Slate and graywacke

Slate and graywacke. Includes the Rove (~1,836 to 1,777 Ma), Virginia (~1,832 Ma near base), and Thompson Formations (youngest zircons in the Thompson Formation ~1,790 Ma).
State Minnesota
Name Slate and graywacke
Geologic age Paleoproterozoic
Lithologic constituents
Sedimentary > Clastic > Sandstone > Graywacke (Bed)
Metamorphic > Metasedimentary > Metaclastic > Slate
Comments Part of the Animikie Group. Part of the Geon 18 intrusions and supracrustal rocks (syn- to late Penokean orogenesis).

Jirsa, Mark A., Boerboom, Terrence J., Chandler, Val W., Mossler, John H., Runkel, Anthony C., and Setterholm, Dale R., 2011, S-21 Geologic Map of Minnesota-Bedrock Geology; Minnesota Geological Survey, State Map Series S-21. Scale 1:500,000.

NGMDB product
Counties Aitkin - Carlton - Cass - Cook - Crow Wing - Hubbard - Itasca - Morrison - Otter Tail - Saint Louis - Stearns - Todd - Wadena