The

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

Scherr Formation is a mapped

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

unit in Pennsylvania, Maryland, Virginia and West Virginia.

Description

The Scherr Formation consists predominantly of

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

and

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

. Lower part of unit includes considerable fine-grained sandstone, while upper two thirds contains almost no sandstone. It weathers light olive gray.

Stratigraphy

Dennison (1970) renamed the old Chemung Formation the Greenland Gap Group and divided it into the lower Scherr Formation and the upper

Foreknobs Formation The Devonian Foreknobs Formation is a mapped bedrock unit in Pennsylvania, Maryland, Virginia, and West Virginia. Description The Foreknobs Formation contains massive sandstones; siltstone; "redbeds" of brownish-gray sandstone, siltstone, and sha ...

. De Witt (1974) extended the Scherr and Foreknobs into Pennsylvania but did not use the term Greenland Gap Group. Boswell et al. (1987), does not recognize the Scherr and Foreknobs Formations in the subsurface of West Virginia, and thus, these formations are reduced from "group" to "formation" as the Greenland Gap Formation. The Minnehaha Springs Member is a "

clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks ...

bundle" consisting of interbedded medium gray siltstone and olive-gray shale with some grayish-red siltstone and shale and some sandstone. It is interpreted as turbidites. This same member is proposed to exist at the base of the Scherr's lateral equivalent, the Lock Haven Formation.Warne, A.G., and McGhee, G.R., Jr., 1991, Stratigraphic subdivisions of the Upper Devonian Scherr, Foreknobs, and Lock Haven Formations near the Allegheny Front of central Pennsylvania: Northeastern Geology, v. 13, no. 2, p. 96-109. USGS 2006 1237 Fig7b

Notable outcrops

* Type section: along West Virginia Route 42, Grant County

Age

Relative age dating places the Scherr in the late

Paleontology

The Scherr Formation is the likely origin of the trace fossil ''

Thinopus ''Thinopus'' is the name given to a trace fossil ( ichnotaxon) found in late Devonian rocks in Pennsylvania. The only specimen was described by paleontologist Othniel Charles Marsh in a brief note published in 1896, with the only ichnospeci ...

'', which was described in 1896 by Othniel Charles Marsh as the earliest known tetrapod (land vertebrate). Later research, however, identified this fossil as coprolites (fossilized feces) of fishes.

References

Geologic formations of Maryland Geologic formations of Pennsylvania Geologic formations of Virginia Geologic formations of West Virginia Shale formations of the United States Siltstone formations Devonian System of North America Devonian Maryland Devonian geology of Pennsylvania Devonian geology of Virginia Devonian West Virginia {{Maryland-geologic-formation-stub