Brallier Formation

The Devonian Brallier Formation is a mapped bedrock unit in Pennsylvania, Maryland, West Virginia, and Virginia.

Brallier Formation
Stratigraphic range: Frasnian - Famennian[1]
Outcrop of Brallier Formation on north side of Pennsylvania Turnpike, central Bedford County, near Mile Marker 138
Typesedimentary
Sub-unitsBlack Creek Siltstone Member,[2] Minnehaha Springs Member[3]
UnderliesGreenland Gap Group and Scherr Formation
OverliesHarrell Formation
Thickness1350 to 1800 feet in central PA[4]
Lithology
Primaryshale, sandstone
Location
RegionAppalachian Mountains
CountryUnited States
ExtentMaryland, Pennsylvania, Virginia, and West Virginia
Type section
Named byCharles Butts, 1918[4]

Description

The Brallier Formation was described by Charles Butts in 1918 as a fine-grained, siliceous shale with few fine-grained sandstone layers, from outcrops in central Pennsylvania. Others expanded usage of the term to rocks in other states.

Stratigraphy

The Brallier is roughly equivalent to the Scherr Formation.

The contact with the underlying Harrell Formation is generally gradational.

Fossils

Hasson and Dennison reported the following fossils from outcrops of the lower Brallier at Keyser, West Virginia, Ridgeville, West Virginia, and McCoole, Maryland:[5]

  • Bivalvia: Buchiola retrostriata, Paracardium doris, Pterochaenia fragilis
  • Cephalopoda: Bactrites, Orthoceras filosum
  • Cricoconarida (class of Mollusca): Styliolina fissurella
  • Annelida: Pteridichnites biseriatus

Notable Exposures

Type locality is at a railway station 6 miles northeast of Everett, Bedford County, Pennsylvania.[4]

A large exposure is located in Huntingdon, Pennsylvania, along the ramp from U.S. Route 22 west to Route 26 north.[6]

  • Part of the exposure at Huntingdon (2017)
    Part of the exposure at Huntingdon (2017)
  • Another view at Huntingdon (1924)
    Another view at Huntingdon (1924)

Another good exposure is on the Pennsylvania Railroad bed just west of Altoona, Pennsylvania.[6]

Age

Relative age dating places the Brallier in the late Devonian.

References
  1. Paleozoic Sedimentary Successions of the Virginia Valley & Ridge and Plateau
  2. Avary, K.L., and Dennison, J.M., 1980, Back Creek Siltstone Member of Devonian Brallier Formation in Virginia and West Virginia: Southeastern Geology, v. 21, no. 2, p. 121-153.
  3. Lyke, W.L., 1986, The stratigraphy, paleogeography, depositional environment, faunal communities, and general petrology of the Minnehaha Springs Member of the Scherr Formation: Southeastern Geology, v. 26, no. 3, p. 173-192.
  4. Butts, Charles, 1918, Geologic section of Blair and Huntingdon Counties, central Pennsylvania: American Journal of Science, 4th series, v. 46, p. 523-537.
  5. 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
  6. Charles Butts, 1945. Hollidaysburg-Huntingdon folio, Pennsylvania, Folios of the Geologic Atlas 227. United States Geological Survey.


This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.