Powder Mill Group; Siemens Creek Volcanics

Dark-gray basalt and minor porphyritic andesite. Generally strongly magnetic with reversed remanent magnetism. Underlain by a thin unit of quartzose sandstone (Bessemer Quartzite).
State Michigan
Name Powder Mill Group; Siemens Creek Volcanics
Geologic age Middle Proterozoic
Lithologic constituents
Igneous > Volcanic > Mafic-volcanic > Basalt (Flow)
Igneous > Volcanic > Mafic-volcanic > Andesite (Flow)
Comments This unit is labeled ""Ysb"" on the paper map of Sims (1992) and ""Ys"" in Cannon and others (1997). Unit description is from the unit labeled ""Ysb"" from Sims (1992).
NGMDB product
Counties Gogebic - Houghton - Ontonagon