The regional climate of western and northwestern U.S.S.R. is favorable to podzolization, yet Podzols are interspersed with Brown Forest-Lessivé and Brown-Pseudopodzolic soils in the area. These last two soils, commonly classified as subtypes within the type of podzolic soils, have formed because of medium- to fine-textured Quaternary materials in which “geochemical sieves” have been caused by carbonates, or by double layering of somewhat coarse over finer deposits. The processes of lessivage and pseudopodzolization, by which these two soils formed, have altered and translocated materials within the solum, whereas the podzolization process actually sweeps significant quantities of material out of the solum.