| State | Michigan |
|---|---|
| Name | Portage Lake Volcanics |
| Geologic age | Middle Proterozoic |
| Lithologic constituents |
Major
Igneous > Volcanic > Mafic-volcanic > Basalt (Flow)Lava flows, mostly basalt, andesite and felsite flows and subordinate interflow sedimentary rocks
Minor
Igneous > Volcanic > Mafic-volcanic > Basaltic-andesite (Flow)Lava flows, mostly basalt, andesite and felsite flows and subordinate interflow sedimentary rocks
Incidental
Igneous > Volcanic > Felsic-volcanic > Rhyolite (Flow)Lava flows, mostly basalt, andesite and felsite flows and subordinate interflow sedimentary rocks
Sedimentary > Clastic > Mixed-clastic > Sandstone-mudstone (Bed)Lava flows, mostly basalt, andesite and felsite flows and subordinate interflow sedimentary rocks
|
| Comments | This unit is the same as unit ""Yp"" on paper map of Sims (1992). Description is taken from that unit description. |
| References | Davis, D.W., and Paces, J.B., 1990, Time resolution of geologic events on the Keweenaw Peninsula and implications for development of the Midcontinent rift system: Earth and Planetary Science Letters, v. 97, p. 54-64.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.https://pubs.er.usgs.gov/publication/i2185 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).https://pubs.er.usgs.gov/publication/ofr97455 |
| NGMDB product | |
| Counties | Gogebic - Houghton - Keweenaw - Ontonagon |