1 Introduction The Black Sea (Fig. 1) with a surface area of 432.000 km2 and water depths exceeding 2200 meters is a semi-enclosed and the largest modern anoxic basin in the world having characteristic hydrographic, morphological and geological conditions varied with space and time (Degens and Ross, 1974; Ross et al., 1978; Sorokin, 1983). Geologically, the formation of the greate Black Sea basin can be traced back to the Late Cretaceous subduction of the Tethys Ocean beneath the Euroasi…