Bald Eagle Formation
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The Ordovician Bald Eagle Formation (Obe) is a mapped bedrock unit in central Pennsylvania. It is a ridge-forming unit in the Appalachian Mountains.
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[edit] Description
The Bald Eagle is defined as a gray to olive-gray and grayish-red, fine to coarse-grained crossbedded sandstone or greywacke. A conglomeratic member, called the Lost Run member (Obelr), exists in some locations.[1]
[edit] Depositional Environment
The Bald Eagle has always been intrepreted as molasse resulting from the Taconic orogeny.
[edit] Fossils
Very few fossils exist in the Bald Eagle Formation, and most of them are trace fossils.
[edit] Age
Relative age dating of the Bald Eagle places it in the Upper Ordovician period, being deposited between 488.3 to 443.7 (±10) million years ago. It rests conformably atop the Reedsville Formation and conformably below the Juniata Formation.[2]
[edit] Economic Uses
The Bald Eagle is a good source of road material, riprap and building stone.[3] However, iron pyrite inclusions may lead to acidic rainwater runoff.
[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.
- ^ 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
