Geologic units in Oneida county, Wisconsin

Mafic metavolcanic rocks (Early Proterozoic) at surface, covers 51 % 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.

Granite-tonalite (Early Proterozoic) at surface, covers 26 % 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

Metagabbro (Early Proterozoic) at surface, covers 9 % of this area

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

Bimodal mafic and felsic metavolcanic rocks (Early Proterozoic) at surface, covers 8 % of this area

High-aluminum basalt to low-silica andesite pillowed flows and interlayered dacite to rhyolite tuffs and porphyries in Monico and Mountain areas, northeastern Wisconsin. A rhyolite porphyry at Jennings (Oneida County) has an age of 1869 +/- 6 Ma. Rocks are host to massive sulfide deposits (Crandon and Pelican River)

Mafic to felsic metavolcanic rocks (Early Proterozoic) at surface, covers 3 % of this area

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

Granitic rocks of 1760-Ma age group (Early Proterozoic) at surface, covers 2 % of this area

In northern Wisconsin, granite to granodiorite of varied texture. In southern Wisconsin (not mapped separately), red to pink alkali-feldspar granophyric granite associated with rhyolites of both peraluminous and metaluminous affinities (unit Xr of Marshfield terrane).

Quartz diorite (Early Proterozoic) at surface, covers 0.2 % of this area

Includes Marinette Quartz Diorite of Dunbar Dome (Sims and others, 1985a) and nearby Twelve Foot Falls Quartz Diorite