Micromorphology and paleogeographical conditions of formations of the Horokhiv fossil soil complex of the Podolian upland

The Horokhiv fossil soil complex was formed during the Eemian interglacial and early interstadials of the Upper Pleistocene (MIS 5) within the Podolian Upland. It can be considered as a marking horizon which is quite easy to diagnose. During the Eemian interglacial forest soil was formed and during the early interstadials of the Upper Pleistocene, there were formed three low-thickness and mainly chernozems-like soils which were highly deformed by delluvial-solifluctional processes. These interstadial soils had been called the Kolodiiv soils. All the Kolodiiv soils currently are described only in the Proniatyn section on the Podolian Upland. In the most cases above the Eemian soil, there is the thick humus-accumulative horizon of the second phase Horokhiv soil are developed. It is hard to differentiate this horizon to the distinct soils. Furthermore, it is worth mentioning that on Podillia to the south from Ternopil-Khmelnytskyi latitude during the first (Eemian) stage of soil formation chernozems also were formed. Therefore, it is not always easy to distinguish separate soil horizons of the first and second phases in the profile of Horokhiv pedocomplex. The aim of this work is to investigate the characteristic features of micromorphological structure of the Horokhiv fossil soil complex and on its basis to find out the palaeogeographical conditions of the time when it was formed. A common method of micromorphological studies of fossil soils was used to achieve the goal.General lithological and micromorphological descriptions of the Horokhiv fossil soil complex in a number of key sections of the Podolian Upland are given in the article. The results of micromorphological studies indicate that the soils of the Horokhiv pedocomplex contain a significant amount of carbonate concretions (mainly microcrystalline forms of calcite), often ferruginous, with the numerous evidences of the ferruginous clay movement down the profile in the microstructure. The changing nature of the water-air regime was inherent to them. The nature and content of organic residues, the orientation of the clay material, and the presence of ferruginous manganese concretions make it possible to speak about sufficiently favourable conditions for the development of vegetation. Palaeogeographical interpretation of natural geographical conditions of the Horokhiv fossil soil complex formation based on the analysis of its microstructure allows us to conclude that the pedocomplex could be formed in the conditions of dry steppes and it is similar to modern chernozems. Key words: loess, fossil soil, Horokhiv fossil soil complex, micromorphological analysis, thin sections, Pleistocene, delluvial-solifluctional processes.