Geologic units in Pocahontas county, West Virginia

Additional scientific data in this geographic area

Chemung Group (Devonian) at surface, covers 21 % of this area

Gray to brown siltstone and sandstone with shale and conglomeratic interbeds; mainly marine and sparingly fossiliferous; boundaries gradational. Can be divided into the Voreknobs and Scherr Formations along the Allegheny Front. Parkhead Sandstone Member near base.

Hampshire Formation (Devonian) at surface, covers 13 % of this area

Non-marine shales and fine micaceous sandstones, mostly red to brownish-gray, including siltstone, sandstone and conglomerate. Generally distinguishable from the underlying Chemung by non-marine character and red color.

Bluefield Formation (Mississippian) at surface, covers 12 % of this area

(part of Mauch Chunk Group) - red and green shale and sandstone, with a few thin limestone lenses, such as the Reynolds.

New River Formation (Pennsylvanian) at surface, covers 7 % of this area

(part of Pottsville Group) - predominantly sandstone, with some shale, siltstone, and coal. Grades to nearly all sandstone in the subsurface. Extends from the top of the Upper Nuttall Sandstone to the top of the Flattop Mountain Sandstone. Includes the Iaeger, Sewell, Welch, Raleigh, Beckley, Fire Creek, and Pocahontas Nos. 8 and 9 coals.

Pocono Group (Mississippian) at surface, covers 7 % of this area

Predominantly hard gray massive sandstones, with some shale. In the Eastern Panhandle, has been divided into the Hedges, Purslane, and Rockwell Formations.

Greenbrier Group (Mississippian) at surface, covers 7 % of this area

Marine limestone and marine and non-marine red and gray shale, and minor sandstone beds in numerous formational units.

Hinton Formation (Mississippian) at surface, covers 7 % of this area

(part of Mauch Chunk Group) - red, green, and medium-gray shale and sandstone, with a few thin limestone beds, including the Avis.

Brallier Formation (Devonian) at surface, covers 6 % of this area

Predominantly olive-gray to dark, thickly laminated marine shale, with considerable siltstone and thin sandstone lenses; mainly nonfossiliferous.

Bluestone and Princeton Formations (Mississippian) at surface, covers 4 % of this area

(part of Mauch Chunk Group) - the Bluestone Formation is mostly red, green, and medium-gray shale and sandstone; Princeton Sandstone is underneath.

Kanawha Formation (Pennsylvanian) at surface, covers 4 % of this area

(part of Pottsville Group) - sandstone (approx 50%), shale, siltstone, and coal. Contains several marine zones. Becomes more shaly westward in the subsurface. Extends from the top of the Homewood Sandstone to the top of the Upper Nuttall Sandstone. Includes the Stockton (Mercer), Coalburg, Winifrede, Chilton, Williamson, Cedar Grove, Alma, Peerless, Campbell Creek, Powellton, Eagle, Gilbert, and Douglas coals.

Millboro Shale (Devonian) at surface, covers 3 % of this area

Dark grey to black shale facies of eastern West Virginia. Consists of units: Harrell Shale, Mahantango Formation and Marcellus Formation.

Tonoloway, Wills Creek, and Williamsport Formations (Silurian) at surface, covers 2 % of this area

Includes the thin-bedded platy argillaceous limestones of the Tonoloway, the thin-bedded shale with fossiliferous limestones of the Wills Creek, the Bloomsburg red clastic facies, and the greenish-brown to white Williamsport Sandstone. The Wills Creek contains anhydrite and rock salt, the latter supplying brine from deep wells along the Ohio River.

McKenzie Formation and Clinton Group (Silurian) at surface, covers 2 % of this area

Includes the McKenzie Formation, consisting of shale with thin limestone lenses; the dark Rochester Shale; the white Keefer Sandstone; and the Rose Hill predominantly red shale, with thin sandstone interbeds, some of which are called "iron sandstones" from their reddish-brown color and hematite content.

Oriskany Sandstone and Helderberg Group, undivided (Devonian) at surface, covers 2 % of this area

Oriskany Sandstone: sometimes designated Ridgeley in eastern West Virginia. White to brown coarse- to fine-grained, partly calcareous sandstone, locally pebbly or conglomeratic, and ridge-forming. May be white, nearly pure silica, and a source of glass sand, as at Berkeley Springs, Morgan County. Helderburg Group: mostly cherty limestone, with some sandstone and shale. Contains several named stratigraphic units, including the Keyser Formation, which is partly Silurian and includes the Clifton Forge Sandstone and Big Mountain Shale Members.

