Juniata Formation
Juniata Formation Stratigraphic range: Late Ordovician | |
---|---|
Type | sedimentary |
Underlies | Oswego Formation and Tuscarora Formation |
Overlies | Bald Eagle Formation |
Thickness | 400–1,125 ft (122–343 m) |
Lithology | |
Primary | sandstone, siltstone, shale |
Location | |
Region | Appalachian Mountains |
Extent | Maryland, Pennsylvania, Tennessee, Virginia,[1] and West Virginia |
Type section | |
Named for | Juniata River in Pennsylvania |
Named by | Darton and Taff[2] |
The Ordovician Juniata Formation is a mapped bedrock unit in Pennsylvania and Maryland. It is a relative slope-former occurring between the two prominent ridge-forming sandstone units: the Tuscarora Formation and the Bald Eagle Formation in the Appalachian Mountains.
Description[]
The Juniata is defined as a grayish-red to greenish-gray, thin- to thick-bedded siltstone, shale, and very fine to medium-grained crossbedded sandstone or subgraywacke and protoquartzite with interbedded conglomerate.[3][4] The Juniata is a lateral equivalent of the Queenston Shale in western Pennsylvania.
Depositional environment[]
The depositional environment of the Juniata has always been interpreted as mostly terrestrial or shallow marine deposits resulting in a molasse sequence produced by the Taconic orogeny.
Fossils[]
Very few fossils exist in the Juniata Formation, but different types of trace fossils such as tracks and burrows can commonly be found.
Age[]
Relative age dating of the Juniata places it in the Upper Ordovician period, being deposited between 488.3 and 443.7 (±10) million years ago. It rests conformably atop the Bald Eagle Formation in Pennsylvania and the Martinsburg Formation in Maryland,[4] and conformably below the Tuscarora Formation.[5]
Economic use[]
The Juniata is a good source of road material, riprap and building stone.[6]
References[]
- ^ Paleozoic Sedimentary Successions of the Virginia Valley & Ridge and Plateau
- ^ Darton, N.H., and Taff, J.A., 1896, Description of the Piedmont sheet (West Virginia-Maryland): U.S. Geological Survey Geologic Atlas of the United States, Piedmont folio, no. 28, 6 p.
- ^ 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.
- ^ a b "Allegheny Plateau and Valley and Ridge". Geologic Map of Maryland. Maryland Geological Survey. 1968. Retrieved 2008-01-26.
- ^ Berg, T.M., et al., (1983). Stratagraphic Correlation Chart of Pennsylvania: G75, Pennsylvania Geologic Survey, Harrisburg, Pennsylvania.
- ^ 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. Cite journal requires
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See also[]
- Ordovician System of North America
- Upper Ordovician Series
- Sandstone formations of the United States
- Siltstone formations
- Shale formations of the United States
- Geologic formations of Maryland
- Geologic formations of Pennsylvania
- Geologic formations of Tennessee
- Geologic formations of Virginia
- Ordovician West Virginia
- Ordovician Maryland
- Ordovician geology of Pennsylvania
- Ordovician geology of Tennessee
- Ordovician geology of Virginia
- Southern United States geologic formation stubs
- Maryland geography stubs