Tonoloway Formation
{{Infobox rockunit
| name = Tonoloway Formation
| image = BlueRock2.JPG
| caption = A Tonoloway limestone "fin" known as Blue Rock, Smoke Hole Canyon, West Virginia
| type = sedimentary
| age = Pridoli[http://hdl.handle.net/10919/19078 Paleozoic Sedimentary Successions of the Virginia Valley & Ridge and Plateau]
| period = Pridoli
| prilithology = limestone
| otherlithology = shale
| namedfor = Tonoloway Ridge, Rock Ford, WV
| namedby = E. O. Ulrich, 1911Ulrich, E.O., 1911, Revision of the Paleozoic systems: Geological Society of America Bulletin, v. 22, p. 281-680.
| region = Appalachian Mountains
| country =
| coordinates =
| unitof =
| subunits =
| underlies = Keyser Formation
| overlies = Wills Creek Formation
| thickness = 250+/-20 m
| extent = Pennsylvania, Maryland, Virginia, West Virginia
| area =
| map =
| map_caption =
}}
The Late Silurian Tonoloway Formation is a mapped limestone bedrock unit in Pennsylvania, Maryland, Virginia and West Virginia. The Tonoloway is roughly equivalent to the Salina group that is found to the north and west.
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.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
=Depositional environment=
The depositional environment of the Tonoloway is interpreted as shallow marine.
=Notable exposures=
- Tonoloway Ridge (type section), in Pennsylvania, Maryland, and West Virginia.
- Along Little Juniata River, 2 km northeast of Bellwood, Pennsylvania
- Blue Rock, and other large outcroppings, in the Smoke Hole Canyon of eastern West Virginia
- Trout Pond, in Hardy County, West Virginia
Age
Relative age dating places the Tonoloway in the late Silurian.
References
{{reflist}}
{{Stratigraphic column of Virginia}}
{{Stratigraphic column of West Virginia}}
Category:Geologic formations of Pennsylvania
Category:Silurian geology of Virginia
Category:Silurian West Virginia
Category:Limestone formations of the United States
Category:Silurian south paleopolar deposits
Category:Silurian southern paleotemperate deposits
Category:Shale formations of the United States
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