Washington Formation

TypeFormation

Unit ofDunkard Group^[1]

Sub-unitsUpper 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

UnderliesGreene Formation

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

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.