Geologic units in Ohio (state in United States)

Additional scientific data in this geographic area

Maxville Limestone; Rushville, Logan, and Cuyhoga Formations, Undivided (Mississippian) at surface, covers 14 % of this area

Shale, siltstone, and sandstone, interbedded; various shades of gray, yellow to brown weather similar color; sandstone, silty to granular, local stringers of quartz pebbles. Shale, clayey to silty, locally fossiliferous. Medium to dark gray, thin to thick bedded limestone locally preserved at top of interval where unit crops out in southern half of state. Lithologies percentages vary in different areas where unit crops out; laterial and vertical gradation common at regional scale.

Allegheny and Pottsville Groups, Undivided (Pennsylvanian) at surface, covers 14 % 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.

Salina Group (Silurian) at surface, covers 10 % of this area

Dolomite, gray, yellow-gray to olive-gray, laminated to thin bedded; occasional thin bed and laminae of dark gray shale and anhydrite and/or gypsum; brecciated zones in part.

Conemaugh Group (Pennsylvanian) at surface, covers 8 % 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.

Ohio Shale (Devonian) at surface, covers 8 % of this area

Shale; brownish black to greenish gray, weathers brown; carbonaceous to clayey, laminated to thin bedded, fissile parting; carbonate and/or siderite concretions in lowermost 50 feet; petroliferous odor; 250 to 500+ feet thick. Includes Olentangy Shale south of central Delaware Co.

Tymochtee and Greenfield Formations, Undivided (Silurian) at surface, covers 7 % of this area

Dolomite, olive-gray to yellowish- brown, thin to massive bedded, upper two-thirds commonly contains brownish-black to gray shale laminae; locally developed brecciated zones in lower one third.

Lockport Dolomite (Silurian) at surface, covers 6 % of this area

Dolomite, shades of white to medium gray, medium to massive bedded, fine to coarse crystalline; fossiliferous; vuggy.

Monongahela Group (Pennsylvanian) at surface, covers 4 % 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.

Dunkard Group (Permian and/or Pennsylvanian) at surface, covers 3 % 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.

Berea Sandstone and Bedford Shale, Undivided (Devonian) at surface, covers 3 % of this area

Sandstone and shale; upper portion sandstone; brown, weathers light brown to reddish brown; thin to thick bedded, planar to lenticular bedding; minor shale interbeds; 5 to 75 feet thick, locally 100 to 125 feet thickness in Lorain, Cuyahoga, and Medina Counties; lower portion shale; gray to brown, locally reddish brown; thin to medium bedded, planar to lenticular bedding; interbedded siltstone and sandstone, ripple marks in siltstone beds; 80 to 180 feet thick, locally thin to absent where Berea Sandstone is thick.

Antrim Shale (Devonian) at surface, covers 2 % of this area

Shale; dark brown to black; carbonaceous, thinly laminated; 0 to 230 feet thick.

Waynesville and Arnheim Formations, Undivided (Ordovician) at surface, covers 2 % of this area

Waynesville Formation, shale (70%) and limestone (30%) interbedded; gray to bluish gray weathers light gray; planar to irregular, thin to thick bedded; 90 to 120 feet thick. Arnheim formation, shale (60%) and limestone (40%) interbedded; gray to bluish gray weathers light gray; planar, wavy, irregular, to nodular (in upper portion), thin to thick bedded; 50 to 100 feet thick. Contains multiple sedimentary cycles consisting of the alternation of shale and limestone displaying planar to irregular bedding with limestone and shale exhibiting wavy to nodular bedding. Ranges from 140 to 220 feet. The Geological Survey of Ohio recognizes the Cincinnati Group proposed by Meek and Worthen (1865), but at this time retains it as an informal term. The unit will be formally reinstated as a lithostratigraphic term after revision of its lower boundary and minor lithologic redescription of its units are completed. The ten formations included in the group are the (ascending) Clays Ferry Formation, the Kope Formation, the Fairview Formation, the Miamitown Shale, the Grant Lake Limestone, the Arnheim Formation, the Waynesville Formation, the Liberty Formation, the Whitewater Formation, and the Drakes Formation. Six members have been identified in the course of field mapping: the Point Pleasant Tongue of the Clays Ferry, the informal Bellevue, Corryville, Mount Auburn, and Straight Creek members of the Grant Lake Limestone, and the Preachersville Member of the Drakes Formation. The Backbone Creek and Elk Creek beds are recognized as excellent stratigraphic marker beds (Shrake and others, 1988).

