The
Silurian Tuscarora Formation — also known as Tuscarora Sandstone or Tuscarora Quartzite — is a mapped
bedrock
In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet.
Definition
Bedrock is the solid rock that underlies looser surface material. An exposed portion of be ...
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, Ma ...
,
Maryland
Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), 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; ...
,
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 ...
, and
Virginia
Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the East Coast of the United States, Atlantic Coast and the Appalachian Mountains. The geography an ...
, USA.
Description
The Tuscarora is a thin- to thick-bedded fine-grained to coarse-grained
orthoquartzite. It is a white to medium-gray or gray-green
subgraywacke
Greywacke or graywacke (German ''grauwacke'', signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lit ...
,
sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates ...
,
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, ...
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, especia ...
, cross-stratified and conglomeratic
conglomerate
Conglomerate or conglomeration may refer to:
* Conglomerate (company)
* Conglomerate (geology)
* Conglomerate (mathematics)
In popular culture:
* The Conglomerate (American group), a production crew and musical group founded by Busta Rhymes
** Co ...
in parts, containing a few
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, especia ...
interbeds.
[Berg, T.M., Edmunds, W.E., Geyer, A.R. and others, compilers, (1980). Geologic Map of Pennsylvania: Pennsylvania Geologic Survey, Map 1, scale 1:250,000.]
Details of the type locality and of stratigraphic nomenclature for this unit as used by the U.S. Geological Survey are available on-line at the National Geologic Map Database.
The Tuscarora and its lateral equivalents are the primary
ridge-formers of the
Ridge-and-Valley Appalachians in the eastern
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...
It is typically 935 feet thick in Pennsylvania,
and in Maryland varies from 60 feet to 400 feet thick from east to west.
Notable exposures
The Tuscarora Formation is commonly exposed on various ridge crests and in many
water gaps in the
Ridge and Valley
The Ridge-and-Valley Appalachians, also called the Ridge and Valley Province or the Valley and Ridge Appalachians, are a physiographic province of the larger Appalachian division and are also a belt within the Appalachian Mountains extending ...
physiographic province of the
Appalachians of Pennsylvania, Maryland, and West Virginia, particularly along the
Wills Mountain Anticline.
In Pennsylvania, the Tuscarora is exposed along
US 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 longes ...
on the north and south sides of the
Narrows in central
Bedford County, where it is nearly vertical. It is also well-exposed in the core of Jack's Mountain in Jack's Narrows, where the
Juniata River cuts through the mountain, just west of
Mount Union. The
Standing Stone Trail
The Standing Stone Trail is an linear hiking trail in south-central Pennsylvania, leading from Cowans Gap State Park in Fulton County, north to Detweiler Run Natural Area in Huntingdon County. Most of the trail follows rocky ridgetops in the App ...
traverses this cut, and many of the "Thousand Steps" here are Tuscarora quartzite.
In Maryland, the
National Road
The National Road (also known as the Cumberland Road) was the first major improved highway in the United States built by the Federal Government of the United States, federal government. Built between 1811 and 1837, the road connected the Pot ...
(
US 40) passes arched Tuscarora sandstone outcrops in the
Cumberland Narrows
The Cumberland Narrows (or simply The Narrows) is a water gap in western Maryland in the United States, just west of Cumberland. Wills Creek cuts through the central ridge of the Wills Mountain Anticline at a low elevation here between Wills ...
in
Allegany County.
In West Virginia, the
River Knobs along the
North Fork of the South Branch of the Potomac River in
Pendleton County include dramatic outcrops of nearly vertical Tuscarora sandstone. Some of the better known of these exposures are
Seneca Rocks,
Champe Rocks,
Judy Rocks
Judy Gap is an unincorporated community in Pendleton County, West Virginia, United States. Judy Gap is located at the junction of U.S. Route 33 and West Virginia Route 28, west-northwest of Franklin
Franklin may refer to:
People
* Frank ...
, and
Nelson Rocks. These cliffs are clearly visible along
U.S. Route 33 and West Virginia Routes
28 and
55.
North Fork Mountain, to the east of the River Knobs, is a long
Ridge and Valley
The Ridge-and-Valley Appalachians, also called the Ridge and Valley Province or the Valley and Ridge Appalachians, are a physiographic province of the larger Appalachian division and are also a belt within the Appalachian Mountains extending ...
anticline
In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the ...
ridge capped by Tuscarora sandstone.
Two of the more comprehensive exposures of the Tuscarora Formation are in two quarries at the crest and south end of
Canoe MountainSpruce Creek Quadrangle.
Geographic Extent
The Tuscarora is present 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, Ma ...
,
Maryland
Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), 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; ...
,
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 ...
, and
Virginia
Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the East Coast of the United States, Atlantic Coast and the Appalachian Mountains. The geography an ...
, USA.
Stratigraphic Setting
The Tuscarora rests conformably atop the
Juniata Formation
The Ordovician Juniata Formation is a mapped bedrock unit in Pennsylvania and Maryland. It is a relative slope-former occurring between the two prominent ridge-forming sandstone units: the Tuscarora Formation and the Bald Eagle Formation in ...
and conformably below the
Clinton Group
The Clinton Group (also referred to as the Clinton Formation or the Clinton Shale) is a mapped unit of sedimentary rock found throughout eastern North America. The interval was first defined by the geologist Lardner Vanuxem, who derived the name f ...
