Changes in the soil properties under differently directed climatic fluctuations of the late holocene in the semidesert zone (by the example of the Palasa-Syrt burial mounds in Dagestan)

摘要

A chronosequence of soils in the area of the Palasa-Syrt burial mounds in the Republic of Dagestan is examined. It includes one paleosol under a kurgan of the Middle Bronze Age (end of the third-beginning of the second millennium BC), twelve paleosols buried at the end of the Late Sarmatian period-the beginning of the Great Migration period (second half of the fourth-first half of the fifth centuries AD), and two background soils. As shown by our study, desertification processes during the Middle Bronze period resulted in the replacement of the light chestnut soil by the brown semidesert soil. In the second studied chronointerval, the soils developed in the semidesert zone; however, the first half of this chronointerval was relatively humid, whereas the second half (in the fifth century AD) was more arid, which was reflected in the soil properties. The grouping of the Late Sarmatian paleosols with respect to their properties made it possible to arrange their chronosequence and, thus, to judge the time of their burial, which was confirmed by the archaeological data. The sequence of changes in the soil properties upon changes in the climatic conditions is identified. The first features that disappear upon humidization and reappear upon aridization of the climate are the features of salinization and solonetzic processes and the character of the biological activity. The C-14 age of carbonates also changes. These relatively quick processes are realized in 10-20 years, whereas the changes in the reserves of humus and carbonates require longer periods (supposedly, about 50-100 years).