MICROPEDOLOGY OF THE MAJOR PROFILE TYPES OF THE WEYBURN CATENA

Abstract

Orthic and Eluviated Dark Brown and Humic Eluviated Gleysol soils occurring within a catena of the Weyburn association, in Saskatchewan, were studied by means of thin sections. The Ah horizons are characterized by chernozemic microfabric but the size of peds increases in going from the Orthic Dark Brown to the Humic Eluviated Gleysol profile. The Ae horizon of the Eluviated Dark Brown exhibits very coarse platy microstructures whereas the plates are much finer in the banded fabric of the Humic Eluviated Gleysol Ae. Clay accumulation was least in the Orthic Dark Brown and greatest in the Humic Eluviated Gleysol. Orientation of clays is most pronounced in the upper B horizons of the Chernozemic soils whereas in the Gleysolic soil the orientation is most pronounced in the lower B horizon. Oriented clays occur both within peds and as coatings on the surfaces of peds. These coatings, illuviation cutans, are thin and discontinuous in the B horizon of the Orthic Dark Brown, somewhat better expressed in the Eluviated Dark Brown, and most pronounced in the Humic Eluviated Gleysol. The prismatic structures apparent in the B horizons break down into blocky aggregates which decrease in size from the Orthic Dark Brown to the Humic Eluviated Gleysol. The intensity of weathering which the different soils have undergone during their formation is reflected in their micromorphological features.