The

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 ...

Tuscarora Formation — also known as Tuscarora Sandstone or Tuscarora Quartzite — is a mapped

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 ...

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 ...

, and

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 ...

, USA.

Description

The Tuscarora is a thin- to thick-bedded fine-grained to coarse-grained

orthoquartzite Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tect ...

. It is a white to medium-gray or gray-green subgraywacke,

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, p ...

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, especial ...

, cross-stratified and conglomeratic conglomerate in parts, containing a few

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-former A cliff-former is a geological unit of bedrock that is more resistant to erosion than overlying or underlying strata and consequently produces outcrops with high slope angles. It is more or less equivalent to ''ridge-former'', and may be contra ...

s of the

Ridge-and-Valley Appalachians 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 ...

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 states, a federal district, five major unincorporated territorie ...

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 gap A water gap is a gap that flowing water has carved through a mountain range or mountain ridge and that still carries water today. Such gaps that no longer carry water currents are called wind gaps. Water gaps and wind gaps often offer a prac ...

s 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 physiographic province is a geographic region with a characteristic geomorphology, and often specific subsurface rock type or structural elements. The continents are subdivided into various physiographic provinces, each having a specific characte ...

of the

Appalachians The Appalachian Mountains, often called the Appalachians, (french: Appalaches), are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They ...

of Pennsylvania, Maryland, and West Virginia, particularly along the

Wills Mountain Anticline Wills may refer to: * Will (law), a legal document Places Australia * Wills, Queensland, a locality in the Shire of Boulia * Division of Wills, an Australian electoral division in Victoria United States * Wills Township, LaPorte County, Indiana ...

. 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 longest ...

on the north and south sides of the

Narrows A narrows or narrow (used interchangeably but usually in the plural form), is a restricted land or water passage. Most commonly a narrows is a strait, though it can also be a water gap. A narrows may form where a stream passes through a tilted ...

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 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 U.S. Route 40 or U.S. Highway 40 (US 40), also known as the Main Street of America, is a major east–west United States Highway traveling across the United States from the Mountain States to the Mid-Atlantic States. As with most routes wh ...

) 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 Mo ...

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 Seneca Rocks is a large crag and local landmark in Pendleton County in the Eastern Panhandle of West Virginia, United States. The south peak is one of a small number of peaks inaccessible except by technical rock climbing techniques on the East ...

Champe Rocks Champe Rocks are a pair of large crags in Pendleton County in the Eastern Panhandle of West Virginia, USA. Easily visible from West Virginia Route 28, they are situated within the Spruce Knob–Seneca Rocks National Recreation Area. They are � ...

, Judy Rocks, and

Nelson Rocks Nelson Rocks is a large privately owned rock formation located in the North Fork Valley of Pendleton County, West Virginia, United States. The area is operated under the name of NROCKS Outdoor Adventures, and was previously known as Nelson Rock ...

. These cliffs are clearly visible along

U.S. Route 33 U.S. Route 33 (US 33) is a United States Numbered Highway that runs northwest–southeast for from northern Indiana to Richmond, Virginia, passing through Ohio and West Virginia en route. Although most odd-numbered U.S. routes are north– ...

and West Virginia Routes 28 and 55.

North Fork Mountain North Fork Mountain is a quartzite-capped mountain ridge in the Ridge and Valley physiographic province of the Allegheny Mountains (or "High Alleghenies" or "Potomac Highlands") of eastern West Virginia. Kile Knob, at 4,588 feet (1,398 m), is th ...

, to the east of the River Knobs, is a long

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 Mountain Canoe Mountain is a stratigraphic ridge in central Pennsylvania, United States, running east of the Allegheny Front and west of Tussey Mountain. It forms a continuous ridge with Brush Mountain to the west. To the south, across the water gap fo ...

Spruce Creek Quadrangle
.

Geographic Extent

The Tuscarora is present in

, and

, 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 the ...

and conformably below the Clinton Group in

. The Tuscarora is a lateral equivalent of the Minsi and Weiders members of the

Shawangunk Formation The Silurian Shawangunk Formation is a mapped bedrock unit in eastern Pennsylvania, New Jersey, and New York. It is named for the Shawangunk Ridge for which it is the dominant rock type. The division of the Shawangunk between the Tuscarora Fo ...

in eastern

New Jersey New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware ...

