The Arnheim Formation is a geologic formation in Ohio. It preserves fossils dating back to the Ordovician period.
The Liberty Formation is a geologic formation in Ohio and Indiana. It preserves fossils dating back to the Ordovician period.
The Eggleston Formation is a geologic formation in Virginia. It preserves fossils dating back to the Ordovician period.
The Lenoir Limestone is a geologic formation in Virginia. It preserves fossils dating back to the Ordovician period.
The Mosheim Limestone is a geological formation in Virginia. It preserves fossils dating back to the Ordovician period.
The Moccasin Formation is a geologic formation in Virginia and Tennessee. It preserves fossils dating back to the Ordovician period.
The Longview Formation is a geologic formation in Virginia. It preserves fossils dating back to the Ordovician period.
The Powell Formation or Powell Dolomite is a geologic formation in northern Arkansas, southeast Missouri and Virginia. It contains gastropod, cephalopod, and trilobite fossils dating back to the Ordovician Period.
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 Chepultepec Formation, is an Early Ordovician-age geological formation in the Appalachian regions of Eastern North America. Also known as the Chepultepec Dolomite, it is a unit of the Upper Knox Group, overlying the Copper Ridge Dolomite and underlying the Longview-Kingsport-Mascot sequence. The Chepultepec Formation is a primarily limestone and dolomite formation, the earliest formation of the Ordovician period in its area. Further north, it is equivalent to the Stonehenge Formation of the Beekmantown Group. The formation was first described from Allgood, Alabama, and has also been found in Tennessee and Virginia. Allgood was originally named "Chepultepec", providing its name to the formation as well. In Virginia, the Chepultepec Formation has a habit of forming large natural arches, including Natural Tunnel in Scott County and Natural Bridge in Rockbridge County.
The Bowen Formation is an Ordovician-age geological formation in the Appalachian region of the eastern United States. It occupies a thin stratigraphic range between the Wardell and Witten formations in some areas of southwest Virginia and northeast Tennessee. It is particularly well-exposed in Tazewell County, Virginia. Unlike its encompassing strata, the Bowen Formation is mostly calcareous sandstone and mudrock rather than limestone. The thicker upper part of the formation is composed of layered red mudrock which is replete with mudcracks. The thinner lower part, which is not always preserved, is a coarser unit of dark grey stratified sandstone which weathers to a rusty-brown color. Fossils are rare, restricted to stromatolites and Tetradium fibratum.
The Chambersburg Formation is a geologic formation in Virginia. It preserves fossils dating back to the Ordovician period.
The Gratton Limestone is a geologic formation in Virginia. It preserves fossils dating back to the Ordovician period.
The Bays Formation is a geologic formation in Virginia. It preserves fossils dating back to the Ordovician period.
The Wardell Formation is a geologic formation in Virginia. It preserves fossils dating back to the Ordovician period.
The Athens Formation is a geologic formation in Virginia. It preserves fossils dating back to the Ordovician period.
The Witten Limestone is a geologic formation in Virginia. It preserves fossils dating back to the Ordovician period.
The Whitesburg Formation is a dark limestone with interbedded shales geologic formation in Tennessee and Virginia. It preserves fossils dating back to the Ordovician period.
The Everton Formation is a geologic formation in northern Arkansas that dates to the middle Ordovician Period. Unconformities separate this formation from the underlying Powell Formation and the overlying St. Peter Sandstone Formation. Named for the town of Everton in Boone County, Arkansas in 1907, the Everton Formation is composed primarily of dolomite, limestone, and sandstone.
The Viola Formation is a geologic formation in Oklahoma. It preserves fossils dating back to the Ordovician period.
Virginia 
United States 
