Geologic units in West Virginia (state in United States)

Additional scientific data in this geographic area

Dunkard Group (Permian/Pennsylvanian) at surface, covers 17 % of this area

Non-marine cyclic sequences of sandstone, siltstone, red and gray shale, limestone, and coal. Contains the Greene, Washington and Waynesburg Formations. Extends from the top of the exposed bed rock section to the top of the Waynesburg coal. Includes the Washington coals and limestones. Palynological evidence favors a Pennsylvanian age, at least for the lower portion.

Kanawha Formation (Pennsylvanian) at surface, covers 14 % 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.

Conemaugh Group (Pennsylvanian) at surface, covers 13 % of this area

Cyclic sequences of red and gray shale, siltstone, and sandstone, with thin limestones and coals. Mostly non-marine. May be divided into Casselman and Glenshaw Formations. Extends from the base of the Pittsburgh coal to the top of the Upper Freeport coal. Includes the Elk Lick, Bakerstown, and Mahoning coals, and the Ames and Brush Creek Limestones.

New River Formation (Pennsylvanian) at surface, covers 8 % 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.

Monongahela Group (Pennsylvanian) at surface, covers 8 % of this area

Non-marine cyclic sequences of sandstone, siltstone, red and gray shale, limestone, and coal. Contains the Uniontown and Pittsburgh Formations. Extends from the top of the Waynesburg coal to the base of the Pittsburgh coal. Includes the Waynesburg, Uniontown, Sewickley, Redstone and Pittsburgh coals. Thickness is 170 feet in Mineral and Grant Counties.

Allegheny Formation (Pennsylvanian) at surface, covers 6 % of this area

Cyclic sequences of sandstone, siltstone, shale, limestone, and coal. Includes the Freeport, Kittanning and Clarion coals, also, the Princess coals of Kentucky . Extends from the top of the Upper Freeport coal to the top of the Homewood Sandstone.

Chemung Group (Devonian) at surface, covers 5 % 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 4 % 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.

Quaternary Alluvium (Quaternary) at surface, covers 2 % of this area

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

Hinton Formation (Mississippian) at surface, covers 2 % 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.

Bluefield Formation (Mississippian) at surface, covers 2 % of this area

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

Bluestone and Princeton Formations (Mississippian) at surface, covers 2 % 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.

Greenbrier Group (Mississippian) at surface, covers 2 % of this area

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

Pocono Group (Mississippian) at surface, covers 2 % 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.

Pocahontas Formation (Pennsylvanian) at surface, covers 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 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.

Brallier Formation (Devonian) at surface, covers 1 % of this area

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

Brallier Formation and Harrell Shale, undivided (Devonian) at surface, covers 0.9 % of this area

Brallier Formation : predominantly olive-gray to dark, thickly laminated marine shale, with considerable siltstone and thin sandstone lenses; mainly nonfossiliferous. Harrell Shale: dark gray to black thinly laminated to fissile shale. Calcareous shale and limestone lenses near the base (Tully).

Mahantango Formation (Devonian) at surface, covers 0.9 % of this area

(part of Millboro Shale) - thickly laminated marine shale, siltstone, very fine sandstone, and some limestone, with an occasional coral reef or biostrome. Contains the Clearville and Chaneysville Siltstone Members of Pennsylvania.

Tonoloway, Wills Creek, and Williamsport Formations (Silurian) at surface, covers 0.9 % 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.

Pottsville Group (Pennsylvanian) at surface, covers 0.8 % of this area

Includes the Kanawha, New River, and Pocahontas Formations. Predominantly sandstones, some of which are conglomeratic, with thin shales and coals. Undivided in northern West Virginia.

Marcellus Formation and Needmore Shale, undivided (Devonian) at surface, covers 0.8 % of this area

Marcellus Formation (part of Millboro Shale): predominantly gray-black to black thinly laminated non-calcareous pyritic shale. Contains one or more thin-bedded limestones, including the Purcell Member of Pennsylvania. Needmore Shale (part of Onesquethaw ("Onondaga") Group): predominantly dark grey or green, calcitic, mostly non-fissile shale. Gives strong "kick" on gamma ray logs. Tioga Bentonite near the top. Includes the black Beaver Dam Shale Member. Grades westward into the Huntersville Chert. Not mappable at scale of this map. Included with Dmn.

McKenzie Formation and Clinton Group (Silurian) at surface, covers 0.7 % 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.

Martinsburg Formation (Ordovician) at surface, covers 0.7 % of this area

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.

Mauch Chunk Group (Mississippian) at surface, covers 0.5 % of this area

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

Helderberg Group (Devonian) at surface, covers 0.5 % 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.

Conococheague Formation (Cambrian) at surface, covers 0.4 % of this area

Predominantly algal and mechanically deposited limestone, with interbeds of aphanitic limestone and dolomite. Contains siliceous and dolomitic laminations. Resistant sandy Big Spring Station Member near the base.

Tuscarora Sandstone (Silurian) at surface, covers 0.3 % 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.

Elbrook Formation (Cambrian) at surface, covers 0.3 % of this area

Thin-bedded blue-gray argillaceous limestone and platy shale, with some siliceous limestone and minor dolomite.

Millboro Shale (Devonian) at surface, covers 0.2 % of this area

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

Maccrady Formation (Mississippian) at surface, covers 0.2 % 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.

Juniata and Oswego Formations (Ordovician) at surface, covers 0.2 % 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.

Rockdale Run Formation (Ordovician) at surface, covers 0.2 % of this area

Bluish to light gray and brown, thick-bedded dolomite and limestone, containing gray chert and zones of Cryptozoa and Lecanospira.

Oriskany Sandstone and Helderberg Group, undivided (Devonian) at surface, covers 0.2 % 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.

Stonehenge Limestone (Ordovician) at surface, covers 0.1 % of this area

Gray, thin-bedded to massive, fossiliferous limestone, largely mechanically deposited, with small black chert nodules and beds of "edgewise" conglomerate. The highly resistant Stoufferstown Limestone member is found at the base.

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

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.

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

(part of Millboro Shale) - dark gray to black thinly laminated to fissile shale. Calcareous shale and limestone lenses near the base (Tully).

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

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.

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

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.

Ordovician, middle calcareous units (Ordovician) at surface, covers < 0.1 % of this area

Ordovician - middle calcareous units.

Harpers Formation (Cambrian) at surface, covers < 0.1 % of this area

(Chilhowee Group) - greenish-gray phyllite, with interbeds of fine-grained quartzite.

Waynesboro Formation (Cambrian) at surface, covers < 0.1 % of this area

Variegated shale and sandstone, commonly red or brown. Middle zone contains much dolomite and limestone. Contains the Olenellus fauna of Early Cambrian age, although its upper portion may be of Middle Cambrian age.

Tomstown Dolomite (Cambrian) at surface, covers < 0.1 % of this area

Thick-bedded, blue-gray, aphanitic, saccharoidal, and splintery dolomite, weathering coffee-brown; some siliceous limestone and black chert. Contains commercial beds of white, pure, low-silica dolomite.

Middle and Upper Devonian, undivided (Devonian) at surface, covers < 0.1 % of this area

This unit is predominantly shale, and includes all Devonian beds above the Onesquethaw. Consists of units: Hampshire Formation, Chemung Group, Brallier Formation, Harrell Shale, Mahantango Formation, and Marcellus Formation.

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

(part of Millboro Shale) - predominantly gray-black to black thinly laminated non-calcareous pyritic shale. Contains one or more thin-bedded limestones, including the Purcell Member of Pennsylvania.

McKenzie Formation, Clinton Group and Tuscarora Sandstone, undivided (Silurian) at surface, covers < 0.1 % of this area

McKenzie Formation and Clinton Group: 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. 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.

Pinesburg Station Dolomite (Ordovician) at surface, covers < 0.1 % of this area

Fine- to medium-crystalline, brown to light gray dolomite, containing nodular chert.

Antietam Formation (Cambrian) at surface, covers < 0.1 % of this area

(Chilhowee Group) - gray to white quartzite, sandstone and quartz-schist; thick-bedded, and resistant; contains Scolithus.

Maccrady Formation and Pocono Group, undivided (Mississippian) at surface, covers < 0.1 % of this area

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

Trenton Group (Ordovician) at surface, covers < 0.1 % of this area

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.

