Glacial and periglacial transformation of palaeokarst in the Lublin-Volhynia region (SE Poland, NW Ukraine) on the base of TL dating

Distinctly diverse results of TL dating are obtained for the deposits with similar lithofacial features but filling morphologically differentiated karst palaeoforms (dolines, pipes, pockets). The infillings of dolines and pipes are mostly of the Saalian age. Based on sedimentological analysis, their formation conditions are related to sub- or/and terminoglacial environment. The age obtained for all infillings of pockets is underestimated in comparison with lithostratigraphic data. A close genetic relationship between these forms and periglacial conditions seems to indicate that the reduction of TL signal is mostly influenced by the disintegration of grains resulted from the repeated freezing and thawing of glaciogenic deposits. A considerable influence of frost weathering on the decrease of thermoluminescence intensity of mineral grains is indirectly confirmed by the results of experimental investigations consisting in the repeated TL measurements of pockets’ infillings after successive freeze-thaw cycles.