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Baraga Group; Tyler Formation

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Light- to dark-gray, feldspathic, fine-grained sandstone, argillaceous siltstone, and argillite. Near base, ferruginous argillite contains beds of cherty sideritic and pyritic iron-formation
State Wisconsin
Name Baraga Group; Tyler Formation
Geologic age Early Proterozoic
Lithologic constituents
Major
Sedimentary > Clastic > Siltstone (Bed)Light- to dark-gray, feldspathic, fine-grained sandstone, argillaceous siltstone, and argillite. Near base, ferruginous argillite contains beds of cherty sideritic and pyritic iron-formation
Sedimentary > Clastic > Sandstone (Bed)Light- to dark-gray, feldspathic, fine-grained sandstone, argillaceous siltstone, and argillite. Near base, ferruginous argillite contains beds of cherty sideritic and pyritic iron-formation
Minor
Sedimentary > Chemical > Banded-iron-formation (Bed)Light- to dark-gray, feldspathic, fine-grained sandstone, argillaceous siltstone, and argillite. Near base, ferruginous argillite contains beds of cherty sideritic and pyritic iron-formation
Comments Continental margin assemblage (north of Niagara Fault)
References

Sims, P.K., 1992, Geologic map of Precambrian rocks, southern Lake Superior region, Wisconsin and northern Michigan: U.S. Geological Survey Miscellaneous Investigations Map I-2185, scale 1:500,000.

https://pubs.er.usgs.gov/publication/i2185
NGMDB product
Counties Ashland - Bayfield - Iron