Weverton-Loudoun Formation (Cambrian) at surface, covers < 0.1 % of this area

(Chilhowee Group) - tough quartzitic sandstones, conglomerates, and shale.

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

Predominantly gray aphanitic limestones, with many bioclastic streaks; siliceous in the lower part.

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).

Conemaugh Group (Pennsylvanian) at surface, covers < 0.1 % of this area

Shale, siltstone, and mudstone: Shale, black, gray, green and red; clayey to silty; locally contains marine fossils in lower half of unit; calcareous in part. Siltstone, gray, green and red, locally variegated; clayed to sandy; thin bedded to nonbedded. Mudstone, black, gray, green, red, and yellow, variegated in part; clayey to silty; locally calcareous; commonly nonbedded. Sandstone, green-gray weathers to shades of yellow-brown; mostly very fine to medium grained, locally conglomeratic; thin to massive to cross bedded; locally calcareous. Limestone and coal; thin and discontinuous. Limestone, black, gray and green; micritic to coarse grained; thin bedded to concretionary with marine fossils common in lower half of interval; thin to medium bedded, nonmarine limestone common in upper half of unit. Coal, thin, bituminous, impure; very locally thick enough for economic development. Lateral and vertical lithic variability and gradation common. Unit as much as 500 feet thick.

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.

Allegheny Formation and Pottsville Formation (Pennsylvanian) at surface, covers < 0.1 % of this area

Allegheny Formation - Interbedded sandstone, siltstone, claystone, shale, and coal beds; Upper Freeport coal at top; where present, Brookville coal defines base; thickness 275 feet in northeast, increases to 325 feet in south and west. And Pottsville Formation - Interbedded sandstone, siltstone, claystone, shale, and coal beds; conglomeratic orthoquartzite and protoquartzite at base; thickness 60 feet in northeast, increases to 440 feet in southwest

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

Norton Formation (Campbell, 1893). Siltstone, shale, sandstone, conglomerate, limestone, and coal. Siltstone and shale, light- to medium-gray, with siderite and claystone concretions, fossiliferous; interbedded with and grades into sandstone. Sandstone, feldspathic, micaceous, argillaceous, light- to medium-gray, very-fine- to coarse-grained, thin- to very-thick-bedded, cross-bedded, locally massive, well-cemented. Conglomerate in thin zones in McClure Sandstone Member (lateral equivalent to part of Bee Rock Sandstone Member of the Lee Formation). Lime stone, medium-gray, micrograined, locally in lenses in two zones above the McClure Sandstone Member (Taylor, 1989; Whitlock, 1989). Coal in several beds and zones. A volcanic ash parting is in the Upper Banner coal bed locally (Diffenbach, 1988, 1989; Evans and Troensegaard, 1991; Henika, 1989a). The base of the Norton is defined as the top of the uppermost quartzarenite of the Lee Formation. On the western side of the coalfield the base of the Norton is at the top of the Bee Rock Sandstone Member of the underlying Lee Formation. However, the Bee Rock grades eastward into feldspathic, conglomeratic sandstone of the McClure Sandstone Member of the Norton. Several underlying Lee quartzarenites successively tongue out or grade into finer-grained clastic rocks to the southeast stratigraphically lowering the base of the Norton. This accounts for the great range in thickness of 500 to 2480 feet for the Norton Formation.

Greene Formation (Permian) at surface, covers < 0.1 % of this area

Cyclic sequences of sandstone, shale, red beds, thin limestone, and thin, impure coal; base is at top of Upper Washington limestone.

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

New River Formation (Fontaine, 1874; redefined by Read and Mamay, 1964). Sandstone, siltstone, shale, coal, underclay, and limestone. Sandstone, feldspathic, micaceous, disseminated dark mineral grains, light- to medium-light-gray, very-fine- to coarse-grained, locally conglomeratic with quartz pebbles as much as 3 inches in diameter, thin- to thick-bedded, locally massive, ripple-bedded, cross-bedded; contains carbonaceous fragments. Siltstone, medium-light- to medium-gray, even-bedded, ripple-bedded, deformed locally. Shale, medium- gray to black, evenly to indistinctly bedded, with few very fissile carbonaceous beds, plant fossils, ironstone laminations and concretions. Coal, finely cleated, impure coal partings in several beds, locally grades into black carbonaceous shale. Underclay, medium-gray, clayey to silty, contains root casts. Limestone, medium-gray, argillaceous, in thin discontinuous beds and ellipsoidal concretions locally occurs near base and middle part of formation. Marine invertebrate fossils locally in basal bed. Base is conformable with Pocahontas Formation and placed at bottom of Pocahontas No. 8 coal bed in most outcrop areas (Englund and Thomas, 1990). Northwest of outcrop belt, base is unconformable with the underlying Pocahontas Formation. The New River is thickest in western Tazewell and eastern Buchanan counties (Englund, 1981); it ranges from 1380 to 1925 feet in thickness.

Breathitt Formation, lower part (Pennsylvanian) at surface, covers < 0.1 % of this area

lower part which includes Livingston Conglomerate Member of Lee Formation in eastern Rockcastle County

"Chemung" Formation, Parkhead Sandstone, Brallier Formation, and Harrell Shale (Devonian) at surface, covers < 0.1 % of this area

"Chemung" Formation - Predominantly marine beds characterized by gray to olive-green graywacke, siltstone, and shale; thickened ranges from 2,000 to 3,000 feet; Parkhead Sandstone - Gray to olive-green sandy shale, conglomeratic sandstone and graywacke; present in Washington County, identification uncertain in west; thickness averages 400 feet; Brallier Fomation - (Woodmont Shale of earlier reports). Medium to dark gray, laminated shale and siltstone; weathers to light olive-gray; grain size coarsens upward; thickness about 2,000 feet in west, about 1,7000 feet in east; and Harrell Shale - Dark gray laminated shale; absent in east where Brallier lies directly on Mahantango, Tully Limestone lies near base in west, in subsurface of Garrett County; total thickness in west 140 to 300 feet.

Keefer, Rose Hill, and Tuscarora Formations (Silurian) at surface, covers < 0.1 % of this area

Keefer Sandstone (Ulrich, 1911). Sandstone, light-gray, fine-grained, cross-laminated, medium-bedded, very resistant. Thins northward and southwestward from a maximum of over 300 feet in Craig and western Botetourt counties. To the north it appears to interfinger with the Wills Creek and McKenzie Formations. The Keefer is equivalent to the upper portion of the Massanutten Sandstone. (The Keefer Sandstone, as used in this report, includes all of the quartzarenites with minor Skolithus-bearing red sand stone and minor calcite cemented quartzarenite in the interval above the Rose Hill Formation and below the Tonoloway Limestone in Botetourt, Rockbridge, and Augusta counties between Eagle Rock and Augusta Springs (Lampiris, 1976). Rose Hill Formation (Swartz, 1923). Sandstone, dark grayish-red, fine- to coarse-grained, poorly-sorted, argillaceous; hematite cemented, quartz sandstone interbedded with red or yellowish-green clay shale and greenish-gray, fine-grained sandstone. It is largely siltstone and shale with minor sandstone and thin limonitic iron ore beds in Southwest Virginia. Conformable with the underlying Tuscarora Formation, the Rose Hill Formation ranges up to 500 feet in thickness in northern and western Virginia but pinches-out in southwest ern Botetourt and Roanoke counties where the Keefer and Tuscarora For ma tions merge. It is present with other Silurian rocks everywhere except in the Massanutten Mountains or where an unconformity exists in exposures east of Walker Mountain. Tuscarora Formation (Darton and Taff, 1896). Quartzite, quartzarenite, and minor shale. Quartzite, light-gray with few nearly white, porcelaneous beds, fine- to medium-grained, with quartz-pebble conglomerate locally near base, quartz cemented, thick-bedded, and cross-bedded, resistant, cliff- and ledge-former, generally not more than 75 feet thick, comprises entire unit in many areas or is upper member where unconformably overlying a lower quartzarenite and shale member. Quartzarenite, light-yellowish-brown or medium-gray, fine-grained, thin-bedded, ranges in thickness from 0 to 175feet. Shale, light- to medium-brownish-gray, arenaceous, thin interbeds in quartzarenite. Conformably overlies the Juniata Formation in central western Virginia. Where lower member is absent the upper member unconformably overlies the Juniata, Oswego, Martinsburg, or Reedsville Formations or may be conformable with the Juniata Formation in northern Virginia. In southwestern Virginia grayish-red, fine-grained, ferruginous sandstone with lenses of coarse-grained, quartz sandstone and quartz-pebble conglomerate are included in the upper part of the formation. The Tuscarora is equivalent to the Clinch Formation and to the lower part of the Massanutten Sandstone.

