ИСТИНА

The chocolate-colored clays representing exotic sediment facies missing in both the older and younger formations of Caspian Pleistocene are widely distributed in North Caspian region amongst the Early Khvalynian transgression deposits. They are frequent in pre-Khvalynian terrain depressions in the valleys of Volga, Ural and some of their tributaries. The outcrops Raigorod, Cherniy Yar and Kopanovka, located on the right bank of the Lower Volga provided the material for this work. They cover Pleistocene deposits coming out on the surface, with a very complex structure typical for a large valley sporadically flooded by the sea. In Raigorod and Cherniy Yar outcrops the ostracod fauna of chocolate-colored clays is represented by the species typical for Khvalynian deposits: Caspiolla spp., Amnicythere? quinquetuberculata (Schweyer, 1949), Euxinocythere virgata (Schneider, 1962), E. bacuana (Livental, 1929), E. relicta (Schornikov, 1964), E. tumulii (Aslanova in Mandelstam et al., 1962), Loxocaspia gibboides (Livental in Schweyer, 1949) and others. At the Kopanovka outcrop the fauna of chocolate-colored clays is represented by a specific ostracod assemblage. The samples contain 5 ostracod species; mollusks and foraminifers are not present. Most abundant are the representatives of genus Galolimnocythere (3 species), while Rectocypris? spр. is less numerous. The single valve of Scordiscia dorsotuberculeata (Negodaev, 1957) was found in deposits from Raigorod outcrop section (11040±460 14 C BP) along with large amounts of Caspian ostracods. These findings indicate that in the North Caspian region, apparently, brackish lakes existed earlier. Specific fauna of those lakes has not spread into the Caspian Sea, but settled expansively in continental brackish lakes. The elements of this fauna occur in brackish lakes of Kazakhstan at present, and Scordiscia vara (Liepin in Liubimova et al., 1960) inhabited Aral Sea before ecological disaster took its place there (Schornikov, 2008).