The Diagnostic Horizons Argillic horizons are horizons of accumulated translocated silicate clays. When a thin slice of an argillic horizon is viewed under a polarizing microscope, the presence of translocated clay is confirmed. The yellow areas in this thin section are the translocated clay-skins or cutans.
Natric horizons are argillic horizons that have high amounts of exchangeable sodium.
They frequently have columnar soil structure. The tops of the columns are sometimes bleached, as shown here due to clay removal. Calcic horizons have pronounced accumulations of calcium carbonate, or of calcium and magnesium carbonate. They are normally very light in color and must meet specific criteria of carbonate content and thickness. Gypsic horizons have significant accumulations of gypsum.