Porcupine Volcanics; Rhyolite (MIYpr;0)

State	Michigan
Name	Porcupine Volcanics; Rhyolite
Geologic age	Middle Proterozoic
Original map label	Ypr
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 This has been replaced by the naming the unit, the Porcupine Volcanics, and using the symbol "Ypv", or, as in the case here, "Ypr" for the rhyolite members of the Porcupine Volcanics.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	Major 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 [http://pubs.er.usgs.gov/publication/i2185]
Geographic coverage	Gogebic - Ontonagon