Cincinnati Group as used by Wickstrom (1990) (Ordovician) at surface, covers 2 % of this area

Shale, dolomite and limestone, interbedded. Various shades of gray; thin to medium bedded; Data from core holes. Occurs beneath glacial drift.

Grant Lake and Fairview Formations, Miamitown Shale, Undivided (Ordovician) at surface, covers 1 % of this area

Limestone (50%) and shale (50%), interbedded; gray to bluish-gray weathers light gray to yellowish-gray;, planar to lenticular, thin to medium bedded in lower half; wavy to irregular to nodular, thin to thick bedded in upper half; fossiliferous. Interval of shale (90%) with limestone (10%), as much as 35 feet thick, near middle of unit.

Drakes, Whitewater and Liberty Formations, Undivided (Ordovician) at surface, covers 1 % of this area

Drakes Formation; shale (90%) and limestone/dolomite (10%), interbedded; gray and maroon, weathers yellowish gray; planar to irregular, thin to thick bedded; 20 to 30 feet thick. Whitewater Formation, limestone (60%) and shale (40%) interbedded; gray weathers yellowish gray; irregular to wavy, thin to medium bedded; 20 to 80 feet thick. Liberty Formation, limestone (50%) and shale (50%), interbedded; gray weathers yellowish gray; planar to irregular, thin to medium bedded; 20 to 40 feet thick. Interval ranges from 60 to 150 feet in thickness. The Geological Survey of Ohio recognizes the Cincinnati Group proposed by Meek and Worthen (1865), but at this time retains it as an informal term. The unit will be formally reinstated as a lithostratigraphic term after revision of its lower boundary and minor lithologic redescription of its units are completed. The ten formations included in the group are the (ascending) Clays Ferry Formation, the Kope Formation, the Fairview Formation, the Miamitown Shale, the Grant Lake Limestone, the Arnheim Formation, the Waynesville Formation, the Liberty Formation, the Whitewater Formation, and the Drakes Formation. Six members have been identified in the course of field mapping: the Point Pleasant Tongue of the Clays Ferry, the informal Bellevue, Corryville, Mount Auburn, and Straight Creek members of the Grant Lake Limestone, and the Preachersville Member of the Drakes Formation. The Backbone Creek and Elk Creek beds are recognized as excellent stratigraphic marker beds (Shrake and others, 1988).

Columbus Limestone (Devonian) at surface, covers 1 % of this area

Limestone and dolomite; gray to brown, weathers brown; massive bedding; upper 2/3 fossiliferous, gray limestone, lower 1/3 brown dolomite; 0 to 105 feet thick.

Grant Lake Limestone and Fairview Formation, Undivided (Ordovician) at surface, covers 1 % of this area

Limestone and shale, interbedded; gray to bluish-gray weathers light gray to yellowish-gray; planar to lenticular, thin to medium bedded in lower half; wavy to irregular to nodular, thin to thick bedded in upper half; fossiliferous.

Clinton and Cataract Groups, Undivided (Silurian) at surface, covers 1.0 % of this area

Dolomite, limestone and shale, interbedded. Various shades of gray, olive green, yellow and reddish-gray; laminated to thick bedded; argillaceous, glauconitic, pyritic, ferruginous and/or phosphatic; locally fossiliferous. Data from core holes. Occurs beneath glacial drift.