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).

Monongahela Group (Pennsylvanian) at surface, covers < 0.1 % of this area

Shale, siltstone, and mudstone; black, red, gray and green to variegated red and yellow in the southeastern areas of Ohio; clayey to sandy; nonbedded to thin bedded; locally calcareous. Sandstone, greenish-gray weathers to shades of yellow-brown, silty to locally conglomeratic; thin to massive to cross bedded; locally calcareous. Limestone, gray, micritic, clayey to silty, thin to medium bedded; generally more common in middle and lower portions of unit. Coal, banded, bituminous, thin to as much as 8 feet thick in central and northern areas, thinner to absent in southeastern Ohio. Lateral and vertical lithic variability and gradation common. Unit as much as 350 feet thick.

Lower Devonian and Silurian Formations Undivided (Silurian-Devonian) at surface, covers < 0.1 % of this area

Some landslides with intact stratigraphic units in Craig County area. Includes: Dsu, Skrt, Sm. (Shrc?)

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

Cyclic sequences of shale, siltstone, sandstone, red beds, thin, impure limestone, and thin, nonpersistent coal; red beds are associated with landslides; base is at top of Ames limestone.

Monongahela Group (Pennsylvanian) at surface, covers < 0.1 % of this area

Cyclic sequences of limestone, shale, sandstone, and coal; commercial coals present; base is at bottom of Pittsburgh coal.

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

Cyclic sequences of sandstone, shale, limestone, clay, and coal; includes valuable clay deposits and Vanport Limestone; commercially valuable Freeport, Kittanning, and Brookville-Clarion coals present; base is at bottom of Brookville-Clarion coal.

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

Cyclic sequences of shale, sandstone, red beds, and thin limestone and coal; includes four marine limestone or shale horizons; red beds are involved in landslides; base is at top of Upper Freeport coal.

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

Includes the rocks between the base of the Pittsburgh coal and the top of the Upper Freeport coal; consists of two unnamed members which are separated by the Barton coal; both members are gray and brown claystone, shale, siltstone and sandstone, with several coal beds; lower member also contains redbeds and fossiliferous marine shales; thickness 825 to 925 feet.

Hamilton Group (including Mahantango Formation and Marcellus Shale), and including Tioga Metabentontite Bed, and Needmore Shale (Devonian) at surface, covers < 0.1 % of this area

Hamilton Group including Mahantango Formation - Dark gray, laminated shale, siltstone, and very fine-grained sandstone; thickness 600 feet in west, increases to 1,200 feet in east, and Marcellus Shale - Gray-black, thinly laminated, pyritic, carbonaceous shale; thickness 250 feet in east, increases to 500 feet in west. Also includes Tioga Metabentonite Bed - Brownish-gray, thinly laminated shale containing sand-size mica flakes; thickness less than one foot; and Needmore Shale - Olive-gray to black shale and dark, thin-bedded, fossiliferous, argillaceous limestone; thickness ranges from 70 to 145 feet.

Allegheny and Pottsville Groups, Undivided (Pennsylvanian) at surface, covers < 0.1 % of this area

Shale, siltstone, and underclay: Shale, black, gray, and olive; clayey to silty; locally contains marine fossils; calcareous in part. Siltstone, gray, greenish and olive; clayey to sandy; thin bedded to medium bedded; locally contain marine fossils. Underclay, gray and olive; generally 3 feet or less in thickness; clayey to silty; commonly rooted and underlying coal beds; nonbedded; locally varies from flint to plastic clay. Sandstone, light to medium gray weathers to shades of yellow-brown; mostly very fine to medium grained, locally quartzose and conglomeratic in lower one-third of unit; thin to massive to cross bedded; locally calcareous; Limestone, flint and coal. Limestone, black to light gray; micritic to medium grained; locally grades into flint; thin to medium bedded to discoidal concretions containing marine fossils; locally nonmarine, micritic limestones occur beneath coal beds in upper one third of unit. Coal, mostly banded bituminous, locally cannel; thin to locally as much as 12 feet thick; generally in discrete beds but locally contain shale partings and split into multiple beds. Lateral and vertical lithic variability and gradation common. Unit as much as 700 feet thick.

Washington Formation (Permian) at surface, covers < 0.1 % of this area

Cyclic sequences of sandstone, shale, limestone, and coal; includes some red shale; base is at bottom of Washington coal.

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

Interbedded red shale, red mudstone, and red to brown cross-bedded siltstone and sandstone; some thin green shale; greenish-gray sandstone and shale toward top; fragmentary plant fossils; thickness 1,400 to 2,000 feet in west, increases to 3,800 feet in east.

Conococheague Limestone (Upper Cambrian to Lower Ordovician) at surface, covers < 0.1 % of this area

Dark blue, laminated, oolitic, argillaceaous, and siliceous limestone, algal limestone, and flat-pebble conglomerate; siliceous shale partings; some sandstone and dolomite; thickness 1,600 to 1,900 feet.

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

Pennington Group (Campbell, 1893). Bluestone Formation, Princeton Sandstone, and Hinton Formation. Raised to Group rank by Harris and Miller (1958). The group consists of shale, sandstone, mudstone, conglomerate, siltstone, minor limestone, and coal locally. The shale, siltstone, and mud stone are gray to black and shades of red, and mottled red and gray. The sandstone is locally quartzose and conglomeratic, and ranges from shades of gray to brown, and only locally mottled within red shales; many sandstones pinch out southwestward in the Tazewell County area, but two persist farther west and southwest. The limestone is gray to brown, generally near the middle of the group, and is the most widespread marine unit. The Bluestone and Hinton For ma tions thin to the westsouthwest in southwestern Virginia; the widespread sandstone and limestone members nearly converge southwestward to with in 80 feet of each other from about 600 feet of separation in northern Tazewell County. The Princeton Sandstone wedges out in Tazewell County. The top of the Pennington Group is intertonguing to unconform ble with the overlying Lee Formation in the western part of the Southwest Virginia coalfield; basal contact is conformable. The Group thins westward; variation in thickness partly due to intertonguing and the unconformity. The Pennington Group ranges from 235 feet in thickness without the Pinacle Overlook Member of the Lee (as interpreted from Vanover and others, 1989) in the south west to 2355 feet (Trent and Spencer, 1990) in Tazewell County and 1335 feet in a partial section in Washington County (Bartlett and Webb, 1971), where it is mapped as the Pennington Formation. Bluestone Formation (Campbell, 1896). Sand stone, siltstone, shale, mudstone, minor limestone, coal, and underclay. Sand stone, argillaceous, micaceous, locally quartzose, verylight to dark-gray, light-olive- to greenish-gray, yellowish-orange to dark-yellowish-brown, moderate-red, very-fine- to medium-grained, thin- to very-thick-bedded, cross-bedded, locally ripple-bedded, interbedded with shale and siltstone; forms ledges and cliffs. Sand stone in middle of formation in Scott and Russell counties is conglomeratic with quartzite pebbles and other rock clasts (Evans and Troensegarrd, 1991; Nolde and Diffenbach, 1988). Upper part intertongued with Lee in northern Lee County (Miller and Roen, 1973). Siltstone, shale, and mudstone, partly calcareous, greenish-gray, dark gray to grayish-black, pale- to moderate-red and mottled red and greenish-gray; siderite nodules in variegated shales and silt stones; fossils in dark-gray shale (Englund, 1968). Limestone, argillaceous, medium-gray, thin, lenticular, fossiliferous, in middle of formation, and in thin discontinuous beds at the base of the formation in the sub sur face in western Tazewell and eastern Buchanan Counties (Englund, 1981). Thin coal bed in upper part of formation in northern Lee County (Miller and Roen, 1973); coal and impure coal in thin discontinuous beds in middle of formation in northern Tazewell County; underlain by underclay, locally as much as three feet thick, with root casts (Englund, 1968). Top un con form able with the overlying Lee Formation in northwestern Wise and Dickenson counties and extreme northwestern Buchanan County but is intertonguing to the southeast (Mill er, 1974) and southwest in northern Lee County (Miller and Roen, 1973). Base conformable with the underlying Princeton Sandstone in northern Tazewell County, but is disconformable to the southwest because the Princeton wedges out southwestward in Tazewell County and the Bluestone lies on the Hinton Formation (Englund and Thomas, 1990). Bluestone thins northwestward and ranges in thickness from 40 feet in southwestern Lee County (Englund, Landis, and Smith, 1963) to as much as 850 feet to the northeast in Tazewell County (Englund and Thomas, 1990). Princeton Sandstone (Campbell and Mendenhall, 1896). Sandstone, light-gray to light-greenish-gray, weathered locally to pale-reddish-brown, fine- to coarse-grained, thin- to very thick- bedded, locally cross-bedded, calcite cemented, becomes friable upon weathering, contains conglomerate lenses as much as two feet thick with well-rounded to angular pebbles of quartz, shale, silt stone, limestone, chert, and ironstone; fossils in limestone clasts (Englund, 1968, 1979; Trent and Spencer, 1990). Wedges out southwestward in west-central Tazewell County (Englund, 1979). The Princeton as mapped in Lee County and southwestern Scott County (Harris and Miller, 1958; Miller and Roen, 1973) is a different sandstone. The Princeton ranges from 0 to 60 feet in thickness. Hinton Formation (Campbell and Mendenhall, 1896). Shale, siltstone, mudstone, sandstone, limestone, minor coal, underclay. Shale, siltstone, and mudstone, partly calcareous, grayish-red, medium-gray, and greenish-gray, fossiliferous. Sandstone, quartzose, feldspathic, very-light- to medium-light gray, greenish-gray, yellowish-brown, pale- to moderate-red, locally mottled, very-fine- to medium-grained, thin- to very thick- bedded, contains quartz-pebble con lomerate, tree trunk impressions, and coal fragments; cobbles in lowest member locally; interbedded with dark-gray to grayish-black shale. A widespread conglomeratic sandstone in the upper part of the formation has been misidentified as the stratigraphically higher Princeton Sandstone (Englund, 1979). Limestone, argillaceous, light-grayish-brown, medium-gray, thin-bedded, nodular, very fossiliferous, contains marine fossils of Chesterian age and is most widespread marine unit (Little Stone Gap Member) in the Hinton (Englund, 1979). Base conformable. The formation ranges from 164 feet in thickness in southwestern Lee County to 1320 feet in northern Tazewell County (Englund, 1968, 1979).

