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Mineral Resources > Online Spatial Data > Geology > by state > Michigan Geology

Geologic units in Dickinson county, Michigan

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

Mafic metavolcanic rocks - 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.

Lithology: basalt; andesite; gabbro; ultramafic intrusive rock

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

Baraga Group; Michigamme Formation, undivided - 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

Lithology: graywacke

Trempealeau Formation (Late Cambrian) at surface, covers 7 % of this area

Trempealeau Formation

Lithology: sandstone; shale; dolostone (dolomite)

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

Menominee and Chocolay Groups, undivided - Mapped where units are too thin to show separately on map

Lithology: metasedimentary rock; metavolcanic rock

Dickinson Group, undivided (Late Archean) (Late Archean) at surface, covers 8 % of this area

Dickinson Group, undivided (Late Archean) - Metavolcanic and metasedimentary rocks in Dickinson County, Mich. From youngest to oldest, consists of Six-Mile Lake Amphibolite, Solberg Schist, and East Branch Arkose.

Lithology: amphibolite; schist; metasedimentary rock; gneiss

Munising Formation (Late Cambrian) at surface, covers 13 % of this area

Munising Formation

Lithology: sandstone; shale; conglomerate

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

Menominee Group, undivided - Includes Negaunee Iron-formation, Siamo Slate, and Ajibik Quartzite in areas where units are too thin to map individually.

Lithology: slate; quartzite; iron formation

Mafic metavolcanic rocks (Early Proterozoic) at surface, covers 0.9 % of this area

Mafic metavolcanic rocks - 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.

Lithology: basalt; andesite; gabbro; ultramafic intrusive rock

Menominee and Chocolay Groups, undivided (Early Proterozoic) at surface, covers 5 % of this area

Menominee and Chocolay Groups, undivided - Mapped where units are too thin to show separately on map

Lithology: metasedimentary rock; metavolcanic rock

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

Granitic rocks - Gray to pinkish-gray, mottled, medium-grained syenite, granite, and granodiorite. Moderately strong propylitic alteration and weak cataclasis. Forms small bodies south of Crystal Falls, MI (James and others, 1968). A body near Tobin Location has a U-Pb concordia intercept age of 1840 +/-5 Ma (Z.E. Peterman, written communication, 1988). Includes porphyritic red granite that intrudes Lake Archean Dickinson Group - Red mylonitic gneissic granite (about 1970 Ma).

Lithology: syenite; granite; granodiorite

Migmatitic gneiss and amphibolite (Late to Early Archean) (Archean) at surface, covers 29 % of this area

Migmatitic gneiss and amphibolite (Late to Early Archean) - 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.

Lithology: gneiss; migmatite; amphibolite

Badwater Greenstone (Early Proterozoic) at surface, covers 1.0 % of this area

Badwater Greenstone - 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.

Lithology: basalt; pyroclastic

Menominee Group; Hemlock Formation (Early Proterozoic) at surface, covers 1.0 % of this area

Menominee Group; Hemlock Formation - Predominantly mafic to intermediate volcanic flows and pyroclastic rocks with interlayered slate and tuff beds

Lithology: basalt; andesite; pyroclastic; slate; tuff

Chocolay Group, undivided (Early Proterozoic) at surface, covers 4 % of this area

Chocolay Group, undivided - 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

Lithology: quartzite; dolostone (dolomite); slate

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

Badwater Greenstone - 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.

Lithology: basalt; pyroclastic

Baraga Group; Michigamme Formation, undivided (Early Proterozoic) at surface, covers 31 % of this area

Baraga Group; Michigamme Formation, undivided - 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

Lithology: graywacke; metasedimentary rock

Metagabbro (Early Proterozoic) at surface, covers 0.2 % of this area

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

Lithology: gabbroid; ultramafic intrusive rock; diorite

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

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

Lithology: gabbro; ultramafic intrusive rock; diorite