Peebles Dolomite, Lilley and Bisher Formations, Undivided (Silurian) at surface, covers 0.8 % of this area

Peebles Dolomite, bluish gray weathers light gray; planar to irregular, thick to massive bedded; 0 to 120 feet thick; vuggy to cavernous porosity; cliffs former. Lilley Formation, dolomite with minor limestone, chert, and shale; bluish gray to gray weathers reddish gray to gray; planar to irregular, thin to thick bedded; 20 to 80 feet thick; fossiliferous. Bisher Formation, dolomite with minor shale; bluish gray to gray weathers yellowish-orange; argillaceous and silty in part; planar to lenticular, thin to thick bedded; 20 to 90 feet thick; Interval ranges from 80 to 160 feet in thickness. Peebles Dolomite overlies Lilley Formation and underlies Greenfield Dolomite, Hillsboro Sandstone, or Ohio Shale in southern OH. Age is Silurian (Wenlockian and Ludlovian) (Rexroad and Kleffner, 1984). Wenlockian age of the Lilley Formation is based on 10 species of conodont fauna. The Lilley Formation, Lilley-Peebles transition unit, and the Peebles Dolomite compose the upper Niagaran sequence along the east flank of the Cincinnati arch in southern OH. The Lilley consists of two main lithologies: 1) gray to blue gray, fine-grained argillaceous, variably fossiliferous uneven- to thin-bedded dolomite with dolomitic shale partings and 2) light-gray, medium to coarse-grained fossiliferous dolomite. Thickness averages 15 m in Adams and southeastern Highland Cos. and thickens to 24 m in western and northwestern Highland Co. Eustatic sea-level fall in early to middle Wenlockian is proposed as the cause for shoaling during deposition. Underlies Peebles Dolomite and overlies Bisher Formation (Kleffner, M.A., 1990).

Black Hand Sandstone Member of Cuyahoga Formation (Mississippian) at surface, covers 0.8 % of this area

Sandstone and conglomerate; yellow-gray to white, weathers shades yellow, brown, red, and gray; very fine grained to pebbles, mostly medium to coarse grained with lenses and layers of pebbles; massive to crossbedded to laminated; grades laterally into shale and siltstone; quartzose.

Coldwater Shale (Mississippian) at surface, covers 0.8 % of this area

Shale; gray; clayey thin bedded; siderite nodules common; as much as 150 feet thick.

Sunbury Shale, Berea Sandstone, and Bedford Shale, Undivided (Devonian and/or Mississippian) at surface, covers 0.8 % of this area

Shale and sandstone; upper 10 to 50 feet shale; black to brown, weathers light brown; carbonaceous; thin, planar bedding. Underlain by 10 to 50 feet sandstone; brown, weathers light brown to reddish brown; thin to thick bedded, planar to lenticular bedding; minor shale interbeds. Basal 80 to 100 feet shale and interbedded sandstone; gray to brown, weathers light gray to light brown; thin to medium bedded, planar to lenticular bedding; thick. Interval thickness ranges from 100 to 200 feet.

Kope Formation (Ordovician) at surface, covers 0.8 % of this area

Shale (75%) and limestone (25%) interbedded; gray to bluish gray weathers light gray to yellowish gray; planar, thin to thick bedded; 200 to 260 feet thick.

Preacherville Member of the Drakes Formation, Waynesville and Arnheim Formation, Undivided (Ordovician) at surface, covers 0.7 % of this area

Shale, limestone, and dolomite, interbedded; gray to maroon in upper part, weathers yellowish-gray to light-gray; planar to irregular to wavy to nodular, thin to thick bedded; shale increases upward.

Estill Shale (Silurian) at surface, covers 0.7 % of this area

Shale and minor dolomite interbedded, reddish to greenish gray, weathers light gray, planar to irregular bedding, thin to thick bedded, 30 to 180 feet thick. Diagnostic features include dominance of shale and the units susceptibility to be unstable on slopes and cause landslides.

Traverse Group (Devonian) at surface, covers 0.7 % of this area

Dolomite and shale interbedded with limestone; upper part dolomite; gray to light brown; thin to medium bedded; abundant chert; lower part shale interbedded with limestone; olive gray; thin to medium bedded; very fossiliferous; as much as 170 feet thick.

