Old Port Formation
Encyclopedia
The Devonian
Old Port Formation is a mapped bedrock unit in Pennsylvania
, Maryland
, and West Virginia
. Members of the unit are also mapped in New Jersey
and Virginia
as parts of other formations or groups.
, which are (in ascending stratigraphic
order): New Creek Member (limestone), Corriganville Member (limestone), Mandata Member (shale), Shriver Member (cherty limestone), and Ridgeley Member (sandstone). Where the Shriver Chert does not occur it may be replaced by the Licking Creek Limestone. It was originally combined from the Helderberg Group and Oriskany Group by Conlin and Hoskins in 1962 to form a single Formation with the above members.
The type locality is at the town of Ridgeley
, Mineral County
, West Virginia.
The sandstone of the Ridgeley Member has been extensively mined due to its very pure quartz
suitable for glass
. The glass derived from the sandstone was used for lenses on the Hubble Space Telescope
.
A separate formation, the Oriskany Sandstone, is a lateral equivalent of the Ridgeley Member, but bounded above and below by unconformities
.
, Maryland, and was originally mapped as the basal unit of the Oriskany Formation.
In Maryland and West Virginia, the Shriver is mapped as part of the Helderberg Group.
In central Pennsylvania it is mapped as part of the Old Port Formation.
In New Jersey it is mapped as the middle unit of the Oriskany Group.
.
, Maryland, as a gray limestone with chert. C. R. Wood first mapped it as part of the Old Port Formation in Pennsylvania.
The type locality is a railroad cut 0.3 mi southeast of Corriganville
, Alleghany County, Maryland.
, Maryland. Bowen later described it as a massive limestone overlying the Keyser Formation. C. R. Wood first mapped it as part of the Old Port Formation in Pennsylvania.
, about one mile east of Warren Point, Franklin County
, Pennsylvania.
s are occasionally abundant (as casts) in the Ridgeley Member.
The brachiopods Costispirifer arenosus, Beachia immatura, Leptocoelia flabellites, Metaplasia paucicostata, Plicoplasia tribuarius, and Chonetes hudsonicus are present in the Shriver Member around the type locality of Shriver Ridge. Ostracods are also present in the Shriver Member.
The Old Port Formation contains conodonts.
See also type localities listed in subsections above.
period. It rests conformably
atop the Keyser Formation
and usually unconformably
below the Needmore Formation
or below the Onondaga Formation.
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
Old Port Formation is a mapped bedrock unit in Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...
, Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...
, and West Virginia
West Virginia
West Virginia is a state in the Appalachian and Southeastern regions of the United States, bordered by Virginia to the southeast, Kentucky to the southwest, Ohio to the northwest, Pennsylvania to the northeast and Maryland to the east...
. Members of the unit are also mapped in New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
and Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
as parts of other formations or groups.
Description
The Old Port Formation consists of several members with varying lithologiesLithology
The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples or with low magnification microscopy, such as colour, texture, grain size, or composition. It may be either a detailed description of these characteristics or be a summary of...
, which are (in ascending stratigraphic
Stratigraphy
Stratigraphy, a branch of geology, studies rock layers and layering . It is primarily used in the study of sedimentary and layered volcanic rocks....
order): New Creek Member (limestone), Corriganville Member (limestone), Mandata Member (shale), Shriver Member (cherty limestone), and Ridgeley Member (sandstone). Where the Shriver Chert does not occur it may be replaced by the Licking Creek Limestone. It was originally combined from the Helderberg Group and Oriskany Group by Conlin and Hoskins in 1962 to form a single Formation with the above members.
Ridgeley Member
The Ridgeley Member was first described as a member of the Oriskany Formation by Swartz and others (1913), as a calcareous sandstone which passes into an arenaceous limestone. It is still mapped as part of the Oriskany Group in New Jersey.The type locality is at the town of Ridgeley
Ridgeley, West Virginia
Ridgeley is a town in Mineral County, West Virginia, United States, and part of the Cumberland Metropolitan Statistical Area. The population was 762 at the 2000 census but has fallen to 575 with the 2010 census....
, Mineral County
Mineral County, West Virginia
Mineral County is a county located in the U.S. state of West Virginia. It is part of the Cumberland, MD-WV Metropolitan Statistical Area. As of 2010, the population was 28,212. Its county seat is Keyser.-Ancient history:...
, West Virginia.
The sandstone of the Ridgeley Member has been extensively mined due to its very pure quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
suitable for glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
. The glass derived from the sandstone was used for lenses on the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
.
A separate formation, the Oriskany Sandstone, is a lateral equivalent of the Ridgeley Member, but bounded above and below by unconformities
Unconformity
An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe...
.
Shriver Member
The Shriver Member, or Shriver Chert, was first described as a member of the Oriskany Formation by Swartz and others (1913), as dark siliceous shale with much black impure chert in nodules or layers of nodules. It is named after Shriver Ridge (the type locality), Allegany CountyAllegany County, Maryland
Allegany County is a county located in the northwestern part of the US state of Maryland. It is part of the Cumberland, MD-WV Metropolitan Statistical Area. As of 2010, the population was 75,087. Its county seat is Cumberland...
, Maryland, and was originally mapped as the basal unit of the Oriskany Formation.
In Maryland and West Virginia, the Shriver is mapped as part of the Helderberg Group.
In central Pennsylvania it is mapped as part of the Old Port Formation.
In New Jersey it is mapped as the middle unit of the Oriskany Group.
