Revisions of Stratigraphic Nomenclature within the Keweenawan Supergroup of Northern Michigan (Chapter A). Geochemistry, Petrography, and Volcanology of Rhyolites of the Portage Lake Volcanics, Keweenaw Peninsula, Michigan (Chapter B)

摘要

A new formation name (Porcupine Volcanics) and a new group name (Bergland Group) are proposed for Middle Proterozoic volcanic units in northern Michigan, and a sedimentary unit (Copper Harbor Conglomerate) is recorrelated in the first section. The second section summarizes the geochemistry, petrography, and field relations of rhyolites of the Portage Lake Volcanics of the Keweenaw Peninsula, Mich., the only rhyolites that were erupted within the central rift graben in the central Lake Superior region.