As defined in the Lake Superior region (Cannon, 1973; Sims and Peterman, 1983), has a distinct tectonic-stratigraphic zonation. Early Proterozoic epicratonic sedimentary and volcanic rocks, which overlie Archean basement on the north, are separated from a volcanic-plutonic (Wisconsin magmatic) terrane (Van Schmus, 1980) on the south by a major ductile shear zone (Niagara fault; Sims and others, 1985; Sedlock and Larue, 1985). The shear zone is interpreted as a suture formed at about 1.85 Ga when the magmatic (island) arc collided with the continental margin and its superjacent cover. This event triggered the Penokean Orogeny. Areal limits shown on tectonic map of Precambrian basement (fig. 3). Age shown to be about 1.85 Ga (Early Proterozoic).

Source: GNU records (USGS DDS-6; Denver GNULEX).

Penokean orogen is a zone of weakly to intensely deformed and metamorphosed Early Proterozoic and Archean rocks adjacent to and along southern margin of Superior province of Canadian Shield. Penokean orogeny refers to compressional stage of deformation in the orogen which followed Early Proterozoic Marquette Range Supergroup deposition --between 1,840 and 1,860 Ma. Orogen divisible into northern stable and southern deformed zones. Southern margin of orogen covered by younger Proterozoic rocks. Is equivalent to the Hudsonian foldbelt.

Source: GNU records (USGS DDS-6; Denver GNULEX).