The outermost Keewatin moraines, within sight of the Rocky Mountains, are as youthful topographically as is the Late Wisconsin Altamont terminal moraine in eastern Alberta and western Saskatchewan. Differences in outline of the ice front, however, indicate that all moraines west of the Altamont are the product of an earlier advance. The moraine pattern records a southern Alberta convexity or lobe, limited on the west by the foothills of the Rocky Mountains and on the south by the Arctic Ocean-Gulf of Mexico divide. A complicated succession of melt-water dischargeways and associated glacial lakes is intimately related to the moraine succession. Escape of all this drainage was across the divide and to the Missouri River in Montana. Correlation of discontinuous moraine units is possible because drainage held close to the edge of the Keewatin ice sheet as it retreated down the slope of the Great Plains. Moraine outside (higher than) any one drainage channel thus is older than moraine inside (lower than) the channel.

First Page Preview

First page PDF preview
You do not currently have access to this article.