Soil-Archaeological Study of the Votikeevo Medieval Archeological Site in the Northern Forest-Steppe Zone of the Southern Cis-Ural Region

Abstract

Soil-archaeological studies were performed in the area of the Votikeevo archaeological site dating back to the Bakhmutin culture of the early Middle Ages (5th–7th centuries AD) and located 30 km north of Ufa (Bashkortostan Republic), in the northern forest-steppe subzone of the southern Cis-Ural region. Soil morphology and properties were examined, parameters of the structural state of humic acid molecules were determined using 13C NMR spectroscopy, and the major elementary pedogenic processes were identified. Light clayey dark gray soils (Phaeozems) predominate in the studied area. Their humus horizons of up to 51 cm in thickness are characterized by the organic carbon content of 1.5–3.6%, neutral reaction, cation exchange capacity of 29–35 cmol(+)/kg soil, and a predominance of exchangeable calcium. The soils of the archeological site are rich in total phosphorus in the upper 50 cm (up to 4631 mg/kg), which is related to the living activity of ancient humans, but does not have a significant impact on the contents of available phosphorus and potassium and alkaline-hydrolyzable nitrogen. Lenses of a lighter color with an admixture of fine sand, fragments of pottery, and bones were found at the depth of 30–42 cm. They represent the material transported by ancient humans and are characterized by an increased total phosphorus content (up to 7295 mg/kg soil) and higher values of electrical resistance (1130 Ω m) in comparison with the enclosing mass. The analysis of 13С NMR spectroscopy data demonstrated the presence of humic acids with a strong peak of aromatic compounds of substituted and unsubstituted types in the humus horizon and in the material moved by ancient humans. These compounds are associated with the polymerized structures of macromolecules of humic substances, which is typical of chernozems. The functioning of this archaeological site coincided with the period of climate warming in the Early Subatlantic period.