Paleoclimatic and stratigraphic significance of Belgrandia marginata (Michaud) in Late Quaternary malacofauna of Belarus and Lithuania

The fauna and flora of each Quaternary interglacial epoch of the middle latitudes possesses general and specific connections with climate. The presence of the Atlantic and West European mollusc Belgrandia marginata (Michaud) is distinctive in the freshwater malacofauna of the Eemian (Muravian, Merkine) interglacial in Belarus, Lithuania, and Poland. This species is present in eight malacofaunas of the region, with exclusively Eemian age. Paleontologic researches show that the species occupied reservoirs in this territory only during an optimum Eemian interglacial, giving it stratigraphical value in the region. The 1000 km sublatitudinal extent of the species through the Central European plain and Russian plain to the Dnieper River reflects, most likely, the direction of circulation of Atlantic air masses deep into the continent. The Eemian extent of B. marginata in the upstream Dnieper basin is imposed on the range of the Ponto-Caspian mollusc Dreissena polymorpha, which also occupied the upstream Dnieper basin only in the Eemian Interglacial. Both species are characteristic representatives of the Eemian (Muravian) freshwater malacofauna of Belarus.