Evolution of palaeolake environment in Poland during the Eemian Interglacial based on oxygen and carbon isotope data from lacustrine carbonates

The results of oxygen and carbon stable isotope investigations of eight Eemian lacustrine sediments from Poland are presented. The values of δ18O changed from ca. −11 to −1‰, and δ13C values oscillated between −3.5 and +7.0‰. The isotopic record correlated well with pollen, cladoceran, and diatom data. The evolution of the palaeolakes in Poland was reconstructed. The palaeolakes originated during the final phase of the Wartanian (Late Saalian) Glaciation. The δ18O and δ13C values of that time reflect the input of detrital carbonates into the basins. The boundary between the glaciation and the interglacial period is expressed by a significant decrease in δ18O and δ13C values. During the early Eemian, a positive trend in δ 18O values confirms the gradual climatic changes. The Eemian optimum is characterized by constant δ18O and δ13C values. During the Early Vistulian (Weichselian) Glaciation, the palaeolake declined. The varying δ18O values likely reflect frequent changes in water balance between precipitation and evaporation associated with an influence of marine circulation. The fluctuations of the isotopic curves in the upper parts of the successions (the post-optimum) were caused by a shallowing of the basin by infilling with sediments. The observed shifts in the isotopic curves are due to the proximity of the Baltic Sea and earlier strong oceanic influences.