Two early Proterozoic successions in central Wisconsin and their tectonic significance

Sedimentary-volcanic-plutonic successions. The older succession unconformably overlies Archean rocks; it is characterized by amphibolite-facies metamorphism. The younger succession consists primarily of a greenschist-facies calc-alkaline basalt-rhyolite sequence that unconformably overlies the older amphibolite-facies rocks. The older amphibolitic sequence may correlate with the Chocolay Group farther north in the Lake Superior region, and the younger green-schist rocks with the Menominee and/or Baraga groups. If this correlation is correct, the deformation, metamorphism, and intrusion of the green-schist succession would have occurred during the Penokean Orogeny.--Modified journal abstract.