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| Nachusa Formation | |
|---|---|
| Stratigraphic range: Ordovician | |
| Type | Formation |
| Location | |
| Region |  Illinois |
| Country |  United States |
The Nachusa Formation is a geologic formation in Illinois. It preserves fossils dating back to the Ordovician period.
The Claiborne Formation or Claiborne Group is a geologic formation in Arkansas, Illinois, Kentucky, and Texas. It preserves fossils dating back to the Paleogene period.
The Chouteau Limestone is a geologic formation in Illinois, Iowa, Kansas, and Missouri. It preserves fossils dating back to the Carboniferous period.
The Iola Formation is a geologic formation in Illinois and Oklahoma. It preserves fossils dating back to the Carboniferous period.
The Keokuk Limestone is a geologic formation in Illinois, Iowa and Missouri. It preserves fossils dating back to the Mississippian sub-period.
The Paint Creek Formation is a geologic formation in Illinois. It preserves fossils dating back to the Carboniferous period.
The Warsaw Formation is a geologic formation in Illinois, Iowa and Missouri. It preserves fossils dating back to the Mississippian subperiod.
The Altamont Formation is a geologic formation in Illinois. It preserves fossils dating back to the Carboniferous period.
The Little Cedar Formation is a geologic formation in Illinois. It preserves fossils dating back to the Devonian period.
The Grand Tower Limestone is a geologic formation in Illinois. It preserves fossils dating back to the Devonian period.
The St. Laurent Formation is a geologic formation in Illinois. It preserves fossils dating back to the Devonian period.
The Dunleith Formation is a geologic formation in Illinois. It preserves fossils dating back to the Ordovician period.
The Ion Formation is a geologic formation in Illinois. It preserves fossils dating back to the Ordovician period.
The Wise Lake Formation is a geologic formation in Illinois. It preserves fossils dating back to the Ordovician period.
The Glenwood Formation is a geologic formation in Illinois. It preserves fossils dating back to the Ordovician period.
The Grand Detour Formation is a geologic formation in Illinois. It preserves fossils dating back to the Ordovician period.
The Neda Formation is a geologic formation in Illinois. It preserves fossils dating back to the Ordovician period.
The Mifflin Formation is a fossil bearing geologic formation in Illinois dating to the Ordovician period.
The Quimbys Mill Formation is a geologic formation in Illinois. It preserves fossils dating back to the Ordovician period.
The Mosalem Formation is a geologic formation in Illinois. It preserves fossils dating back to the Silurian period.
The Sugar Run Dolomite is a geologic formation in Illinois. It is a finely-bedded dolomite, preserving fossils dating back to the Silurian period. This formation is named for the Sugar Run stream in Joliet, along which it is well exposed. The dolomite is off-white/grey on freshly cut surfaces, but over time oxidizes to a distinctive cream yellow color, due to trace presence of iron. It is a member of the Niagaran series.
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