Menominee Group; Blair Creek Formation

Dominantly dark-gray, massive, porphyritic tholeiitic basalt. Includes a basal conglomerate and a lean iron-formation in middle of formation
State Wisconsin
Name Menominee Group; Blair Creek Formation
Geologic age Early Proterozoic
Lithologic constituents
Major
Igneous > Volcanic > Mafic-volcanic > Basalt (Flow)Dominantly dark-gray, massive, porphyritic tholeiitic basalt
Minor
Sedimentary > Chemical > Banded-iron-formation (Bed)
Metamorphic > Metasedimentary > Metaclastic > Metaconglomeratebasal metacomglomerate
Comments continental margin assemblage (north of Niagara Fault)
References
NGMDB product
Counties Ashland - Iron - Vilas