Dunkard Group

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Dunkard Group
Stratigraphic range: Pennsylvanian-Permian
Sandstone (Greene Formation, Dunkard Group, Lower Permian; Clark Hill section, Long Ridge, Monroe County, Ohio, USA) 10 (31206070732).jpg
Sandstone (Greene Formation, Dunkard Group, Lower Permian; Monroe County, Ohio)
Type Group
Sub-units Greene Formation, Washington Formation, Waynesburg Formation [1]
UnderliesIgneous intrusives
Overlies Monongahela Formation
Lithology
Primary Shale, sandstone, siltstone, coal
Other Limestone
Location
RegionFlag of Ohio.svg  Ohio, Flag of Pennsylvania.svg  Pennsylvania, Flag of West Virginia.svg  West Virginia, and Flag of Maryland.svg  Maryland
CountryFlag of the United States.svg  United States
Type section
Named forDunkard Creek
Named byI.C. White in 1891

The Permian Dunkard Group (Pd) is an area of rock, Early Permian in age, in the south of Ohio, southwestern Pennsylvania, West Virginia and the hilltops of the Georges Creek Basin of Maryland. [2] 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. In addition, it is the youngest surface rock in the state of Ohio.

Contents

Description

It consists of red and green shale, siltstone, and sandstone, with thin lenticular beds of argillaceous limestone and thin beds of impure coal The base of the layer contains thick-bedded, white conglomeratic sandstone. The layer's thickness is greater than 200 feet in Maryland. [2]

The fossils found in the Dunkard Group are similar to ones found in Texas and Oklahoma of similar age.

Stratigraphy

The Dunkard contains three formation. Starting at the base (oldest) is the Waynesburg Formation, Washington Formation, and Greene Formation. The base is marked by the Waynesburg Coal, with the Monongahela Group below. The Washington Coal is found at the base of the Washington Formation and its base marks the boundary between the lower Waynesburg and the Washington formation above. The top of the Upper Washington Limestone marks the line between the Washington Formation and the upper Greene formation.

Fossil content

PortraitName
Dimetrodon grandis 3D Model Reconstruction.png Dimetrodon
Ctenospondylus2DB2.jpg Ctenospondylus
Archaeothyris BW.jpg Archaeothyris
Edaphosaurus-Field Museum.jpg Edaphosaurus
Eryops1DB.jpg Eryops
Xenacanth.png Xenacanthus
Ophiacodon FMNH.jpg Ophiacodon
Diploceraspis12DB.jpg Diploceraspis
Protorothyris.jpg Protorothyris
Diadectes1DB.jpg Diadectes
Isodectes obtusus.jpg Isodectes
Brachydectes NT small.jpg Brachydectes
Phlegethontia.jpg Phlegethontia
Baldwinonus
Sagenodus
Sysciophlebia balteata

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References

  1. Berryhill, Jr., Henry L.; Swanson, Vernon E. (1962). "Geological Survey research 1962; Short papers in geology and hydrology" (PDF). U.S. Geological Survey Professional Paper. 450-C: 43–46. Retrieved 30 June 2018.
  2. 1 2 "Allegheny Plateau and Valley and Ridge". Geologic Map of Maryland. Maryland Geological Survey. 1968. Retrieved 2008-01-26.

Further reading