Molluscan assemblages in Late Holocene deposits in Busko-Zdrój (Nida Basin, Southern Poland)

Late Holocene deposits containing abundant and well-preserved malacofauna were exposed within the Spa Park in Busko-Zdrój. Molluscan shells were found in sand, dark muds and calcareous muds. Dark and calcareous muds are intercalated by fine-grained sand and peat devoid of malacofauna. Ali these deposits were accumulated on swampy, flat bottom of wide river valley. The result of radiocarbon dating has shown that the formation of the deposits started in the upper part of the Subboreal Phase. Numerous Late Medieval portery shards were found in several topmost profile sections. The identified malacofauna suggests that similar climatic and habitat conditions prevailed throughout the entire sedimentation period. Snails typical of open habitats, accompanied by hygrophilous taxa, play a dominant role. Mesophilous and aquatic taxa occur in accessory proportions, while shadow-loving forms are virtually absent.