Reedsville Formation

{{Infobox rockunit

| name = Reedsville Formation

| image = Reedsville Formation 522.jpg

| caption = Outcrop of Reedsville Formation on south side of U.S. Route 522, Blacklog Gap, Huntingdon County, Pennsylvania.

| type = sedimentary

| age = Late Ordovician

| period = Late Ordovician

| prilithology = shale

| otherlithology = sandstone

| namedfor = Reedsville, Pennsylvania

| namedby = E. O. UlrichUlrich, E.O., 1911, Revision of the Paleozoic systems: Geological Society of America Bulletin, v. 22, p. 281-680.

| region = Appalachian Mountains

| country =

| coordinates =

| unitof = Chickamauga Group (TN only)Harris, L.D., 1965, Geologic map of the Wheeler quadrangle, Claiborne County, Tennessee, and Lee County, Virginia: U.S. Geological Survey Geologic Quadrangle Map, GQ-435, 1 sheet, scale 1:24,000 http://ngmdb.usgs.gov/Prodesc/proddesc_903.htm

| subunits =

| underlies = Bald Eagle Formation and Juniata Formation

| overlies = Antes Gap Shale, Trenton Limestone in TN and Utica Shale in WV

| thickness =

| extent = Maryland, Pennsylvania, Tennessee, Virginia,[http://hdl.handle.net/10919/19078 Paleozoic Sedimentary Successions of the Virginia Valley & Ridge and Plateau] West Virginia

| area =

| map =

| map_caption =

}}

The Ordovician Reedsville Formation is a mapped surficial bedrock unit in Pennsylvania, Maryland, Virginia, West Virginia, and Tennessee, that extends into the subsurface of Ohio. This rock is a slope-former adjacent to (and stratigraphically below) the prominent ridge-forming Bald Eagle sandstone unit in the Appalachian Mountains. It is often abbreviated Or on geologic maps.

Description

The Reedsville Formation is an olive-gray to dark-gray siltstone, shale, and fine-grained sandstone.Berg, T.M., Edmunds, W.E., Geyer, A.R. and others, compilers, (1980). Geologic Map of Pennsylvania: Pennsylvania Geologic Survey, Map 1, scale 1:250,000. In Central Pennsylvania along the Nittany Arch, and extending into the subsurface of northern West Virginia, the base of the Reedsville formation includes the black calcareous Antes Shale formation.{{cite map|url=http://pubs.usgs.gov/imap/i-2264/IMAP_2264.pdf|publisher=U.S. Geological Survey|author=Robert T. Ryder|year=1991|title=Stratigraphic Framework of Cambrian and Ordovician Rocks in the Central Appalachian Basin From Richland County, Ohio, To Rockingham County, Virginia}}

Image:Reedsville Fm calc ss.jpg bed of Reedsville Formation from along Rt. 36 near Loysburg, Bedford Co., PA. Soft-sediment deformation evident. Contains sparse fossils (black in section image) - probably brachiopods and bryozoans.]]

=Type section=

The type locality is at Reedsville, Pennsylvania.

=Age=

Relative age dating of the Reedsville places it in the Upper Ordovician. It rests conformably atop the Upper Ordovician Coburn Formation at the top of the Trenton Group limestone and conformably below the Bald Eagle Formation.{{cite web |url=http://www.geosc.psu.edu/news/features/gold/skytop.html |title= Geological Report on the Skytop Road Cuts |accessdate=2008-01-26 |author1=Gold, David P. |author2=Doden, Arnold G. |name-list-style=amp |work=Geosciences: Feature Article|publisher=Pennsylvania State University College of Earth and Mineral Sciences }}

Isotopic dating of shale mylonite in Pennsylvania reveals a K-Ar age of 372+/-8 Ma.Lapham, D.M., and Root, S.I., 1971, Summary of isotopic age determinations in Pennsylvania: Pennsylvania Geological Survey Information Circular, 4th series, no. 70, 29 p.

Economic uses

The Reedsville is quarried locally in borrow pits for road material and fill.{{citation |url=http://www.dcnr.state.pa.us/topogeo/openfile/mcalevysfort.pdf|archive-url=https://web.archive.org/web/20110609185124/http://www.dcnr.state.pa.us/topogeo/openfile/mcalevysfort.pdf|url-status=dead|archive-date=June 9, 2011|author1=Doden, Arnold G. |author2=Gold, David P. |name-list-style=amp |year=2008|title=Bedrock Geologic Map of The Mc Alevys Fort Quadrangle, Huntingdon, Centre, and Mifflin Counties, Pennsylvania|publisher=Pennsylvania Geological Survey}}

Palaeontology

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Taxa ! Class ! Description ! Images
* Kinoceras{{Cite journal\|last1=Lehman\|first1=David\|last2=Pope\|first2=John K.\|title=Upper Ordovician Tempestites from Swatara Gap, Pennsylvania: Depositional Processes Affecting the Sediments and Paleoecology of the Fossil Faunas\|journal=PALAIOS\|volume=4\|issue=6\|pages=553–564\|doi=10.2307/3514745\|jstor=3514745\|year=1989\|bibcode=1989Palai...4..553L }} \| Cephalopod \| \| rowspan="99" \|

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Taxa

! Class

! Description

! Images

* Kinoceras{{Cite journal|last1=Lehman|first1=David|last2=Pope|first2=John K.|title=Upper Ordovician Tempestites from Swatara Gap, Pennsylvania: Depositional Processes Affecting the Sediments and Paleoecology of the Fossil Faunas|journal=PALAIOS|volume=4|issue=6|pages=553–564|doi=10.2307/3514745|jstor=3514745|year=1989|bibcode=1989Palai...4..553L }}

| Cephalopod

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| rowspan="99" |