The plains of western Canada contain dozens of saline and hypersaline lakes which range in size from small (< 1 sq km) prairie “potholes” to relatively large (> 300 sq km) bodies of water. The shallowest lakes exhibit playa characteristics, flooding with water during the wet season but drying up during the summer and fall. The sediments of these lakes are composed of a mixed suite of siliclastics, carbonates, and evaporitic minerals. The major detrital minerals are quartz, dolomite, feldspars, and clay minerals. The authigenic carbonate minerals are aragonite, normal calcite, and high-Mg calcite. Evaporitic minerals include mirabilite, thernardite, gypsum, and bloedite.
Spatially, the modern subenvironments in these basins usually exhibit a roughly concentric distribution, with a saline mud flat/sand flat occurring nearest the shore, followed by an ephemeral lake zone, and possibly a perennial lake. Although differing in scale and stage of development from basin to basin, all of the lakes have roughly similar near-surface stratigraphic profiles and facies distribution. The upper 25 to 50 cm consist of a thin (1 to 5 cm) crystalline crust overlying a thicker (5 to 50 cm) layer of mirabilite-thernardite-bloedite mush. Salt crust development, growth of large, euhedral mirabilite crystals, surface desiccation, and mineral dissolution all operate to create an extremely dynamic near-surface environment on a diurnal and seasonal basis. Underlying these upper units is a zone of relatively dense salt crystal with minor mud interbeds. This unit can range in thickness from < 1 m to > 40 m. Finally, underlying this dense crystal layer is a black, highly reducing, organic-rich, muddy clastic unit with variable salt crystal content.