Abstract

Sheetlike layers of sediment consisting of coarse clasts in a fine-grained matrix occur at the bases of steep meltwater-channel slopes north and northwest of Calgary. Individual layers are separated by thin organic horizons which are probably accumulations of water-transported burned organic matter. The deposits are interpreted to be products of a series of unchannelled water–sediment slurries created whenever heavy rains fell on denuded or destroyed grass cover stripping the soil from the steep upper parts of the valley slopes. Fire was most likely responsible for periodically destroying the grass cover. At least 24 erosion–alluviation events occurred in one of the channels in the last 15 000 years. These alluviation events seem to be the main process by which the meltwater channels are being infilled.

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