Sunbury and Bedford Formations, Undivided (Devonian and/or Mississippian) at surface, covers 0.6 % of this area

Shale and siltsone; shale, black to brownish-black, carbonaceous in upper one third of interval, gray to bluish-gray, clayey with occasional siltstone lamina and thin beds in lower two-thirds of interval.

Dundee Limestone (Devonian) at surface, covers 0.5 % of this area

Limestone; olive gray to brown; upper part thin bedded, lower part medium to thick bedded; fossiliferous in upper part becomes cherty dolomite in lower part; as much as 105 feet thick.

Cedarville, Springfield, Euphemia, and Laurel Dolomites; Massie Shale, Undivided (Silurian) at surface, covers 0.5 % of this area

Cedarville Dolomite, white to gray to blue gray weathers gray; abundant intercrystalline, moldic, and vuggy porosity, massive bedded, 0 to 100 feet thick. Diagnostic features include porosity, cliff-forming nature of unit, and pentamerid brachiopod fossil zone near contact with Springfield Dolomite. Springfield Dolomite, gray to tan, mottled with brownish gray, massive bedded where unweathered and layered brick-like where weathered, 5 to 10 feet thick. Euphemia Dolomite, dolomite to dolomitic limestone, gray to bluish gray, massive bedded, 5 to 15 feet thick. Diagnostic features include large, blocky bedding where weathered and cliff forming nature. Massie Shale, gray to bluish gray, minor limestone and dolomite beds, calcareous, slakes easily, planar to irregular bedding, thin to thick bedded, 0 to 10 feet thick. Diagnostic feature includes calcareous shale with limestone and dolomite. Laurel Dolomite, gray to tan, weathers brown, argillaceous to nonargillaceous, wavy bedding, thin to medium bedded, 5 to 10 feet thick. Interval ranges from 115 to 140 feet thick. Euphemia Dolomite averages 1.6 to 2.6 m in thickness. Environment of deposition was normal marine offshore, free from clastic influence; similar to Cedarville Dolomite. Unconformably overlies Massie Shale. Correlates with Bisher Formation to the southeast. Age is Wenlockian (Ausich, 1987).

Cedarville, Springfield, and Euphemia Dolomites, Undivided (Silurian) at surface, covers 0.5 % of this area

Cedarville Dolomite, white to gray to blue gray, weathers gray, abundant intercrystalline, moldic, and vuggy porosity, massive bedded, 0 to 100 feet thick. Diagnostic features include porosity, cliff-forming nature of unit, and pentameriid brachiopod fossil zone near contact with Springfield Dolomite. Springfield Dolomite, gray to tan, mottled with brownish gray, massive bedded where unweathered and layered bricklike where weathered, 5 to 10 feet thick. Euphemia Dolomite, dolomite to dolomitic limestone, gray to bluish gray, massive bedded, 5 to 15 feet thick. Diagnostic features include large, blocky bedding where weathered and cliff forming nature. Interval ranges from 10 to 125 feet in thickness. Euphemia Dolomite averages 1.6 to 2.6 m in thickness. Environment of deposition was normal marine offshore, free from clastic influence; similar to Cedarville Dolomite. Unconformably overlies Massie Shale. Correlates with Bisher Formation to the southeast. Age is Wenlockian (Ausich, 1987).

Sunbury Shale (Mississippian) at surface, covers 0.5 % of this area

Carbonaceous shale; black to brownish-black; very thinly laminated; 30 to 120 feet thick.

Detroit River Group (Devonian) at surface, covers 0.5 % of this area

Dolomite; brown to gray; medium to thick bedded; laminated; nodules or interbeds of anhydrite and/or gypsum; basal part becomes sandy dolomite or fine-grained sandstone; as much as 170 feet thick.

Delaware Limestone (Devonian) at surface, covers 0.5 % of this area

Limestone; gray to brown; thin to massive bedded; argillaceous partings, nodules and layers, carbonaceous, petroliferous odor; as much as 45 feet thick.

