Palaeoenvironmental and climatic changes from the lateglacial of the Saalian to the Late Weichselian in central Poland: a multiproxy study from Józefów

This study presents a multiproxy reconstruction of palaeoenvironment under variable climatic conditions from the retreat of the Saalian ice sheet (MIS 6a) to the Late Weichselian (MIS 2), based on an analysis of mineral and biogenic sediments from a palaeolake at the Józefów site (central Poland). The diversity and disturbances of sediments studied at Józefów highlight the general need to combine multiple research techniques for a comprehensive reconstruction; however, they also demonstrate the limitations of methods used in such analyses. Lithological, geochemical and palaeobotanical analyses of a 7.5 m sediment succession from the CO‐1 core and several outcrops completed using previous OSL dating reveal that lacustrine accumulation started in the active permafrost layer. Pollen, macrofossils and geochemical records indicate that, during the lateglacial of the Saalian (MIS 6a), the lake was initially surrounded by steppe–tundra plant communities, then supplemented by pioneering birch and pine patches, followed by a deterioration in conditions expressed as increased amounts of open‐steppe vegetation and intensified erosion processes. This record indicates traces of climate oscillations in the Late Saalian. At the onset of the Eemian interglacial (MIS 5e), the lake became shallow and transitioned into a peat bog during a mesocratic phase, remaining so until the middle of the oligocratic phase. Sediment accumulation in the basin continued into the Early Weichselian (MIS 5d–a), ceasing around 58 ka, confirming the typical development succession of Eemian–Early Weichselian lakes in the Polish lowlands. No deposits or direct traces of erosion from MIS 4 and MIS 3 were identified, which reflects a widespread hiatus across central‐eastern Europe. OSL dates can be rejuvenated by a highly dynamic periglacial environment and therefore do not correlate precisely with palaeobotanical data. Thermal contraction fissures formed due to intense permafrost aggradation (MIS 2, Leszno phase, 25–21 ka), supporting a previous hypothesis that a frost mound existed at Józefów. The Weichselian is recorded in mineral sediments deposited as a result of intensive mass‐flow processes and sedimentation from suspension in a shallow lake during gradual degradation of permafrost (after the Leszno phase) and in aeolian sediments from the final stage of the Late Weichselian (Oldest/Younger Dryas). The Józefów case study provides a detailed record of environmental and climate changes and confirms the main traces of Late Pleistocene landscape morphogenesis in central‐eastern Europe.