Sandstone with some dolomite and shale, undivided; includes Trempealeau, Tunnel City, and Elk Mound Formations
Quartzofeldspathic gneiss and less abundant amphibolite and migmatite. Includes granitoid rocks. Granitic gneiss at Port Edwards, WI on Wisconsin River has a U-Pb zircon age of 2870 +/- 13 Ma, and gneiss at Jim Falls in Chippewa River valley has a U-Pb zircon age of 2522 +/- 22 Ma (Sims and others, 1989)
Volcanic rocks in areas of sparse geologic data and nondefinitive magnetic and gravity data
Interlayered quartzofeldpathic gneiss and amphibolite between Athens shear zone and Owen fault, central Wisconsin
Mafic to felsic flows, pyroclastic rocks, impure quartzite, and conglomerate in Eau Claire River, Eau Claire and northern Clark Counties. Rhyolite has zircon ages of 1,858 +/- 5 Ma. Possibly correlative with Milladore Volcanic Complex.
Gray, weakly foliated to massive granite in poorly exposed areas.
Pale-red, medium- to fine-grained, leucocratic, mylonite gneiss exposed near Neillsville, Wisc.
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.
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
Pink and gray, layered quartzofeldspathic schist of intermediate volcanic composition and associated thin iron-formation. Felsic gneiss at Arbutus Dam on Black River at Hatfield has U-Pb zircon age of about 2800 Ma (Sims and others, 1989)