian plates caused inversion of the relief and at the place of intra-arc and back-arc basins were formed two fold-and thrust belts of the Greater and Lesser Caucasus with the intermontane depression in between. Regional seismic reflection profiles shows that the Achara-Trialeti fold and thrust belt of eastern Caucasus is an active thick-skinned fold and thrust belt. Seismic reflection data reveal the presence of basement wedge, backthrust (south-vergent fault-propagation folds), forethrusts and duplexes. Present day's geometry of the eastern Achara-Trialeti fold and thrust belt is related to the northward thrusting of the basement wedge and had been developed during late Alpine times. The rocks are involved in the deformation range from Paleozoic basement rocks to Mesozoic-Neogene rocks. On the basis of interpreted seismic profiles of the frontal part of the Achara-Trialeti fold and thrust belt two different thrust systems have been found: (1) an upper thrust sheet and (2) lower duplex. Upper thrust sheet is represented by Cretaceous-Paleogene strata. The lower duplex sequence consists of Cretaceous-Paleogene strata that have been formed by passive-roof duplex style of deformation. Southern part of Kura basin is represented by Neogene strata that have been deformed and uplifted by passive back thrusting at the triangle zone. Analysis (geometrical) of growth strata in seismic profiles and well data from frontal part of eastern Achara-Trialeti fold and thrust belt documents that evolution of deformation has been continuing during the last ~ 16 Ma (M. Miocene) together with the thrust system kinematics. The geometry of growth strata in associated footwall syncline and kavtiskhevi piggy-back basin. Balanced cross-section across Kavtiskhevi area shows that growth strata connected to limb rotation.