Eemian-Weichselian palaeoenvironmental record from the Mickūnai glacial depression (Eastern Lithuania)

Abstract

An extensive area of distribution of palaeolacustrine sediments (sand, silt with humus and interlayers of gyttja), occurring above the Eemian (Merkinė) Interglacial deposits and below the relief forming the Upper Weichselian till, was determined in the Mickūnai glaciodepression (in the vicinities of Vilnius, East Lithuania). These sediments were interpreted as being formed in a shallow palaeolake or lacustrine system, which occupied the depression during the Early-Middle Weichselian. Four boreholes were drilled in the central part of the Mickūnai depression and their sections were studied using lithostratigraphic and pollen analyses and datings by the optically stimulated luminescence (OSL) method. On the basis of the lithological composition and pollen and spores data the studied sections were tentatively subdivided into thermomers (time periods with relatively warmer climate) and cryomers (time intervals with colder periods). In the Mickūnai site seven thermomers and eight cryomers occurring above the Eemian Interglacial were determined. The thermomers of Middle Weichselian, however, were defined only by slight climatic changes in the background of general climatic deterioration. The Mickūnai sequence reflects presence of nonglacial palaeoenvironments from the end of the Eemian Interglacial to the Late Weichselian ice advance.