Geologic units in Huron county, Ohio

Ohio Shale (Devonian) at surface, covers 35 % 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.

Berea Sandstone and Bedford Shale, Undivided (Devonian) at surface, covers 34 % 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.

Maxville Limestone; Rushville, Logan, and Cuyhoga Formations, Undivided (Mississippian) at surface, covers 25 % 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.

Sunbury Shale (Mississippian) at surface, covers 4 % of this area

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

Prout Limestone (Devonian) at surface, covers 0.7 % 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 0.4 % of this area

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

Columbus Limestone (Devonian) at surface, covers 0.4 % 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.

Delaware Limestone (Devonian) at surface, covers 0.3 % 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.

Olentangy Shale (Devonian) at surface, covers < 0.1 % 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.