The Geometry of the Two Orogens Convergence and Collision Zones in Central Georgia: New Data from Seismic Reflection Profiles

摘要

The thrust front of the central Lesser Caucasus and southern part of the Greater Caucasus orogens is one of the key regions of an apparent convergence zone between two orogens. The formation of the complex structure of the Lesser Caucasus-Greater Caucasus convergence zone is governed by the northward and southward-directed thrusting. Here we show the structural style of deformation of a convergence zone between Lesser Caucasus retro-wedge and Greater Caucasus pro-wedge based on seismic reflection profiles. Seismic profiles reveal the transition between convergence and the initial collision zone within the study area. The frontal part of the Lesser Caucasus retro-wedge is represented by a shallow triangle zone and north-vergent structural wedge. The thrust front of Greater Caucasus pro-wedge is represented by south-vergent fault-related folds. Between the Lesser Caucasus and Greater Caucasus frontal parts, the undeformed Kura foreland basin is located. The structure of the Lesser Caucasus-Greater Caucasus initial collision zone is fairly complex. The orogens collision zone is represented by south-vergent imbricate thrusts. Under the triangle zone, there are two structural wedges. The frontal part of the eastern Achara-Trialeti fold-and-thrust belt exhibit structural variations along strike within the study area. Near the Lesser Caucasus-Greater Caucasus convergence zone is located Tbilisi city, where the north-and-south-vergent thrusts of this collision zone represent a significant seismic hazard.