Mandata Member
The Mandata Shale of the Helderberg Group was first introduced by F. M. Swartz in 1938, mainly with reference to the overlying Licking Creek Limestone. The type locality is about 0.25 miles south of Mandata, Pennsylvania, on Route 225Pennsylvania Route 225
Pennsylvania Route 225 is an long state highway located in Dauphin and Northumberland counties in Pennsylvania. The southern terminus is at US 22/US 322 in Dauphin...
.
Corriganville Member
The Corriganville Limestone was first described by J. W. Head in 1972 as part of the Helderberg Group in Allegany CountyAllegany County, Maryland
Allegany County is a county located in the northwestern part of the US state of Maryland. It is part of the Cumberland, MD-WV Metropolitan Statistical Area. As of 2010, the population was 75,087. Its county seat is Cumberland...
, Maryland, as a gray limestone with chert. C. R. Wood first mapped it as part of the Old Port Formation in Pennsylvania.
The type locality is a railroad cut 0.3 mi southeast of Corriganville
Corriganville, Maryland
Corriganville is an unincorporated town in Allegany County, Maryland, USA. The town lies north of Cumberland at the confluence of Wills Creek and Jennings Run...
, Alleghany County, Maryland.
New Creek Member
The New Creek Member was first described by Bowen only as a limestone that is replaced by the Elbow Ridge Sandstone near HancockHancock, Maryland
Hancock is a town in Washington County, Maryland, United States. The population was 1,725 at the 2000 census. The Western Maryland community is notable for being located at the narrowest part of the state...
, Maryland. Bowen later described it as a massive limestone overlying the Keyser Formation. C. R. Wood first mapped it as part of the Old Port Formation in Pennsylvania.
Licking Creek Member
The Licking Creek Limestone of the Helderberg Group was first introduced by F. M. Swartz in 1938, and was described more fully in 1939. The unit consists of layers and nodules of black chert interbedded with light-gray crystalline limestone. The type locality is a bluff on the south side of Licking CreekLicking Creek
Licking Creek is a tributary of the Potomac River in Pennsylvania and Maryland in the United States.Licking Creek is born on the west slope of Tuscarora Mountain, near Cowans Gap State Park, flows through eastern Fulton County and a corner of Franklin County in Pennsylvania, and then enters...
, about one mile east of Warren Point, Franklin County
Franklin County, Pennsylvania
As of the census of 2000, there were 129,313 people, 50,633 households, and 36,405 families residing in the county. The population density was 168 people per square mile . There were 53,803 housing units at an average density of 70 per square mile...
, Pennsylvania.
Fossils
BrachiopodBrachiopod
Brachiopods are a phylum of marine animals that have hard "valves" on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection...
s are occasionally abundant (as casts) in the Ridgeley Member.
The brachiopods Costispirifer arenosus, Beachia immatura, Leptocoelia flabellites, Metaplasia paucicostata, Plicoplasia tribuarius, and Chonetes hudsonicus are present in the Shriver Member around the type locality of Shriver Ridge. Ostracods are also present in the Shriver Member.
The Old Port Formation contains conodonts.
Notable Exposures
- Old quarry in TyroneTyrone, PennsylvaniaTyrone is a borough in Blair County, Pennsylvania, northeast of Altoona, on the Little Juniata River. Tyrone was of considerable commercial importance in the twentieth century. It was an outlet for the Clearfield coal fields, and it was noted for the manufacture of paper products. There were...
, Pennsylvania, west of Sink Run and along U.S. Route 22U.S. Route 22U.S. Route 22 is a west–east route and is one of the original United States highways of 1926, running from Cincinnati, Ohio, at US 27, US 42, US 127, and US 52 to Newark, New Jersey, at U.S. Route 1/9 near the Newark Liberty International Airport.US 22 also carries the names of the William... - Two exposures in EverettEverett, PennsylvaniaEverett is a borough in Bedford County, Pennsylvania, United States. The population was 1,905 at the 2000 census.Everett's original name was Bloody Run, after a creek which was the site of a battle between settlers and Native Americans...
, Pennsylvania:- U.S. Route 30U.S. Route 30 in PennsylvaniaIn the U.S. state of Pennsylvania, U.S. Route 30 runs east–west across the southern part of the state, passing through Pittsburgh and Philadelphia on its way from the West Virginia state line east to the Benjamin Franklin Bridge over the Delaware River into New Jersey...
(Everett Bypass) roadcut through Warrior Ridge north of Everett - Another exposure along business Route 30 on the west side of Everett (pictured above)
- U.S. Route 30
- The Sinnett-Thorn Mountain Cave System is developed in the Keyser FormationKeyser FormationThe Late Silurian to Early Devonian Keyser Formation is a mapped limestone bedrock unit in Pennsylvania, Maryland, Virginia, and West Virginia.-Description:...
and overlying New Creek and Corriganville Limestone Members
See also type localities listed in subsections above.
Age
Relative age dating of the Old Port places it in the Lower DevonianDevonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
period. It rests conformably
Unconformity
An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe...
atop the Keyser Formation
Keyser Formation
The Late Silurian to Early Devonian Keyser Formation is a mapped limestone bedrock unit in Pennsylvania, Maryland, Virginia, and West Virginia.-Description:...
and usually unconformably
Unconformity
An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe...
below the Needmore Formation
Needmore Formation
The Devonian Needmore Formation or Needmore Shale is a mapped bedrock unit in Pennsylvania, Maryland, Virginia, and West Virginia.-Description:...
or below the Onondaga Formation.