Regional Diversity of Mineralogical Composition of Solonetzes in Russia

Resumo

The quantitative and qualitative diversity of the clay fraction (<1 µm) from parent materials (BC and C horizons), albic (suprasolonetzic eluvial SEL) horizons, and clay-illuvial solonetzic (BSN) horizons of Solonetzes in different regions of the East European and West Siberian plains is described. The contents of smectitic phase (1.7 nm) (SM), illites (1.0 nm) (IL), and the sum of kaolinite and chlorite (0.7 nm) were calculated by the Biscaye method for all the samples. Overall, data on the mineralogical composition of 394 samples of soil horizons in 71 Solonetz soil profiles were summarized. The empirical statistical cumulative and differential distribution curves of clay minerals were obtained. The frequency of occurrence of different types of mineral distribution in the profile was assessed. It was found that Solonetzes do not have a single type of distribution of clay minerals in the profile because of the differences in the mineralogical composition of parent materials and soil forming conditions. The eluvial–illuvial distribution pattern of illites in the bulk soil mass (IL_SEL < IL_BSN > IL_BC) was the most frequent variant; its occurrence frequency varied from 25 to 65% in separate groups of Solonetzes and comprised 57% of the total data sample. Traditionally, the eluvial–illuvial distribution of smectitic phase (SM_SEL < SM_BSN > SM_BC) is considered to be typical of Solonetzes. However, its occurrence frequency varied from 10 to 30% in separate groups of Solonetzes and comprised just 20% of the total data sample.