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

Geologic units in Marathon county, Wisconsin

Stettin pluton (about 1520 Ma) (Middle Proterozoic) at surface, covers 1 % of this area

Stettin pluton (about 1520 Ma) - Pyroxene syenite, amphibole syenite, tabular syenite, and nepheline syenite. Age approximately 1520 Ma (Sood and others, 1980).

Lithology: syenite

Foliated tonalite (Early Proterozoic) at surface, covers 1 % of this area

Foliated tonalite - Medium-gray, mottled, medium-grained, equigranular tonalite and granodiorite. Intrudes rocks of the Milladore Volcanic Complex.

Lithology: tonalite; granodiorite

Mafic metavolcanic rocks (Early Proterozoic) at surface, covers 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

Wolf River batholith (1470 Ma); Wolf River Granite (Middle Proterozoic) at surface, covers 12 % of this area

Wolf River batholith (1470 Ma); Wolf River Granite- Red, coarse-grained rapakivi granite consisting of large (1-3 cm) ovoid alkali feldspar sporadically mantled by plagioclase, interstitial plagioclase, quartz, biotite, hornblende, and ilmenite

Lithology: granite

Wausau Pluton; Aplite (Middle Proterozoic) at surface, covers 0.9 % of this area

Wausau Pluton; Aplite- Pale-orange to pink, fine-grained porphyritic aplite

Lithology: aplite

Fault rocks (Archean to Early Proterozoic) at surface, covers 4 % of this area

Fault rocks - Mylonitic rocks of uncertain lithology in Eau Pleine shear zone

Lithology: mylonite

Felsic metavolcanic rocks of 1835- to 1845-Ma age group (Early Proterozoic) at surface, covers 10 % of this area

Felsic metavolcanic rocks of 1835- to 1845-Ma age group - Rhyolite to dacite and, locally, andesite tuff, breccia, and minor sedimentary rocks, including conglomerate. Exposed in central Wisconsin.

Lithology: meta-rhyolite; metavolcanic rock; tuff

Alkali feldspar granite of 1835 Ma age group (Early Proterozoic) at surface, covers 12 % of this area

Alkali feldspar granite of 1835 Ma age group - Red to pink, medium-grained leucocratic alkali feldspar granite; contains miarolitic cavities; biotite is altered to opaque oxide minerals; contains fluorite locally. Called red granite previously (Sims, 1990). Exposed in both Pembine-Wausau and Marshfield terranes.

Lithology: granite

Wolf River Batholith; Anorthosite (Middle Proterozoic) at surface, covers 2 % of this area

Wolf River Batholith; Anorthosite- Gray, coarse-grained (1-20 cm) plagioclase-rich (An45-53) rock containing interstitial orthopyroxene, clinopyroxene, Fe-Ti oxides, and apatite.

Lithology: anorthosite

Granitic rocks, undivided (Early Proterozoic) at surface, covers < 0.1 % of this area

Granitic rocks, undivided - Gray, weakly foliated to massive granite in poorly exposed areas.

Lithology: granite

Granite near Cherokee (1853 +/- 21 Ma) (Early Proterozoic) at surface, covers 3 % of this area

Granite near Cherokee (1853 +/- 21 Ma) - Pink, coarse-grained granite consisting of microcline microperthite and oligoclase phenocrysts in a fine-grained matrix of quartz, potassium feldspar, and oligoclase. Hornblende and (or) biotite occur in clots

Lithology: granite

Rhyolite at and near Cary Mound and near Brokaw (about 1835 Ma) (Early Proterozoic) at surface, covers 1 % of this area

Rhyolite at and near Cary Mound and near Brokaw (about 1835 Ma) - Flow-banded rhyolite, welded tuff, volcanic conglomerate, and volcanogenic sedimentary rocks. Exposed in both Pembine-Wausau and Marshfield terranes.

Lithology: rhyolite; conglomerate; tuff

Wausau Pluton; Granite near Big Eau Pleine Reservoir (Middle Proterozoic) at surface, covers 1 % of this area

Wausau Pluton; Granite near Big Eau Pleine Reservoir - pink to red, medium- to fine-grained granite containing miarolitic cavities

Lithology: granite

Wausau Pluton; Quartz syenite (Middle Proterozoic) at surface, covers 4 % of this area

Wausau Pluton; Quartz syenite- Contains flow-oriented xenoliths of biotite schist and sillimanite-bearing quartzite

Lithology: syenite

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

Granite gneiss - Medium-grained granodiorite gneiss in northwestern Marathon County.

Lithology: granitic gneiss

Wolf River batholith (1470 Ma); Red River Granite (Middle Proterozoic) at surface, covers 3 % of this area

Wolf River batholith (1470 Ma); Red River Granite - Contains alkali feldspar phenocrysts (0.5-2 cm), subordinate plagioclase and quartz, and rare clusters of biotite with or without hornblende

Lithology: granite

Gneiss and amphibolite (Early Proterozoic) at surface, covers 6 % of this area

Gneiss and amphibolite - Interlayered quartzofeldpathic gneiss and amphibolite between Athens shear zone and Owen fault, central Wisconsin

Lithology: gneiss; amphibolite

Cambrian, undivided (Cambrian) at surface, covers 3 % of this area

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

Lithology: sandstone; dolostone (dolomite); shale

Milladore Volcanic Complex (about 1860 +/- 7 Ma) (Early Proterozoic) at surface, covers 2 % of this area

Milladore Volcanic Complex (about 1860 +/- 7 Ma) - Succession of poorly exposed interlayered metavolcanic and metasedimentary rocks. Lithic units described in Sims (1990)

Lithology: metasedimentary rock; metavolcanic rock

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

Granodiorite-tonalite - Gray, medium-grained intrusive rocks, including intrusion breccias. Exposed in central Wisconsin. Zircon ages range from 1837 to 1847 Ma

Lithology: granodiorite; tonalite

Gabbro (Early Proterozoic) at surface, covers 2 % of this area

Gabbro - Massive to layered intrusive gabbroic rocks; weakly metamorphosed and deformed. Exposed in both Pembine-Wausau and Marshfield terranes

Lithology: gabbro

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

Mafic to felsic metavolcanic rocks - Volcanic rocks in areas of sparse geologic data and nondefinitive magnetic and gravity data

Lithology: mafic metavolcanic rock; felsic metavolcanic rock

Porphyritic granite (Early Proterozoic) at surface, covers 5 % of this area

Porphyritic granite - Granite containing plagioclase, microcline, and quartz phenocrysts in a fine-grained granophyric matrix. Probably subvolcanic intrusions related to volcanic rocks of 1835- to 1845-Ma age group

Lithology: granite

Wausau Pluton; Granite near Nine Mile Swamp (Middle Proterozoic) at surface, covers 5 % of this area

Wausau Pluton; Granite near Nine Mile Swamp - Orange to pink, coarse-grained massive granite composed of alkali feldspar sporadically mantled by plagioclase, quartz, and biotite; contains miarolitic cavities

Lithology: granite