Paleoenvironmental history of the Middle Dnieper Area from the Dnieper to Weichselian Glaciation: A case study of the Maksymivka loess profile

摘要

The paper presents the results of interdisciplinary studies on environmental characteristics of the Middle and Upper Pleistocene (MIS 8-2) of central Ukraine based on an example of the new research site at Maksymivka. The tested profile is situated on the left bank of the Dnieper River on the western edge of the Dnieper Plain. It is a representative section of the cliff of the east lakeshore of the Kremenchuk Reservoir, located in the border zone both in longitudinal and latitudinal terms. It is located in the southern part of the Dnieper terraced plateau on the border of two varieties of forest-steppes with an admixture of meadow steppes, defined as left-bank-Dnieper and Dniester-Dnieper. To the south of the site extends a typical steppe zone. The transient position of the research site is a good point to start to trace the history of the volatility of the vegetation cover and the shift of the landscape-vegetation boundaries according to the climatic fluctuations. To reconstruct environmental changes in the analysed time interval the litho-, pedo-and palaeobotanical methods were used. To determine the chronology of changes a number of parallel datings of the loess-paleosol sequence were conducted: TL (Gdansk, Kyiv, Lublin), OSL (Gliwce). The profile is comprised of glacial and loess parts. The bottom section is built of glacigenic sediments of the marginal zone of the Dnieper Glaciation. The overlying loess-soil sequence of the last two glacial-interglacial cycles underwent detailed analyses. This section is composed of multiple soil levels, whose participation in the entire thickness of the layer dominates over primary loess. The studies have confirmed that they are lower stratigraphic rank soils of the Vytachiv (vt) unit (=MIS 3), and two complex higher rank units: Pryluky (pl; MIS 5) and Kaydaky (kd; MIS 7). For the distinguished litho-and pedostratigraphic units, paleoenvironmental characteristics were developed. The stratigraphic rank of these units was confirmed by dating. The results of the TL and OSL dating of the samples show good agreement between the laboratories, particularly in relation to the last cycle. However, the OSL dates for the penultimate cycle are significantly underestimated in relation to the TL dates, which in turn relate well to the global time framework. The reasons of the OSL dates underestimation might be connected with the post-sedimentation pedogenic changes.