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, Ma ...
.
The Tuscarora is a lateral equivalent of the Minsi and Weiders members of the
Shawangunk Formation in eastern
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, Ma ...
,
New Jersey
New Jersey is a U.S. state, state in the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. It is bordered on the north and east by the state of New York (state), New York; on the ea ...
, and
New York, and of the
Massanutten Formation in
Virginia
Virginia, officially the Commonwealth of Virginia, is a state in the Mid-Atlantic and Southeastern regions of the United States, between the East Coast of the United States, Atlantic Coast and the Appalachian Mountains. The geography an ...
, and the Clinch Sandstone farther south. Butts (1940) indicated that in the Appalachian Valley and Ridge Province the name "Tuscarora Sandstone" should be applied to these strata from Pennsylvania in the north to 38deg N latitude, and that the name "Clinch Sandstone" should be applied to these strata south of 38deg N latitude.
There is one named
member of the formation: Castanea, occurring at the top, leaving the Lower and Middle Tuscarora Formation at the bottom.
This formation has been called the "White Medina Sandstone" in West Virginia.
Fossils
Very few fossils exist in the Tuscarora, and most of them are
trace fossils.
At least two hughmilleriid
Eurypterids (sea scorpions) have been discovered in the Tuscarora.
[Boucot, A.J., Gray, Jane, and Hoskins, D.M., 1994, New hughmilleriid (Eurypterida) occurrence from the Tuscarora Formation, central Pennsylvania, and its environmental interpretation, IN Landing, Ed, ed., Studies in stratigraphy and paleontology in honor of Donald W. Fisher: New York State Museum Bulletin, no. 481, p. 21-23.]
Age
Relative age dating of the Tuscarora places it in the Lower
Silurian period, being deposited between 440 and 417 (±10) million years ago.
Interpretations of Depositional Environment
The
depositional environment of the Tuscarora has always been interpreted as mostly terrestrial or shallow marine deposits resulting in a
molasse sequence produced by the
Taconic orogeny. It is thought to represent a vast sand shoal along the margin of the
Iapetus Ocean.
Ripple marks are seldom found, but do support interpretation as a shallow marine depositional environment.
Economic uses
The Tuscarora may have been used as a
ganister for making furnace liners in 19th century
iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...
smelting
Smelting is a process of applying heat to ore, to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals. Smelting uses heat and a ...
blast furnace
A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally pig iron, but also others such as lead or copper. ''Blast'' refers to the combustion air being "forced" or supplied above atmospheric p ...
s of central Pennsylvania.
[
The Tuscarora has become very important to the tourism industry of eastern West Virginia, where the formation has many conspicuous outcrops visible from such roads as U.S. Routes 33 and 50 and West Virginia Routes 28 and 55. Tuscarora-capped North Fork Mountain and various Tuscarora cliffs are prominent in scenic views from such sites as Spruce Knob and Dolly Sods.
Seneca Rocks in ]Pendleton County, West Virginia
Pendleton County is a County (United States), county located in the U.S. state of West Virginia. As of the 2020 United States census, 2020 census, the population was 6,143, making it the second-least populous county in West Virginia. Its county ...
, has become a world-renowned rock climbing location. It is the only "true peak" (a peak inaccessible except by technical rock climbing techniques) on the East Coast of the United States. Two climbing schools near the outcrop and many other guide services offer guided climbing trips on the 300+ climbing routes on the west-facing cliff. Seneca Rocks is managed by the U.S. Forest Service, and is located within the Spruce Knob–Seneca Rocks National Recreation Area of the Monongahela National Forest.
The Nelson Rocks Preserve, located near Circleville, West Virginia, is a privately owned and operated nature preserve dedicated to preserving Nelson Rocks and the surrounding environment as a cultural, educational, and recreational resource. The preserve offers a via ferrata climbing trail, one of six in the United States.
See also
* Big Mountain (Pennsylvania)
* Bald Eagle Mountain
*Brush Mountain Brush Mountain may refer to:
United States
The USGS Geographical Names Information System lists 35 summits, including:
Other countries
* Brush Mountain (Alberta) Brush Mountain may refer to:
United States
The US ...
* Germany Valley
* Geology of Pennsylvania
* Massanutten Mountain
* Mount Nittany
* North Fork Mountain
* Tussey Mountain
*River Knobs (West Virginia) ''For other "River Knobs", see River Knobs (disambiguation).''
The River Knobs — formerly known as East Seneca Ridge — are a ridge and series of knobs in western Pendleton County, West Virginia, USA, along a stretch of the North Fork South ...
* Seneca Rocks
* Champe Rocks
* Nelson Rocks
References
{{Stratigraphic column of West Virginia
Silurian System of North America
Quartzite formations
Sandstone formations of the United States
Shale formations of the United States
Siltstone formations
Silurian United States
Silurian Maryland
Silurian geology of Pennsylvania
Silurian geology of Virginia
Silurian West Virginia
Cliff-formers
Aeronian
Telychian