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 |
| Named by | David Dale Owen |
| Paleozoic Stratigraphy of the Upper Midwest, USA |
|---|
| Dates approximate |
| Maquoketa Group (446–440 Ma) |
| Galena Group (454–446 Ma) |
|
| Platteville Limestone (455–454 Ma) |
| Glenwood Shale (~455 Ma) |
| St. Peter Sandstone (~459–~455 Ma) |
| Knox Unconformity (~470-~459 Ma) |
| Knox Supergroup (~497-~470 Ma) |
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 David Dale Owen (1847) 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. In eastern Missouri, the stone consists of quartz sand that is 99.44% silica.