CHARACTERISTICS OF THE CLAY FRACTIONS IN A CHERNOZEMIC TO PODZOLIC SEQUENCE OF SOIL PROFILES IN SASKATCHEWAN

Abstract

The clay fractions of four Saskatchewan soils ranging from Orthic Black to Orthic Grey Wooded have undergone small but significant changes as a result of pedogenic processes. The fine clay fractions (< 0.2 μ) are composed almost entirely of montmorillonite and illite which occur in a ratio of approximately three to one. Trace amounts of kaolinite and chlorite are present. Montmorillonite and illite, occurring in about equal amounts in the coarse clay fractions (2.0—0.2 μ), account for less than three-quarters of the total weights; kaolinite, chlorite and primary minerals make up the remainder of the fractions.The fixation of potassium by expanding-type clay minerals has resulted in an increase in illite content within the sola of all four profiles. Illitization is most pronounced in the Ah horizon of the Black soil. The chlorite content of the clays decreases within the sola of all profiles, the greatest decrease occurring in the Ae of the Grey Wooded soil, indicating more intensive weathering in the Podzolic than in the Chernozemic soil.Surface area and cation exchange capacity data substantiate, to some degree, currently held views on the close relationship between micas and expanding 2:1 layer silicate minerals in soils. The lack of preferential movement of montmorillonite within profiles in which marked clay translocation has occurred may serve as a good indication that montmorillonite and illite occur as interstratified clays and as such cannot move separately within these soils.