- Juniata Formation
OrdovicianJuniata Formation (Oj) is a mapped bedrock unit in Pennsylvaniaand Maryland. It is a relative slope-formeroccurring between the two prominent ridge-forming sandstoneunits: the Tuscarora Formationand the Bald Eagle Formationin the Appalachian Mountains.
The Juniata is defined as a grayish-red to greenish-gray , thin- to thick-bedded
siltstone, shale, and very fine to medium-grained crossbedded sandstoneor subgraywacke and protoquartzitewith interbedded conglomerate.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.] cite web |url=http://www.mgs.md.gov/esic/geo/lgdalleg.html |title=Allegheny Plateau and Valley and Ridge | work = Geologic Map of Maryland | year = 1968 | publisher=Maryland Geological Survey|accessdate=2008-01-26 |format= |work=] The Juniata is a lateral equivalent of the Queenston Shalein western Pennsylvania.
The Juniata has always been intrepreted as
molasseresulting from the Taconic orogeny.
Very few fossils exist in the Juniata Formation.
Relative age dating of the Juniata places it in the Upper
Ordovicianperiod, being deposited between 488.3 to 443.7 (±10) million years ago. It rests conformably atop the Bald Eagle Formationin Pennsylvania and the Martinsburg Formationin Maryland,cite web |url=http://www.mgs.md.gov/esic/geo/lgdalleg.html |title=Geologic Maps of Maryland: |accessdate=2008-01-26 |format= |work=] and conformably below the Tuscarora Formation. [Berg, T.M., et al., (1983). Stratagraphic Correlation Chart of Pennsylvania: G75, Pennsylvania Geologic Survey, Harrisburg, Pennsylvania.]
The Juniata is a good source of road material,
riprapand building stone.cite paper|url=http://www.dcnr.state.pa.us/topogeo/openfile/mcalevysfort.pdf|format=pdf|author= Doden, Arnold G. and Gold, David P.|year=2008|title=Bedrock Geologic Map of The Mc Alevys Fort Quadrangle, Huntingdon, Centre, and Mifflin Counties, Pennsylvania|publisher=Pennsylvania Geological Survey]
Geology of Pennsylvania
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Martinsburg Formation — A sample of the Martinsburg shale from the Pennsylvania Turnpike (Northeast Extension) at mile post 66. The Ordovician Martinsburg Formation (Om) is a mapped bedrock unit in Pennsylvania, New Jersey, Maryland, Virginia, and West Virginia. It is… … Wikipedia
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