The tectonophysical researches of the Semisamskaya anticline (North-Western Caucasus fold and thrust belt)

Abstract

Structural paragenetic and cataclastic analysis methods were applied to study tectonic fracturing within one of the folds of the southern wing of the North-Western Caucasus fold-and-thrust belt. The object of the study was the Semisamskaya anticline (Fig. 1 and 2) comprising the Upper Cretaceous and Paleogenic layered terrigenic-carbonate sediments that contain various well-developed geological indicators of palaeostresses (Fig. 3, 5, 7, and 9). In the folded structure under study, a paragenesis is revealed which is associated with the effect of sub-horizontal minimum compression (deviator extension) stresses of the north-western orientation (NW 320°) and traced by detached normal fault systems striking in the north-eastern direction (Fig. 6, 8, 10, 11, and 17). Upthrust-overthrust systems of the north-western strike (NW–SE), which are of importance for the whole folded structure of the North-Western Caucasus, are mainly manifested in the wings of the Semisamskaya anticline (Fig. 6, 12, and 13). The overall field of stresses related to formation of the folded structure is significantly variable as evidenced by the pattern of local parameters of the paleostress field, which are calculated by the cataclastic analysis method (Figure 15, 16, and 17). It is established that the geodynamic regime within the anticline is considerably variable by types (Fig. 18). Areas with horizontal extension in the axial part of the fold are replaced by areas of horizontal compression at its wings (Fig. 19).