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Keyser_Formation Latitude and Longitude:
38°18′N 79°36′W / 38.3°N 79.6°W / 38.3; -79.6
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Keyser Formation
Stratigraphic range: Pridoli- Lochkovian [1]
Outcrop of the Keyser Formation on U.S. Route 522 in Fulton County, Pennsylvania, north of Warfordsburg
TypeSedimentary
Unit of Helderberg Group
Sub-unitsByers Island, Jersey Shore & La Vale Members
Underlies New Creek Limestone and Old Port Formation
Overlies Tonoloway Formation
Thickness33 m (108 ft) at Allegheny Furnace
Lithology
Primary Limestone
Location
Coordinates 38°18′N 79°36′W / 38.3°N 79.6°W / 38.3; -79.6
Approximate paleocoordinates 36°18′S 41°30′W / 36.3°S 41.5°W / -36.3; -41.5
Region Pennsylvania, Maryland, Virginia, West Virginia
Country  United States
Extent Appalachian Mountains
Type section
Named for Keyser, West Virginia
Named byE. O. Ulrich
Year defined1911 [2]
Keyser Formation is located in the United States
Keyser Formation
Keyser Formation (the United States)
Keyser Formation is located in Virginia
Keyser Formation
Keyser Formation (Virginia)

The Late Silurian to Early Devonian Keyser Formation is a mapped limestone bedrock unit in Pennsylvania, Maryland, Virginia, and West Virginia.

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.

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 columnals. Above the calcarenite is 6 m of fossiliferous, banded calcisiltite. The uppermost 15 m is a sequence alternating between laminated, stromatolitic calcisiltite, and calcilutite and calcisiltite that are argillaceous and fossiliferous. [3]

Depositional environment

The depositional environment of the Keyser is interpreted as shallow marine and tidal flats, occurring in cycles. [4]

Stratigraphy

Contact with Tonoloway Formation is probably conformable, but sharp enough to suggest an unconformity. Upper contact with the Old Port Formation is conformable.

The Keyser was divided into three members by J. W. Head in 1972. [5] 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, Lycoming County, Pennsylvania. The type locality of the La Vale Member is at the Corriganville quarry, Allegany County, Maryland, and is named for the nearby town of La Vale. This nomenclature is accepted by the USGS.

In Virginia and West Virginia the Keyser is divided into Upper and Lower Members by the Big Mountain Shale Member. [6]

Fossil content

Crinoid fragments at the Old Eldorado Quarry outcrop along I-99, Blair County, PA
Stromatoporoids at the Old Eldorado Quarry outcrop along I-99, Blair County, PA
Tabulate coral in the New Enterprise New Paris Quarry on Chestnut Ridge in Bedford County, PA. Probably Halysites.

Notable outcrops

Age

Relative age dating places the Keyser in the late Silurian to early Devonian, with the transition occurring near the top of the formation. Denkler and Harris used conodont biostratigraphy to confirm this. [7]

See also

Wikimedia Commons has media related to Keyser Formation.

References

  1. ^ Paleozoic Sedimentary Successions of the Virginia Valley & Ridge and Plateau
  2. ^ Ulrich, E.O., 1911, Revision of the Paleozoic systems: Geological Society of America Bulletin, v. 22, p. 281-680
  3. ^ Faill, R.T., Glover, A.D., and Way, J.H., 1989, Geology and mineral resources of the Blandburg, Tipton, Altoona, and Bellwood quadrangles, Blair, Cambria, Clearfield and Centre Counties, Pennsylvania: Pennsylvania Geological Survey Topographic and Geologic Atlas, 4th series, 86, 209 p., scale 1:24,000 and 1:48,000
  4. ^ Anderson, E.J., Goodwin, P.W., and Sinclair, C.J., 2003, Facies and paleoenvironments of the Keyser Formation in the context of its cyclic structure, in Way, J.H., and others, eds., Geology on the edge: selected geology of Bedford, Blair, Cambria, and Somerset Counties, Guidebook, 68th Annual Field Conference of Pennsylvania Geologists, Altoona, PA, p. 1-18
  5. ^ Head, J.W., III, 1972, Upper Silurian-Lower Devonian stratigraphy and nomenclature in the central Appalachians, IN Guidebook for the 37th annual field conference of Pennsylvania geologists: Field Conference of Pennsylvania Geologists, no. 37, p. 96-103.
  6. ^ a b c d Helfrich, C. T., 1978, A Conodont Fauna from the Keyser Limestone of Virginia and West Virginia, Journal of Paleontology, Vol. 52, No. 5 (Sep., 1978), pp. 1133-1142 [1]
  7. ^ a b 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 [p. B1-B13] IN Sando, W.J., ed., Shorter contributions to paleontology and stratigraphy. [2]
  8. ^ 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 .
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