Modern beach sediments of the Danube — Dniester segment of the Black Sea (lithology and genesis)

Abstract

The acumulative beach deposits of the western-north coast of the Black Sea in the area from the village of Liman (Katran spit) to the village of Carolino-Bugaz (Odesa region) have been studied. The length of the coastal line in the study area is approximately 86 km. The following forms of beach areas are widespread here: spit, spills, sloping beaches. 35 samples were taken and analyzed from all types of beach depressions by the same methodology during the summer period. The sampling was carried out at all accessible for sampling places of beach deposits from the middle part of the near5shore beaches (between the water level and the shore) and at a distance of 5—7 m from the water’s edge on the headlands and spits in the period when there are no storms. For this purpose standard plastic containers with a capacity of 1 liter were used. The samples were taken from a depth of 30 cm from the surface with a stripping area of 30´30 cm. At each point the description of the coastal zone structure and the character of beach deposits was carried out, then recorded in the logbook and were connected to the coordinates by GPS system. Granulometric and mineralogical analysis was carried out. It was determined that fractions 0,25—0,5 mm prevail in the granulometric composition among all types of beach deposits, which makes 66%, and 0,1—0,25 mm — 30%. In the minimum quantities there are coarse-grained and aleuropelite fractions. The main places of localization of drilled-grained psammite and aleuropelite fractions are the areas with low influence of coastal tidal processes. However, during the periods of increased hydrodynamic activity (autumn5winter), additional resuspension of material takes place, which results in displacement of other fractions from the deposits and their transfer to the seaside. Beach sediments are 90—95% quartz. The other — calcite, feldspar, mica, technogenic substances. Ore minerals are represented by magnetite, lime spheroids, ilmenite, acerbic garnets, stavrolite, actinolite. The main sources of terrigenous material for the formation of beach deposits on the studied area of the coastline are: underwater bench, river flow of the Dniester and the coastal abrasion. The direction along the coastal stream from Odessa to the Danube is the strongest in the distribution of sediments. In general, the beach deposits of this segment of the coastare environmentally clean, with no radioactive minerals and the content of man5made material does not exceed 0,1%.