Geologicheskii Vestnik

The paper presents the malacological data on the Tyurkyan Horizon of the Lower Neopleistocene of the borehole 2 Kosika section (Lower Volga region). The age of the mollusсs in the borehole was determined according to their stratigraphic position in the section under the marine sediments characterized by the Baku marine mollusс complex and the presence of freshwater mollusсs in the studied sediments indicating the formation of facies in the river valley. Alluvial and lacustrine-limanian sediments of the Tyurkyan horizon were distinguished in the interval of the 142–112 m depths with total thickness of 30 m. The development from the river (floodplain) conditions to the formation of the hydromorphic soil followed by overlaing it sediments of a salinating liman was traced. The results of the malacological studies indicate the formation of the sediments in rivers and lakes that were inhabited by freshwater molluscs in the continental conditions of the humid climate. The Tyurkyan time (the beginning of the Neopleistocene) was the period of regression of the Apsheronian Sea.

Lower Volga, Lower Neopleistocene, Tyurkyan Horizon, molluscs

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