WThe Ordovician Bald Eagle Formation is a mapped bedrock unit in central Pennsylvania, USA. It is a ridge-forming unit in the Appalachian Mountains.
WThe Broad Vein Mudstone Formation is an Ordovician lithostratigraphic group in Mid Wales. The rock of the formation is silty mudstone, intensely bioturbated in places. It varies in colour from a pale to a medium blue. This formation has been commercially quarried as slate in several locations along its length. The formation is between 400 metres (1,300 ft) and 560 metres (1,840 ft) thick and runs from Dinas Mawddwy south-west to Cardigan Bay at Tywyn.
WThe Ceiswyn Formation is an Ordovician lithostratigraphic group in Mid Wales. The rock of the formation is made up of interleaved beds of silty mudstones and siltstones with some sandstones and tuffs also present in small amounts. The formation runs diagonally across Mid Wales from close by Bala Lake to Cardigan Bay near Tywyn.
WThe Garnedd-Wen Formation is an Ordovician lithostratigraphic group in Mid Wales. The rock of the formation is a mixture of mudstones, siltstones, fine- to coarse-grained sandstones, greywackes and conglomerates. The formation extends from Dinas Mawddwy in the north-east to Tywyn in the south-west.
WThe Ordovician Juniata Formation is a mapped bedrock unit in Pennsylvania and Maryland. It is a relative slope-former occurring between the two prominent ridge-forming sandstone units: the Tuscarora Formation and the Bald Eagle Formation in the Appalachian Mountains.
WThe Kope Formation is one of the three component bedrock formations of the Maquoketa Group that primarily consists of shale (75%) with some limestone (25%) interbedded. In general, it has a bluish-gray color that weathers light gray to yellowish-gray and it occurs in northern Kentucky, southwest Ohio, and southeast Indiana, United States.
WThe Llanbedrog Volcanic Group is an Ordovician lithostratigraphic group in northwest Wales. The name is derived from the village of Llanbedrog on the Llyn Peninsula where the strata are exposed.
WThe Llewelyn Volcanic Group is an Ordovician lithostratigraphic group in Snowdonia, north-west Wales. The name is derived from Carnedd Llewelyn, the highest peak in the Carneddau range where it outcrops.
WThe Narrow Vein Mudstone Formation is an Ordovician lithostratigraphic group in Mid Wales. The rock of the formation is silty, homogenous or finely-laminated mudstone. It generally a medium blue colour. This formation has been commercially quarried as slate in several locations along its length. The formation is between 400 metres (1,300 ft) and 560 metres (1,840 ft) thick and runs from Dinas Mawddwy south-west to Cardigan Bay at Tywyn.
WThe Nod Glas Formation is an Ordovician lithostratigraphic group in Mid Wales. The rock of the formation is made up of pyritous, graptolitic mudstone that is generally black in colour. It weathers to a soft, very well cleaved and coal-like material. The formation runs from Conwy in the north, down to Cardigan Bay in the area around Aberdyfi and Tywyn, though it is not a continuous over this area.
WThe Snowdon Volcanic Group is an Ordovician lithostratigraphic group in Snowdonia, north-west Wales. The name is derived from Snowdon, the highest peak in Wales where it outcrops. This assemblage of rocks has also been referred to as the Snowdon Volcanic Series.
WThe Whitewater Formation is a geologic formation in Ohio and Indiana. It preserves fossils dating back to the Ordovician period.