Evo lu tion of Early and Middle Pleis to cene river val ley sys tems in Pol ish-Ukraine-Belarus cross-bor der ar eas based on geo log i cal and malacological prox

The geo log i cal set ting of the Bug–Pripyat interfluve and the close prox im ity of the source of the Pripyat River to the well-de vel oped Mid dle Bug River val ley sug gest that these rivers may have been con nected in the past. Anal y sis of geo log i cal cross-sec tions around the Pol ish-Ukraine-Belarus cross-bor der ar eas to gether with study of as so ci ated Pleis to cene palaeoflora shows that bur ied al lu vial de pos its of the proto-Bug and proto-Pripyat clearly rep re sent the Preglacial (MIS 103-23), Podlasian/Turskian-Donian/Brest Inter gla cial (Cromerian I-II; MIS 21-17) and the Mazovian/Likhvinian/Al ex an drian Inter gla cial (Holsteinian; MIS 11c). Their el e vated po si tion in mid-east ern Po land sug gests the pos si bil ity of ac cu mu la tion by proto-Bug wa ters flow ing eastwards, which de ter mined the for ma tion and de vel op ment of the lower-ly ing proto-Pripyat val ley sys tem in northwest ern Ukraine at those times. The oc cur rence of the Ponto-Cas pian spe cies Lithoglyphus naticoides (C. Pfeif fer, 1828), Borysthenia naticina (Menke, 1845) and Corbicula fluminalis (O.F. Müller, 1774) in the mol lusc as sem blages of the Mazovian/Likhvinian/Al ex an drian Inter gla cial im plies that the main wa ter shed be tween the Bal tic Sea and the Black Sea drain age bas ins might have been sit u ated in the north ern part of the area stud ied. Pre sum ably its main part was drained by the wa ters of the proto-Bug catch ment con nected with the proto-Pripyat and flow ing far ther to the east to wards the Dnie per River en ter ing the Black Sea.