STRATIPHICATION AND CORRELATION OF QUATERNARY ALLUVIAL DEPOSITS OF THE SOUTH-WESTERN PART OF THE EASTERN- EUROPEAN PLATFORM ACCORDING TO UNIONIDAE DATA

On the base of studying the collection of fossil Unionidae in the alluvium deposits of the Dniestr, Danube, Prut valleys the stages of their development were defined. The stages correspond to general changes of climate. Also Unionidae are a good bench mark for correlation of distant sections, due to their wide distribution not only in alluvial but in estuary, lacustrine, and marine deposits. In the second half of the Late Pliocene in the fresh-water reservoirs of the South-Western part of the Eastern-European platform the representatives of the Bogatschevia genus - the B. tamanensis group (Rashkiv complex, alluvium of the X terrace) had a wide distribution in the Tamanian deposits of the Akchagil and Upper Akchagil. The cooling that occurred in the Eburonian (after forming alluvium of the X terrace) caused the extinction of majority of sculptured forms of Unionidae and wide distribution of ancient forms of modern Unionidae. This gives grounds for setting a boundary between the Pliocene and Eopleistocene over alluvium of the X terrace. In the stratigraphic scale this cooling is correlated with the Early Apsheronian of the Pricaspian area. In Boshernitsky complex Unionidae of the B. sturi group had a wide distribution. Their distribution was limited by the narrow stratigraphic diapason - alluvium of the IX terraces of the Dniester, Prut, Danube. It corresponds to the Eopleistocene and is correlated with the Lower Apsheronian, Gurian. Alluvium of the VIII terrace is clearly correlated in the vast territories according to the composition of fresh-water mollusk species: Potomida sublitoralis, Bogatschevia (Pseudosturia) caudata, Unio chasaricus etc. Finds of typical forms in the Middle Apsheronian deposits give an opportunity to correlate them with alluvium of the VIII terrace of the Dniester. Alluvium of the VII terrace, on the basis of faunistic and palaeomagnitic data is correlated with the Upper Gurian, Lower Chaudinsky deposits of the Caucasian seacoast of the Black Sea. Alluvium deposits of the V terrace are correlated with Upper Chaudinsky deposits and underlying continental loams on the Chauda cape. The loams are correlated with the lower alluvium thickness of the Kolkotov terrace with Psedunio moldavica. Alluvium of the IV terrace is correlated with old Euksin deposits. Karangatsky deposits are correlated with alluvium of the II terrace.