Clipping of Portage County
from the Bedrock Geologic Map of Wisconsin

 

Table of Explanation

Color Symbol Rock Type Description Time (million years ago) Period Era Eon

Cu Sedimentary Rock sandstone with some dolomite and shale, undivided  550 Cambrian Paleozoic Phanerozoic

Pwu Wolf River Batholith granitic and syenitic rocks of the Wolf River Batholith, undivided 1475-1525 Middle Proterozoic Proterozoic Precambrian

Pwr Wolf River Batholith quartz monzonite near the Red River, Shawano County 1475-1525 Middle Proterozoic Proterozoic Precambrian

Pwq Wolf River Batholith rapakivi-textured quartz monzonite near Waupaca 1475-1525 Middle Proterozoic Proterozoic Precambrian

Pgr Intrusive Rocks intermediate to granitic intrusive rocks generally discrete, weakly to moderately deformed bodies 1850-1950 Early Proterozoic Proterozoic Precambrian

Pmg Intrusive Rocks metamorphosed ultramafic to mafic intrusive rocks; includes a layered sequence near Merrill and magnetic units of unknown composition 1850-1950 Early Proterozoic Proterozoic Precambrian

Pvu Metavolcanic and Metasedimentary Rocks mafic, intermediate and felsic metavolcanic rocks with subordinate metasedimentary rocks; dominantly of greenschist metamorphic facies; more than one metavolcanic sequence is recognized; widely distributed in north central areas 1850-1950 Early Proterozoic Proterozoic Precambrian

Agn Igneous & Metamorphic Rocks quartzofeldspathic gneiss, migmatite and amphibolite 2800 Late Archean Archean Precambrian

To view the more detailed Bedrock Geology of Portage County, Wisconsin Map, click here.

(Source:  Greenberg and Brown 14)

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