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

Pocahontas Formation (Campbell, 1896; also mapped with Pz and Pl ). Sandstone, siltstone, shale, underclay, and coal. Sandstone, feldspathic, micaceous, dark and light lithic fragments, pale-orange, light-brownish-gray, and medium to dark-gray, very-fine- to medium-grained, fine- to coarse-grained in northern outcrop area, thin- to thick-bedded and massive, sparsely cross-bedded, ripple-marked, with local shale interbeds and dark laminations; contains well-rounded quartz pebbles as much as 1 inch in diameter, locally in channel-fill deposits and basal beds; thin-bedded sandstone contains shale interbeds, shale fragments, ironstone nodules, coal debris, and sparse plant fossils. Few quartzose sandstones commonly interbedded with thin, dark-gray shales and siltstones in subsurface in Buchanan, Dickenson, and Wise counties (Miller, 1974). Sandstone comprises 70 per cent of formation (Englund,1979). Siltstone and shale, medium- to dark-gray, laminated, even- to irregulary bedded, fissile to fl ggy, fossiliferous with fresh and brackish water animal and plant fossils (Englund, 1979). Coal, finely cleated. Underclay, medium-gray, clayey to silty, contains root casts. Basal part gradational to intertonguing with underlying Bluestone Formation of the Pennington Group; base placed at top of red, green, or gray calcareous, marine shales of the underlying Bluestone Formation (Miller, 1974). The Pocahontas wedges out in the subsurface in the northwestern parts of Lee, Wise, Dickenson, and Buchanan Counties (Englund, 1979; Miller, 1974) and is thickest in western and northern Tazewell County. It ranges from 0 to 970 feet in thickness.

Juniata, Oswego, Martinsburg (Reedsville and Dolly Ridge), and Eggleston Formations (Ordovician) at surface, covers < 0.1 % of this area

Juniata Formation. Refer to description under Ous. Oswego Formation (Prosser, 1890). Sandstone, greenish gray, fine- to coarse-grained, conglomeratic with chert, quartz, and lithic pebbles. Minor interbeds of olive-gray shale with thin sandstone layers. Conformable with underlying Reedsville Shale. Present northeast of Bath and Augusta counties but thins in all directions from a maximum thickness of 500 feet in western Rockingham County (Diecchio, 1985). Reedsville Shale. Refer to description under Ou. Dolly Ridge Formation (Perry, 1972). Limestone, medium-gray, fine-grained, thin-bedded, argillaceous, with interbedded olive-gray, calcareous claystone, silty argillaceous limestone, gray shale and thin K-bentonite beds. Thickness about 400 feet in Bath and Highland counties; laterally equivalent to the Trenton Limestone and part of the lower Martinsburg Formation of previous reports in western Virginia. It is gradational with the underlying Eggleston Formation. Eggleston Formation. Refer to description under Ou. Martinsburg Formation. Refer to Om (Martinsburg and Oranda Formations) for description. The Martinsburg is only present with this map unit (Oun) in northern Rockingham County where it occupies the Reedsville Shale - Dolly Ridge Formation interval.

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

Millboro Shale (Cooper, 1939; Butts, 1940). Shale, black, fissile, pyritic, with septarian concretions locally, gradational with underlying Needmore Shale; present southwest of Shenandoah County except in southwesternmost Virginia; thickness is as much as 1000 feet in north-central western Virginia. Laterally equivalent to the Marcellus Shale and Mahantango Formation to the north east and the lower part of the Chattanooga Shale to the southwest. It is gradational with the underlying Needmore Formation. Needmore Formation. Refer to description under Dmrn.

Waynesburg Formation (Permian and Pennsylvanian) at surface, covers < 0.1 % of this area

Cyclic sequences of sandstone, shale, limestone, and coal; commercial coals present; base is at bottom of Waynesburg coal.

Dunkard Group (Permian and/or Pennsylvanian) at surface, covers < 0.1 % of this area

Mudstone, shale, and siltstone (60-70 percent); shades of red, yellow, olive, and/or brown in southern areas of Ohio to gray, green and black in northern areas; clayey to sandy; nonbedded to thin bedded; locally calcareous. Sandstone (25-35 percent); blue-gray weathers to shades of yellow-brown; fine grained to locally conglomeratic; thin to massive to cross bedded. Limestone and coal (5 percent): Limestone, gray, micritic, clayey to silty, thin to medium bedded in northern areas of Ohio, nodular bedded to argillaceous in southern areas. Coal, black, banded, thin, discontinuous, impure; poorly developed in southern areas of Ohio. Limestones and coals best developed in lower 90 to 200 feet. Lateral and vertical lithic variability and gradation common. Unit greater than 600 feet thick in southeast Ohio.

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

Wise Formation (Campbell, 1893) . Sandstone, siltstone, shale, limestone, coal, and underclay. Sandstone, lithic, feldspathic, micaceous, argillaceous, carbonaceous locally, light- to medium-gray to moderate- and pale-yellow- brown, fine- to coarse-grained, locally pebbly, thin- to thick-bedded, cross-bedded to even-bedded, locally massive, well-cemented; contains fragments of shale, siltstone, and carbonized plant fossils locally. Siltstone and shale, light olive- gray, medium- to dark-gray and grayish-black, contains siderite ironstone in very-thin beds and nodules, carbonized plant fossils; invertebrate fossils in dark-gray to black shale and micrograined limestone in the upper part of formation (Miller, 1969; Miller and Roen, 1973; Nolde, Henderson, and Miller,1988; Nolde, Whitlock, and Lovett, 1988a). Limestone, medium- to dark-gray, micrograined, in very-thin lenses and beds in shale and siltstone in two to three zones in lower part of formation (Taylor, 1989; Whitlock, Lovett, and Diffenbach, 1988). Coal interbedded with shale, siltstone, and sandstone. Underclay, light-gray, root casts, beneath coal; as much as 5 feet thick under the Williamson coal bed in Buchanan County (Henika, 1989b). A dark-gray to brownish-gray, flint clay in the Phillips (Fire Clay; No.7) coal bed in northern Lee County (Miller and Roen, 1973) and western Wise County is a volcanic ash deposit (Seiders, 1965) that covers parts of Kentucky, Tennessee, Virginia and West Virginia; it has been dated at an age of 311 - 312 million years (Lyons and others, 1992; Rice and others, 1990). Base of formation at bottom of Dorchester coal bed. Thickness 2150 to 2268 feet.

