St. Peter Sandstone

St. Peter Sandstone
Stratigraphic range: Middle Ordovician
Old mine entrances in the St. Peter Sandstone formation in Pacific, Missouri, where it is still actively quarried nearby.
Type	Formation
Unit of	Ancell Group
Underlies	Dutchtown Formation, Glenwood Shale, Joachim Dolomite, and Wells Creek Formation
Overlies	Beekmantown Dolomite, Everton Formation, Shakopee Dolomite
Location
Region	Midwest
Country	United States
Extent	Arkansas, Illinois, Indiana, Iowa, Minnesota, Missouri, Wisconsin and West Virginia
Type section
Named for	St. Peters River (now Minnesota River), Minnesota[1]
Named by	David Dale Owen

The St. Peter Sandstone is an Ordovician geological formation. It belongs to the Chazyan stage of the Champlainian series in North American regional stratigraphy, equivalent to the late Darriwilian global stage. This sandstone originated as a sheet of sand in clear, shallow water near the shore of a Paleozoic sea and consists of fine-to-medium-size, well-rounded quartz grains with frosted surfaces. The extent of the formation spans north–south from Minnesota to Arkansas and east–west from Illinois into Nebraska and South Dakota. The formation was named by Owen (1847)^[2] after the Minnesota River, then known as the St. Peter River. The type locality is at the confluence of the Mississippi and Minnesota Rivers near Fort Snelling, Minnesota.^[3] In eastern Missouri, the stone consists of quartz sand that is 99.44% silica.