Transformation Pathway of Carbonate Pedofeatures Based on Their Micromorhology and Carbon Isotope Data in the Northern Caucasus Region,Russia

Carbonate pedofeatures (CPs) in a chronosequence of paleosols buried under kurgans in the Northern Caucasus region of Russia in a period from the end of the 4th to the middle of the 5th centuries AD (It seams that there is no time left) were studied by using a set of morphological and isotopic methods. The CPs in chernozem-type soils of Russia are usually represented by crystallomorphic calcite whereas the non-segregated carbonates occurred at the same horizons-by collomorphic one. Those two morphotypes of calcite have the differences in elemental composition and isotopic composition of carbon and, hence, should have different origins-from true and colloidal solutions, respectively. The same differences including radiocarbon age have been revealed for pseudomycelium of the ABca horizon of the youngest paleosols as compared with the same CPs of other paleosols in the chronosequence studied. Our assumption is that it was succeeded in finding that the pseudomycelium right away after its precipitation from a colloidal solution migrated from the lower soil horizons to the surface horizons during the periods of climatic aridization. After a short time interval (not more than 25-50 years) collomorphic calcite in the pseudomicelium of the yongest paleosols mentioned above will likely become by "usual" acicular calcite.