"Pimple" Mound Micro-Relief In Southern Saskatchewan, Canada

Mounds less than 1 m (3') high and up to 20 m (65') in diameter are generally referred to as "pimple mounds" in southern Saskatchewan. These low-relief mounds may be considered the northernmost documented occurrence of this geomorphological feature. When truncated by cultivation, former mounds are evident on aerial photographs as a pattern of small, light-toned patches contrasting with the surrounding darker soil. In many cases, these photographs are the only existing evidence of former mound topography. Using aerial photographs and direct field observation, the spatial distribution and characteristics of ten "pimple mound" sites were identified and mapped. Evidence of mound topography was found in the flat to undulating grasslands of the Canadian Prairie Ecozone and in the meltwater channels and gravelly outwash plains associated with glacial spillways. An examination of mound morphology and stratigraphy indicate that bioturbation by burrowing animals had a major impact on the size and shape of present day mounds. Statistical analysis of both intact and truncated mounds at the Little Manitou Lake Site, indicate that mounds form a more regular than random pattern, and suggest creation by bioturbative forces. Saskatchewan mounds were compared to the morphology and spacing of mounds from at least 30 other documented “mound” sites in North America. While most mounds had a greater relief and denser spacing, mounds from Texas, Wyoming and Colorado were most similar and also found in prairie landscapes with thinly developed soils and heavily disturbed by burrowing rodents.