Geologic units in Union county, Ohio

Salina Group (Silurian) at surface, covers 65 % 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 28 % 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.

Columbus Limestone (Devonian) at surface, covers 6 % 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.

Lockport Dolomite (Silurian) at surface, covers 2 % of this area

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

Delaware Limestone (Devonian) at surface, covers 0.2 % 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.