Interplenivistulian (MIS 3) environmental changes recorded in sub-till lake deposits at Wildno, Dobrzyń Lakeland (Polish Lowland)

A complex of clays and sandy-silt deposits with mollusc remains covered by a till correlated with the Main Stadial of the Vistulian (Weichselian) Glaciation was investigated at Wildno in the Dobrzyń Lakeland (Polish Lowland). A few taxa of snails: Bithynia tentaculata, Valvata piscinalis, Theodoxus cf. fluviatilis, Valvata sp., Viviparus sp. as well as bivalves Pisidium cf. amnicum and Sphaerium sp. were identified amongst poorly-preserved shell fragments. No pollen grains were present in mollusc-bearing deposits, whereas the pollen spectrum of clays lying below the latter points their accumulation in oligotrophic water body in a cool climate (Pediastrum kawraiskii) and woodless area. Radiocarbon age of shell detritus (4 samples) ranges from >43.7 cal ka to c. 32.1 ± 0.8 cal ka. Both the geological situation and the results of dating suggest that sub-till sediments with molluscs were deposited in the upper part of Interplenivistulian (MIS 3) = the Grudziądz Interstadial, while accumulation of clays may be correlated with its earlier and cooler part.