Galena Group

The Galena Group or Galena Limestone refers to a sedimentary sequence of Ordovician limestone 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.^[2]

Galena Group
Stratigraphic range: Darriwilian-Sandbian
Unidentified Trochonema from the Galena Group
Type	Group
Sub-units	Decorah Shale, Dunleith Formation, Wise Lake Formation, Dubuque Formation[1]
Underlies	Maquoketa Group
Overlies	Platteville Limestone
Location
Country	United States
Extent	Minnesota, Wisconsin and Illinois

References

1. Raatz, William; Ludvigson, Greg (1996). "Depositional environments and sequence stratigraphy of Upper Ordovician epicontinental deep water deposits, eastern Iowa and southern Minnesota". Special Paper of the Geological Society of America. 306 – via ResearchGate.
2. 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.