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

Predominantly gray sandstone and conglomerate; also contains thin beds of shale, claystone, limestone, and coal; includes Olean and Sharon conglomerates of northwestern Pennsylvania; thin marine limestones present in Beaver, Lawrence, and Mercer Counties; minable coals and commercially valuable high-alumina clays present locally.

Catoctin Formation (Cambrian/Precambrian) at surface, covers < 0.1 % of this area

Predominantly a greenstone. Basic lava flows, schist and gneiss, containing chlorite, plagioclase, amphibolite, and epidote. Includes minor quantities of arkose and thin clastics. Western subsurface extension presently unknown.

Clinton Group, including Rochester Shale (Silurian) at surface, covers < 0.1 % of this area

Gray, thin-bedded calcareous shale and dark gray, thin- to medium-bed7 ded lenticular limestone; thickness 25 to 40 feet; Keefer Sandstone - White to yellowish-gray, thick-bedded protoquartzite and orthoquartzite; calcareous to west; thickness 10 feet in west, increases to 35 feet in east; and Rose Hill Formation - Olive-gray to drab, thin-bedded shale; some purple shale and gray, thin-bedded sandstone; including Cresaptown Iron Sandstone Member - Purple, hematite-cemented, quartzose sandstone; thickness 5 to 30 feet; occurs in lower half of formation; total thickness 300 feet in east, increases to 570 feet in west.

Moccasin or Bays Formation through Blackford Formation (Ordovician) at surface, covers < 0.1 % of this area

Moccasin Formation, Bays Formation, Unit C, Unit B, and Unit A. Moccasin Formation (Campbell, 1894). Mudstone, shale, imestone, and sandstone. Mudstone and shale, dusky-red to dark-reddish-brown, calcareous, ripple-marks, and mud cracks common. Limestone, light-olive-gray, weathers very-light gray, aphanic with "birds-eyes", locally fossiliferous. The limestone generally is the middle member of the Moccasin southwest of Giles County. In eastern Giles County and northeastward a thin medium-grained, gray sandstone occurs near the base of the Moccasin. The thickness ranges from 0 in northern Alleghany County to about 600 feet in Scott County. Bays Formation (Keith, 1895). Siltstone, sandstone, mudstone, and limestone. Siltstone, grayish-red, olive- to light-olive-gray, locally calcareous, sandy in part. Sandstone, light-gray to yellowish-gray, fine- to very-coarse-grained, locally conglomeratic, calcareous. Mudstone, grayish-red, olive- to light-olive-gray, mudcracks common. Limestone, grayish-red to light-olive-gray, aphanic. Five distinct K-bentonites reported by Hergenroder (1966). Contacts are conformable except perhaps in Botetourt, Roanoke, and Montgomery counties. Thickness ranges from 105 feet north of Wytheville to 890 feet near Daleville in Botetourt County. From Scott and Washington counties to Highland County and northwest of the Pulaski and North Mountain faults, a multitude of stratigraphic names have been applied to the rocks between the Bays or Moccasin (above) and the Beekmantown or Knox (below). The lack of detailed geologic mapping, except in Scott and Giles counties, the restricted area of the two major stratigraphic studies (Cooper and Prouty, 1943; Kay, 1956), and the general disagreement as to mappability and correlation of units makes it impossible to apply specific stratigraphic nomenclature at this time. Therefore, the rocks are described as three packages of lithologies (from youngest to oldest): Unit C, Unit B, and Unit A. Unit C. Limestone, medium- to dark-gray, aphanic to fine-grained with thin, medium- to coarse-grained beds, argillaceous, nodular to planar-bedded, locally very fossiliferous. The following names have been applied to Unit C: Witten, Bowen, Wardell, Gratton, Benbolt, Chatham Hill, Wassum, Rich Valley, Athens, Ottesee, Liberty Hall, Fetzer, and Giesler. Unit B. Limestone, light- to dark-gray, aphanic to coarsegrained, black and gray chert nodules, carbonate mound buildups. This unit is characterized by grainstone with interbedded micrite and chert. The overlying Unit C is very argillaceous and lacks chert. The following names have been applied to Unit B: Wardell, Gratton, Benbolt, Lincolnshire, Big Valley, McGlone, McGraw, Five Oaks, Peery, Ward Cove, Rockdell, Rye Cove, Effna, Whitesburg, Holston, Pearisburg, and Tumbez. Unit A. Dolostone, light- to medium-gray, fine-grained, locally conglomeratic, cherty. Limestone, medium- to dark gray, fine-grained, locally cherty. Shale, light-gray to dusky red. A basal chert-dolomite conglomerate with clasts as much as cobble size is locally present on the unconformity surface. The following names have been applied to Unit A: Blackford, Elway, Tumbez, Lurich (lower part), and "basal clastics".

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

Juniata Formation (Darton and Taff, 1896). Siltstone, shale, sandstone, and limestone. Siltstone, shale, and sandstone, locally calcareous, grayish-red, locally fossiliferous; with some interbeds of greenish-gray shale, quartzarenite, and argillaceous limestone. Cycles consisting of a basal, crossbedded quartzarenite with a channeled lower contact; a middle unit of interbedded mudstone and burrowed sandstone; and an upper bioturbated mudstone are commonly present north of New River (Diecchio, 1985). The Juniata Formation ranges from less than 200 to more than 800 feet in thickness. In southwestern Virginia the red, unfossiliferous, and argillaceous Juniata Formation is present in the southeastern belts. It is equivalent to the gray, fossiliferous, and limy Sequatchie Formation of western belts (Thompson, 1970; Dennison and Boucot, 1974). Even though the beds along Clinch Mountain, in Scott County, contain minor amounts of carbonate rock (Harris and Miller, 1958) the majority is grayish- red siltstone, which is typical of the Juniata Formation. Reedsville Shale. Refer to description under Ou. Trenton Limestone. Refer to description under Ou. Eggleston Formation. Refer to description under Ou.

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

Grayish-red shale, siltstone, sandstone, and some conglomerate; some local nonred zones. Includes Loyalhanna Member (crossbedded, sandy limestone) at base in south-central and southwestern Pennsylvania; also includes Greenbrier Limestone Member, and Wymps Gap and Deer Valley Limestones, which are tongues of the Greenbrier. Along Allegheny Front from Blair County to Sullivan County, Loyalhanna Member is greenish-gray, calcareous, crossbedded sandstone.

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

Upper one-third gray, mottled, cherty dolomite and dolomitic limestone; lower two-thirds gray, cherty argillaceous calcarenite and algal limestone with interbedded dolomite and oolitic limestone; thickness at least 1,700 feet east of Conococheague Creek, increases to about 2,500 feet in west.

Ridgeley Sandstone, Helderberg and Cayugan Groups (Silurian-Devonian) at surface, covers < 0.1 % of this area

