Wills Creek Formation

Description

The Wills Creek is defined as a moderately well bedded greenish-gray shale containing local limestone and sandstone zones, or more specifically as an olive to yellowish-gray, thin-bedded sandstone, calcareous shale, dolomite, argillaceous limestone, and sandstone. Red shale and siltstone occur in the lower part of the formation. The formation has a thickness between 450 feet and 600 feet in Maryland and 445 to 620 feet in Pennsylvania.

The Wills Creek forms the bedrock of the valley around and to the east of Lewistown, Pennsylvania.

Fossils

The Wills Creek Limestone contain fossils from the Pridoli to the Ludlow epoch, or 422.9 to 418.1 Ma.

Dean et al. (1985) describe the Wills Creek as sparsely fossiliferous.

Conodonts have been identified in the Wills Creek in Virginia (Ozarkodina snajdri crispa Zone).

Notable outcrops

• Type section at Wills Creek at Cumberland, Allegany County, Maryland
• Roundtop Hill, Maryland, along railroad grade

Age

Relative age dating of the Wills Creek places it in the Silurian period. It rests conformably a top the Bloomsburg Formation and below the Tonoloway Formation.

Economic use

The Wills Creek is a poor source of construction material and is only suitable as common fill.

References

References

1. Uhler, P.R., 1905, The Niagara period and its associates near Cumberland, Maryland: Maryland Academy of Science Transactions, v. 2, p. 19-26.
2. (2004). "Table 1. Paleozoic Stratigraphic Section in Central Pennsylvania". [[Pennsylvania State University]] Department of Geosciences.
3. McElroy, Thomas A.. (2004). "Bedrock Geologic Map of the Lewistown Quadrangle, Mifflin and Juniata Counties, Pennsylvania". Pennsylvania Geological Survey.
4. "Wills Creek Limestone Formation". Advisory Board of the Paleobiology Database.
5. Dean, S.L., Kulander, B.R., and Lessing, Peter, 1985, Geology of the Capon Springs, Mountain Falls, Wardensville, Woodstock, and Yellow Springs quadrangles, Hampshire and Hardy Counties, West Virginia: West Virginia Geological and Economic Survey Map, 26, 1 sheet, scale 1:24,000
6. Harris, A.G., Stamm, N.R., Weary, D.J., Repetski, J.E., Stamm, R.G., and Parker, R.A., 1994, Conodont color alteration index (CAI) map and conodont-based age determinations for the Winchester 30' x 60' quadrangle and adjacent area, Virginia, West Virginia, and Maryland: U.S. Geological Survey Miscellaneous Field Studies Map, MF-2239, 40 p., 1 sheet, scale 1:100,000 [https://ngmdb.usgs.gov/Prodesc/proddesc_294.htm]
7. (1968). "Allegheny Plateau and Valley and Ridge". Maryland Geological Survey.
8. (2008). "Bedrock Geologic Map of The Mc Alevys Fort Quadrangle, Huntingdon, Centre, and Mifflin Counties, Pennsylvania". Pennsylvania Geological Survey.