A biotic record of paleoenvironmental changes during the last interglacial-glacial cycle in a sub-Carpathian river valley; a case study of the Radymno loess section (SE Poland)

Abstract

The studied Radymno loess section is located in the large, fore-Carpathian San River valley (Sandomierz Basin, SE Poland) and shows the sequence building the Pleistocene cover of middle terrace of the San River. Such sequence is quite rare in loess deposits because it combines different depositional environments: subaqueous – the late Eemian-Early Vistulian alluvial-swamp facies of loess with inserts of gyttja type, and subaerial – the Plenivistulian aeolian loess. The main goal of the study was to reconstruct the Late Pleistocene paleoenvironmental changes recorded in this section. For this purpose, pollen and fossil Ostracoda analyses were conducted. These data were supplemented with sedimentological and pedo-lithological analyses. Additionally, the results of earlier investigations published so far have been used: lithological and malacological analyses as well as luminescence (IRSL and TL) dating. Based on the analysis of many indicators, the paleoenvironmental changes have been correlated with those recorded in pollen diagrams obtained from other regions. This correlation indicates that in the Radymno section there is evidence of the vegetation succession typical of the Eemian Interglacial with climatic optimum and of the short-term oscillations in the Early Vistulian and then in the Lower Pleniglacial of Vistulian. The analysis of fossil Ostracoda, which were found in some parts of the profile, provided information about short-term paleohydrological changes, and especially about the functioning of surface water bodies in changing periglacial conditions of the bottom of the San River valley in MIS 5d – MIS 2. High humidity in the environment was caused mainly by floods and high groundwater level, which indirectly conditioned the formation of water bodies in the valley bottom. Correlation with palynological data indicated that these water bodies existed also under dry climate conditions. This proves that the local conditions of the studied area strongly modified the environmental changes dependent on paleoclimate.