Juniata Formation
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The Ordovician Juniata Formation (Oj) 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.
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[edit] 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.[1][2] The Juniata is a lateral equivalent of the Queenston Shale in western Pennsylvania.
[edit] Depositional Environment
The Juniata has always been intrepreted as molasse resulting from the Taconic orogeny.
[edit] Fossils
Very few fossils exist in the Juniata Formation.
[edit] Age
Relative age dating of the Juniata places it in the Upper Ordovician period, being deposited between 488.3 to 443.7 (±10) million years ago. It rests conformably atop the Bald Eagle Formation in Pennsylvania and the Martinsburg Formation in Maryland,[2] and conformably below the Tuscarora Formation.[3]
[edit] Economic Uses
The Juniata is a good source of road material, riprap and building stone.[4]
[edit] References
- ^ 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. Maryland Geological Survey (1968). Retrieved on 2008-01-26.
- ^ Berg, T.M., et al., (1983). Stratagraphic Correlation Chart of Pennsylvania: G75, Pennsylvania Geologic Survey, Harrisburg, Pennsylvania.
- ^ Doden, Arnold G. and Gold, David P.. "Bedrock Geologic Map of The Mc Alevys Fort Quadrangle, Huntingdon, Centre, and Mifflin Counties, Pennsylvania" (pdf). . Pennsylvania Geological Survey
