Climate oscillations in the 20 000-11 000 cal BP range recorded in the Piaski and Szerokie Formations in the Bełchatów Opencast Lignite Mine: a look through radiocarbon date analysis

This paper presents the results of analysis of 25 radiocarbon dates out of 31 age determinations of organic sediments taken from the Piaski and Szerokie Formations in the Bełchatów Opencast Lignite Mine. The Sum function in the calibration program OxCal v4.4.4 and the latest version of the calibration curve IntCal20 were used to produce so-called Probability Density Function (PDF) curves of calibrated dates in the range of 20 000-11 000 cal BP. Analysis of the shape of the distributions indicated that the position of the peaks of the probability density distribution of radiocarbon dates on the time axis coincided with the course of the oxygen curve in the Greenlandic ice core of the NGRIP. A clustering of dates was observed in several time ranges corresponding primarily to the GS-2b/GS-2a transition (about 17 800-17 300 cal BP, Kamion phase) and GS-2a/GI-1e (about 15 200-14 300 cal BP). Also clearly recorded were the transitions between cooler and warmer periods within GI-1 (14 700-12 900 cal BP), where the grouping of dates around GI-1d (14 100-13 800 cal BP), GI-1c2 (13 600-13 550 cal BP) and GI-1b (13 250-13 050 cal BP) was distinguished. The youngest analysed dates are associated with the second half of the GS-1 (Younger Dryas, 12 500-11 700 cal BP).