Gneiss, migmatite, and amphibolite

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)
State Wisconsin
Name Gneiss, migmatite, and amphibolite
Geologic age Late Archean
Lithologic constituents
Major
Metamorphic > Gneiss
Minor
Metamorphic > Migmatite
Metamorphic > Amphibolite
Incidental
Igneous > Plutonic > Granitic
Comments Marshfield terrane
References

Sims and others, 1989, Tectonostratigraphic evolution of the Early Proterozoic Wisconsin magmatic terranes of the Penokean orogen: Canadian Journal of Earth Sciences, v. 26, p. 2145-2158.

Sims, P.K., 1992, Geologic map of Precambrian rocks, southern Lake Superior region, Wisconsin and northern Michigan: U.S. Geological Survey Miscellaneous Investigations Map I-2185, scale 1:500,000.

https://pubs.er.usgs.gov/publication/i2185

NGMDB product
Counties Adams - Chippewa - Clark - Eau Claire - Jackson - Juneau - Portage - Taylor - Wood