Climate change records in coversand deposits from the eastern margin of the Tarnów Plateau (southeast Poland)

Abstract

Coversands (CSs) are one of the most distinctive sediments within the European Sand Belt. Their extraordinary thickness, exceeding 6 m, was recorded at the Góra Motyczna site located at the edge of the Wisłoka River valley in the Tarnów Plateau (southeast Poland). The sedimentary record of the studied CSs sets their arrangement into one of two sedimentary cycles. Each consists of sandy (A1 and A2) and silty (B1 and B2) lithofacies, forming an A1 ⇒ B1 ⇒ A2 ⇒ B2 sequence that is considered to be a record of climate change during the Weichselian Late Pleniglacial. Sandy lithofacies accumulation occurred under dry and snow‐free climatic conditions, whereas silty lithofacies accumulation marks an increase in humidity as a result of the presence of snow‐cover. Sediment optical dating indicated that the studied CSs were deposited in a period from ~18–17 to ~16–15 ka. The period of accumulation was therefore short, which is confirmed by the analysis of quartz‐grain shape and surface type. Due to this brevity of aeolian processes during this period, the only change expressed is in grain‐surface microrelief; thus, the quartz grains had already inherited their shape and degree of rounding from their source environments and earlier processes. The source sediments could have been artefacts of Miocene and Quaternary deflationary sediments associated with blowouts.