Natural conditions of paleosol formation in the first third of the subatlantic period in Baturino section (Southern Ural)

The aim of this article is to analyze characteristics of the paleoenvironment of the sub-Atlantic first third period identified on the composition and properties of paleosols and soil components on the example of a local area within the modern southern forest-steppe of Southern Urals. Pedohumus method, suggested by M.I. Dergacheva, was used for the reconstruction of pedogenesis conditions with applying of database available for the group of authors on ecology-humus relations in modern soils. The age of paleo- sol humus horizon in Baturino quarry is 2073 ± 259 years (NSKA) and 2132 ± 89 years (NSKA) according to radiocarbon dating of humic acids. The morphological structure of the sub-Atlantic soil allowed its attributing to analogues of chernozems on the bases of all inherent in this type of soil horizons with the appropriate characteristics. The paleosol was formed on two-layer sediments, detectable primarily in particle size distribution and magnetic susceptibility. The upper strata of paleosol differs from the lower in more acid reaction of soil solution, the lack of carbonates and another composition of exchangeable cations. The conditions of paleosol formation period were diagnosed on the basis of the reconstructed humus content, its humate composition, ratio of the structural elements in the composition of humic acids, values of optical density, the color coefficients, and the first moment in the luminescence spectra. They were similar to modern conditions of chernozem functioning in the southern forest-steppe zone or the northern part of the steppe. Climatic conditions were favourable for the steppe soil formation on the local area within the modern southern forest-steppe of southern trans-Uralian at the beginning of the sub-Atlantic period. In comparison with the current conditions, the climate might have been slightly warmer and characterized by moderate humidity.