The Mineral Composition of Fine-Dispersed fractions (<1, 1-5, 5-10 μm) of agro soddy-podzolic soils with complicated organic profile in Kama River area within Vyatka region

Abstract

The mineral composition of the fine fractions (<1, 1-5, 5-10 μm) is investigated. These fractions were separated from agro soddy-podzolic soils (Eutric Retisol Episiltic, Endoclayic, Aric, Cutanic, Greyzemic) with the second humus layer, which were developed on the clay loam mantle of silty large pulverescent clay loams of driftless area of Kama River area within Vyatka region. The soils have texture differentiation according to eluvial and illuvial type due to <1 μm fraction. The mineral composition of a fraction <1 μm of clay loam mantle is presented by complex interstratifications with mixed layers. They are characterized by segregation of the following packs: smectitic, micaceous, chloritic, and vermiculitic. Hydromicas, smectite, kaolinite, and chlorite are present among the individual minerals. Podzol formation led to the changes of correlations of the major mineral phases and the type of structure of formations with mixed layers. The increasing of hydromicas and chlorites occurred within the eluvial part of the profile. Individual smectite and mica-smectites disappeared. The type of alternation of packs of 1.4 nm phase of the fraction also changed: this phase is presented by chlorite- vermiculite instead of mica-smectites. mica-smectite neoformations along with chlorite- vermiculite are presented within the transitional horizon BEL. Their number is increased downwards the profile, and reachs its maximum within the BT1 horizon and parent material. The higher content of individual smectite and chlorite is marked within the deposits of Kama River area within Vyatka region in comparison to clay loam mantle of Klin-Dmitrov Ridge. The distribution of fine silt fraction (1-5 μm) has a very complicated character: equal content within the parent material and the upper layers, and the minimal content at the BT horizon in the middle part of the profile. It is a result of the particulate outflow of the fine silt fraction from the eluvial part of the profile. The outflow of fine silt fraction is lower than the outflow of clay. The total relative decrease of 1-5 μm fraction is due to eluvial-illuvial distribution of the clay fraction. The mineral composition of fine silt fraction sharply differs from that of <1 μm fraction by the significant quartz content and potassic feldspars. The highest amount of potassic feldspars is observed within AELhh horizon. The following fact may be specified in distribution of layered silicates: the eluvial part of the profile includes hydromicas, kaolinite, chlorite, and chlorite-vermiculite interstratifications. Downwards the profile there are observed chlorite-smectite interstratifications. Their maximal amounts were detected within the carbonatic part of the profile BCca,nc,dc from the depth of 115-125 cm.