The Sediments from the Black Sea

Abstract

The sediment pattern in the nearshore zone of the Black Sea is governed by surface and longshore bottom currents and wave action (Ross et al. in Black sea sedimentary framework, 1978). In the deep basin, the sediment pattern is controlled by an isolated cyclonic current system and bottom morphology. Large quantities of detritus from the Danube, Dnieper, etc. are deposited and trapped on the broad western shelf, whereas the terrigenous material derived from the geosyncline drainage areas (Pontic and Caucasus mountains, and Krimean peninsula) easily crosses the narrow shelf and enters the deep basin, often in the form of turbidite deposits. Textural analyses of cores from the western and eastern basins reflect these differences in the shelf morphology. A rather uniform sedimentation pattern of mainly fine-grained material predominates in the western basin, whereas abundant turbidites and silty material in the cores off the eastern coast indicate high variability in the sedimentation pattern. Recent sedimentation in the Black Sea is governed by the deposition of terrigenous allochthonous material of low carbonate content and the autochthonous production of large quantities of biogenic carbonate material (coccolithophorids). The highest clay and carbonate content is in central areas of the western and eastern basins. Because the biogenic constituents are composed of clay-sized calcite, the total carbonate content, as well as the amount of the >2 μm fraction, increase simultaneously with the Coccolith portion.