The Hamilton Group is a

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wh ...

-age

geological group In geology, a group is a lithostratigraphic unit consisting of a series of related formations that have been classified together to form a group. Formations are the fundamental unit of stratigraphy. Groups may sometimes be combined into superg ...

in the

Appalachia Appalachia () is a cultural region in the Eastern United States that stretches from the Southern Tier of New York State to northern Alabama and Georgia. While the Appalachian Mountains stretch from Belle Isle in Newfoundland and Labrador, C ...

n region of the

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 Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

. It is present in

New York New York most commonly refers to: * New York City, the most populous city in the United States, located in the state of New York * New York (state), a state in the northeastern United States New York may also refer to: Film and television * '' ...

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 t ...

Ohio Ohio () is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Of the List of states and territories of the United States, fifty U.S. states, it is the List of U.S. states and territories by area, 34th-l ...

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 ...

, northwestern

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 are ...

and

Ontario, Canada Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

. It is mainly composed of marine

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, especiall ...

with some

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 silicat ...

. There are two main formations encompassed by the group: the

Mahantango Formation The Devonian Mahantango Formation is a mapped bedrock unit in Pennsylvania, West Virginia, and Maryland. It is named for the North branch of the Mahantango Creek in Perry and Juniata counties in Pennsylvania. It is a member of the Hamilton Grou ...

and the

Marcellus Shale Marcellus may refer to: * Marcellus (name) * Marcus Claudius Marcellus, Roman commander Places * Marcellus, Lot-et-Garonne, France * Marcellus Township, Michigan ** Marcellus, Michigan, a village in Marcellus Township ** Marcellus Community Sch ...

. In southwestern

, where the two sub-units are not easily distinguishable, the Hamilton Group is broadly equivalent to the Millboro Shale or Millboro Formation. The group is named for the village of Hamilton, New York. These rocks are the oldest

strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as e ...

of the Devonian gas shale sequence. USGS 2006 1237 table2 Stratigraphy Middle Devonian

Stratigraphic Setting

The Hamilton Group consists of the

, a gray, dark gray, brown, and olive laminated shale; siltstone; and very fine-grained sandstone or claystone containing marine fossils. The uppermost clay layers of the

are particularly rich in fossils. It overlies the

, a

fissile In nuclear engineering, fissile material is material capable of sustaining a nuclear fission chain reaction. By definition, fissile material can sustain a chain reaction with neutrons of thermal energy. The predominant neutron energy may be t ...

gray-black to black, thinly laminated, pyritic,

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon ma ...

aceous thin shale with sparse marine fauna and siderite concretions. The total thickness of the Hamilton Group in Pennsylvania runs about 970 feet. In New York State, it thickens from 250 feet near

Lake Erie Lake Erie ( "eerie") is the fourth largest lake by surface area of the five Great Lakes in North America and the eleventh-largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and therefore also ha ...

to over 2,500 feet in

Ulster Ulster (; ga, Ulaidh or ''Cúige Uladh'' ; sco, label= Ulster Scots, Ulstèr or ''Ulster'') is one of the four traditional Irish provinces. It is made up of nine counties: six of these constitute Northern Ireland (a part of the United Kin ...

and

Greene Greene may refer to: Places United States *Greene, Indiana, an unincorporated community *Greene, Iowa, a city *Greene, Maine, a town ** Greene (CDP), Maine, in the town of Greene *Greene (town), New York ** Greene (village), New York, in the town ...

counties. Depths ranging from outcrops to 8,000 feet below the surface of Sullivan County, in the southeastern part of the state. In the interior lowlands of New York, the Hamilton Group contains the Marcellus, Skaneateles, Ludlowville, and

Moscow Moscow ( , US chiefly ; rus, links=no, Москва, r=Moskva, p=mɐskˈva, a=Москва.ogg) is the capital and largest city of Russia. The city stands on the Moskva River in Central Russia, with a population estimated at 13.0 million ...

Formations, in ascending order, with the Tully Limestone above. These units are divided by the

Stafford Stafford () is a market town and the county town of Staffordshire, in the West Midlands region of England. It lies about north of Wolverhampton, south of Stoke-on-Trent and northwest of Birmingham. The town had a population of 70,145 in th ...

, Centerfield, and

Tichenor Tichenor is a variant of Tickner, an English topographic surname for someone who lived at a crossroad or a fork in the road.. A more likely origin for the surname is that of a family located in 16th century Sussex whose name derives from the villa ...

limestones. In

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

, Canada, the Hamilton Group formations are, in ascending order,

Bell A bell is a directly struck idiophone percussion instrument. Most bells have the shape of a hollow cup that when struck vibrates in a single strong strike tone, with its sides forming an efficient resonator. The strike may be made by an inte ...

