The

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Pale ...

Dunkard Group (Pd) is an area of rock, Early Permian in age, in the south of

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 ...

, southwestern

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 ...

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 the hilltops of the

Georges Creek Basin Georges Creek Valley is located in Allegany County, Maryland along the Georges Creek. The valley is rich in wide veins of coal, known historically as "The Big Vein." Coal was once extracted by deep mines but is only mined today through surface ...

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; ...

. In Ohio, it is found primarily in Washington County. It is notable for being one of the few areas of Permian sediment east of the

Mississippi River The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it ...

. In addition, it is the youngest surface rock in the state of Ohio.

Description

It consists of red and green

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 ...

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

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 ...

, with thin lenticular beds of

argillaceous Clay minerals are hydrous aluminium phyllosilicates (e.g. kaolin, Al2 Si2 O5( OH)4), sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. Clay mineral ...

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

and thin beds of impure

coal Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen ...

The base of the layer contains thick-bedded, white conglomeratic sandstone. The layer's thickness is greater than 200 feet in Maryland. The fossils found in the Dunkard Group are similar to ones found in

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

and Oklahoma of similar age.

Fossil content

* ''

Dimetrodon ''Dimetrodon'' ( or ,) meaning "two measures of teeth,” is an extinct genus of non- mammalian synapsid that lived during the Cisuralian (Early Permian), around 295–272 million years ago (Mya). It is a member of the family Sphenacodo ...

'' * '' Ctenospondylus'' * ''

Archaeothyris ''Archaeothyris'' is an extinct genus of ophiacodontid synapsid that lived during the Late Carboniferous and is known from Nova Scotia. Dated to 306 million years ago, ''Archaeothyris'', along with a more poorly known synapsid called '' Echinerpe ...

'' * ''

Edaphosaurus ''Edaphosaurus'' (, meaning "pavement lizard" for dense clusters of teeth) is a genus of extinct edaphosaurid synapsids that lived in what is now North America and Europe around 303.4 to 272.5 million years ago, during the Late Carboniferous t ...

'' * ''

Eryops ''Eryops'' (; from Greek , , 'drawn-out' + , , 'face', because most of its skull was in front of its eyes) is a genus of extinct, amphibious temnospondyls. It contains the single species , the fossils of which are found mainly in early Permian ( ...

'' * ''

Xenacanthus ''Xenacanthus'' (from Ancient Greek ξένος, xénos, 'foreign, alien' + ἄκανθος, akanthos, 'spine') is a genus of prehistoric sharks. The first species of the genus lived in the later Devonian period, and they survived until the end of ...

'' * ''

Ophiacodon ''Ophiacodon'' (meaning "snake tooth") is an extinct genus of synapsid belonging to the family Ophiacodontidae that lived from the Late Carboniferous to the Early Permian in North America and Europe. The genus was named along with its type s ...

'' * '' Diploceraspis'' * ''

Diplocaulus ''Diplocaulus'' (meaning "double caul") is an extinct genus of lepospondyl amphibians which lived from the Late Carboniferous to the Late Permian of North America and Africa. ''Diplocaulus'' is by far the largest and best-known of the lepospondy ...

'' * ''

Baldwinonus ''Baldwinonus'' is an extinct genus of basal synapsids from the Early Permian. The type species is ''Baldwinonus trux'', named in 1940 from the Cutler Formation of New Mexico. A second species, ''Baldwinonus dunkardensis'', was named in 1952 ...

'' * '' Protorothyris'' * ''

Diadectes ''Diadectes'' (meaning ''crosswise-biter'') is an extinct genus of large reptiliomorphs or synapsids that lived during the early Permian period ( Artinskian- Kungurian stages of the Cisuralian epoch, between 290 and 272 million years ago). '' ...

'' * '' Isodectes'' * ''

Sagenodus ''Sagenodus'' is an extinct genus of prehistoric lungfish. It is a lungfish from the Permo-Carboniferous period found in Europe and North America. See also * Sarcopterygii * List of sarcopterygians * List of prehistoric bony fish A ''list'' ...

'' * ''

Brachydectes ''Brachydectes'' is an extinct genus of lysorophian amphibian that lived from the Carboniferous. It had a very small head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, an ...

'' * ''

Phlegethontia ''Phlegethontia'' is an extinct genus of aïstopod stegocephalians from the Carboniferous and Permian periods of Europe and North America. It was about long, and possessed a lightly built skull with many openings, unlike some earlier relativ ...

Description

Fossil content

See also

References

Further reading