Washington Formation

{{Short description|American geologic formation}}

{{Infobox rockunit

| name = Washington Formation

| image = Bituminous coal (Washington Coal, Upper Pennsylvanian; Narrows Run South roadcut, near Powhatan Point, Ohio, USA) 2.jpg

| caption = Bituminous coal (Washington Coal, Upper Pennsylvanian; Ohio)

| type = Formation

| age = Permian

| period = Permian

| prilithology = limestone, sandstone, coal

| otherlithology = shale

| namedfor =

| namedby =

| region = {{Flag|Ohio}} and {{Flag|West Virginia}}

| country = United States

| coordinates =

| unitof = Dunkard Group{{cite journal |last1=Berryhill |first1=Henry L. Jr.|last2=Swanson |first2=Vernon E. |title=Geological Survey research 1962; Short papers in geology and hydrology |journal=U.S. Geological Survey Professional Paper |date=1962 |volume=450-C |pages=43–46 |url=https://pubs.usgs.gov/pp/0450c/report.pdf |access-date=30 June 2018}}

| subunits =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

| thickness =

| extent =

| area =

| map =

| map_caption =

}}

The Washington Formation is a coal, sandstone, and limestone geologic formation located in Ohio, Pennsylvania and West Virginia. It dates back to the Lower Permian period, with its base at or near the Permian/Carboniferous boundary.{{Cite journal |last=Wayne Martin, Bernard Henniger |date=1965 |title=The Hockingport and Waynesburg Sandstones (Pennsylvanian and Permian) of the Dunkard Group: ABSTRACT |url=http://dx.doi.org/10.1306/a66335b4-16c0-11d7-8645000102c1865d |journal=AAPG Bulletin |volume=49 |doi=10.1306/a66335b4-16c0-11d7-8645000102c1865d |issn=0149-1423|url-access=subscription |doi-access=free }}{{Cite journal |last=M. A. Rendina, Wayne D. Martin |date=1985 |title=Provenance of Selected Sandstones and Mud Rocks of Dunkard Group (Upper Pennsylvanian-Permian) in Ohio, West Virginia, and Pennsylvania: ABSTRACT |url=http://dx.doi.org/10.1306/94885417-1704-11d7-8645000102c1865d |journal=AAPG Bulletin |volume=69 |doi=10.1306/94885417-1704-11d7-8645000102c1865d |issn=0149-1423|url-access=subscription |doi-access=free }} 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.{{Cite journal |last=Haq |first=Bilal U. |last2=Schutter |first2=Stephen R. |date=2008-10-03 |title=A Chronology of Paleozoic Sea-Level Changes |url=http://dx.doi.org/10.1126/science.1161648 |journal=Science |volume=322 |issue=5898 |pages=64–68 |doi=10.1126/science.1161648 |issn=0036-8075|url-access=subscription }} 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.