ИСТИНА

A detailed analysis of a soil chronosequence located in well drained upland positions within broadleaf subzone of the Russian plain was performed to investigate the possible transformation of pedogenic pathways related to the climatic changes during the Late Holocene. The soil chronosequence included a soil buried under fortification (earthen) wall constructed in Early Iron Age and a day surface soil developing under natural (broadleaf forest) vegetation. Different pedogenic processes were evaluated using a number of methods including elemental geochemistry. The field examination of the two soils showed similar morphology of the soils that were classified as Retisols. For more detailed conclusion we used the quantitative comparison of their horizons on the basis of major and minor element chemistry determined by XRFS analysis (29 samples) and physicо-chemical data on organic matter content, C/N ratio, calcium carbonate content, pH, grain-size distributions, the concentrations of “free” and “active” iron compounds. For many of geochemical parameters (concentrations of elements, their depth distributions), related to the textural differentiation, we found the similarity. The revealed differences between the surface and buried soils include (i) the signals of anthropogenic impact that have been preserved and were chemically detected in the upper horizons of the buried soil and (ii) the signs of diagenetic transformations after the soil burial that were manifested in accumulation of carbonates and a decrease in humus content. Paleoclimatic signals in the modern surface soil can be derived from better expressed and deeper skeletons and higher Si/Al ratio, indicating progressive development of retic properties. The development of these features indicate that in this area, located at the southern boundary of the forest zone, during the considered time period, the soils experienced a one way evolution due to the relatively stable character of landscape conditions that was also supported by the results of phytolith analysis. However, the study of “free” iron contents and Mn distribution in the paleosol revealed slightly wetter conditions of the soil development and phytolith data implied that forest vegetation could have had mixed deciduous-coniferous composition.