Ridgeley Sandstone and Helderberg and Cayuga Groups. Ridgeley Sand stone (Swartz, 1913). Sandstone, gray, fine-to coarse-grained, locally conglomeratic, weathers yellowish- to dark-yellowish-brown, friable, calcareous, and fossiliferous. Thickness ranges up to 150 feet but is highly variable locally; occurs in western Virginia north of Craig County. Same as the Oriskany Sandstone of Butts (1933), and is continuous with the Rocky Gap Sandstone to the southwest. It grades downward into the Licking Creek Limestone and has been extensively mined for iron ore (Lesure, 1957). Helderberg Group: Licking Creek Limestone (Swartz, 1929). Upper member is light-gray, coarse-grained, arenaceous limestone; lower member is medium-to dark-gray, fine-grained, chert bearing limestone. Thickness ranges from 0 to150 feet and is present northeastward from Craig County; same as the Becraft (upper member) and New Scotland (lower member) of Butts (1940). It conformably over lies the Heal ng Springs Sandstone where the sandstone is present. It was extensively mined for iron with the Ridgeley Sandstone. Healing Springs Sandstone (Swartz, 1929). Sandstone, light-gray, medium- to coarse-grained, cross-laminated, and calcareous with local lenses of chert. Present in Alleghany, Bath, and Augusta Counties where it is generally less than 20 feet thick and conformably overlies the New Creek Lime stone. It appears to be a northeast extending tongue of Rocky Gap Sandstone. New Creek Limestone (Bowen, 1967; Coeymans Limestone of earlier reports). Limestone, light- to-medium gray with pink calcite crystals, very-coarse-grained, crinoidal, with lenses of quartz sandstone locally in the lower part. Occurs as local reefoidal buildups northeast of Alleghany County. Keyser Formation (Swartz, 1913). Limestone, sandstone, and shale. Limestone (upper), medium- to dark-gray, fine- to medium-grained, nodular, scattered, small chert nodules, biohermal, fossiliferous. Limestone (lower), medium- to dark-gray, fine- to coarse-grained, medium- to thick-bedded, very nodular, shaly, with thin (1- to 3-inch thick) crinoidal layers. Sandstone, medium-light-gray, medium-grained, calcareous, cross-bedded. Shale, medium-gray, calcareous. Upper and lower boundaries are conformable north of Clifton Forge. Thickness ranges from 250 feet in Highland County to 50 feet in Augusta County. In Highland and Bath counties the upper and lower limestones are separated by a calcareous shale unit (Big Mountain Shale Member). To the south and southeast the shale is replaced by sandstone (Clifton Forge Sandstone Member). From Craig County southwestward, the Keyser becomes all sandstone and is equivalent to the lower portion of the Rocky Gap Sandstone. Southwest of Newcastle the lower contact is disconformable. For mapping purposes the Keyser is considered to be part of the Helderberg Group. Cayuga Group: Tonoloway Limestone (Ulrich, 1911). Limestone, very-dark-gray, fine-grained, thin-bedded to laminated, with some arenaceous beds; celestite locally occurs in vugs and as veins. Thickness ranges from a few feet in southwestern Virginia to more than 500 feet in Highland County. It is conformable with the underlying Wills Creek Formation and equivalent to the Hancock Formation of Southwest Virginia. Wills Creek Formation (Uhler, 1905). Limestone, medium-to dark-gray, fine-grained, arenaceous, thin-bedded, with calcareous shale and mudstone, and thin, quartzose sandstone beds. Occurs only in western Virginia where the thickness ranges from 0 to more than 400 feet. It conformably over lies the Bloomsburg Formation and is laterally equivalent to the upper part of the Keefer Sandstone to the east and southwest of Craig County where the typical Wills Creek lithology is absent. Bloomsburg Formation (White, 1893): Sandstone, reddish-gray, fine-grained, thick-bedded with red mudstone interbeds. Thickness ranges from 35 to 400 feet between Frederick County and the northern Massanutten Mountains respectively. It grades into the Wills Creek Formation to the southwest, and is probably equivalent, in part, to the Keefer Sandstone southwest of Craig and Botetourt counties. McKenzie Formation (Stose and Swartz, 1912): Shale, medium-gray, yellowish weathering and interbedded sandstone, medium-gray, medium-grained, friable, thin-bedded and calcareous. Thickens northeastward from a few feet in Bath County to about 200 feet in Frederick County. It is probably equivalent in part to the Keefer Sandstone to the southwest and southeast and appears to be conformable with the Keefer Sandstone in northwestern Virginia.

Burgoon Sandstone (Mississippian) at surface, covers < 0.1 % of this area

Buff, medium-grained, crossbedded sandstone; includes shale and coal; in places, contains conglomerate at base; contains plant fossils; equivalent to Pocono Formation of Ridge and Valley province.

Catoctin Formation - Metabasalt (Proterozoic Z-Cambrian) at surface, covers < 0.1 % of this area

Grayish-green to dark-yellowish-green, fine-grained, schistose chlorite- and actinolite-bearing metabasalt, commonly associated with epidosite segregations. Mineralogy: chlorite + actinolite + albite + epidote + titanite ± quartz + magnetite. Relict clinopyroxene is common; biotite porphyroblasts occur locally in southeastern outcrop belts. Geophysical signature: The Catoctin as a whole has a strong positive magnetic signature. However, between Warrenton and Culpeper the lowest part of the Catoctin, which consists of low-titanium metabasalt and low-titanium metabasalt breccia, is non-magnetic, and displays a strong negative anomaly. Metabasalt (CZc) is by far the most widespread unit comprising 3000 feet or more of section (Gathright and others, 1977). Primary volcanic features are well preserved in many places. In the north west ern outcrop belt, these include vesicles and amygdules, sedimentary dikes, flow-top breccia, and columnar joints (Reed, 1955; Gathright, 1976; Bartholomew, 1977); relict pillow structures have been reported in Catoctin greenstones east of Buena Vista (Spencer and others, 1989). In the southeastern outcrop belt, amygdaloidal metabasalts are common, as are volcanoclastic rocks interbedded with basaltic fl ows (Rossman, 1991). Fragmental zones occur locally between individual lava fl ows; map-scale hyaloclastite pillow breccias occur at three strati raphic levels within the southeastern outcrop belt (CZcb, CZhb, CZlb; Espenshade, 1986; Kline and others, 1990).

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

Upper part red calcareous shale and sandstone interbedded with greenish-gray and reddish-gray argillaceous limestone; Loyalhanna Limestone Member: Gray to red, cross-bedded, arenaceous calcarenite; total thickness 200 to 300 feet.

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

Brallier Formation (Butts, 1918). Shale, sandstone, and siltstone. Shale, partly silty, micaceous, greenish-gray, gray ish-brown and medium- to dark-gray, black, weathers light-olive-gray with light-yellow, brown and purple tints; black shale in thin beds and laminae, sparsely fossiliferous. Sandstone, micaceous, medium-light-gray, very-fine- to fine-grained, thin- to thick-bedded, and light-brown siltstone interbedded with shale. Locally siltstone is in very-thin, nodular, ferruginous lenses (Bartlett, 1974). Lower contact transitional; base at lowest siltstone bed above relatively nonsilty dark-gray shale. Equivalent to part of the Chattanooga Shale. Formation thins southwestward; it ranges from 940 feet in thickness in southwestern Washington County (Bartlett and Webb, 1971) to more than 2200 feet in Augusta County (Rader, 1967).

Tonoloway Limestone (Silurian) at surface, covers < 0.1 % of this area

Gray, thin-bedded limestone, dolomitic limestone, and calcareous shale; thin sandstone member in east 20 feet above base; fossiliferous; thickness 400 feet in east, increases to 600 feet in west.

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

Red and green shale, reddish-purple mudstone, and red, green, brown, and gray thin-bedded and cross-bedded sandstones; thickness 500 feet in west, increases to about 800 feet in east.

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

Upper part rhythmically interbedded graywackes, siltstones, and dark shales; lower part dark brown, dark gray, and black, thin-bedded fissile shale; thickness 2,000 to 2,500 feet.

Wills Creek Shale and Bloomsburg Formation (Silurian) at surface, covers < 0.1 % of this area

Wills Creek Shale - Olive to yellowish-gray, thin-bedded mudstone, calcareous shale, argillaceous limestone, and sandstone; thickness 450 feet in west, increases to 600 feet in east; and Bloomsburg Formation - Bright red, hematitic, thin- to thick-bedded sandstone and shale; some dark sandstone and green shale; Cedar Creek Limestone Member - Dark gray, fine- to medium-grained argillaceous limestone, occurs in middle part of formation; total thickness 20 feet in west, increases to 200 feet in east.

Alluvium (Pleistocene to Holocene) at surface, covers < 0.1 % of this area

Alluvium; includes glacial deposits along the Ohio River and its tributaries west of Cannelton locks

Chilhowee Group; Weverton Formation (Late Precambrian - Cambrian) at surface, covers < 0.1 % of this area

Interbedded white to dark gray, thin-bedded, micaceous, ferruginous, and sericitic quartzites, phyllites, and white, thick-bedded, ledge-making quartzites; some gray to brown ferruginous quartz conglomerate and purple-banded phyllite; thickness approximately 100 feet in south, increases to 425 feet in north.

Chilhowee Group; Harpers Formation (Cambrian) at surface, covers < 0.1 % of this area

Brown to dark bluish-gray banded shale, to light bluish-gray, finely laminated phyllite; distinctively pale purple in basal part; bedding obscured by cleavage; increasingly metamorphosed toward east from shale to slate and phyllite; estimated thickness 2,000 feet.

