ИСТИНА

The properties of buried soils reflect the paleoclimatic and ecological conditions of past eras. The study of these properties in pedo-chrono-sequences, the duration of functioning of which does not exceed several hundred years, allows reconstructing climate changes with the greatest possible accuracy for the studied period. The paleosols buried under burial mounds (kurgans) and surface soils were studied on the territory of the southeastern margin of the Russian Plain, in the Southern Cis-Urals (Orenburg region). Soils are developed on reddish-brown loess-like loam and sandy loam with an admixture of native rocks of the Tatarian stage of the Permian system. The buried soils were opened under 5 kurgans in the Krasikovo I kurgan cemetery, built by tribes of the Pit-grave archaeological culture in the second half of the 4th millennium BC. This is the earliest, Repino, stage of this culture in the Southern Cis-Urals. The main objective of our work was to study the properties of buried and surface soils of the cemetery and reconstruct the paleoenvironment conditions for the Repino stage of Pit-grave culture. Morphological and physico-chemical properties of soils (granulometric composition, contents of organic carbon, carbonate carbon and gypsum, magnetic susceptibility, cation exchange capacity) were studied, and micro-morphological analysis was performed. In addition to the soils’ properties, the 14C-dates of archaeological materials from burials were used to arrange a pedo-chrono-sequence. As a result of paleopedological analysis and radiocarbon dating, the studied kurgans in the cemetery were divided into three groups. The kurgan 1 was firstly built, and then 3 and 4, and 2 and 5 were the last. From the beginning to the end of the kurgan cemetery functioning and the successive construction of the kurgans on it, in the paleosols of the studied pedo-chrono-sequence intensification of the "arid" properties is observed. There is a decrease in the content of organic carbon and cation exchange capacity, and an increase in the carbonate carbon content, gypsum content and magnetic susceptibility values. According to the micromorphological analysis, the signs of mesofauna activity and the number of coprogenic aggregates in the upper horizons decrease in the studied pedo-chrono-sequence. In the lower horizons the degree of impregnation of the fine material with carbonates increases, and the variety of forms of carbonate accumulations becomes less. The Repino stage of the Pit-Grave culture was evidently characterized by increased aridization of climate, which is consistent with the previously obtained paleopedological data for this region.