Geologic units in Champaign county, Ohio

Salina Group (Silurian) at surface, covers 24 % 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.

Tymochtee and Greenfield Formations, Undivided (Silurian) at surface, covers 24 % 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.

Cincinnati Group as used by Wickstrom (1990) (Ordovician) at surface, covers 19 % of this area

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

Lockport Dolomite (Silurian) at surface, covers 19 % of this area

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

Clinton and Cataract Groups, Undivided (Silurian) at surface, covers 11 % 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.

Detroit River Group and Columbus Limestone, Undivided (Devonian) at surface, covers 1.0 % of this area

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

Cedarville, Springfield, and Euphemia Dolomites, Undivided (Silurian) at surface, covers 0.8 % 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).

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.

Ohio Shale (Devonian) at surface, covers 0.3 % 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.