, Rockport Quarry, Arkona, Hungry Hollow, Widder, and

Ipperwash The Ipperwash Crisis was a dispute over Indigenous land that took place in Ipperwash Provincial Park, Ontario, in 1995. Several members of the Stoney Point Ojibway band occupied the park to assert claim to nearby land which had been expropriat ...

; the

Kettle Point Formation The Kettle Point Formation, also known as the Kettle Point (black) Shale, is a geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes ...

of the late Devonian lies unconformably above. The Mahantango Formation includes these members in descending order: Tully argillaceous limestone, Sherman Ridge, Montebello sandstone, Fisher Ridge, Dalmatia, and Turkey Ridge. In south-central Pennsylvania, it includes Clearville, Frame, Chaneysville, and Gander Run Members. Its thickness in Maryland ranges from 600 feet in the west, increasing to 1,200 feet in the east, and approximately 1000 feet thick in central Pennsylvania. The Marcellus Formation contains a local limestone Purcell Member and Tioga bentonite at the base in eastern Pennsylvania. Its thickness in Maryland ranges from 250 feet in east, increasing to 500 feet in the west, but is only about 70 feet thick in central Pennsylvania. The Hamilton Group, Tioga Metabentonite Bed, and Needmore Shale were formerly called the

Romney Formation The Marcellus Formation or the Marcellus Shale is a Middle Devonian age unit of sedimentary rock found in eastern North America. Named for a distinctive outcrop near the village of Marcellus, New York, in the United States, it extends throughou ...

. * The

Geneseo Shale The Burket Shale is the lowest member of the Harrell Shale/ Genessee Group. The Burket is an organic-rich black shale that rests just above the Tully Limestone member of the Mahantango Formation. The geographical extent of the formation inclu ...

is a dark grey to black shale that overlies the Tully Limestone; it includes the Filmore beds. * The Tully Limestone is a shallow-water carbonaceous unit. * The Moscow Formation (Middle Devonian / Givetian) comprises grey to black shales interbedded with limestones and calcareous mudstones and usually bioturbated.

Age

Relative age dating of the Hamilton places it in the middle and lower

period. In Maryland, it rests conformably atop the Tioga Metabentonite, a thin layer of laminated shale lying over the Needmore Shale. In other regions, the Needmore Shale is replaced by laterally equivalent units such as limestone and shale of the

Onondaga Formation The Onondaga Limestone is a group of hard limestones and dolomites of Devonian age that form an important geographic feature in some areas in which it outcrops; in others, especially its Southern Ontario portion, the formation can be less promine ...

, or chert of the Huntersville Chert. The Hamilton Group lies conformably below the

Brallier Formation The Devonian Brallier Formation is a mapped bedrock unit in Pennsylvania, Maryland, West Virginia, and Virginia. Description The Brallier Formation was described by Charles Butts in 1918 as a fine-grained, siliceous shale with few fine-graine ...

(formerly Woodmont Shale, dark laminated shale) at its southern extent. Further north, it is overlain by the Tully Limestone, though some consider the Tully Limestone a subunit of the Mahantango Formation. The Tully Limestone is succeeded by the dark laminated

Harrell Shale The Devonian Harrell Formation is a mapped bedrock unit in Pennsylvania, Maryland, West Virginia, and Virginia. Description The Harrell Formation was first described by Charles Butts in 1918. Hasson and Dennison (1978) state "The Harrell Shale c ...

. In 2012, Read and Erikson reported the group as dating from the

Eifelian The Eifelian is the first of two faunal stages in the Middle Devonian Epoch. It lasted from 393.3 ± 1.2 million years ago to 387.7 ± 0.8 million years ago. It was preceded by the Emsian Stage and followed by the Givetian Stage. North American ...

Famennian The Famennian is the latter of two faunal stages in the Late Devonian Epoch. The most recent estimate for its duration estimates that it lasted from around 371.1 million years ago to 359.3 million years ago. An earlier 2012 estimate, still used ...

in Virginia.

Economic Resources

The Hamilton is a good source of road material,

riprap Riprap (in North American English), also known as rip rap, rip-rap, shot rock, rock armour (in British English) or rubble, is human-placed rock or other material used to protect shoreline structures against scour and water, wave, or ice erosion. ...

and building stone, that is used locally for shale aggregate and common fill.

References

{{Coord, 40, 44, 05, N, 77, 46, 42, W, source:enwiki-plaintext-parser, display=title Shale formations of the United States Claystone Devonian geology of Pennsylvania Devonian geology of Virginia Geologic groups of Pennsylvania Geologic groups of Virginia Devonian southern paleotemperate deposits Devonian West Virginia

Stratigraphic Setting

Age

Economic Resources

See also

References