David S. Fullerton

Stratigraphy and correlation of the glacial deposits on the Montana Plains

Till units representing at least three pre-Illinoian continental glaciations, at least one Illinoian glaciation, and a late Wisconsin glaciation have been identified on the Montana Plains. Early Wisconsin or middle Wisconsin till units have not been identified. The southernmost limit of late Wisconsin glaciation is in Montana, more than 170 km south of the Lethbridge moraine in Alberta, Canada (Figs 1 and 2). An interpretation that the Lethbridge moraine is the limit of late Wisconsin glaciation (Stalker, 1977, 1980, 1983b; Stalker and Harrison, 1977; Rutter, 1980, 1981; Jackson, 1983) is incompatible with stratigraphic and morphologic evidence from Montana.

Limits of mountain and continental glaciations east of the Continental Divide in northern Montana and north-western North Dakota, U.S.A.

Publisher Summary This chapter provides an overview of the limits of glaciations and glacial history in, and east and south-east of, Glacier National Park, Montana, and on the Northern Plains further east in Montana and north-western North Dakota. The term “Laurentide glacier” was applied to a continental ice sheet east of the Rocky Mountains in North America. It describes Laurentide Ice Sheet as any Quaternary continental ice sheet east of the Rocky Mountains in the United States and Canada. Laurentide till refers to till deposited by a Laurentide Ice Sheet. A Laurentide continental ice sheet is distinguished from a Cordilleran continental ice sheet in the Cordilleran region in parts of Washington, Idaho, and Montana in the United States and in adjacent Canada. Clague indicated that Cordilleran Ice Sheets formed several times during the Pleistocene. The chapter also reviews that the base for the digital map is simplified. Selected hydrographic features, selected towns and cities, selected physiographic features, and a grid of 1° × 2° topographic quadrangles are included to aid the reader in location of the glacial limits and other features depicted here on other maps at different scales.