Geologic units in Allen county, Indiana

Muscatatuck Group (Devonian) at surface, covers 73 % of this area

Limestone and dolomite

Wabash Formation (Silurian) at surface, covers 16 % of this area

Limestone, dolomite, and argillaceous dolomite

Antrim Shale (Devonian) at surface, covers 11 % of this area

Black shale; gray shale and limestone in lower part

Salina Group (Silurian) at surface, covers < 0.1 % 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 < 0.1 % 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.