Subkurgan Paleosoils of the Lower Volga Steppes as Indicators of Climate Dynamics over an Historical Epoch

The studies of paleosoils buried beneath burial mounds of the Early, Middle, and Late Sarmatian time (4th c. BC to 4th c. AD) were carried out in the dry and desert steppes of the Lower Volga river area (the Volga and Yergenino uplands, the Caspian lowland). It was established that within the chronological interval of 2400–1600 years ago temporal variability of morphological, chemical, microbiological, and magnetic properties of paleosoils was rhythmical, being conditioned by the centennial dynamics of climate humidity with oscillations of mean annual precipitation rate within ±30–50 mm. The periodic change of humid and arid climatic epochs considerably influenced soil salinization-desalinization, solonetz and humus formation processes, and biological activity of paleosoils of the solonetz alkali soil complexes. This stimulated essential changes in the structure of the soil covering with reversal evolutionary transformations of paleosoils on the levels of types, genera or species within several decades. The natural conditions within the existence of the Sarmatian culture society may be characterized as alternation of micropluvial and microarid periods with 100–200-year duration. In particular, both in dry (Volga-Don interfluve) and in desert (Trans-Volga) steppes, the 1st c. BC, AD 1st and 4th cc. were characterized by relatively humid conditions, while the 4th–3rd cc. BC and second half of the 2nd to first half of the 3rd cc. AD were most arid. Intermediate humidity situation close to modern time was characteristic of the period from the first half of the 2nd to the second half of 3rd century AD. The evolution of climatic conditions is generally consistent with the rhythms of natural processes in other steppe and desert regions of Eurasia.