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] Lucas et al 2013 discusses the fauna of the formation. ^[5]

Fishes

Genus	Species	Notes	Images
Orthacanthus	O. Texanensis	Large 3m cartilaginous fish
Ectosteorhachis	Indeterminate [6]	Large 2m lobe finned fish
Xenacanthus	X. luedersensis	Small 1m cartilaginous fish
Dipnoan	Indeterminate	Indeterminate lungfish
Palaeonisciformes	Indeterminate	Indeterminate palaeonisciformes
Barbclabornia	B. luederensis [7]	Large 5m xenacanthid

Amphibians

Genus	Species	Notes	Image
Eryops	E. megacephalus	Large 2m amphibian
Diploceraspis	D. burkei	Small 50cm amphibian
Zatrachys	Z. sp	Terrestrial amphibian
Trimerorhachis	T. insignis	1m aquatic amphibian
Acheloma	A. cumminsi	Terrestrial amphibian

Synapsids

Genus	Species	Notes	Images
Dimetrodon	D. limbatus	Large sphenacodontid
Edaphosaurus	E. boanerges	Large edaphosaurid
Ophiacodon	O. retroversus	Large ophiacodontid

Diadectomorpha

Genus	Species	Notes	Images
Diadectes	D. sp	large diadectomorph