Washington Formation

The Washington Formation is a coal, sandstone, and limestone geologic formation located in Ohio, Pennsylvania and West Virginia.^[1] It dates back to the Lower Permian period, with its base at or near the Permian/Carboniferous boundary.^[2][3] The Washington formation and the Dunkard Group as a whole was deposited at a time when the continents were in the process of forming the "Super Continent" Pangaea as well as a gradual drop in sea levels.^[4] The result during this period was coals being thinner and impure with high ash content. The limestones found with in the formation are exclusively freshwater deposits.

Washington Formation
Stratigraphic range: Permian
Bituminous coal (Washington Coal, Upper Pennsylvanian; Ohio)
Type	Formation
Unit of	Dunkard Group[1]
Sub-units	Upper Washington Jollytown coal Hundred sandstone Upper Marietta Washington “A” coal Middle Washington Lower Washington Lower Marietta Washington (No. 12) coal Little Washington coal Mannington sandstone Waynesburg “A” coal Waynesburg Sandstone Elm Grove limestone Cassville
Underlies	Greene Formation
Overlies	Waynesburg Formation
Lithology
Primary	limestone, sandstone, coal
Other	shale
Location
Region	Ohio and West Virginia
Country	United States

Paleofauna

The Paleo fauna of the Washington formation is considered similar to that of the Texas red beds, sharing many taxa of fish and tetrapods with the red beds. Some of the taxa listed suggest an Artinskian age ^[5]

Fishes

Orthacanthus

Xenacanthus

Ectosteorhachis

Dipnoa

Amphibians

Eryops

Trimerorhacis

Zatrachys

Diploceraspis

Acheloma

Synapsids

Edaphosaurus boanerges

Dimetrodon limbatus

Ophiacodon retroversus

Diadectomorpha

Diadectes