Tectonic paleostress fields and structural evolution of the NW-Caucasus fold-and-thrust belt from Late Cretaceous to Quaternary.

The NW-Caucasus fold-and thrust belt essentially corresponds to the inverted western Flysch Zone of the Great Caucasus Mountains, a deep basin that developed from Late Jurassic to Eocene times between the Scythian Plate to the north and the Transcaucasian terranes to the south (the Shatsky Ridge, SW of the NW-Caucasus zone). The Flysch Basin was strongly affected by compression in Late Eocene times, when the characteristic WNW trending folds and thrusts of the NW-Caucasus belt developed (some authors regard the main compressive deformation as Miocene in age). By means of remote sensing analysis, we elucidate the geometry of major structures in the belt: WNW trending south-vergent thrusts and folds, and major vertical and transverse NNE - SSW to NE - SW deep fault zones. The later structures are interpreted as ancient faults that were active during the development of the Flysch Basin. Paleostress investigations reveal seven main tectonic episodes in the evolution of the NW-Caucasus since Late Cretaceous. Combining structural interpretation, remote sensing analysis and paleostress field reconstruction, we propose a model for the structural evolution of the belt. During the Late Cretaceous - Paleocene, the western Caucasus zone was under transtensional regime with an E - W to NE - SW trending σ