Tonoloway Formation

The Late Silurian Tonoloway Formation is a mapped limestone bedrock unit in Pennsylvania, Maryland, Virginia and West Virginia.

Tonoloway Formation
Stratigraphic range: Pridoli[1]
A Tonoloway limestone "fin" known as Blue Rock, Smoke Hole Canyon, West Virginia
Typesedimentary
UnderliesKeyser Formation
OverliesWills Creek Formation
Thickness250+/-20 m
Lithology
Primarylimestone
Othershale
Location
RegionAppalachian Mountains
ExtentPennsylvania, Maryland, Virginia, West Virginia
Type section
Named forTonoloway Ridge, Rock Ford, WV
Named byE. O. Ulrich, 1911[2]

Description

The basal 50 m consists of medium-dark-gray laminated to thin-bedded calcisiltite with shale partings and interbeds. Overlying 5 m are light-yellowish-gray to olive-gray mudstone and shale. Above this interval are 75 m of laminated calcisiltite with interbeds of thick to very thick bedded calcisiltite. The remainder of the formation is cyclic, consisting of three or four resistant ledges of laminated limestone and shale. Uppermost 20 m contains a variety of limestones. Lower contact with the Wills Creek is probably conformable. Upper contact is conformable and undulatory, occurring at the base of the "calico" limestone of the Keyser Formation.[3]

Depositional environment

The depositional environment of the Tonoloway is interpreted as shallow marine.

Notable exposures

Age

Relative age dating places the Tonoloway in the late Silurian.

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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


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