Short chronosequences of paleosols from the Skvortsovka kurgans in the Buzuluk River valley of Orenburg oblast.

摘要

Paleosols buried under kurgans of the Yamnaya (the third millennium BC) and Srubnaya (the 18th-17th centuries BC) cultures within the Skvortsovka group of kurgans in the Buzuluk River valley in Orenburg oblast have been studied. This is the area of the dry steppe zone. The changes in the paleosol properties make it possible to distinguish between relatively short-term chronointervals separately for the Yamnaya and Srubnaya cultures. The paleosol data and radiocarbon dating have been used for revealing the relative order of the construction of the kurgans within these chronointervals and for the paleoclimatic reconstruction. Quite definite changes took place in the soil formation from the beginning to the end of the particular chronointervals: the contents of humus and exchangeable bases and the portion of calcium ions in the composition of the exchangeable cations increased in parallel with the enhanced leaching of carbonates and the enhanced biological activity. These changes attest to the increasing amount of precipitation. In general, the climate of the Srubnaya cultural epoch was less continental, whereas the climate of the Yamnaya cultural epoch was relatively close to the modern climate. The 14C dates of the pedogenic carbonates in the upper meter of the paleosol profiles have been used as auxiliary data to confirm the sequence of the soil's burial during the short chronointervals corresponding to the humid stages of the paleosol's evolution, and the 14C dates of the diagenetic carbonates have been used to determine the dates of construction of the kurgans with due account for some time gap between the construction of the kurgans and the appearance of these carbonates in the buried soil profiles.