The Late

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

to Early

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 ...

Keyser Formation is a mapped

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

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 Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...

Virginia Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the Atlantic Coast and the Appalachian Mountains. The geography and climate of the Commonwealth ar ...

, and

West Virginia West Virginia is a state in the Appalachian, Mid-Atlantic and Southeastern regions of the United States.The Census Bureau and the Association of American Geographers classify West Virginia as part of the Southern United States while the Bur ...

Description

The Keyser is a nodular limestone overlain by thick- and thin-bedded limestone and laminated limestone at its type locality in

Keyser, West Virginia Keyser () is a city in and the county seat of Mineral County, West Virginia. It is part of the Cumberland, MD-WV Metropolitan Statistical Area. The population was 4,853 at the 2020 census. History Keyser, the county seat of Mineral County, is ...

. In central Pennsylvania, the basal "calico" limestone is a fossiliferous, medium-light- to medium-gray very thick bedded calcilutite containing numerous small irregular patches of clear calcite. The abundantly fossiliferous, nodular limestone at the base overlies the "calico". Overlying this is 5 to 6 m of fragmental calcarenite containing abundant

crinoid Crinoids are marine animals that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, which are ...

columnals. Above the calcarenite is 6 m of fossiliferous, banded

calcisiltite Calcisiltite is a type of limestone that is composed predominantly, more than 50 percent, of detrital (transported) silt-size carbonate grains. These grains consist either of the silt-size particles of ooids, fragments of fossil shells, fragments of ...

. The uppermost 15 m is a sequence alternating between laminated, stromatolitic calcisiltite, and

calcilutite Calcilutite (also known as cementstone) is a type of limestone that is composed of predominantly, more than 50 percent, of either clay-size or both silt-size and clay-size detrital (transported) carbonate grains. These grains consist either of foss ...

and calcisiltite that are argillaceous and fossiliferous.

Depositional environment

The

depositional environment In geology, depositional environment or sedimentary environment describes the combination of physical, chemical, and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be ...

of the Keyser is interpreted as shallow marine and tidal flats, occurring in cycles.

Stratigraphy

Contact with Tonoloway Formation is probably conformable, but sharp enough to suggest an

unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

. Upper contact with the

Old Port Formation The Devonian Old Port Formation is a mapped bedrock unit in Pennsylvania, USA. Details of the type section and of stratigraphic nomenclature for this unit as used by the U.S. Geological Survey are available on-line at the National Geologic Map Da ...

is conformable. The Keyser was divided into three members by J. W. Head in 1972. These are, from lowest to highest, the Byers Island Member, Jersey Shore Member, and La Vale Member. The type locality of the Byers Island Member is at Selinsgrove, Pennsylvania, where it is 93 feet thick. The type locality of the Jersey Shore Member is at

Jersey Shore The Jersey Shore (known by locals simply as the Shore) is the coastal region of the U.S. state of New Jersey. Geographically, the term encompasses about of oceanfront bordering the Atlantic Ocean, from Perth Amboy in the north to Cape May Po ...

Lycoming County Lycoming County is a county in the Commonwealth of Pennsylvania. As of the 2020 census, the population was 114,188. Its county seat A county seat is an administrative center, seat of government, or capital city of a county or civil parish. ...

, Pennsylvania. The type locality of the La Vale Member is at the

Corriganville __NOTOC__ Corriganville Movie Ranch was a working film studio and movie ranch for outdoor location shooting, as well as a Western-themed tourist attraction. The ranch, owned by actor and stuntman Ray "Crash" Corrigan, was located in the foothil ...

quarry, Allegany County, Maryland, and is named for the nearby town of La Vale. This nomenclature is accepted by the

USGS The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, a ...

. In Virginia and West Virginia the Keyser is divided into Upper and Lower Members by the Big Mountain Shale Member.