Maccrady Formation (Mississippian) at surface, covers 1 % of this area

Red shale and mudrock, red and green sandstone, and minor limestone. Present only from Pendleton County southward. Contains rock salt and gypsum in southwestern Virginia.

Quaternary Alluvium (Quaternary) at surface, covers 0.9 % of this area

Alluvial deposits of sand, gravel, silt, and clay.

Tuscarora Sandstone (Silurian) at surface, covers 0.4 % of this area

Medium- to thick-bedded, white to gray or pinkish sandstone, fine to coarse, quartzitic, ridge-forming. Equivalent to the Clinch Sandstone of Tennessee.

Hampshire Formation (Devonian) at surface, covers 0.1 % of this area

Wildcat Valley Sandstone (Miller, Harris, and Roen, 1964). Sandstone, limestone, and shale. Sandstone, locally calcareous, locally quartzose, light-gray, grayish-orange, and dark-yellowish-brown, very-fine- to coarse-grained, thin- to massive-bedded, fossiliferous, friable, locally glauconitic; with chert nodules and beds. Locally dark-reddish-brown ironstone replaces sandstone. Limestone, gray, pinkish-gray, and light-brownish-gray, coarse-grained, thick- to massive bedded, sandy, locally present. Shale, yellowish-green to gray, locally present. Where the Wildcat Valley Sandstone is present it uncomformably overlies the Silurian Hancock Formation. The Wildcat Valley Sandstone is absent through out most of Lee County (Englund, 1964; Harris, 1965; Miller and Roen, 1973) but reaches a maximum of 60 feet in thickness to the northeast (Lower Devonian sandstone of Harris and Miller, 1963).

Mauch Chunk Group (Mississippian) at surface, covers < 0.1 % of this area

Red, green, and medium-gray shale and sandstone, with a few thin limestones.

Chemung Formation (redefined as Foreknobs Formation) (Devonian) at surface, covers < 0.1 % of this area

Chemung Formation (Hall, 1839). Redefined as the Foreknobs Formation (Dennison, 1970). Sandstone and shale, dark-gray and greenish-gray, fine-grained, thin- to thick-bedded, lithic sandstone and interbedded greenish gray, fissile, clay shale. Minor quartz-pebble conglomerate, thin red sandstone, and locally, fossil shell beds. Very thin or absent in southwestern Virginia; thickens to about 2500 feet northeastward in Frederick County. Gradational contact with underlying Brallier Formation and equivalent to part of the Chattanooga Shale to the southwest. Redefined and described as part of the Greenland Gap Group by Dennison (1970).

Pocono Formation (Mississippian) at surface, covers < 0.1 % of this area

Pocono Formation (Lesley, 1876). Quartzitic sandstone, light-gray or tan, medium- to coarse-grained, locally conglomeratic, thick-bedded, resistant, interbedded with thin, gray, organic shale and a few very-thin coal beds. Conformable with underlying Hampshire Formation; formation present northeast of Alleghany and Roanoke Counties. Thickness may exceed 750 feet. It is laterally equivalent to the Price Formation to the southwest.

Juniata and Oswego Formations (Ordovician) at surface, covers < 0.1 % of this area

The Juniata is a thin-bedded, blocky, red sandstone and shale. In places it is underlain by the thick-bedded, gray Oswego Sandstone.

Helderberg Group (Devonian) at surface, covers < 0.1 % of this area

Mostly cherty limestone, with some sandstone and shale. Contains several named stratigraphic units, including the Keyser Formation, which is partly Silurian and includes the Clifton Forge Sandstone and Big Mountain Shale Members.

Pocahontas Formation (Pennsylvanian) at surface, covers < 0.1 % of this area

(part of Pottsville Group) - sandstone, approx. 50%, with some shale, siltstone, and coal. Extends from the top of the Flattop Mountain Sandstone to the top of the Mississippian. Includes from bottom upward Pocahontas coals Nos. 1 through 7.

Oriskany Sandstone and Huntersville Chert (Devonian) at surface, covers < 0.1 % of this area

Oriskany Sandstone: sometimes designated Ridgeley in eastern West Virginia. White to brown coarse- to fine-grained, partly calcareous sandstone, locally pebbly or conglomeratic, and ridge-forming. May be white, nearly pure silica, and a source of glass sand, as at Berkeley Springs, Morgan County. Huntersville Chert (part of Onesquethaw ("Onondaga") Group): ranges from a nearly pure slightly calcitic or dolomitic chert to an inter-tonguing of such chert and the Needmore Shale. Grades westward in the subsurface to a limestone, commonly considered as "Onondaga". Contains the "glauconitic" Bobs Ridge Sandstone Member. Not mappable at scale of this map. Included with Do.