A MICROMORPHOLOGICAL STUDY OF CALCAREOUS SOIL HORIZONS IN SASKATCHEWAN SOILS

Abstract

The nature and distribution of carbonates in calcareous horizons from several Saskatchewan soils were examined micromorphologically. Carbonate minerals were found to occur in several distinct forms which included skeletal grains and plasma, cutanic accumulation, glaebular separations and crystallaria. Carbonates which occurred as individual grains consisted of calcite and dolomite, inherited from the original parent materials. However, finer crystallites of secondary origin within the plasma were also observed. Maximal accumulations of secondary carbonates within the plasma, as evidenced in a Turkish soil, imparted a crystic plasmic fabric to the horizon. Cutanic accumulations were observed as cutans (calcans, carbonatic argillans), neocutans (neocalcitans) and as quasicutans, the latter occurring subcutanically to natural ped surfaces or void walls. The cutanic accumulation forms were most pronounced in Cca horizons of well-drained soils. Three types of carbonatic glaebules were observed in the soils studied. Those with sharp boundaries were associated with dry environments whereas those with diffuse boundaries appeared to be related to soils developed under more humid conditions. A third form, sesquioxidic carbonatic glaebules, were evident in soil horizons affected by poor drainage. Biorelicts, in the form of individual shell fragments, lithorelicts as original calcareous rock fragments, and crystallaria in the form of intercalary crystals and acicular crystals within tubes were other types of carbonates found in the soils studied.