In the Canadian Northwest Territories west of Hudson Bay, the postglacial marine transgression was more extensive than in any other part of North America. Although there are numerous isolated observations of strand lines and other raised marine features, there has been no systematic study of the maximum depth of this sea and the form of the subsequent emergence of the land.

Measurements made during 3 summer's field work in the area show that on the mainland the sea reached a depth of 360–400 feet. On the islands in the north of Hudson Bay the depth was 550–650 feet. The difference is explained by unequal waning of the ice sheet. In the western part of the Thelon and Dubawnt basins a large proglacial lake preceded the invasion of the sea. The lake fell by clearly defined stages. Subsequent emergence from the sea was continuous until the final 100 feet when there were two periods of temporary stability. There is widespread evidence that the land is still rising.

In the areas that were submerged, unconsolidated debris has been reworked by wave action into beaches, spits, bars, and other shoreline features. Along the shallower coasts these have completely changed the character of the landscape. The marine transgression did not last long enough to produce erosional features in consolidated rock.

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