LITHOLOGICAL AND MINERALOGICAL STRUCTURE OF ACCUMULATIVE BEACH DEPOSITS OF THE BLACK SEA DANUBE-DNIESTER SEGMENT

Abstract

The investigations of accumulative-sand deposits of the Black Sea coastline on the area from the village Liman (Katranka spit) to the village Karolina Bugaz (Odessa region) have been carried out. The length of the coastal line in the study area is close to 85 km. There are a lot of beach areas: spits, beach breaks, beaches on the shoreline. 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 near-shore beaches (between the water level and the shore) and at a distance of 5–7 m from the water edge on the headlands and spits in the period when there are no storms. For this purpose we used standard plastic containers with a capacity of 1 liter. 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 were carried out, which were 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 smallest quantities there are coarsegrained and aleuro-pelitic 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 (spring-autumn), additional resuspension of material takes place, which leads to displacement of other fractions from the deposits and their transfer to the sea side. Beach sediments are 90–95 % quartz. Others are calcite, feldspar, technogenic substances. Ore minerals are represented by magnetite, lignite spheroids, ilmenite, acerbic garnets, stavrolite, actinolite. The main sources of terrigenous material for the formation of beach deposits are the underwater bench, the Dniester river runoff, and coastal abrasion. Decisive in the distribution of sediments is the direction along the coastal current in the direction from Odessa city towards the delta of the Danube