Maquoketa Formation
| Maquoketa Formation | |
|---|---|
| Stratigraphic range: Darriwilian-Hirnantian (Edenian-Richmondian) | |
| Type | Formation |
| Unit of | Maquoketa Group |
| Sub-units | Brainard, Clermont & Elgin members |
| Underlies | Thebes Formation & Wapsipinicon Group |
| Overlies | Cape & Dubuque Formations |
| Thickness | 10–100 ft (3.0–30.5 m) |
| Lithology | |
| Primary | Shale, dolomite |
| Other | Limestone, phosphorite |
| Location | |
| Coordinates | 42°30′N 91°18′W / 42.5°N 91.3°W |
| Approximate paleocoordinates | 20°36′S 63°42′W / 20.6°S 63.7°W |
| Region | Minnesota, Wisconsin, Illinois, Iowa, Kentucky, Kansas |
| Country | United States |
| Extent | Illinois Basin |
The Maquoketa Formation is a geologic formation in Illinois, Indiana. Iowa, Kansas, Minnesota, Missouri, and Wisconsin. It preserves mollusk, coral, brachiopod and graptolite fossils dating back to the Darriwilian to Hirnantian stages (Edenian to Richmondian in the regional stratigraphy) of the Ordovician period.