Geologic units in Forest county, Wisconsin

Mafic to felsic metavolcanic rocks (Early Proterozoic) at surface, covers 40 % of this area

Volcanic rocks in areas of sparse geologic data and nondefinitive magnetic and gravity data

Mafic metavolcanic rocks (Early Proterozoic) at surface, covers 38 % of this area

Dominantly tholeiitic basalt and basaltic andesite flows and tuffs; associated with sheet dikes, massive and layered metagabbro, and ultramafic rocks. In northeastern Wisconsin, rocks have been named the Quinnesec Formation.

Granite-tonalite (Early Proterozoic) at surface, covers 12 % of this area

Gray to pinkish-gray, medium-grained, generally equigranular granite to tonalite and granitoid gneiss; locally includes diorite. Intrudes older metavolcanic rocks. Zircon ages range from 1852 +/- 15 to 1862 +/- 5 Ma

Bimodal mafic and felsic metavolcanic rocks (Early Proterozoic) at surface, covers 6 % of this area

High-aluminum basalt to low-silica andesite pillowed flows and interlayered dacite to rhyolite tuffs and porphyries in Monico and Mountain areas, northeastern Wisconsin. A rhyolite porphyry at Jennings (Oneida County) has an age of 1869 +/- 6 Ma. Rocks are host to massive sulfide deposits (Crandon and Pelican River)

Metagabbro (Early Proterozoic) at surface, covers 0.8 % of this area

Mafic to ultramafic bodies defined and delineated principally by positive magnetic and gravity anomalies; includes diorite bodies. Comagmatic with unit Xmi

Quartzite (Early Proterozoic) at surface, covers 0.8 % of this area

Maroon but locally white, gray, and red quartzite (quartz arenite) with a basal quartzose conglomerate. At Flambeau Ridge (Chippewa County) consists of conglomerate. Distinguished from other quartzite units in being strongly deformed and metamorphosed. Includes Flambeau, Rib Mountain, McCaslin, and Thunder Mountain Quartzites of local usage

Quartz diorite (Early Proterozoic) at surface, covers 0.6 % of this area

Includes Marinette Quartz Diorite of Dunbar Dome (Sims and others, 1985a) and nearby Twelve Foot Falls Quartz Diorite

Baraga Group; Michigamme Formation, undivided (Early Proterozoic) at surface, covers 0.6 % of this area

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

Badwater Greenstone (Early Proterozoic) at surface, covers 0.5 % of this area

Dark-greenish-gray, pillowed to massive tholeiitic basalt and pyroclastic rocks. Correlated with the Hemlock Formation on basis of geology and similarity in chemical composition.

Wolf River batholith; High Falls Granite (Middle Proterozoic) at surface, covers 0.3 % of this area

Gray to pink, equigranular to porphyritic granite to granodiorite containing microcline microperthite, concentrically zoned plagioclase, quartz, biotite, and hornblende

Chocolay Group, undivided (Early Proterozoic) at surface, covers < 0.1 % of this area

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

Mafic metavolcanic rocks (Early Proterozoic) at surface, covers < 0.1 % of this area

Dominantly tholeiitic basalt and basaltic andesite flows and tuffs; associated with sheet dikes, massive and layered metagabbro, and ultramafic rocks. In northeastern Wisconsin, rocks have been named the Quinnesec Formation.

Chocolay Group, undivided (Early Proterozoic) at surface, covers < 0.1 % of this area

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

Wolf River batholith; Hager Formation; Rhyolite member (Middle Proterozoic) at surface, covers < 0.1 % of this area

Gray to reddish-gray, slightly foliated, porphyritic rhyolite containing aligned phenocrysts of alkali feldspar and lesser amounts of plagioclase in a fine-grained matrix of feldspar, biotite, amphibole, and sparse quartz

Paint River Group; Lower part (Early Proterozoic) at surface, covers < 0.1 % of this area

Includes Stambaugh Formation, Hiawatha Graywacke, Riverton Iron-formation, and Dunn Creek Slate (James and others, 1968). Correlated with lower part of Baraga Group

Baraga Group; Michigamme Formation, undivided (Early Proterozoic) at surface, covers < 0.1 % of this area

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

Badwater Greenstone (Early Proterozoic) at surface, covers < 0.1 % of this area

Dark-greenish-gray, pillowed to massive tholeiitic basalt and pyroclastic rocks. Correlated with the Hemlock Formation on basis of geology and similarity in chemical composition.

Paint River Group; Lower part (Early Proterozoic) at surface, covers < 0.1 % of this area

Includes Stambaugh Formation, Hiawatha Graywacke, Riverton Iron-formation, and Dunn Creek Slate (James and others, 1968). Correlated with lower part of Baraga Group