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
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.
Gray, medium-grained intrusive rocks, including intrusion breccias. Exposed in central Wisconsin. Zircon ages range from 1837 to 1847 Ma
Rhyolite to dacite and, locally, andesite tuff, breccia, and minor sedimentary rocks, including conglomerate. Exposed in central Wisconsin.
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.
Interlayered quartzofeldpathic gneiss and amphibolite between Athens shear zone and Owen fault, central Wisconsin
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
Orange to pink, coarse-grained massive granite composed of alkali feldspar sporadically mantled by plagioclase, quartz, and biotite; contains miarolitic cavities
Mylonitic rocks of uncertain lithology in Eau Pleine shear zone
Contains flow-oriented xenoliths of biotite schist and sillimanite-bearing quartzite
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
Contains alkali feldspar phenocrysts (0.5-2 cm), subordinate plagioclase and quartz, and rare clusters of biotite with or without hornblende
Sandstone with some dolomite and shale, undivided; includes Trempealeau, Tunnel City, and Elk Mound Formations
Gray, coarse-grained (1-20 cm) plagioclase-rich (An45-53) rock containing interstitial orthopyroxene, clinopyroxene, Fe-Ti oxides, and apatite.
Succession of poorly exposed interlayered metavolcanic and metasedimentary rocks. Lithic units described in Sims (1990)
Massive to layered intrusive gabbroic rocks; weakly metamorphosed and deformed. Exposed in both Pembine-Wausau and Marshfield terranes
Medium-gray, mottled, medium-grained, equigranular tonalite and granodiorite. Intrudes rocks of the Milladore Volcanic Complex.
Pink to red, medium- to fine-grained granite containing miarolitic cavities
Pyroxene syenite, amphibole syenite, tabular syenite, and nepheline syenite. Age approximately 1520 Ma (Sood and others, 1980).
Flow-banded rhyolite, welded tuff, volcanic conglomerate, and volcanogenic sedimentary rocks. Exposed in both Pembine-Wausau and Marshfield terranes.
Pale-orange to pink, fine-grained porphyritic aplite
Medium-grained granodiorite gneiss in northwestern Marathon County.
Gray, weakly foliated to massive granite in poorly exposed areas.
Volcanic rocks in areas of sparse geologic data and nondefinitive magnetic and gravity data