The

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

Harrell Formation is a mapped

bedrock In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface material. An exposed portion of bed ...

unit in

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, and

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Description

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."

Fossils

Hasson and Dennison reported the following fossils from several outcrops of the Harrell: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 197

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Bivalvia Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

: ''Buchiola livonae'' (?), ''B. retrostriata'', ''Paracardium doris'', ''Pterochaenia fragilis'', ''Lunlulicardium'' (?) *

Cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

a: ''Bactrites aciculum'', ''Probeloceras lutheri'' *Cricoconarida (class of

Mollusca Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum ...

): ''Styliolina fissurella''

Notable Exposures

Type locality is at Horrell Station,

Blair County, Pennsylvania Blair County is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 122,822. Its county seat is Hollidaysburg, and its largest city is Altoona. The county was created on February 26, 1846, from parts of Hu ...

(). In 1918, when Butts described and named the type section, the USGS topo map spelled the location "Harrell", but the local spelling was "Horrell".

Age

Relative age dating places the Harrell in the late

References

{{Clear Devonian System of North America Shale groups of the United States Devonian Maryland Devonian geology of Pennsylvania Devonian Pennsylvania Devonian geology of Virginia Devonian West Virginia Devonian southern paleotemperate deposits Sandstone groups of the United States Geologic groups of Maryland Geologic groups of Pennsylvania Geologic groups of Virginia Geologic formations of West Virginia