DISTRIBUTION OF SEDIMENTS AT THE MAIN MOUTHS OF THE KILIA DENUBE DELTA AND THEIR SEDIMENTATION VALUE

Abstract

Purpose: In the article the basic purpose is determination and analysis by distribution natural conformities of deltaic sediments after its movement across every arm, under impact of sea waves separation and influence of the coastal hydrogenetic factors. The noted peculiarities have important practical significance. Additionally, they explain the marine margin dynamics and sediment forming of deltaic types. Data & Methods: This article is based on natural datum of sedimentary material sampling around of marine margin of the dynamical Danube delta, NW Coast of the Black Sea. The sampling was made in region from head of Zhebriyan bay in north side to Musura bay in south side during 2010–2020 period in different environment and synoptical conditions. Laboratory elaborations were made with representative instruments usage and mathematical methods of treatment. Samples of suspended and coarse drifts were elaborated and analyzed within conditions of different sides of marine margin of the Delta. Results: The general definitions of protruding deltas state that the delta cone of protrusion is composed of alluvial sediments. But in the studied delta, a significant place is occupied by coastal-marine facies of wave action. In addition, the newest river sedimentary material changes during the passage through deltaic watercourses (especially long ones). Therefore, on the delta coast within the marine wave field, sediments with a slightly changed composition appear. Therefore, several facies environments can be defined in the Danube delta: a) typically riverine; b) alluvial-delta; c) coastal sea with separated sediments; d) aeolian center of influence of the wind factor; e) typical marine on the outer strip of the sea. We recommend that all the mentioned features be taken into account during the analysis of the Danube’s flow sediments to the bottom of the Black Sea and the determination of sedimentation rates. The main paper outlines provisions of the lithodynamic model of delta-type sediments’ formation in the conditions of a generous influx of river sediments, a steep underwater slope, a non-tidal sea and strong wave action. Fractions of 0.1–0.01 mm dominate along the coastal edge, with integral Md = 0.048 mm, and the concentration of fractions > 1.0 mm is sharply reduced. The content of CaСО3 is lower in comparison with sediments in Zhebriyansk Bay in the area of final dispersion of a strong alongshore flow of sand sediments. Within the studied deltaic natural system, the surrounding physical and geographical conditions actively influence the composition of delta sediments, create a sedimentary diversity of the facies network and tracts. The different composition of sediments leads to different density of the sediment layer, with different amounts of water content, mostly from 1% to 5%, different influence of river and sea factors. Accordingly, specific facies cells of the botanical and zoological substrate are formed in the areas of dominant influence of these factors. In the new parts of the delta, some cells settle first, others later, and the third – last in the life cycle. Therefore, in different areas, we meet the settlement of the primary territories of the delta by different plants and animals that are located in different parts of the warm period of the year.