Glacial and Periglacial Transformation of Palaeokarst in the Lublin-Volhynia Region (Se Poland, NW Ukraine) on the Base of TL Dating

Abstract

Abstract: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.

Role of Periglacial Processes in Epikarst Morphogenesis: A Case Study from Chełm Chalk Quarry, Lublin Upland, Eastern Poland

“…The periglacial deformational environment is also indirectly evidenced by the TL age of the deposits filling pockets, ranging from 37 ka to 86.5 ka (Dobrowolski, ). In the opinion of Dobrowolski and Fedorowicz (), this is not the age of burial but, rather, is related to the time of Weichselian transformation of Saalian glaciogenic deposits in periglacial conditions (frost weathering and corrasion). The thesis that the change in mechanical properties of deposits has been influenced by cryogenic processes and the resulting zeroing of the TL signal to residual level have been confirmed experimentally by measuring the dose absorbed by mineral grains subjected to repeated freeze‐thaw cycles (Dobrowolski and Fedorowicz, ).…”

“…Structural transformations in the epikarst zone are probably evidence of repeated periglacial conditions associated with successive glacial advance and retreat cycles. However, the final formation of involutions at the Chełm site is most likely to have been related to the Pleniweichselian, as earlier TL dating has confirmed (Dobrowolski, ; Dobrowolski and Fedorowicz, ).…”

“…According to Vandenberghe (), Vandenberghe and Pissart () and Huijzer and Isarin (), such structures are formed in the active layer when the mean annual air temperature is ≤ −1 °C. Therefore, their Pleniweichselian stratigraphic position determined from TL dating (treated as an indicator of the age of the process that deformed the deposit) is highly probable (Dobrowolski and Fedorowicz, ).…”

“…The lithology and origin of these deposits vary: they are usually glaciolacustrine sands and silts and/or diamictic sands interpreted as flow tills. Moreover, primary glaciogenic depositional features bear distinct traces of periglacial transformation (Dobrowolski, ; Dobrowolski and Fedorowicz, ). For these reasons, the question remains open as to the role of periglacial processes in epikarst morphogenesis, both in the formation of the depressions and the timing of their sedimentary infilling: syn‐ or epigenetic?…”

“…The study examined pockets containing glaciogenic infill of Saalian age, with the aim of reconstructing the mechanisms leading to their formation in periglacial conditions and, in particular, of developing a model of Pleistocene epikarst development in the active layer above permafrost. The study combines sedimentological (lithofacies), micromorphological and grain‐size analyses with the results of earlier thermoluminescence (TL) dating (Dobrowolski and Fedorowicz, ).…”