Galena Group

Paleozoic Stratigraphy of the Upper Midwest, USA Dates are approximate, and deposition occurred at slightly different times in different areas

Ordovician :Maquoketa Group (446–440 Ma) ::Neda Formation Brainard Formation Fort Atkinson Formation Scales Formation :Galena Group (454–446 Ma) ::Dubuque Formation (447–446 Ma) Wise Lake Formation (449.4–447 Ma) Dunleth Formation (452–449.4 Ma) Decorah Shale (454–452 Ma) Platteville Limestone / Group (455–454 Ma) Ancell Group (454–455 Ma) Glenwood Shale (~455 Ma) St. Peter Sandstone (~459–~455 Ma) --- Major Erosional Unconformity --- :Knox Supergroup ::--- Major Erosional Unconformity --- Everton Dolomite (only in S. Indiana) --- Major Erosional Unconformity --- Dunleth Formation Prairie du Chien Group * Shakopee Dolomite * New Richmond Sandstone (only in S. Indiana) * Oneota Dolomite * Dunleth Formation * Gunter Sandstone Cambrian :Knox Supergroup (ct'd) ::Jordan Sandstone Potosi Dolomite Potsdam Supergroup/Potsdam Sandstone Megagroup Munising Group Davis Formation Franconia Formation Ironton Sandstone Galesville Sandstone Eau Claire Formation Mount Simon Sandstone

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.^[1]

References

1. 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.