Glacial stratigraphy of northern and central Manitoba

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Stratigraphic sections exposed along river banks and road cuts, and in boreholes across northern Manitoba, reveal a record of multiple glaciations and at least two interglaciations. The sections in northeast Manitoba contain the most complete records, whereas those in the west more commonly relate to late Wisconsin events and ice retreat phases. Evidence exists for separate early Keewatin and Labradorean ice flows that extended father south and west than those of the late Wisconsin glaciation. During the late Wisconsin glaciation, carbonate content in the upper till suggests an intermingling of Keewatin and Labradorean ice in the area, and a shifting zone of convergence that ultimately lay along the Etawney-Settee moraine. Small amounts of matrix carbonate and limestone clasts in the uppermost till sheet in the Leaf Rapids area are thought to have been incorporated from underlying tills. There is a record of several readvances of Keewatin and Labradorean ice into Glacial Lake Agassiz, both of which incorporated calcareous glaciolacustrine silt into the upper till unit.