Reedsville Formation

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Reedsville Formation
Stratigraphic range: Late Ordovician
Reedsville Formation 522.jpg
Outcrop of Reedsville Formation on south side of U.S. Route 522, Blacklog Gap, Huntingdon County, Pennsylvania.
Typesedimentary
Unit ofChickamauga Group (TN only) [1]
Underlies Bald Eagle Formation and Juniata Formation
Overlies Antes Gap Shale, Trenton Limestone in TN and Utica Shale in WV
Lithology
Primary shale
Other sandstone
Location
Region Appalachian Mountains
Extent Maryland, Pennsylvania, Tennessee, Virginia, [2] West Virginia
Type section
Named for Reedsville, Pennsylvania
Named byE. O. Ulrich [3]

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.

Contents

Description

The Reedsville Formation is an olive-gray to dark-gray siltstone, shale, and fine-grained sandstone. [4] 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. [5]

Etched section of carbonaceous sandstone 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. Reedsville Fm calc ss.jpg
Etched section of carbonaceous sandstone 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. [6]

Isotopic dating of shale mylonite in Pennsylvania reveals a K-Ar age of 372+/-8 Ma. [7]

Economic uses

The Reedsville is quarried locally in borrow pits for road material and fill. [8]

Palaeontology

TaxaClassDescriptionImages
Cephalopod

Related Research Articles

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<span class="mw-page-title-main">Juniata Formation</span>

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<span class="mw-page-title-main">Bald Eagle Formation</span>

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<span class="mw-page-title-main">Clinton Group</span> Lithostratigraphic unit

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The Devonian Mahantango Formation is a mapped bedrock unit in Pennsylvania, West Virginia, and Maryland. It is named for the North branch of the Mahantango Creek in Perry and Juniata counties in Pennsylvania. It is a member of the Hamilton Group, along with the underlying the Marcellus Formation Shale. South of Tuscarora Mountain in south central Pennsylvania, the lower members of this unit were also mapped as the Montebello Formation. Details of the type section and of stratigraphic nomenclature for this unit as used by the U.S. Geological Survey are available on-line at the National Geologic Map Database.

<span class="mw-page-title-main">Pottsville Formation</span>

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<span class="mw-page-title-main">Tonoloway Formation</span>

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<span class="mw-page-title-main">Foreknobs Formation</span> Geological formation in the United States

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Canoe Mountain is a stratigraphic ridge in central Pennsylvania, United States, running east of the Allegheny Front and west of Tussey Mountain. It forms a continuous ridge with Brush Mountain to the west. To the south, across the water gap formed by the Frankstown Branch Juniata River, the ridgeline continues as Lock Mountain.

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References

  1. 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
  2. Paleozoic Sedimentary Successions of the Virginia Valley & Ridge and Plateau
  3. Ulrich, E.O., 1911, Revision of the Paleozoic systems: Geological Society of America Bulletin, v. 22, p. 281-680.
  4. 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.
  5. Robert T. Ryder (1991). Stratigraphic Framework of Cambrian and Ordovician Rocks in the Central Appalachian Basin From Richland County, Ohio, To Rockingham County, Virginia (PDF) (Map). U.S. Geological Survey.
  6. Gold, David P. & Doden, Arnold G. "Geological Report on the Skytop Road Cuts". Geosciences: Feature Article. Pennsylvania State University College of Earth and Mineral Sciences. Retrieved 2008-01-26.
  7. 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.
  8. Doden, Arnold G. & Gold, David P. (2008), Bedrock Geologic Map of The Mc Alevys Fort Quadrangle, Huntingdon, Centre, and Mifflin Counties, Pennsylvania (PDF), Pennsylvania Geological Survey
  9. Lehman, David; Pope, John K. (1989). "Upper Ordovician Tempestites from Swatara Gap, Pennsylvania: Depositional Processes Affecting the Sediments and Paleoecology of the Fossil Faunas". PALAIOS. 4 (6): 553–564. Bibcode:1989Palai...4..553L. doi:10.2307/3514745. JSTOR   3514745.

See also