A detailed palaeosol record of Middle and Upper Pleistocene from the central part of the Volyn’ Upland (the NW Ukraine)

The Volyn’ Upland is a “loess island” in the middle of the European loess belt. In the previously studied sections of this region, the Pleistocene palaeosols are mainly polygenetic; therefore, the pedocomplexes comprise no more than two soils. The study of the sections located both on the slopes of the river valleys and in the buried gullies, contributed to detailed stratigraphy of the pedocomplexes.  

Three pedocomplexes have been distinguished in the sections, which, according to palaeopedological and palynological data, were tentatively correlated with MIS 5, 7 and 9, respectively. The lower pedocomplex (S3, MIS 9) comprises two soils. The lower soil (S3-II) is a Luvisol with multi-phased clay coatings in the Bt horizon. However, micromorphology detects a clear primary A horizon with abundant coprolites. The upper soil (S3-I) has a well-developed A horizon and Ag horizon in the depression. However, clay coatings in the Bt horizon testify to the clay translocation.

The middle pedocomplex (S2, MIS 7) comprises two welded soils separated by a thin loess bed. The lower soil (S2-II) is a Luvisol, in places marked by a pronounced A horizon, in which clay coatings occur, whereas in the E horizon secondary carbonate nodules appear.  In places, the upper soil (S2-I) turns into two separate soils: the lower Haplic Chernozem and the upper Cambisol, both densely dissected by soil veins. These soils are dark, leached of carbonates, with crumby and granular microstructure. Many krotovinas occur in the subsoil.

The upper pedocomplex (S1, MIS 5) is subdivided into three sub-pedocomplexes, interbedded with sandy facies in depressions and thin loess-like deposits at the topographically higher positions. The lower sub-pedocomplex (S1-III, MIS 5e) is represented, depending on the parent material, by Luvisol, Retisol or Podzol with abundant clay coatings in the Bt horizon. In places, the forest soil is overlain by Entic Podzol with a more pronounced A horizon and is underlain by a Gleysol in depression. The middle sub-pedocomplex (S1-II, MIS 5c) comprises three soils: the lower Entic or Albic Podzol, the middle Chernozem and the upper Cambisol. A distinguished feature of these soils is the rapid increase in sand content in almost all studied sections. The upper sub-pedocomplex (S1-I, MIS 5a) is interpreted as a Cambisol, in places with a well-developed A horizon. In the upper soils of S1, pale brown spots occur.

Three Gleysols have been distinguished in the upper thick loess unit (L1, MIS 2-4). The lower Gleysol (MIS 3) is better developed and mostly polygenetic; in places the soil turns into a pedocomplex consisting of two or three soils: the lower Gleysol, the middle Gleyic Cambisol and the upper Calcaric Cambisol. The middle Gleysol appears to be polygenetic, as evidenced by palynology and micromorphology. Large ice-wedge pseudomorphs are associated with the upper Gleysol, which makes it possible to interpret soil as tundra-gley.

The study was supported by the National Research Foundation of Ukraine, grant number 2020.02/0406.