Reedsville Formation
| Reedsville Formation | |
|---|---|
| Stratigraphic range: Late Ordovician | |
| File:Reedsville Formation 522.jpg Outcrop of Reedsville Formation on south side of U.S. Route 522, Blacklog Gap, Huntingdon County, Pennsylvania. | |
| Type | sedimentary |
| Unit of | Chickamauga 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 by | E. 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.
Description
[edit | edit source]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]
Type section
[edit | edit source]The type locality is at Reedsville, Pennsylvania.
Age
[edit | edit source]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
[edit | edit source]The Reedsville is quarried locally in borrow pits for road material and fill.[8]
Palaeontology
[edit | edit source]| Taxa | Class | Description | Images |
|---|---|---|---|
| Cephalopod |
References
[edit | edit source]- ^ 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 https://ngmdb.usgs.gov/Prodesc/proddesc_903.htm
- ^ Paleozoic Sedimentary Successions of the Virginia Valley & Ridge and Plateau
- ^ Ulrich, E.O., 1911, Revision of the Paleozoic systems: Geological Society of America Bulletin, v. 22, p. 281-680.
- ^ 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.
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ 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.
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
- ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
See also
[edit | edit source]
- Sandstone formations of the United States
- Shale formations of the United States
- Ordovician geology of Pennsylvania
- Ordovician Ohio
- Ordovician Pennsylvania
- Ordovician United States
- Ordovician Tennessee
- Ordovician West Virginia
- Ordovician southern paleotemperate deposits
- Ordovician Maryland
- Geologic formations of Maryland
- Ordovician geology of Virginia
- Geologic formations of Virginia
- Geologic formations of Tennessee
- United States geologic formation stubs