Geologic units in Williams county, Ohio

Coldwater Shale (Mississippian) at surface, covers 60 % of this area

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

Antrim Shale (Devonian) at surface, covers 25 % of this area

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

Sunbury and Bedford Formations, Undivided (Devonian and/or Mississippian) at surface, covers 14 % 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.

Coldwater Shale (Mississippian) at surface, covers 0.4 % of this area

Coldwater Shale

Coldwater Shale (Mississippian) at surface, covers 0.2 % of this area

Mostly gray shale

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

Black shale; gray shale and limestone in lower part

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

Green shale; some black shale in lower part