Our studies have shown that the initially homogeneous red-earth deposits serve as soil-forming rock for both well-differentiated and slightly differentiated soils. The textural differentiation of the soil profile is governed by the destruction (acidic hydrolysis) and lessivage of clay minerals; it is also accompanied by deep transformation of clay minerals (from chlorite to vermiculite). The weak differentiation of the soil profile is the result of metamorphic transformation of the soil-forming material with some browning of the topsoil and low intensity of lessivage processes. Different tendencies in the soil formation are related to the mineralogical composition of the red-earth deposits. The presence of carbonates and the relatively high hematite content (responsible for the bright red color of the deposits) prevent soil differentiation. Slightly differentiated raw-humus brown taiga soils (burozems) are developed in the case of the shallow occurrence of calcareous material (calcite, dolomite) or in the case of carbonate-free heavy clay substrate with a predominance of hydromicas in the fine silt and clay fractions. Well-differentiated podzolic soils are formed on loamy carbonate-free or deeply (>100 cm) calcareous red-earth deposits with the clay fraction represented by mica-smectitic minerals.