Periglacial markers within the Late Pleistocene loess–palaeosol sequences in Poland and Western Ukraine

Abstract

Stratigraphic loess–palaeosol sequences represent exceptional, climate-controlled, terrestrial records of interglacial–glacial cycles. One of the most spectacular features within the northern part of the European loess belt is the occurrence of well-preserved relicts of the periglacial structures. From a variety of periglacial structures, three types are especially useful to reconstruct the former periglacial environment: cryogenic wedges with primary mineral infilling, cryoturbation and gelifluction structures; and ice-wedge casts. These structures form well-distinguishable horizons within loess–palaeosol sequences and their stratigraphic positions are not random. Periglacial horizons recorded in the Late Pleistocene loess–palaeosol sequences in the study area were formed as a result of extreme climatic conditions and/or rapid environmental changes during cold events of the Last Glacial period. These horizons are noted in almost all investigated sections, and thus they can be used as stratigraphic markers. The number of periglacial horizons and their morphological features vary, depending on their geographical settings and local conditions. The periglacial record indicates the occurrence of four main cold stages during the Last Glacial period. Two earlier stages are recorded in the last interglacial–early glacial palaeosol complex. Their onset was probably rapid. These short cold periods can be correlated with MIS 5d and 5b. The next two periglacial stages most probably correspond with MIS 4 and 2. Only during the last two stages were ice-wedges formed in the northern zone of the investigated loess area. This record indicates the twofold expansion and disappearance of the permafrost during the Last Glacial period.