Bald Eagle Formation

The Ordovician Bald Eagle Formation (Obe) is a mapped bedrock unit in central Pennsylvania. It is a ridge-forming unit in the Appalachian Mountains.

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.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.]

=Depositional Environment=

The Bald Eagle has always been intrepreted as molasse resulting from the Taconic orogeny.

Fossils

Very few fossils exist in the Bald Eagle Formation, and most of them are trace fossils.

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. [Berg, T.M., et al., (1983). Stratagraphic Correlation Chart of Pennsylvania: G75, Pennsylvania Geologic Survey, Harrisburg, Pennsylvania.]

Economic Uses

The Bald Eagle is a good source of road material, riprap and 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] However, iron pyrite inclusions may lead to acidic rainwater runoff.

References

ee also

*Geology of Pennsylvania