Massie and Osgood Shales; Dayton and Brassfield Limestones; Laurel Dolomite; Undivided (Silurian) at surface, covers 0.3 % of this area

Massie Shale; gray to bluish gray; planar to irregular, thin to thick bedded; calcareous; slakes; minor limestone and dolomite beds; 0 to 10 feet thick. Laurel Dolomite; gray to tan, weathers brown; argillaceous to nonargillaceous; wavy, thin to medium bedded; 5 to 10 feet thick. Osgood Shale, blue gray to gray weathers brown; thin to massive bedded; calcareous with minor limestone and dolomite; slakes and slumps readily in outcrop; 3 to 25 feet thick. Dayton Limestone; gray to bluish-gray weathers grayish-white; medium to thick bedded; fine grained; dolomitic; 5 to 15 feet thick. Brassfield Limestone; white to pink, locally gray to reddish brown; irregular, thin to medium bedded; coarsely crystalline; abundant pelmatozoan fossils; grayish-green glauconitic partings; cliff forming; 20 to 50 feet thick. Interval ranges from 32 to 100 feet in thickness.

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

Shale; greenish gray to medium gray; clayey; laminated to thin bedded; thin beds of brownish-gray shale in upper 2/3, limestone nodules in lower 1/3; 20 to 55 feet thick.

Point Pleasant Formation (Ordovician) at surface, covers 0.2 % of this area

Limestone (60%) and shale (40%) interbedded; gray to bluish gray weathers light gray; planar to lenticular, thin to medium bedded; 0 to 80 feet thick.

Dayton and Brassfield Limestones (Silurian) at surface, covers 0.2 % of this area

Dayton Limestone; gray to bluish-gray weathers grayish-white; medium to thick bedded; fine grained; dolomitic; 5 to 15 feet thick. Brassfield Limestone; white to pink, locally gray to reddish brown; irregular, thin to medium bedded; coarsely crystalline; abundant pelmatozoan fossils; grayish-green glauconitic partings; cliff forming; 20 to 50 feet thick. Interval ranges from 32 to 100 feet in thickness.

Drowning Creek Formation (Silurian) at surface, covers 0.2 % of this area

Limestone, and shale, interbedded; limestone, shades bluish, greenish, and yellowish gray to grayish-pink weathers light gray to shades of red; planar to irregular to nodular, thin to thick bedded; fine to very coarse grained; locally silty, dolomitic, cherty, glaconitic; moderate to abundant fossils. Shale, greenish-gray to bluish-gray weathers light gray, thin bedded; silty.

Detroit River Group and Columbus Limestone, Undivided (Devonian) at surface, covers 0.1 % of this area

Dolomite, pale yellow-gray to light brown weather brown; thin to massive bedded; fine crystalline; local quartz sand in lower portion.

Quaternary Alluvium (Quaternary) at surface, covers < 0.1 % of this area

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

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

Shale and argillaceous limestone; gray; thin bedded fossiliferous; 0 to 40 feet thick.

Prout Limestone (Devonian) at surface, covers < 0.1 % of this area

Limestone; olive gray; dolomitic in part; hard, siliceous; irregular bedding; pyrite, glauconite and phosphatic bone fragments at upper contact; 0 to 9 feet thick. Devonian (Givetian) Prout Limestone in OH contains corals superficially similar to those of lower part of Jaycox Shale Member of Ludlowville Formation in NY (Oliver, in press).

Grant Lake and Fairview Formations, Undivided (Ordovician) at surface, covers < 0.1 % of this area

Limestone and shale, interbedded; gray to bluish-gray weathers light gray to yellowish-gray; planar to lenticular, thin to medium bedded in lower half; wavy to irregular to nodular, thin to thick bedded in upper half; fossiliferous. Percent limestone increases from about 50% of interval in lower half to as much as 80% in upper half of unit.

