The Liberty Formation is a geologic formation in Ohio and Indiana. It preserves fossils dating back to the Ordovician period.
The Cincinnati Group is a geologic group in Kentucky, Ohio and Indiana. It is Upper Ordovician.
The Salem Formation is a geologic formation in Illinois, Indiana, Kentucky, and Missouri. It preserves fossils dating back to the Mississippian subperiod.
The Davis Formation is a geologic formation in Indiana and Missouri. It preserves fossils dating back to the Cambrian period.
The Osgood Formation, also known as the Osgood Shale is a geologic formation in Indiana, Kentucky, and Ohio. It preserves fossils dating back to the Silurian period.
The Black River Group is a geologic group in Illinois and West Virginia. It preserves fossils dating back to the Ordovician period.
The Keokuk Limestone is a geologic formation in Illinois, Iowa and Missouri. It preserves fossils dating back to the Mississippian sub-period.
The Warsaw Formation is a geologic formation in Illinois, Iowa and Missouri. It preserves fossils dating back to the Mississippian subperiod.
The Shakopee Formation is a geologic formation in Illinois, Indiana, Wisconsin, and Minnesota. It preserves fossils dating back to the Ordovician period. It is named after the town of Shakopee, Minnesota, where the formation can be seen in bluffs along the Minnesota River
The Rockdale Run Formation is a geologic formation in Maryland, Pennsylvania, Virginia and West Virginia. It preserves fossils dating back to the Ordovician period.
The Tomstown Dolomite or Tomstown Formation is a geologic formation in Maryland, Pennsylvania, Virginia and West Virginia. It preserves fossils dating to the Cambrian Period.