Carbonate karst and its relationship with geodynamic conditions of the Odessa city (Ukraine)

Abstract

A connection between karst and geodynamic features in the area of the city of Odessa (Black Sea karst region) was considered. The geodetic, geological and hydrogeological researches showed divergent vertical and horizontal movements of the individual units of the Neogene–Quaternary structural stage. It was found that the main orientations of passages in the caves in the Moldavansky and Kryvobalkovsky sites are NNW–SSE, WNW–ESE and NNE–SSW. This agrees well with the direction of the diagonal lineament network disclosed in recent years. The main directions of cave passages in the Bugaevsky site coincide with the main directions of the lineaments WNW–ESE, NNW–SSE located in the immediate vicinity of the zones of influence of the lineaments of the orthogonal networks N–S, SSW–NNE, and W–E. These findings suggest that caves developed along the directions of the lineaments of two tectonic networks of Neogene structural stage—diagonal and orthogonal. These networks of tectonic fractures were mapped and analyzed previously by applying the geological and hydrogeological methods and analyzing digital maps of the Neogene surfaces. Results of the research were compared to a map of isolines of long-term average velocity of vertical deformations of ground surface, and of zones of influence of lineaments identified in the surface topography of Upper Miocene clay, limestone and Pliocene red-brown clay. They show that the karst areas are mainly located in the gradient zones of vertical deformation of ground surface, and zones where Upper Miocene limestone is compartmentalized by diagonal and orthogonal lines of fracture. These areas could be considered as tectonically weakened.