Paleoclimatic reconstructions based on the study of structures of large kurgans of the Bronze Age and soils buried under different structures for the steppe zone of Russia

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.

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.

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_H2O 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).

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_H2O from the center to the periphery of the kurgan.

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.