Geologic units in Henry county, Ohio

Antrim Shale (Devonian) at surface, covers 39 % of this area

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

Dundee Limestone (Devonian) at surface, covers 24 % of this area

Limestone; olive gray to brown; upper part thin bedded, lower part medium to thick bedded; fossiliferous in upper part becomes cherty dolomite in lower part; as much as 105 feet thick.

Traverse Group (Devonian) at surface, covers 16 % of this area

Dolomite and shale interbedded with limestone; upper part dolomite; gray to light brown; thin to medium bedded; abundant chert; lower part shale interbedded with limestone; olive gray; thin to medium bedded; very fossiliferous; as much as 170 feet thick.

Salina Group (Silurian) at surface, covers 10 % 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.

Detroit River Group (Devonian) at surface, covers 8 % of this area

Dolomite; brown to gray; medium to thick bedded; laminated; nodules or interbeds of anhydrite and/or gypsum; basal part becomes sandy dolomite or fine-grained sandstone; as much as 170 feet thick.

Sunbury and Bedford Formations, Undivided (Devonian and/or Mississippian) at surface, covers 2 % 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.