Geologic units in Seneca county, Ohio

Lockport Dolomite (Silurian) at surface, covers 29 % of this area

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

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.

Columbus Limestone (Devonian) at surface, covers 14 % 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.

Ohio Shale (Devonian) at surface, covers 12 % 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.

Salina Group (Silurian) at surface, covers 12 % 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.

Olentangy Shale (Devonian) at surface, covers 6 % 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.

Delaware Limestone (Devonian) at surface, covers 3 % 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.

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).

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.