Glacial Lake Great Falls and the Late-Wisconsin-Episode Laurentide Ice Margin

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Stratigraphic sequences containing sediments related to the glacial Lake Great Falls are exposed within the Missouri River valley in the region extending from around Helena to east of Great Falls, in west-central Montana (cf. Alden 1932; Calhoun 1906; Feathers and Hill 2011; Hill 2001; Hill and Valppu 1997; Lemke 1977; Lemke and Maughan 1977; Maughan 1961; Maughan and Lemke 1991; Montagne 1972; Robinson et al. 1969; Schmidt 1972, 1977, 1986; Stickney 1987; Vuke et al. 1995). The sediments were deposited in a lake formed when the Missouri River was blocked by a lobe of the Laurentide Ice Sheet (LIS). Direct dating of sediments using luminescence measurements appears to support a late-Wisconsin age for these stratigraphic sequences. This implies that a lobe of the LIS advanced into northern Montana and reached the present-day location of the Missouri Valley during the Last Glacial.

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