, and New York, and of the Massanutten Formation in

, 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 Member may refer to: * Military jury, referred to as "Members" in military jargon * Element (mathematics), an object that belongs to a mathematical set * In object-oriented programming, a member of a class ** Field (computer science), entries in ...

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 A trace fossil, also known as an ichnofossil (; from el, ἴχνος ''ikhnos'' "trace, track"), is a fossil record of biological activity but not the preserved remains of the plant or animal itself. Trace fossils contrast with body fossils, ...

. At least two hughmilleriid

Eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 Myr, million yea ...

s (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

period, being deposited between 440 and 417 (±10) million years ago.

Interpretations of 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 Tuscarora has always been interpreted as mostly terrestrial or shallow marine deposits resulting in a

molasse __NOTOC__ The term "molasse" () refers to sandstones, shales and conglomerates that form as terrestrial or shallow marine deposits in front of rising mountain chains. The molasse deposits accumulate in a foreland basin, especially on top of flysc ...

sequence produced by the

Taconic orogeny The Taconic orogeny was a mountain building period that ended 440 million years ago and affected most of modern-day New England. A great mountain chain formed from eastern Canada down through what is now the Piedmont of the East coast of the Unit ...

. It is thought to represent a vast sand shoal along the margin of the Iapetus Ocean.

Ripple marks In geology, ripple marks are sedimentary structures (i.e., bedforms of the lower flow regime) and indicate agitation by water (current or waves) or wind. Defining ripple cross-laminae and asymmetric ripples * ''Current ripple marks'', ''unidi ...

are seldom found, but do support interpretation as a shallow marine depositional environment.

Economic uses

The Tuscarora may have been used as a

ganister A ganister (or sometimes gannister ) is hard, fine-grained quartzose sandstone, or orthoquartzite,Jackson, J. A., 1997, ''Glossary of geology'', 4th ed. American Geological Institute, Alexandria. used in the manufacture of silica brick typically ...

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 f ...

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 ...

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

and various Tuscarora cliffs are prominent in scenic views from such sites as

Spruce Knob Spruce Mountain, located in eastern West Virginia, is the highest ridge of the Allegheny Mountains. The whale-backed ridge extends for only from northeast to southwest, but several of its peaks exceed in elevation. The summit, Spruce Knob (4863 ...

and

Dolly Sods The Dolly Sods Wilderness – originally simply Dolly Sods – is a U.S. Wilderness Area in the Allegheny Mountains of eastern West Virginia, US, and is part of the Monongahela National Forest (MNF) of the U.S. Forest Service (USFS). Dolly Sods ...

Pendleton County, West Virginia Pendleton County is a county located in the U.S. state of West Virginia. As of the 2020 census, the population was 6,143, making it the second-least populous county in West Virginia. Its county seat is Franklin. The county was created by the ...

, has become a world-renowned

rock climbing Rock climbing is a sport in which participants climb up, across, or down natural rock formations. The goal is to reach the summit of a formation or the endpoint of a usually pre-defined route without falling. Rock climbing is a physically and ...

location. It is the only "true peak" (a peak inaccessible except by technical

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.

is managed by the U.S. Forest Service, and is located within the

Spruce Knob–Seneca Rocks National Recreation Area Spruce Knob–Seneca Rocks National Recreation Area is a national recreation area in the Monongahela National Forest of eastern West Virginia. The national recreation area protects three prominent West Virginia landmarks: * Spruce Knob, the highe ...

of the

Monongahela National Forest The Monongahela National Forest is a national forest located in the Allegheny Mountains of eastern West Virginia, USA. It protects over of federally managed land within a proclamation boundary that includes much of the Potomac Highlands Regi ...

. The Nelson Rocks Preserve, located near

Circleville, West Virginia Circleville is an unincorporated community located in Pendleton County, West Virginia, United States. Circleville was originally named Zyrkleville after John Zyrkle, who ran a dry goods store in the town. The old Circleville School is listed on ...

, 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 A via ferrata (Italian for "iron path", plural ''vie ferrate'' or in English ''via ferratas'') is a protected climbing route found in the Alps and certain other locations. The term "via ferrata" is used in most countries and languages except n ...

climbing trail, one of six in the United States.

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