Environmental and climate change during the Late Saalian–Eemian Interglacial at the Struga site (Central Poland): A diatom record against the background of palynostratigraphy

Abstract The main aim of the study was to determine the environmental history and climatic change taking place during the Late Saalian/Eemian transition, particularly at the start of the Eemian interglacial. Paleolake sediments from two cores from the Garwolin Plain (Central Poland) were subjected to diatom analysis. Altogether, 63 genera including 335 species and varieties were recognized. A clear shift in diatom composition was observed, from an assemblage dominated by periphytic species including Fragilaria sensu lato taxa to a planktonic one comprising Cyclotella sensu lato species. These changes in diatom assemblages and the relative abundance of the dominant and sub-dominant taxa indicated fluctuations in water level and regional climate oscillation. The transition from the Late Saalian to the Eemian was marked by a gradual increase in the contribution of summer-blooming diatom species, indicating the presence of a growing season and humid warm conditions, together with a rise in water level. The predominance of an alkaliphilous assemblage indicates alkaline conditions in the paleolake. The local diatom assemblage zones correspond very closely with the palynostratigraphy of the period under examination.