Geologic units in Taylor county, Wisconsin

Mafic to felsic metavolcanic rocks (Early Proterozoic) at surface, covers 79 % of this area

Volcanic rocks in areas of sparse geologic data and nondefinitive magnetic and gravity data

Gneiss, migmatite, and amphibolite (Late Archean) at surface, covers 7 % of this area

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)

Metagabbro (Early Proterozoic) at surface, covers 4 % of this area

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

Granite-tonalite (Early Proterozoic) at surface, covers 4 % of this area

Gray to pinkish-gray, medium-grained, generally equigranular granite to tonalite and granitoid gneiss; locally includes diorite. Intrudes older metavolcanic rocks. Zircon ages range from 1852 +/- 15 to 1862 +/- 5 Ma

Gneiss and amphibolite (Early Proterozoic) at surface, covers 4 % of this area

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

Felsic volcanic and volcanogenic rocks (Early Proterozoic) at surface, covers 1 % of this area

Tuff, argillite, graywacke, and minor volcanic rocks of lower greenschist-facies in southern Rusk County. Could be younger in age than adjacent metavolcanic rocks.

Mafic metavolcanic rocks (Early Proterozoic) at surface, covers 0.3 % of this area

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.