Concentration of Metals Associated with the Native Copper .
Quartzite, Powder Mill Group, Portage Lake Volcanics, Copper Harbor Conglomerate, Nonesuch Shale, and the Freda Sandstone in ascending order. The oldest unit in the Keweenawan Supergroup is the Powder Mill Group, a series of subaerial basalt to basalticandesite flows associated with the earliest stages of