The northernmost Polish Eemian palaeolake near Łęczyce − Stratigraphic and palaeoecological implications for a MIS 6a − MIS 5d sediment record

We report the results of high-resolution multi-proxy studies of a 10 m thick sedimentary profile from Łęczyce, Poland. It reveals a continuous lacustrine succession from the Eemian Interglacial. On this basis, we have distinguished seven sedimentary units (U7a-U7f) and ten local palynological zones (LPAZ Lec 1 − Lec 10), revealing the evolution of the lake from the moment of dead-ice melting, through the continuous filling of the lake basin with organic mud, to the final stage of shallowing and transformation into a peat bog. This northernmost known Eemian site was investigated for the first time, therefore, the reconstructed changes in local conditions were correlated with global changes from the final phase of the penultimate glaciation through the Eemian Interglacial to the beginning of the last glaciation. The results show that the melting of dead ice blocks at this site was delayed compared to central Poland, with lacustrine processes starting as glaciolimnic sedimentation. Furthermore, the delayed start of vegetation development around the lake resulted in the absence of a Pinus-Betula-Ulmus E2 level. During the Eemian, local conditions were generally stable, and sedimentation took place in a relatively deep basin with well-defined epilimnion and hypolimnion zones. Climatic instability at the end of the Eemian resulted in reduced vegetation cover. During the first climatic deterioration in the Weichselian (presumably the Herning Stadial), lacustrine sedimentation was reduced and the deposition of fine-grained mineral material predominated. This was followed by the complete drying out of the lake and the development of soil formation. The subsequent climatic warming (Brørup Interstadial?) recorded in the uppermost part of the profile (U7f) was characterised by the plant community Lec 10 (Carpinus-Corylus-Picea) and was presumably warmer than commonly assumed. Multi-proxy studies show that the development of the lake was more similar to that of southern Scandinavia than to that of Poland.