| 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′N91°18′W / 42.5°N 91.3°W |
| Approximate paleocoordinates | 20°36′S63°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, [1] Indiana, [2] Iowa, Kansas, [3] Minnesota, [4] Missouri, [5] and Wisconsin. [6] It preserves mollusk, coral, brachiopod and graptolite fossils [5] dating back to the Darriwilian to Hirnantian stages (Edenian to Richmondian in the regional stratigraphy) of the Ordovician period. [7]