Polygenesis of Soils in the Mondy Basin (Eastern Sayan Mountains)

New data on the morphology and composition of solid-phase components of soils in the Mondy Basin are given. The soil profiles include features that correspond to the modern environment and relic ones inherited from past pedogenesis stages. The biogenic-accumulative distribution of Feox and Fed species and the absence of eluvial-illuvial profile redistribution of Fe in the middle horizons are revealed in both pale-yellow and cryoaridic soils. The analysis of the micromorphology of the BPL horizons shows that their atypically bright brown color is associated with enrichment in humus and iron oxides. These data are consistent with the pronounced rise in Fed compounds, which may be in general a relic feature preserved from more humid phases of soil formation. One of the important consequences of polygenesis of soils in the basin consists in the multicomponent carbonate profile: its particular components differ in genesis, morphology, and age. Multilayered thick coatings on coarse skeletal particles, the carbonate material of which is colored to different rates by Fe-humus compounds, are most common. Their stratification and radiocarbon age show that they are the most ancient secondary carbonates in the studied soils, reflect the long history of their profile differentiation, and indicate their polychronous formation. A long-lasting pedogenesis started in the Early Holocene, was characteristic of the basin side slopes, which were first free from the upper Pleistocene ice cover. The history of the soils in the central part of the basin is shorter and began about 6000 years ago due to the stabilization of exogenous relief-forming processes, accompanying deglaciation. The cryoaridic soils of the central part of the basin acquired their modern features about 3500 years ago at the stage of climate aridization, which caused the expansion of the area of steppe in the region.