Frenchman Valley extends about 340 km from the Cypress Hills, Saskatchewan, to its confluence with the Milk River in Montana. In one area, the valley is 3 km wide, and it was 180 m deep prior to deposition of as much as 80 m of landslide debris, channel sand and gravel, and alluvial and colluvial deposits. Six radiocarbon ages ranging from 3440 to 11 460 BP suggest the Frenchman Valley is Wisconsinan. The Frenchman Valley could not have formed in its side-hill position if Late Wisconsinan ice had not been present south at the Cypress Hills.

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