GEOCHEMICAL EVOLUTION OF SOILS DEVELOPED ON LOESS LOAM IN THE HOLOCENE
L.N. Ryabova
E-mail: vkuzn@ns.igs.ac.by
E-mail: vkuzn@ns.igs.ac.by
Geochemical investigations of Holocene soils on loess loam allow the following conclusions to be drawn. A soil profile including the secondary humus horizon bear records of 5 stages of the soil evolutionary development, each of them being of importance for the soil formation and influencing its morphological and geochemical properties.
The Late Pleistocene cryogenic stage was responsible for banding formation (whitish and pale-yellow layers) in the lower part of the mineral profile. The major pedogeochemical process was the eluvial-illuvial redistribution of clay particles, Fe, Ca, Mn and trace elements within the B horizon.
At the Early Atlantic stage the soil profile differentiation into the eluvial (podzolic) A2 and illuvial B1 horizons took place. Fe, Al, Cr, Co, V, Ni, Ti were partly removed from soil and partly redeposited, but Ca and Mg were intensively enleached.
During the Late Atlantic stage the humate-calcium organic substance was accumulated and intensive biogenic deposition of Fe, Al, Ca, Mg, Mn, Cu, Pb, Cr occurred.
The Subboreal stage resulted in the formation of the secondary humus horizons, replacement of the humate-calcium organic substance by the present-day humate-fulvate or fulvate-humate one. During this epoch an insignificant biogenic deposition of Mn, Cu and Fe, Mg, Ca, Al, P, V, Ni, Cr removing from the eluvial soil part took place.
The Subatlantic stage was responsible for the biogenic deposition of P, Ca, Mn in the sod and Mn, Al, Cu, Ti, Cr in humus horizons. During this time Fe and Al were washed from the top part of the soil profile.
The studies carried out suggest that the climatic fluctuations during the Holocene had influenced the intensity of processes of the sedimentary material transformation under the influence of pedogenesis. This influence was manifested in changes of morphological, granulometric and geochemical soil properties. Similar investigations are of importance for forecasting the soil evolution, intensity of the element migration and accumulation when the bioclimatic parameters and hydrological regime are changed.