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Mineral Resources > Online Spatial Data > Geology > by state > Virginia Geology

Geologic units in Alleghany county, Virginia

[Additional scientific data in this geographic area]

Beekmantown or Lower Ordovician Group (Ordovician) at surface, covers < 0.1 % of this area

Beekmantown or Lower Ordovician Group - mainly thick-bedded limestone and dolomite. Various units produce much chert on outcrop. Consists of units: Pinesburg Station Dolomite, Rockdale Run Formation, and Stonehenge Limestone.

Lithology: limestone; dolostone (dolomite); chert

Martinsburg Formation (Ordovician) at surface, covers < 0.1 % of this area

Martinsburg Formation - predominantly gray to dark shale, yellowish in the upper portion. Contains scattered thin limestone and sandstone interbeds, particularly in the lower portion. The upper portion constitutes the Reedsville Shale.

Lithology: shale; limestone; sandstone

St. Paul Group (Ordovician) at surface, covers < 0.1 % of this area

St. Paul Group - includes the New Market and Row Park Limestones. Predominantly medium-gray aphanitic limestone, containing very low-silica, cream-colored member of considerable economic importance. Chert nodules and dolomite occur in the Row Park.

Lithology: limestone; chert; dolostone (dolomite)

Knox Group (Cambrian-Ordovician) at surface, covers 0.3 % of this area

Knox Group - dolostone, limestone, sandstone. Includes the Mascot Dolomite, Kingsport Dolomite, Chepultepec Dolomite, Copper Ridge Dolomite. (Includes: Ob, Omk, Occo, Cco, Occc.)

Lithology: dolostone (dolomite); limestone; chert; sandstone

Oriskany Sandstone and Helderberg Group, undivided (Devonian) at surface, covers < 0.1 % of this area

Oriskany Sandstone and Helderberg Group, undivided - 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.

Lithology: sandstone; limestone; shale

Tuscarora Sandstone (Silurian) at surface, covers < 0.1 % of this area

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

Lithology: sandstone

Pocono Formation (Mississippian) at surface, covers 3 % of this area

Pocono Formation - Sandstone, conglomeratic sandstone, and shale with carbonaceous partings and impure coal beds.

Lithology: sandstone; shale; coal

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

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

Lithology: sandstone; shale

Juniata, Reedsville, Trenton, and Eggleston Formations (Ordovician) at surface, covers 5 % of this area

Juniata, Reedsville, Trenton, and Eggleston Formations - Dusky-red shale and mudstone and sandstone; shale and limestone. Note: one area in southeastern Bland County has landslides with intact stratigraphic units.

Lithology: shale; mudstone; sandstone; limestone

Hampshire Formation (Devonian) at surface, covers 0.5 % of this area

Hampshire Formation - Dusky-red to grayish-red shale, mudrock, and sandstone.

Lithology: sandstone; limestone; shale

Juniata, Oswego, Martinsburg (Reedsville and Dolly Ridge), and Eggleston Formations (Ordovician) at surface, covers 2 % of this area

Juniata, Oswego, Martinsburg (Reedsville and Dolly Ridge), and Eggleston Formations - Dusky-red shale and mudstone and sandstone; graywacke; shale and sandstone; and limestone.

Lithology: shale; mudstone; sandstone; graywacke; limestone

Chemung Group (Devonian) at surface, covers 0.3 % of this area

Chemung Group - 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.

Lithology: siltstone; sandstone; shale; conglomerate

Chemung Formation (redefined as Foreknobs Formation) (Devonian) at surface, covers 14 % of this area

Chemung Formation - Shale and sandstone with a few thin, quartz-pebble conglomerates and red-beds.

Lithology: shale; sandstone; conglomerate

Beekmantown Group (Ordovician) at surface, covers 0.3 % of this area

Beekmantown Group - Dolomite, limestone, and chert. Includes Pinesburg Station Dolomite, Rockdale Run Formation, Beekmantown Formation, Stonehenge Limestone, and Chepultepec Formation.

Lithology: dolostone (dolomite); limestone; chert

Ridgeley Sandstone, Helderberg and Cayugan Groups (Silurian-Devonian) at surface, covers 14 % of this area

Ridgeley Sandstone, Helderberg and Cayugan Groups - Calcareous sandstone; partly cherty limestone; calcareous shale; fossiliferous.

Lithology: limestone; sandstone; shale

Millboro Shale and Needmore Formation (Devonian) at surface, covers 19 % of this area

Millboro Shale and Needmore Formation - Black, fissile shale; gray calcareous shale; Tioga metabentonite at top of Needmore.

Lithology: black shale; shale; bentonite; limestone

Lower Devonian and Silurian Formations Undivided (Silurian-Devonian) at surface, covers 0.9 % of this area

Lower Devonian and Silurian Formations Undivided - Some landslides with intact stratigraphic units in Craig County area. Includes: Dsu, Skrt, Sm. (Shrc?)

Lithology: sandstone; limestone; shale

Pocono Group (Mississippian) at surface, covers 0.2 % of this area

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

Lithology: sandstone; shale

Maccrady Shale (Mississippian) at surface, covers 0.2 % of this area

Maccrady Shale - Dusky-red and green shale and mudstone; and evaporite deposits.

Lithology: shale; siltstone; evaporite; limestone; mudstone; sandstone

Keefer, Rose Hill, and Tuscarora Formations (Silurian) at surface, covers 12 % of this area

Keefer, Rose Hill, and Tuscarora Formations - Quartzarenite, dusky-red shale, and sandstone, Some landslides with intact stratigraphic units in Craig County area..

Lithology: arenite; shale; sandstone

Trenton Group and Black River Group, undivided (Ordovician) at surface, covers < 0.1 % of this area

Trenton Group and Black River Group, undivided - Trenton Group: dark, crystalline, nodular, and argillaceous limestones, with some metabentonite streaks. Includes the Nealmont, Oranda, Edinburg, and the upper part of the Chambersburg Limestones of northeastern West Virginia; also the Moccasin and Eggleston Formation of Mercer and Monroe Counties. Black River Group: predominantly gray aphanitic limestones, with many bioclastic streaks; siliceous in the lower part.

Lithology: limestone; bentonite

Millboro Shale (Devonian) at surface, covers < 0.1 % of this area

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

Lithology: shale; black shale

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

Hampshire Formation - 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.

Lithology: shale; sandstone; siltstone; conglomerate

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

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

Lithology: shale; siltstone; sandstone

Newark Supergroup; Jurassic Basalt (Lower Jurassic) at surface, covers < 0.1 % of this area

basalt

Lithology: basalt

Brallier Formation (Devonian) at surface, covers 26 % of this area

Brallier Formation - Micaceous shale, siltstone, and sandstone.

Lithology: shale; siltstone; sandstone

Moccasin or Bays Formation through Blackford Formation (Ordovician) at surface, covers 2 % of this area

Moccasin or Bays Formation through Blackford Formation - Dusky-red shale and mudstone; sandstone; limestone, in part cherty; and calcareous shale.

Lithology: shale; mudstone; sandstone; limestone; chert