The soil layer of littoral steppe landscapes has a common structural scheme regardless of the soil type, from arid soils on eluvial slopes to humid soils of accumulative depressions. The aim of this work is to define the conditions of soil formation at the bottom of the steppe littoral catena. Miсrobiomorphic analysis, granulometric composition and carbon dating of soil were employed. The study was carried out in the North Kulunda lacustrine-alluvial plain located in the southern part of the West Siberian lowland within the Ob-Irtysh interfluve. The horizon morphology of the studied soils is described. Microbiomorphs were found to be of indicative value in reconstructions of soil profile formation conditions; photographs are provided. A qualitative and quantitative assessment of phytoliths, sponge spicules and diatoms was performed. The granulometric composition of the soil profile has a binomial distribution that refers to a specific synlithogenic stage of its formation. The upper, sandy and sandy-loamy part of the profile corresponds to the alluvium (0-45 cm). The lower part (below 45 cm) is buried soil of loamy and heavy loamy granulometric composition. Miсrobiomorphic data from light-humus stratozems enabled the detection of multiple water level fluctuations in the Lake Bagan. This led to a succession of steppe, meadow and reed vegetation complexes within the littoral zone. The microbiomorphic spectrum corresponds to 1920 ± 80 BP, reflecting an arid climatic period within the Subatlantic episode of Holocene. The absence of phytoliths and the presence of sponge spicules in the accumulative-carbonate horizon of light alkali soils bears evidence of periodical moistening of the surface at the time of its formation. There was also a redeposition of water-flow, which is consistent with the considerable particle size distribution of the horizon. Our findings confirm the common evolutionary and genetic relationships of littoral accumulative and transitonal accumulative landscapes.