Louisville Limestone through Brassfield Limestone (Silurian) at surface, covers < 0.1 % of this area

Sexton Creek Limestone at base in Kentland area and on cross-section

Mississippian and Devonian Undifferentiated (Devonian and/or Mississippian) at surface, covers < 0.1 % of this area

Sandstone and shale, interbedded. Occurs only in Serpent Mound Impact Structure.

Coldwater Shale (Mississippian) at surface, covers < 0.1 % of this area

Coldwater Shale

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

Black shale; gray shale and limestone in lower part

Estill Shale and Drowning Creek Formation, Undivided (Silurian) at surface, covers < 0.1 % of this area

Estill Shale, reddish to greenish gray, weathers light gray, minor interbedded dolomite, planar to irregular bedding, thin to thick bedded, 30 to 180 feet thick. Forms unstable slopes susceptible to landslides. Drowning Creek Formation; dolomite with minor shale; bluish gray to gray weathers yellowish orange; argillaceous and silty in part; planar to lenticular, thin to thick bedded; 20 to 90 feet thick.

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.

Berea Sandstone through Venango Formation, undivided (Devonian) at surface, covers < 0.1 % of this area

Greenish-yellow and gray sandstone, siltstone, and shale succession, becoming more shaly and more gray downward; bottom of interval is bottom of Panama Conglomerate; Venango not mapped separately because upper key bed (Woodcock Sandstone) is missing. Includes, in descending order: Berea Sandstone, Bedford Shale, Cussewago Sandstone, Riceville Shale, and Venango Formation equivalent; contains marine fossils.

Coldwater Shale (Mississippian) at surface, covers < 0.1 % of this area

Mostly gray shale

Dunkard Group (Permian/Pennsylvanian) at surface, covers < 0.1 % 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.

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.

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

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

Medium-gray siltstone and dark-gray shale containing interbedded light-gray, flaggy sandstone. Includes, in descending order: Meadville Shale, Sharpsville Sandstone, and Orangeville Shale; marine fossils common.

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

Limestone and dolomite

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

Shale, dolomite, and limestone, interbedded; various shades of gray; thin to medium bedding, structurally disturbed. Occurs only in Serpent Mound Impact Structure.

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.

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

Dolomite, limestone, and argillaceous dolomite

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

Light-gray sandstone and some beds of medium-gray shale and siltstone; upper third of formation is more shaly; contains a few marine fossils.

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

Argillaceous, ashen-gray, flaky shale and siltstone; included in Conneaut Group and "Chemung" of earlier workers; marine fossils rare.

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

Skeletal limestone and calcareous shale; dolomitic mudstone (S, Saluda Member) at base

Garrard Siltstone and Kope and Clays Ferry Formations, undivided (Ordovician) at surface, covers < 0.1 % of this area

Garrard Siltstone and Kope and Clays Ferry Formations, undivided

Monongahela Group (Pennsylvanian) at surface, covers < 0.1 % 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.

Ellsworth Shale (Devonian-Mississippian) at surface, covers < 0.1 % of this area

Green shale; some black shale in lower part

Salina Group (Late Silurian) at surface, covers < 0.1 % of this area

Salina Group

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

Skeletal limestone and calcareous shale

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

Light-gray or brownish siltstone and some sandstone, interbedded with medium-gray shale; included in Conneaut Group and "Chemung" of earlier workers; marine fossils common; includes "pink rock" of drillers.

Conemaugh Group (Pennsylvanian) at surface, covers < 0.1 % 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.

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

Limestone, dolomite, and argillaceous dolomite

Allegheny Formation (Pennsylvanian) at surface, covers < 0.1 % 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.

Ordovician rocks, undifferentiated (Silurian) at surface, covers < 0.1 % of this area

Shale and limestone; upper part of Maquoketa Group in deep buried valleys; Maquoketa to upper part of Knox Supergroup in Kentland area

Ashlock Formation, Grant Lake and Calloway Creek Limestones, and Fairview Formation, undivided (Ordovician) at surface, covers < 0.1 % of this area

Ashlock Formation, Grant Lake and Calloway Creek Limestones, and Fairview Formation, undivided

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

Shale and thin skeletal limestone