The Duluth Complex includes much of Minnesota's Arrowhead Region north of Lake Superior. From the west near Duluth, Minnesota, it arcs north and northeast to about 48° north latitude south of Knife Lake, proceeds east at that latitude some five to twenty kilometers distant from and south of the Canadian border to about 90° west longitude where it joins the border at the Pigeon River, and thence runs east near and along the border to Lake Superior. The Duluth and Beaver Bay complexes lie south of this line.
Near Lake Superior these intrusive formations intermingle in a complex mosaic with the rocks of the associated North Shore Volcanics, which also are relics of the Midcontinent rifting event. The Duluth and Beaver Bay Complexes extend a short distance under Lake Superior south of the present lakeshore, but in most places along and near that shore their southern reaches are overlain by the North Shore Volcanic Group.
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