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Porcupine Volcanics; Rhyolite

Porcupine Volcanics; Rhyolite
State Michigan
Name Porcupine Volcanics; Rhyolite
Geologic age Middle Proterozoic
Comments previously called the "unnamed formation", including on paper map of Sims (1992). The unit symbol on that map is "Yu". This has been replaced by the naming the unit, the Porcupine Volcanics, and using the symbol "Ypv", or, as in the case here, "Ypr" for the rhyolite members of the Porcupine Volcanics.
Primary rock type rhyolite
Secondary rock type
Other rock types
Lithologic constituents
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Flow)rhyolite
Map references
Cannon, W.F., Kress, T.H., Sutphin, D.M., Morey, G.B., Meints, Joyce, and Barber-Delach, Robert, 1997, Digital Geologic Map and mineral deposits of the Lake Superior Region, Minnesota, Wisconsin, Michigan: USGS Open-File Report 97-455 (version 3, Nov. 1999), on-line only
Unit references
Zartman and others, 1997, U-Th-Pb zircon ages of some Keweenawan Supergroup rocks from the south shore of Lake Superior: Canadian Journal of Earth Sciences, v. 34, p. 549-561
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
Counties Gogebic - Ontonagon