ANALYSIS OF SOME PROCESSES OCCURRED IN THE BLACK SEA AND BOSPORUS STRAIT DURING HOLOCENE

One of the key parameters of Holocene transgression is the volume and a sign of fresh-water balance W of the Black Sea during glacial age. Based on the fact that rivers’ runoff currently exceeds the difference between precipitation and evaporation by 5-6 times, we (Yesin, 1987) have supposed, that the fresh-water balance of the sea was positive during glacial age. Subsequently Kislov and Toropov (2006) have presented results of calculation of glacial age conditions and fresh-water balance of the sea according to climatic models. Considering the sea area decrease and at present-day evaporation volume, it is +25 km³/year. It is proved by existence of southern delta of the Bosporus strait (Hiscott, 2002). Without the Black Sea water flow the Sea of Marmara could dry up by hundreds of meters. For the description of the Black Sea level fluctuations the following mathematical model (Yesin, Kukleva, 2007) is offered: S(dH/dt) = W-(gh³l/3v)(H-h)/x₀, where S - sea area, t - time, H and h - accordingly the levels of the Black Sea and the Sea of Marmora counted from a bottom of the threshold in Bosporus strait, x₀ - length of the strait, g – gravity acceleration, l - width of the strait, v – water viscosity. Numerical solutions show that the strait could not pass incoming water in the beginning of Holocene. Most of water collected in the sea, raising its level. When water flow was 20000-40000 m³/s (Chepalyga, 2006), the level of the Black Sea could rise by 50-70 meters for 100-200 years. Amplitude of the Black Sea level fluctuations decreases while the strait depth increases. Erosion of ancient sediments discovered by Ryan (2006) on a shelf of the Black Sea should be considered from the point of view of underwater erosion. It is confirmed by 4000 age deposit on ancient sediments. If the bottom of the sea has been eroded during a flood process of sea sedimentation would begin right after a flood.