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

Bluefield Formation (Campbell, 1896). Shale, siltstone, and limestone, with minor sandstone, coal, and underclay. Shale and siltstone, calcareous in part, medium- to medium dark-gray, light-greenish- to greenish-gray, grayish-red; interbedded with limestone,thin sandstone and a few thin beds of black carbonaceous shale. Limestone, argillaceous, lower part dolomitic, light-olive-gray to medium-gray, light-bluish gray and brownish-gray, micrograined to medium-grained, thin-bedded, very fossiliferous; black chert nodules in lower part; interbedded with fossiliferous light-greenish-gray shale. Sandstone, quartzose to feldspathic, light-gray to greenish gray, very-fine- to medium-grained, thin- to thick-bedded, ripple-bedded, contains root casts in up per part, pyrite nodules, and shale and siltstone interbeds. Coal, locally impure in upper half of formation (Englund, 1968; Windolph, 1987). Underclay, medium-gray, clayey to silty, contains root casts. The Bluefield probably is equivalent to upper part of the Newman Limestone (Englund, 1979) and is a transition zone between carbonates of the underlying Greenbrier Limestone and clastics of the overlying Pennington Group. It is conformable and gradational with underlying formation. Formation thins westward; it ranges in thickness from 150 feet near Kentucky-Virginia boundary (Miller, 1974, p. 25) to 1250 feet in Tazewell County (Cooper, 1944, p. 169).

Greenbrier Limestone (Mississippian) at surface, covers < 0.1 % of this area

Greenbrier Limestone (Rogers, in Macfarlane, 1879). Limestone, dolomite, and minor shale. Limestone, very-light olive-to olive-gray and brownish-gray, and medium- to dark gray, micrograined to coarse-grained, thin- to thick- bedded, thinner bedded in upper part, even- to cross-bedded; few shaly beds in upper part; oolitic in upper part and in cross-laminated beds near base; black chert near middle of formation, gray to pale-red near base; very fossiliferous. Pale-brown dolomite near upper chert zone, minor dolomite locally in lower part. Few interbeds of greenish-gray and grayish-red, calcareous, silty shale. Limestone is petroliferous locally in upper part (Henika, 1988). Base locally unconformable with underlying Maccrady Shale. Formation thickens to east, ranging from 200 feet in western Wise County to 3500 feet in Washington nd Scott counties. The Greenbrier is equivalent to (descending): Gasper Limestone, Ste. Genevieve Limestone, St. Louis Limestone (Hillsdale Limestone), and Little Valley Limestone (Warsaw equivalent), and to lower part of the Newman Limestone (Butts, 1940; LeVan and Rader, 1983). Newman Limestone (Campbell, 1893). Limestone and shale. Limestone, light-olive-gray in lower half, medium-gray to olive-gray in upper half, aphanic to fine-grained, partly oolitic, partly argillaceous, with basal beds of dark-gray chert nodules and local dolomite. Shale, medium-gray to medium dark-gray, partly calcareous, interbedded with limestone in upper half of unit. The Newman Limestone ranges from 550 to 600 feet in thickness and is equivalent to the Bluefield Formation and Greenbrier Limestone. Fort Payne Chert. (Smith, in Squire, 1890). Greenish gray chert in thin beds (2 - 6 inches thick); with shale partings. The Fort Payne Chert ranges from 0 to 20 feet in thickness and pinches out to the northeast. Grainger Formation (Campbell, 1893). Shale, pale-olive or greenish-gray to dark-greenish-gray, locally gray ish-red in lower half and at top; with some interbedded pale-olive-gray siltstone and very-fine-grained sandstone, locally abundant siderite nodules near base. The Grainger Formation ranges from 250 to 325 feet in thickness and is the lateral equivalent of the Maccrady Shale and Price Formation.

Oriskany Group including Ridgeley Sandstone and Shriver Chert (Devonian) at surface, covers < 0.1 % of this area

Oriskany Group, including Ridgeley Sandstone - White, medium- to coarse-grained, fossiliferous, calcareous orthoquartzite; thickness 160 feet in west. Medium to dark gray cherty, arenaceous limestone in east; thickness 50 feet; and Shriver Chert - Dark gray, brown, and black silty shales, cherty shales, and nodular and bedded black chert; fossiliferous; thickness 170 feet in west, upper boundary gradational with Ridgeley. Thickness 14 feet in east where the lower Shriver intertongues with the Licking Creek Limestone Member of the Helderberg Formation

McKenzie Formation (Silurian) at surface, covers < 0.1 % of this area

Gray, thin-bedded shale and argillaceous limestone; interbedded red sandstone and shale in east; thickness 160 feet in western Washington County, increases to 300 feet in east and 380 feet in west.

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

Mahantango Formation (Willard, 1935). Shale, siltstone, and sandstone. Shale, gray, pale-green, and black, weathers silvery gray, silty with minor interbedded siltstones; lower contact gradational with underlying Marcellus Shale. Siltstone, greenish-gray with interbedded shale. Sandstone, greenish-gray to grayish-brown, fine-grained, fossiliferous. Spheroidal weathering common in all lithologies. Thickness ranges from 0 in southwestern Shenandoah County (Butts, 1940) to approximately 1100 feet in Frederick County (Butts and Edmundson, 1966). Southwest of Shenandoah County the Mahantango Formation is indistinguishable from the underlying Marcellus Shale. They are combined and mapped as a single unit, the Millboro Shale, from southern Shenandoah County to Southwest Virginia (Rader, 1982).

Knox Group (Cambrian-Ordovician) at surface, covers < 0.1 % of this area

Knox Group (Safford, 1869). Dolostone, limestone, and sandstone. Dolostone, light- to medium-gray, very-fine- to fine-grained, locally with pink streaks in the upper part; and very-light-gray to dark-gray and brownish-gray, medium- to coarse-grained, locally argillaceous dolostone near the base of the unit; greenish-gray shale partings locally present; chert is abundant in some parts of the unit. Limestone, blue gray to dark-blue-gray, very-fine- to coarse-grained, locally sandy. Sandstone, gray to brown, fine- to medium-grained. Limestone is dominant in the eastern thrust belts. The Knox Group ranges from 2000 feet in Southwest Virginia to 3560 feet in thickness to the east in Washington County (Bartlett and Webb, 1971). The Knox includes the Mascot, Kingsport, Chepultepec, and Copper Ridge Dolomites and the Maynardville Formation.

Helderberg Formation and Keyser Limestone (Devonian) at surface, covers < 0.1 % of this area

Helderberg Formation, including Licking Creek Limestone Member - (Becraft Limestone of earlier reports.) Present only in east. Medium gray, medium-grained limestone near top; bedded black chert and thin-bedded limestone in middle; silty argillaceous limestone and shale near base; contains tongues of Shriver and Mandata; thickness 110 feet; Mandata Shale Member - Dark brown to black, thin-bedded shale; fossiliferous; thickness 20 to 30 feet in west, intertongues with Licking Creek Limestone Member in east; Corriganville Limestone Member (Head) - (New Scotland Limestone of earlier reports.) Medium gray, medium-grained, medium-bedded limestone, interbedded with chert; fossiliferous; thickness 15 to 30 feet; New Creek Limestone Member - (Coeymans Limestone of earlier reports.) Medium gray, thick-bedded, coarse-grained limestone; fossiliferous; thickness 9 to 10 feet. Limestone changes facies eastward into sandstone, the Elbow Ridge Sandstone Member - Medium-bedded, medium- to coarse-grained, calcarous sandstone; thickness 10 to 18 feet.; and the Keyser Limestone - Dark gray, thin- to thick-bedded, fine- to coarse-grained calcarenite; contains nodular limestone, dolomitic limestone, and calcarous shale; cherty near top; fossiliferous; thickness 200 to 300 feet.

Stonehenge Limestone (Ordovician) at surface, covers < 0.1 % of this area

Upper part gray, thin-bedded, coarse-grained to conglomeratic, oolitic calcarenite; some dolomite; lower part gray, thick-bedded, fine-grained algal limestone; thickness 500 to 800 feet.

