High-resolution color variations of Weichselian loess-palaeosol sequences in the Dnieper River basin (Ukraine)

High-resolution colour analyses of key loess-soil sequences (LPSs) in the Ukrainian part of Dnieper River basin - one of the major European rivers and the largest river in the borderland between Central and Eastern Europe. The subject of the study were LPSs from the Last Glaciation with a thickness of up to 10 meters. The aim of our studies is to reconstruct the Upper Pleistocene paleogeographic transformations recorded in the Dnieper LPSs.

In our study area the causative geomorphological agent was dust was blown away by wind from the exposed surfaces rich in loose fine-grained material (e.g. from a wide valley of a big river) and deposited on the land surface as silt covers of different thickness and spatial extent; in warm (interphase, interstadial) periods of the Weichselian it was fixed by vegetation and was the parent rock for the successively developing soils of different pedogenesis types. In the Last Glaciation the zone of long (~1000 km) and generally sub-meridional valley of the Dnieper River was located in the peri- and extraglacial zone and characterized by strong spatial climate gradient depending on the distance from the ice sheet extent. In our times this river flows across several vegetation-landscape zones (forest→forest-steppe→steppe).

The spectrophotometer made it possible to carry out colour analyses of individual units distinguished within LPSs, taking into account a number of parameters such as: CIELAB color space variables L* (luminance, i.e. lightness [0-100]), a* (>0: red, < 0: green), and b* (>0: yellow, < 0: blue), derived parameters like the Redness Index (RI) and the RGB variables (min., max, average). The analysed LPSs showed relatively high variability of the above mentioned parameters reflecting activity of sedimentation processes (=primary loess) as well as pedogenic changes (soil horizons of different stratigraphic rank) and slope transformations (reworked material). The results of these analyses (presented mainly as curve lines and heatmaps) specify characteristics of environmental conditions of individual litho- and pedostratigraphic units. The advantage of the analysed parameters is their high sensitivity reflecting variability of environmental parameters having global, but also regional or even just local significance.

Research carried out as part of the grant of National Science Centre, Poland as the project no. 2018/31/B/ST10/01507 entitled “Global, regional and local factors determining the palaeoclimatic and palaeoenvironmental record in the Ukrainian loess-soil sequences along the Dnieper River Valley - from the proximal areas to the distal periglacial zone”.