Gunflint (~1,878 Ma), Biwabik, and Emily Iron Formations

Locally includes thin basal sandstone and conglomerate. Capped by an irregular layer of brecciated iron-formation and ejecta derived from the 1,850 Ma Sudbury meteorite impact.
State Minnesota
Name Gunflint (~1,878 Ma), Biwabik, and Emily Iron Formations
Geologic age Paleoproterozoic
Lithologic constituents
Major
Sedimentary > Chemical > Banded-iron-formation (Bed)irregular layer of brecciated iron-formation and ejecta derived from the 1,850 Ma Sudbury meteorite impact
Sedimentary > Clastic > Sedimentary-brecciairregular layer of brecciated iron-formation and ejecta derived from the 1,850 Ma Sudbury meteorite impact
Minor
Sedimentary > Clastic > Sandstone (Bed)
Sedimentary > Clastic > Conglomerate (Bed)
Comments Part of the Animikie Group. Part of the Geon 18 intrusions and supracrustal rocks (syn- to late Penokean orogenesis).
References

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 Cass - Cook - Crow Wing - Itasca - Saint Louis