Stratigraphic range: Middle Devonian-Late Devonian
|Sub-units||Burket Shale Member|
|Underlies||Brallier Formation, Sonyea Formation, Trimmers Rock Formation|
|Overlies||Mahantango Formation, Millboro Shale, and Tully Limestone|
|Named by||Charles Butts, 1918|
The Harrell Formation was first described by Charles Butts in 1918. Hasson and Dennison (1978) state "The Harrell Shale consists of very dark gray, thinly laminated, platy- to sheety-weathering shale underlain in certain areas by the grayish black shale of the Burket Member."
Hasson and Dennison reported the following fossils from several outcrops of the Harrell:
- Bivalvia: Buchiola livonae (?), B. retrostriata, Paracardium doris, Pterochaenia fragilis, Lunlulicardium (?)
- Cephalopoda: Bactrites aciculum, Probeloceras lutheri
- Cricoconarida (class of Mollusca): Styliolina fissurella
Relative age dating places the Harrell in the late Devonian.
- de Witt, Wallace, Jr., Roen, J.B., and Wallace, L.G., 1993, Stratigraphy of Devonian black shales and associated rocks in the Appalachian basin, IN Roen, J.B., and Kepferle, R.C., eds., Petroleum geology of the Devonian and Mississippian black shale of eastern North America: U.S. Geological Survey Bulletin, 1909-B, p. B1-B57.
- Butts, Charles, 1918, Geologic section of Blair and Huntingdon Counties, central Pennsylvania: American Journal of Science, 4th series, v. 46, p. 523-537.
- Hasson, Kenneth O., and Dennison, John M., 1978, STRATIGRAPHY OF THE DEVONIAN HARRELL AND MILLBORO SHALES IN PARTS OF PENNSYLVANIA, MARYLAND, WEST VIRGINIA, AND VIRGINIA, Project Final Report for Energy Research and Development Administration Contract #EY-77-C-21-8153, May 1978