Geologic units in Menominee county, Michigan

Prairie du Chien Group (Early Ordovician) at surface, covers 26 % of this area

Prairie du Chien Group

Trenton Limestone (Late Ordovician) at surface, covers 25 % of this area

Trenton Limestone

Trempealeau Formation (Late Cambrian) at surface, covers 21 % of this area

Trempealeau Formation

Black River Limestone (Late Ordovician) at surface, covers 16 % of this area

Black River Limestone

Munising Formation (Late Cambrian) at surface, covers 8 % of this area

Munising Formation

Dacite and volcanogenic graywacke (Early Proterozoic) at surface, covers 0.8 % 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 0.6 % 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.

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

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

Rhyolite to dacite (Early Proterozoic) at surface, covers 0.4 % of this area

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

Basaltic and andesitic breccia (Early Proterozoic) at surface, covers 0.3 % of this area

Exposed in northeastern Wisconsin

Baraga Group; Michigamme Formation, undivided (Early Proterozoic) at surface, covers 0.3 % 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

Athelstane Quartz Monzonite (Early Proterozoic) at surface, covers 0.2 % 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.

Prairie du Chien Group (Ordovician) at surface, covers 0.2 % of this area

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

Cambrian, undivided (Cambrian) at surface, covers 0.2 % of this area

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

Sinnipee Group (Ordovician) at surface, covers 0.1 % of this area

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

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.

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.

Rhyolite to dacite (Early Proterozoic) at surface, covers < 0.1 % of this area

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

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

Exposed in northeastern Wisconsin

Athelstane Quartz Monzonite (Early Proterozoic) at surface, covers < 0.1 % 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)

Granitic rocks of 1760-Ma age group (Early Proterozoic) at surface, covers < 0.1 % 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).

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