Silts from the Polish Baltic Coast were analysed with respect to their mollusc assemblages and radiocarbon-dated. Four faunae were distinguished: fauna with Vertigo genesii Gredl. (Young Dryas or beginning of Preboreal Phase); fauna with Bithynia tentaculata (L.) (Boreal Phase); fauna with Valvata piscinalis (O. F. Müll.) (Boreal Phase); fauna with Cardium glaucum Brug. (Atlantic Phase).