Continental/Cordilleran ice interactions: a dominant cause of westward super-elevation of the last glacial maximum continental ice limit in southwestern Alberta, Canada

In southwestern Alberta, Canada, a westward-rising last-glacial-maximum con tinental ice limit has been identified. This limit is defined by the upper elevation of Canadian Shield erratics deposited by last-glacial-maximum con tinental ice along the flanks of prominent ridges and buttes within the reg ion. The interpolation be tween ice-limit data points has produced two dist inct slope profiles: 2.9 m/km to the east, and 4.2 m/km to the west of Moko wan Butte, Three hypotheses are proposed to explain this westward rise of t he last-glacial-maximum continental ice limit: (1) regional tectonic uplift , (2) glacio-isostatic uplift, and (3) continental ice-flow convergence due to topographic obstacles and interaction with montane ice. Inferred long-t erm rates of tectonic uplift and glacio-isostatic modelling show that these two mechanisms account for less than 25% of the observed absolute elevatio n increase of the limit between the Del Bonita uplands and Cloudy Ridge in southwestern Alberta. The remaining rise in elevation of the continental ic e-sheet margin in this region is thought to result from continental ice flo w convergence due to the combined effects of the regional topography and in teraction with montane glaciers to the west. The steeper rise in the former continental ice surface west of Mokowan Butte can be explained by the topo graphic obstruction and interaction with montane glaciers in the area of th e Rocky Mountain front.