The margin of a former Laurentide ice sheet is traced through southern and central Alberta, from the Saskatchewan border southeast of Medicine Hat to beyond Rocky Mountain House, southwest of Edmonton. This margin, which marks the limit of a significant glacier advance or readvance, is thought to represent the maximum extent of Laurentide ice on the Canadian prairies during Classical Wisconsin time. In the south this margin follows a well-developed hummocky moraine; in the north it is indicated mainly by a discordance in trend of ice-flow markings, a disruption of drainage, and a change in maturity of topography on either side.

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