Maquoketa Formation | |
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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]