Glenshaw Formation

{{Short description|Geological formation in the United States}}

{{Infobox rockunit

| name = Glenshaw Formation

| image = Island Run (Helmick Bridge, southwest of Eagleport, Morgan County, Ohio, USA) 3 (28488898532).jpg

| caption = Outcrops of Brush Creek Limestone, Glenshaw Formation, in Ohio

| type = sedimentary

| age = Pennsylvanian

| period = Pennsylvanian

| prilithology = shale, siltstone, sandstone, red beds, coal

| otherlithology = limestone

| namedfor =

| namedby = N. K. Flint, 1965Flint, N.K., 1965, Geology and mineral resources of southern Somerset County, Pennsylvania: Pennsylvania Geological Survey County Report, 4th series, no. 56A, 267 p.

| region = Appalachian Plateau

| country = United States

| coordinates =

| unitof = Conemaugh Group

| subunits = Ames Limestone Member, Mahoning Sandstone Member, Brush Creek Limestone

| underlies = Casselman Formation

| overlies = Allegheny Formation

| thickness =

| extent = Pennsylvania, Maryland, West Virginia, Ohio

| area =

| map =

| map_caption =

}}

{{commons}}

The Glenshaw Formation is a mapped sedimentary bedrock unit in Pennsylvania, Maryland, West Virginia, and Ohio, of Pennsylvanian age. It is the lower of two formations in the Conemaugh Group, the upper being the Casselman Formation. The boundary between these two units is the top of the marine Ames Limestone.Assessment of Appalachian Basin Oil and Gas Resources: Carboniferous Coal-bed Gas Total Petroleum System http://pubs.usgs.gov/of/2004/1272/2004-1272.pdf {{Webarchive|url=https://web.archive.org/web/20110629125858/http://pubs.usgs.gov/of/2004/1272/2004-1272.pdf |date=2011-06-29 }} The Conemaugh Group overlies the Upper Freeport coal bed of the Allegheny Formation and underlies the Pittsburgh coal seam of the Monongahela Group.

The Conemaugh Group consists of cyclic sequences of shale, siltstone, sandstone, red beds, thin impure limestone, and thin nonpersistent coal. Red beds are associated with landslides.Casselman Formation https://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=PAPAcc;6 {{Webarchive|url=https://web.archive.org/web/20160306060514/http://mrdata.usgs.gov/geology/state/sgmc-unit.php?unit=PAPAcc;6 |date=2016-03-06 }}

The thickness of the Conemaugh Group averages about 400 feet in Ohio, and it ranges from 450 feet on the Ohio River in West Virginia to 520 feet in Washington County, Pennsylvania, and then to 890 feet in Somerset County, Pennsylvania.Assessment of Appalachian Basin Oil and Gas Resources: Carboniferous Coal-bed Gas Total Petroleum System http://pubs.usgs.gov/of/2004/1272/2004-1272.pdf {{Webarchive|url=https://web.archive.org/web/20110629125858/http://pubs.usgs.gov/of/2004/1272/2004-1272.pdf |date=2011-06-29 }} Citing Arkle and others, 1979; Collins; 1979; Edmunds and others, 1999

The Glenshaw formation was originally mapped in Pennsylvania by Flint, but was extended into West Virginia by Cardwell et al. in 1968.Cardwell, D.H., Erwin, R.B., and Woodward, H.P., 1968, Geologic Map of West Virginia: West Virginia Geological and Economic Survey, 2 sheets, scale 1:250,000 It is also recognized in eastern Ohio.Rice, C.L., Hiett, J.K., and Koozmin, E.D., 1994, Glossary of Pennsylvanian stratigraphic names, central Appalachian basin, IN Rice, C.L., ed., Elements of Pennsylvanian stratigraphy, central Appalachian basin: Geological Society of America Special Paper, 294, p. 115-155.