Lithologic typification of deep sea sediments of the western black sea depression
Khrischev, K.; Ruskova, N.; Georgiev, V.; Kozhukharov, E.
Paleontologiya Stratigrafiya i Litologiya 27: 65-84
The sediments of three lithostratigraphic units are studied: Ic-lutite (Neoeuxinic layers); Ib-sapropel (ancient Black Sea layers); Ia-coccolithic slimes (recent layers). Lithologic typification is made according to a substance-genetic character. Six groups of sediments are formed: terrigenous, biogenic sapropels, biogenic limy coccoliths; biogenic flint diatomic, homogeneous limy and intraclastic brachiopods. Terrigenous sediments are most widely spread in Ic and in terrigenous lithofacies of Ia. Two populations are distinguished in them according to granulometric composition-T1 (more fine-grained slimes with two subpopulations: T1a and T1b) and T2 (stronger silty slimes and silts). Biogenic sediments are inherent to the typical growth of the Holocene lithostratigraphic units. In Ib they are presented by sapropels and slightly sapropelic slimes with a high content of organic substance (most often 15-25%), while in Ia-by coccolithic slimes whose carbonate content exceeds 50%. The diatomic slimes are of local growth with respect to Ic and Ia. Homogeneous carbonate sediments are spread in two levels. In the lower one, comprising the peak of Ic, they are presented by limy slimes of the type "seekreide", which are built of low-magnesia calcite and terrigenous admixtures. On the upper level (Ib) the homogeneous carbonates form thin lamelas and are presented by rice-wise aragonite and more rarely by a high-magnesia calcite and manganese carbonate. Intraclastic breccia are connected with landslides and seismic deformation and breaking of the sediments of Ib and Ia.