Mineralogical comparative analysis of the clay fraction of solonetz and chestnut soil without apparent microrelief in the north-western part of the Caspian lowland

Abstract

A comparative analysis of the mineralogical composition of the clay fraction (< 1 μm) of chestnut soil and solonetz has been performed in the article. Soils were studied in the oldest part of the Caspian lowland in north-west where the microrelief is not quite apparent (microdepressions no more than 5–10 cm depth), but with a contrast soil cover. The content of silt fraction in chestnut soil varies from 25.6 to 33.9%, in the solonetz – from 11.7 to 51.6%. In all horizons of the compared soils, except for the upper surface horizons (SEL, AU1), mixed-layered minerals dominate (39–52% in the fraction) over illite (27–37% in the fraction). In the surface horizons illite (48%) dominates over mixed-layer minerals (35%). The compared soils have some similarities in their crystal-chemical state: the imperfection of the kaolinite structure and the superdispersed state of the mixed-layer phase in the upper horizons, as well as the appearance of individual smectite and chlorite packets in the mixed-layer phase in the lower horizons (BC, C). The degree of perfection of the kaolinite structure both in the solonetz and in the meadow-chestnut soil increases towards the bottom of the profiles. The obtained data allow suggesting that in the meadow-chestnut soil the clay phase retained traces of the solonetzic stage of soil formation.

Keywords

• chestnut soils
• solonetz
• mineralogical composition
• dry steppe complexes
• caspian lowland