Geologic units in Marinette county, Wisconsin

Athelstane Quartz Monzonite (Early Proterozoic) at surface, covers 17 % of this area

Pink, coarse-grained granite to granodiorite containing nearly equal amounts of microcline microperthite, plagioclase, and quartz and 5-10 percent biotite and (or) hornblende. Mafic minerals are interstitial and give a clotty appearance. (1836 +/- 15 Ma)

Cambrian, undivided (Cambrian) at surface, covers 14 % of this area

Sandstone with some dolomite and shale, undivided; includes Trempealeau, Tunnel City, and Elk Mound Formations

Sinnipee Group (Ordovician) at surface, covers 11 % of this area

Dolomite with some limestone and shale; includes Galena, Decorah, and Platteville Formations

Mafic to felsic metavolcanic rocks (Early Proterozoic) at surface, covers 11 % 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 10 % 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.

Prairie du Chien Group (Ordovician) at surface, covers 9 % of this area

Dolomite with some sandstone and shale; includes Shakopee and Oneota Formations

Granite-tonalite (Early Proterozoic) at surface, covers 6 % 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

Granitic rocks of 1760-Ma age group (Early Proterozoic) at surface, covers 4 % of this area

In northern Wisconsin, granite to granodiorite of varied texture. In southern Wisconsin (not mapped separately), red to pink alkali-feldspar granophyric granite associated with rhyolites of both peraluminous and metaluminous affinities (unit Xr of Marshfield terrane).

Quartz diorite (Early Proterozoic) at surface, covers 4 % of this area

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

Wolf River batholith; High Falls Granite (Middle Proterozoic) at surface, covers 3 % of this area

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

Bimodal mafic and felsic metavolcanic rocks (Early Proterozoic) at surface, covers 2 % 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)

Dacite and volcanogenic graywacke (Early Proterozoic) at surface, covers 2 % of this area

Includes andesite tuff. Occurs in northeastern Wisconsin. Dacite has age of 1866 +/- 39 Ma.

Wolf River Batholith; Belongia Granite (Middle Proterozoic) at surface, covers 1 % of this area

Red to pink granite consisting of both a coarse-grained and a fine-grained facies. Probably an epizonal intrusion

Rhyolite to dacite (Early Proterozoic) at surface, covers 0.9 % of this area

Massive to flow-banded rocks of greenschist metamorphic grade in northeastern Wisconsin; virtually undeformed.

Ancell Group (Ordovician) at surface, covers 0.8 % of this area

Orthoquartzitic sandstone with minor limestone, shale and conglomerate; includes Glenwood and St. Peter Formations

Peshtigo Mangerite in the Wolf River batholith; Peshtigo Mangerite (Middle Proterozoic) at surface, covers 0.7 % of this area

Brown to dark-gray, coarse-grained (0.3-1.5 cm) inequigranular monzonite containing subhedral, zoned plagioclase, alkali feldspar, mafic silicates (fayalite, hypersthene, ferroaugite-hedenbergite, hornblende, and biotite), and interstitial quartz

Wolf River batholith; Hager Formation; Rhyolite member (Middle Proterozoic) at surface, covers 0.4 % 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

Basaltic and andesitic breccia (Early Proterozoic) at surface, covers 0.4 % of this area

Exposed in northeastern Wisconsin

Quartzite (Early Proterozoic) at surface, covers 0.3 % 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

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

Trempealeau Formation (Late Cambrian) at surface, covers < 0.1 % of this area

Trempealeau Formation

Munising Formation (Late Cambrian) at surface, covers < 0.1 % of this area

Munising Formation

Dacite and volcanogenic graywacke (Early Proterozoic) at surface, covers < 0.1 % of this area

Includes andesite tuff. Occurs in northeastern Wisconsin. Dacite has age of 1866 +/- 39 Ma.

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

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

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

Trenton Limestone (Late Ordovician) at surface, covers < 0.1 % of this area

Trenton Limestone

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

Basaltic and andesitic breccia (Early Proterozoic) at surface, covers < 0.1 % of this area

Exposed in northeastern Wisconsin

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

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