The Galena Group or Galena Limestone refers to a sedimentary sequence of

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

that was deposited atop the Decorah Shale. It is part of the Ordovician stratigraphy of the Upper Midwestern United States. It was deposited in a calm marine environment, and is fossiliferous.Mossler, J. and Benson, S., 1995, 1999, 2006
Fossil Collecting in the Twin Cities Area
Minnesota at a Glance: Minnesota Geological Survey: University of Minnesota.

References

Geologic groups of Minnesota Ordovician Minnesota {{US-geologic-formation-stub