Variations in the Properties of Chernozems and Paleoenvironmental Conditions in the North Caucasus in the 4th Millennium BC according to the Results of the Study of Essentuksky 1 Kurgan

摘要

A short-term chronosequence of paleosols buried under different structures in the big Essentuksky 1 kurgan (North Caucasus) was studied. The kurgan was constructed in the second quarter of the 4th millennium BC (the Maikop culture). According to archaeological data, the kurgan construction continued for several decades. During this time, the morphological pattern and physicochemical properties of soils changed: the thickness of the humus profile and the content of organic carbon decreased, the contents of gypsum and carbonates increased, the zone of their accumulation shifted upwards the soil profile, and the transformation of carbonate pedofeatures took place. The most "arid" properties were found in the soil buried last in the studied chronosequence: the humus horizon of this soil is the lightest in color and has the lowest organic carbon content; the soil profile is most enriched in carbonates, which is manifested both at the macro- and microlevels of observation; the highest content of exchangeable sodium and magnesium is noted in the composition of exchangeable bases; a decrease in the magnetic susceptibility and a maximum in the gypsum content are observed in the second meter of the soil profile. During the construction of the kurgan, Calcic Chernozems (Loamic, Pachic) evolved into Haplic Calcisols (Loamic). A palynological analysis revealed a decrease in the area of forest vegetation and an increase in the share of herbaceous vegetation in the spectrum, including the appearance of steppe species and xerophytes in the region over the studied time. The climate of the studied time interval (the early stage of the Maikop culture in the North Caucasus) was arid and warmer than that at present.