Fossil content

columnals *

stromatoporoid Stromatoporoidea is an extinct clade of sea sponges common in the fossil record from the Ordovician through the Devonian. They were especially abundant and important reef-formers in the Silurian and most of the Devonian.Stock, C.W. 2001, Stro ...

s *

Brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, w ...

s *

Tabulate coral Tabulata, commonly known as tabulate corals, are an order of extinct forms of coral. They are almost always colonial, forming colonies of individual hexagonal cells known as corallites defined by a skeleton of calcite, similar in appearance to ...

s *

Conodont Conodonts (Greek ''kōnos'', "cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, which ...

s: '' Icriodus woschmidti'',Helfrich, C. T., 1978, A Conodont Fauna from the Keyser Limestone of Virginia and West Virginia,

Journal of Paleontology The ''Journal of Paleontology'' is a peer-reviewed scientific journal covering the field of paleontology. It is published by the Paleontological Society. Indexing The ''Journal of Paleontology'' is indexed in: *BIOSIS Previews *Science Citatio ...

, Vol. 52, No. 5 (Sep., 1978), pp. 1133-114

/ref> ''

Oulodus ''Oulodus'' is a genus of conodonts in the family Prioniodinidae. ''O. elegans'' is found in the Late Silurian to Early Devonian Keyser Formation, a mapped limestone bedrock unit in Pennsylvania, Maryland, Virginia, and West Virginia. Referen ...

elegans'', ''O. cristagalli''

Notable outcrops

(type section), quarry and roadcut east of the town, on West Virginia.Previously, the quarry was exposed on County Route 8 in Mineral County, aka Waxler Road, but Waxler Road was moved to connect its more westward section to Route 46. The quarry is on private property, the site of the now closed Faulks Brothers Scrap Yard
It is visible on Google Maps at 39.43917865242232, -78.95964425171306
. * Old Eldorado Quarry, at Mile Marker 30 along I-99/U.S. Route 220 in

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. The county was created on February 26, 1846, from parts of Huntingdon and Bedford counties. Blai ...

* Alleghany Furnace Quarry, Altoona, Pennsylvania * St. Clairsville/Osterburg Exit of I-99 in Bedford County, Pennsylvania (nearly vertical orientation) * Abandoned quarry in Tyrone, Pennsylvania * Quarry at Canoe Creek, Pennsylvania * New Enterprise New Paris Quarry, Chestnut Ridge, Bedford County, Pennsylvania * Roadcut along

U.S. Route 30 U.S. Route 30 or U.S. Highway 30 (US 30) is an east–west main route in the system of the United States Numbered Highways, with the highway traveling across the northern tier of the country. With a length of , it is the third longest ...

(Everett bypass) through

Warrior Ridge Warrior Mountain is a ridge located in Allegany County, Maryland. Warrior Mountain begins northwest of Oldtown, Maryland and runs northeasterly to the water gap formed by the Murley Branch of Town Creek, south of Flintstone, Maryland. North ...

, Bedford County, Pennsylvania * Strait Creek section on County Road 629, 1.5 miles south of

U.S. Route 220 U.S. Route 220 (US 220) is a spur route of US 20. It runs in a north–south layout in the eastern United States, unlike its parent route as well as conventionally even-numbered highways which run east-west. US 220 extends for f ...

, Strait Creek, Highland County, Virginia * Smoke Hole section on West Virginia Route 2, 1.5 miles west of

, Pendleton County, West Virginia

Age

Relative age dating places the Keyser in the late

to early

, with the transition occurring near the top of the formation. Denkler and Harris used

conodont Conodonts (Greek ''kōnos'', "cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, which ...

biostratigraphy Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock Stratum, strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictiona ...

to confirm this.Denkler, K.E. and Harris, A.G., 1988, Conodont-based determination of the Silurian-Devonian boundary in the Valley and Ridge province, northern and central Appalachians, U.S. Geological Survey Bulletin 1837-B . B1-B13IN Sando, W.J., ed., Shorter contributions to paleontology and stratigraphy

/ref>

References

{{Stratigraphic column of West Virginia Geologic formations of Maryland Geologic formations of Pennsylvania Geologic formations of Virginia Geologic formations of West Virginia Devonian System of North America Silurian System of North America Devonian Maryland Devonian geology of Pennsylvania Devonian geology of Virginia Devonian West Virginia Silurian Maryland Silurian geology of Pennsylvania Silurian geology of Virginia Silurian West Virginia Pridoli geology Lochkovian Stage Limestone formations of the United States Silurian southern paleotemperate deposits Shallow marine deposits Tidal deposits Fossiliferous stratigraphic units of North America Paleontology in Pennsylvania Paleontology in Virginia Paleontology in West Virginia