Thomson Formation  search
BTChronostratigraphic Units
 .Precambrian
 ..Proterozoic
 ...Paleoproterozoic
 ....Thomson Formation
UFThomson Slate
RTWisconsin
 Minnesota
 Animikie Group
 Virginia Formation
SNNE Minnesota and NW Wisconsin. Includes the slate which has been referred to in literature as Thomson, Saint Louis, Cloquet, and Carlton slates. And which has usually been considered an equivalent of the Animikie-Virginia Slate of the Mesabi Range. In NE