Varied gneisses of mostly unknown age in cores of gneiss domes and fault-bounded uplifts (Archean gneiss terranes). Except for the Watersmeet dome (Late to Early Archean), all dated rocks are Late Archean. Includes granite of Late Archean age that transgresses gneisses and amphibolite.
Interlayered quartzofeldspathic gneiss and amphibolite in Marenisco, Mich., area and northwestern Wisconsin. Protoliths are bimodal intermediate and mafic volcanic rocks (Sims and others, 1984).
Red, brown, and white quartzose sandstone, and minor siltstone, shale and conglomerate
Black River Limestone
Prairie du Chien Group
Strongly cleaved. Represents lower stratigraphic part of formation
Derived from mafic to intermediate pyroclastic rocks and massive to pillowed lava flows. Unit mapped as Ramsey Formation by Prinz (1981) south of Gogebic Range; mapped as Mona Schist and Kitchi Schist in northern complex of Marquette District.
Thick and stratigraphically varied formation of sedimentary and less abundant volcanic rocks. Metamorphosed graywacke is predominant rock of Michigamme Formation. Calcareous concretions common. Metamorphosed from cholorite to sillimanite grade (Cannon, 1986). Mapped undivided in poorly exposed areas
Includes Negaunee Iron-formation, Siamo Slate, and Ajibik Quartzite in areas where units are too thin to map individually.
Highly metamorphosed banded iron-formation. Principal iron-formation in Marquette trough and nearby areas. Includes abundant metadiabase sills.
Siamo Slate is laminated green siltstone and argillite. Ajibik Quartzite is white, buff, and pink orthoquartzite and less abundant sericite quartzite.
In Dickinson County, Mich., includes Randville Dolomite, Sturgeon Quartzite, and Fern Creek Formation. In Marquette range, between Marquette Bay and Champion, includes Wewe Slate, Kona Dolomite, Mesnard Quartzite, and Enchantment Lake Formation
Poorly exposed. Includes Clarksburg Volcanics member which is mostly mafic to intermediate pyroclastic rocks in Marquette trough, between Marquette Bay and Champion
Predominantly mafic to intermediate volcanic flows and pyroclastic rocks with interlayered slate and tuff beds
Interlayered fine- to medium-grained metasedimentary rocks and metavolcanic rocks in poorly exposed areas in southern Baraga County, Mich.