PALEOECOLOGICAL HABITAT OF THE LATE QUATERNARY MOLLUSCS OF THE NORTHERN FORE-CASPIAN LOWLAND ON THE EXAMPLE OF THE KOSIKA 1 LOCALITY

Investigations of the Middle-Late Neopleistocene deposits of the Kosika 1 locality and studied malacological complexes permit to understand changes of the main geological events of the territory and to identify molluscs palaeoecologihal habitats. Brakishwater and freshwater lakes existed on the territory after Early Khazarian Sea regression (beginning of the Late Neopleistocene; layer 1). Marine deposits accumulated during Late Khazarian Sea transgression (first half of the Late Neopleistocene; layer 2). Big river (Paleo-Volga) existed after the regression of the Late Khazarian Sea. This river flow to the south in the direction of the coastline retreatment. Fluvial deposits prove river existence (layer 4). Marine deposits with special key mollusc species accumulated during the Khvalynian Sea transgression. Again, river existed after regression of this sea. Alluvium is on the top of the Khvalynian section, it is contain rich complex of the freshwater and marine mollusc species (layer 5). Fluvial-marine deposits form the underwater delta, which accumulated during Late Khvalynian time. These deposits contain shell fragments of freshwater and marine mollusc species. Deposits of the underwater delta form in the relief elongated hills, which are known as “Ber bugor” among geomorphologists.