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