The St. Marys River, Michigan: An Ecological Profile,

The St. Marys River is a former strait which connects Lakes Superior and Huron. The most northern of the Great Lakes connecting channels, it originates from Whitefish Bay in Lake Superior between Point Iroquois, Michigan, and Gros Cap, Ontario. It flows in a southeasterly direction approximately 112 km before emptying into Lake Huron at De Tour, Michigan Figure 1. The river falls about 6.7 m between its headwaters and mouth however, 6.1 m of this drop in elevation occurs at the St. Marys Rapids, 23 km below the headwaters. The river is bounded on the south and west by the Upper Peninsula of Michigan on the north and northeast by the Ontario mainland and on the east, first by St. Joseph Island, Ontario, and then by Drummond Island, Michigan, which forms the most southerly border. The surficial geology of the southwestern St. Marys River Valley is primarily lacustrine sediments and moraines Figure 3. On the southwestern edge of the valley in Michigan, level lakebed plains are interrupted by gently rolling plateaus, low rounded ridges, or lakeshore features such as remnant beach ridges, sand dunes, bluffs, or marshland Veatch et al . 1927 . In Ontario, on the northeastern edge of the valley, knobby Precambrian rock is partially covered by a thin layer of till or lacustrine clay McCuthcheon 1968. Numerous lakes also dot the Precambrian shield area north of the river. Mineral soils in the vicinity of the river are comprised of clays, loams, or sands Table 1. These soils, in general, are highly retentive of water as are the organic soils common west and south of Munuscong Lake.