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This study focuses on a short-term pedochronosequence of Kurgan № 1 at the Boldyrevo IV kurgan cemetery in the Orenburg Region of the Southern Cis-Urals. According to archaeological findings, the kurgan was built over several decades by people of the Yamnaya (Pit-Grave) culture of the Early Bronze Age (around 5500 BP), with the exact time of its building to be confirmed by radiocarbon dating and further archaeological information. A comparative analysis of the four earthen constructions of the kurgan and the paleosols buried under those constructions was conducted. Results suggest that the kurgan building period was accompanied by the following changes in paleosol morphology and physicochemical properties: the humus horizon acquired a tonguing-like lower boundary, decreased organic carbon content and magnetic susceptibility, while the whole profile was characterized by increasing degree of zooturbation; the impregnation by carbonates in the middle part of the profile and the contents of carbonate carbon, gypsum, and exchangeable sodium increased. Similar trends of morphological and physicochemical changes were observed in the materials of the kurgan constructions. Based on these findings it can conclude that the climate went through aridization rise during the period of the kurgan building. The paleobotanical data from palynological and microbiomorphic analyses indicate that there was a tendency for paleoclimate aridization and, possibly a cooling trend during the studied period of the Yamnaya culture, which was probably more arid than the modern climate.

<p>Geoarchaeological studies of soils buried under burial mounds (kurgans) and materials of kurgan structures make it possible to solve a wide range of scientific problems. In the steppe zone of Russia, such studies are carried out in order to determine and compare the composition of buried soils and materials of kurgan structures, as well as to study the structure of earth monuments and to obtain data on the technology used by ancient people for their building.</p><p>We carried out geoarchaeological studies in two key areas: in Krasnodar (kurgan Beisuzhek 9) and Stavropol (kurgan Essentuksky 1) regions. For each object, the particle-size distribution and physicochemical properties of the earthen materials of the kurgans and buried soils were investigated.</p><p>Kurgan Essentuksky 1 was built in the second quarter of the 4th millennium BC (Maykop culture) according to a single plan in a short time (several decades). The kurgan with a height of 5.5-6.0 m and a diameter of 60 m consisted of four earthen and three stone structures. The earthen structures consisted of alternating layers of dark, slightly compacted humified and light dense carbonate-rich material that were taken from buried soils, i.e. dark material from the Ahkb and AhBkb horizons, and light material from the B1kb horizon. This is confirmed by similar changes in the physicochemical properties of paleosols and overlying kurgan structures. A decrease in the organic carbon content and an increase in the content of calcium carbonate, values of pH<sub>H2O</sub> and magnetic susceptibility from the first to the fourth paleosols predetermined similar changes in the materials from the first to the fourth earthen structures (from the center to the periphery of the kurgan).</p><p>In the Beysuzhek 9 kurgan, three earthen structures of different ages were identified: the first and the second - the middle of the 2nd millennium BC (Novotitorovsk culture), the third construction - the beginning of the 2nd millennium BC (Catacomb culture). Each of the subsequent structures overlapped and went beyond the boundaries of the previous one: the second overlapped the first and also untouched soil next to the first; and the third overlapped the second completely and also overlapped previously uncovered soil next to the second structure. The height of the kurgan was more than 4 m, the diameter - about 100 m. The material of each structure was a soil mass from the middle horizons of the buried soils, most likely the Bkb horizon. Samples from the kurgan structures were taken from one column in the middle of the central baulk. Physicochemical analysis of paleosols and earthen structures overlying them showed a decrease in the content of organic carbon and magnetic susceptibility, an increase in the content of carbonate carbon and pH<sub>H2O</sub> from the center to the periphery of the kurgan.</p><p>According to the results of the physicochemical properties of paleosols and materials of both key areas in the second half of the 4th millennium BC there was a climate change in the study region - the average annual temperatures increased and the amount of precipitation decreased.</p>

A geoarchaeological study of the large Essentuksky 1 kurgan in the Stavropol region of Russia analyzed the chemical composition and micromorphological features of the kurgan's earthen materials and established their relationships with buried soils in the context of previously conducted paleoclimatic reconstructions. The kurgan was 5.5-6.0 m high and more than 60 m in diameter, and consisted of four earthen and three stone constructions. It was built in the second quarter of the 4th millennium BC (the Early Maykop culture) using a precise plan and utilizing the building skills and technologies available at that time. The earthen constructions consisted of alternating layers of dark-colored slightly compacted humified and pale-colored dense carbonate-rich materials, which, in the moist state, were rammed down by ancient builders. These materials were sourced mainly from local soils and contained admixtures of river silt and, at the final stage of building, dung. The physicochemical properties of the earthen constructions as well as the paleosols buried under them are indicative of a short-term aridization of the climate within the period of building. A gleyed earth with strong iron staining at the kurgan's base and mortar that held the stone constructions was produced by thoroughly mixing and compacting in a wet state, indicating that they were special construction materials. This kurgan is an example of the ancient earth architecture in the steppe zone of Russia over 5500 years ago.