A high-resolution pollen and diatom record of mid-to late-Eemian at Kozłów (Central Poland) reveals no drastic climate changes in the hornbeam phase of this interglacial

Abstract

In the region of 20 newly-found fossil lakes in the Garwolin Plain (Central Poland), formed during the Eemian interglacial (MIS 5e), the Kozłów site is considered one of the longest examples of sequences of palaeolake deposits. Pollen investigations have revealed an entire Eemian interglacial (MIS 5e) with a very long hornbeam phase. Repeated coring allowed for high-resolution pollen and diatom analysis to be used in tracing climate-driven palaeoenvironmental changes during the mid- and late-Eemian. The resulting thick series of organogenic deposits from Kozłów joins the collection of existing high-resolution long records of this interglacial in central-eastern Europe. It should be emphasized that a very good correlation was found between palynological and diatom data, which allows for drawing consistent conclusions. The warm and humid climate of the Corylus phase at the onset of the mid-Eemian was marked by a great abundance of planktonic Cyclotella sensu lato species, which indicate a rising water level, increased water temperatures, thermal stratification and a warm-wet climate. In the diatom zones correlated with the Carpinus phase, a distinct change was observed, from an assemblage dominated by planktonic species to one composed of benthic ones, including Fragilaria sensu lato taxa. The greater frequency of oceanic air masses must have affected the humidity and thermal conditions in lake and its surroundings in the first part of the interglacial optimum. Climate changes are very clearly visible at the transition between Carpinus and Picea-Abies zones, which were caused by increased influence of continental air masses. However, in the Middle Eemian no drastic changes were observed in both the pollen and diatom records.In the upper part of the core, represented by Pinus pollen, the presence of cold-loving diatom species, and an increase of green algae Pediastrum spp. point to a drop in temperatures at the close of the interglacial. The pollen results were compared to the well-recognized mid-to late-Eemian successions from Poland and West Europe.