Clay minerals of the bottom sediments of the Azov — Black Sea basin

Abstract

The Azov-Black Sea basin is the eastern part of the Paratethys Ocean, surrounded by unevenaged mountain structures of the Crimea and the Caucasus, adjacent to the continental slope of the Archean Ukrainian crystalline massif, as well as the Anatolian mountain system. By their lithological and petrographic composition, geological structures influence the composition of the rocks covering the abyssal sections of the seabed and its modern surface. Deepwater drilling has passed the section of the bottom of the Black Sea and reached the layer of sediments of the Upper Neogene (Upper Sarmatian). The upper layers of the bottom of the Black and Azov Seas are mainly represented by sediments of the Quaternary period belonging to different age intervals, which is associated with repeated changes in the level of the Black Sea basin during continental glaciations. This led to a corresponding change in the level of the basin and, as a consequence, to the influx of terrigenous material (fluvial alluvium and products of destruction of bedrock) into the deep water area. In terms of their lithological and mineralogical composition, bottom sediments reflect the material composition of their sources. At present, the upper layer of seabed sediments up to 7-10 m thick is the most studied. This layer consists of three divisions from 22 thousand years to the present. In lithological terms, this is a layer of pellets enriched in hydrotroilite, a layer of sapropels and modern terrigenous silts. Their origin is closely related to sea level fluctuations and climate change. The study of the lithological composition of bottom sediments can be considered satisfactory, while the knowledge of the finest fraction is insufficient. Preliminary studies of the clay fraction, followed by the participation of the authors in this process, studied the composition and spatial distribution of clay minerals. Among them, hydromicas, montmorillonite, kaolinite, chlorite, and mixed layered formations are the most widespread.