Mineralogy of Soils Developed in Periglacial Deposits of Southwestern Canada

Abstract

AbstractParent materials of glacio‐lacustrine soils, Holocene loess, glacial rock flour, and slate samples from Alberta, Saskatchewan, and Red River plain were characterized mineralogically by X‐ray diffraction (XRD) and chemical techniques. The texture became finer and the fine clay/coarse clay ratios higher (0.5 to 3.6) in progressing from the overthrust mountains, to nearby loess, then to glacio‐lacustrine materials. The clay mineral distribution illustrated lithological, geomorphological, and weathering relationships. The XRD peak broadening indicated weathering to irregularly interstratified phyllosilicate minerals in Holocene loessial materials originating from fresh rock flour carried by the Athabasca River flowing out of the mountains near Jasper. The smectite content increase (4 to 34%) and the mica content decreased (52 to 20%) from near the overthrust mountains to the glacio‐lacustrine plains overlying nonmarine and marine sediments. Mica, smectite, and chlorite (8–20%) constituted the predominant minerals in the clay fractions. Smectite was the most abundant (20–34%) mineral in the clay of the glacio‐lacustrine materials, particularly in the <0.2‐µm fractions (60–85%). This was attributed mainly to glacial movement of weathered ash‐falls of Cretaceous sedimentary provenance. Some vermiculite (5–10%), kaolinite (3–11%), fine or poorly crystalline materials (4–14%), quartz (4–10%), and feldspars (1–2%) were also present. Chlorite, detrital mica, and sodic feldspar in both the clay and silt fractions indicated significant contributions for metamorphic and diagenetic source rocks to all samples, including the most distant “macro‐composite” glacio‐lacustrine samples.