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Mapped bedrock in the United States From Wikipedia, the free encyclopedia
The Devonian Harrell Formation is a mapped bedrock unit in Pennsylvania, Maryland, West Virginia, and Virginia.
Harrell Shale Group | |
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Stratigraphic range: Frasnian | |
Type | Group |
Sub-units | Burket Shale[1] |
Underlies | Brallier Formation, Sonyea Formation, Trimmers Rock Formation |
Overlies | Mahantango Formation, Millboro Shale, and Tully Limestone |
Lithology | |
Primary | shale, sandstone |
Location | |
Region | Appalachian Mountains |
Country | United States |
Type section | |
Named by | Charles Butts, 1918[2] |
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."[3]
Hasson and Dennison reported the following fossils from several outcrops of the Harrell:[3]
Type locality is at Horrell Station, Blair County, Pennsylvania (40°27′N 78°17′W).[2] In 1918, when Butts described and named the type section, the USGS topo map spelled the location "Harrell", [4] but the local spelling was "Horrell".[5][6]
Relative age dating places the Harrell in the late Devonian.