Chilhowee Group (Cambrian) at surface, covers < 0.1 % of this area

Chilhowee Group (Keith, 1903). The Chilhowee Group includes the Antietam, Harpers, and Weverton Formations in the northeastern portion of the Blue Ridge Province and the Erwin, Hampton, and Unicoi Formations in the southwestern portion of the Blue Ridge Province. Antietam Formation (Williams and Clark, 1893). Quartzite, medium-gray to pale-yellowish-white, fine- to medium grained, locally with very minor quartz-pebble conglomerate, cross-laminated, medium- to very-thick-bedded, very resistant, forms prominent cliffs and ledges, contains a few thin interbeds of light-gray phyllite, has calcareous quartz sandstone at the top that is transitional with the overlying Tomstown Dolomite, and many beds contain Skolithos linearras. It is laterally equivalent to the Erwin Formation to the southwest. The formation interfingers with the underlying Harpers Formation and ranges in thickness from less than 500 feet in Clarke County to nearly 1000 feet in Rockingham County (Gathright and Nystrom, 1974; Gathright, 1976). Harpers Formation (Keith, 1894). Metasandstone, metasiltstone, and phyllite. Metasandstone, dark-greenish gray to brownish-gray, fine-grained, sericitic, thin- to medium-planar bedded, locally bioturbated, Skolithos-bearing litharenite; dark-gray, fine-grained, cross-laminated, thickbedded, laterally extensive bodies of quartzite; and very-dark gray, medium- to coarse-grained, thick-bedded, ferruginous, very resistant, quartzitic sandstone. These beds were extensively mined for iron ore north of Roanoke (Henika, 1981). Metasiltstone, dark-greenish-gray, thin, even bedded, sericitic, and locally bioturbated. Phyllite, medium- to light-greenish gray, bronze weathering, laminated, sericitic. The Harpers is laterally equivalent to the Hampton Formation to the southwest and they are so similar that the names have been used interchaneably in the northern Blue Ridge (Gathright, 1976; Brown and Spencer, 1981). The Harpers conformably overlies the Weverton or Unicoi Formations, thickens northeastward from about 1500 feet north of Roanoke to about 2500 feet in Clarke County. The thicker sections are dominated by phyllite and metasiltstone and the thinner sections by metasandstone and quartzite. Weverton Formation (Williams and Clark, 1893). Quartzite, metasandstone, and phyllite. Quartzite, medium- to very dark-gray, weathers light-gray, fine- to coarse-grained, well rounded quartz-pebble conglomerate beds locally, medium- to thick-bedded, cross-bedded, very resistant, with interbedded metasandstone, dark-greenish- gray, feldspathic, thick-bedded, with ferruginous cement in some beds. Phyllite, light- to dark-greenish-gray or dark-reddish-gray, laminated, sericitic, with coarse sand grains and quartz-pebble conglomerate in a few thin beds, generally in lower part. Formation ranges in thickness from more than 600 feet in Clarke County to less than 200 feet in Augusta County (Gathright and Nystrom, 1974; Gathright and others, 1977). The Weverton is lithologically very similar to strata in the upper portion of the Unicoi Formation to the south to which it may be equivalent. The Weverton appears to unconformably overlie the Catoctin and Swift Run Formations and the Blue Ridge basement complex and is present northeast of Augusta County.

Maccrady Shale and Price Formation (Mississippian) at surface, covers < 0.1 % of this area

Maccrady Shale and Price Formation. Refer to individual units for descriptions.

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

Kanawha Formation (Campbell and Mendenhall, 1896). Sandstone, siltstone, shale, coal, and underclay. Sandstone, feldspathic, micaceous, with dark mineral grains, light- to medium-gray, fine- to coarse-grained, upper beds locally conglomeratic, lenticular, thick-bedded to massive, cross-bedded. Siltstone and shale, medium- to dark-gray, even-bedded, interbedded with sandstone, coal, and medium-gray underclay. Base of formation conformable, placed at the bottom of Kennedy coal bed overlying McClure Sandstone Member of New River Formation (Englund, 1981; Meissner and Miller, 1981; Windolph, 1987). Equivalent to the Wise Formation and upper part of the Norton Formation. Thickness: 550 + feet (J.E. Nolde, personal communications, 1993); top part eroded.

Pocono Group, including the Purslane Sandstone and Rockwell Formation (Mississippian) at surface, covers < 0.1 % of this area

Pocono Group - Gray, white, tan, and brown, thin- to thick-bedded, cross-bedded sandstone, locally conglomeratic; interbedded gray and reddish-brown shale, mudstone, and siltstone; fragmentary plant fossils. Undifferentiated in Garrett and western Allegeny Counties. Includes Purslane Sandstone - White, thick-bedded, coarse-grained sandstone and conglomerate with thin coal beds and red shales. Eastern Allegany and Washington Counties. And also inlcudes Rockwell Formation - Coarse-grained arkosic sandstone, fine-grained conglomerate, and buff shale; dark shale with thin coal beds near base. Eastern Allegany and Washington Counties.

Marcellus Shale and Needmore Formation (Devonian) at surface, covers < 0.1 % of this area

Marcellus Shale (Hall, 1839; Butts and Edmundson, 1966). Shale, dark-gray to black, more or less fissile, pyritic. Thickness estimated to be 500 feet in Frederick County and 350 to 400 feet in the Massanutten synclinorium (Rader and Biggs, 1976). Needmore Formation (Willard, 1939). Shale, dark or greenish gray, with thin beds or nodules of black, argillaceous limestone and the Tioga metabentonite beds (Dennison and Textoris, 1970), generally present with the Millboro or Marcellus Shale and is disconformable with the underlying Ridgeley Sand tone. Thickness ranges from 0 to 160 feet and is replaced to the southwest by the Huntersville Chert.

Millboro Shale, Huntersville Chert, and Rocky Gap Sandstone (Devonian) at surface, covers < 0.1 % of this area

Millboro Shale, Huntersville Chert, and Rocky Gap Sandstone. Millboro Shale. Refer to previous description under Dmn. Huntersville Chert (Price, 1929). Chert, white, thin-bedded, iron-stained, blocky, fossiliferous with cherty, glauconitic sandstone and greenish-gray shale. The Huntersville Chert ranges from 10 to 60 feet in thickness (Bartlett and Webb, 1971). Butts (1940, p. 303) states, "The Onondaga [Huntersville Chert] persists to Mendota, Washington County, but 10 miles farther southwest it is absent in a fully exposed section". The Huntersville correlates with the Needmore Formation to the northeast and the upper part of the Wildcat Valley Sandstone in Lee County. Rocky Gap Sandstone (Swartz, 1929): Sandstone, medium- to light-gray, weathers dark-yellowish-orange, coarse-grained, scattered, thin, quartz-pebble conglomerate beds, arenaceous chert in upper ten feet, calcite cement, friable when weathered. Thickness ranges from 0 near McCall Gap, Washington County to about 85 feet in Bland and Giles counties. Equivalent in part to the Wildcat Valley Sandstone of Lee County and the Ridgeley (Oriskany) Sandstone and Helderberg Group north of Craig County. The lower contact is disconformable. The upper contact with the Huntersville Chert appears to be conformable.

Tomstown Dolomite (Cambrian) at surface, covers < 0.1 % of this area

Interbedded light gray to yellowish-gray, thin- to thick-bedded dolomite and limestone; some shale layers; gradational contact with Antietam; thickness 200 to 1,000 feet.

Pinesburg Station Dolomite (Ordovician) at surface, covers < 0.1 % of this area

Light gray, laminated and mottled cherty dolomite; nonfossiliferous; thickness 375 to 500 feet.

Chambersburg Limestone and St. Paul Group (including New Market Limestone and Row Park Limestone) (Ordovician) at surface, covers < 0.1 % of this area

Chambersburg Limestone - Dark gray, fine- to medium-grained, thin-bedded argillaceous limestone; nodular and fossiliferous; thickness 225 to 250 feet; and St. Paul Group, including New Market Limestone - Upper part gray, thick-bedded calcilutite; fossiliferous; lower part light gray, thin-bedded, laminated argillaceous calcilutite; thickness 285 feet in south, increases to 700 feet in north; and Row Park Limestone - Light gray, fine-grained, medium- to thick-bedded calcarenite; calcilutite, and dolomitic limestone; interbedded dark gray, cherty, granular limestone; thickness 100 feet in south, increases to 680 feet in north.

Elbrook Limestone (Cambrian) at surface, covers < 0.1 % of this area

Light blue, laminated, argillaceous limestone and calcareous shale; some dolomite; thickness 1,400 to possibly 3,000 feet.