Geologic units in Robertson county, Tennessee

St. Louis Limestone and Warsaw Limestone (Mississippian) at surface, covers 88 % of this area

St. Louis Limestone - Fine-grained, brownish-gray limestone, dolomitic and cherty. Thickness 100 to 280 feet; and Warsaw Limestone - Coarse-grained, gray, crossbedded limestone; somewhat shaly in the northeast. Thickness 40 to 150 feet.

Fort Payne Formation and Chattanooga Shale (Mississippian) at surface, covers 9 % of this area

Fort Payne Formation - Bedded chert; calcareous and dolomitic silicastone; minor limestone and shale; scattered lenses of crinoidal limestone. Thin green shale (Maury) at base. Average thickness about 250 feet (475 in Wells Creek area); and Chattanooga Shale - Black carbonaceous shale, fissile. Thickness 0 to 70 feet; average about 20 feet. (Mapped as MDc on East-Central and East sheets)

St. Genevieve Limestone (Mississippian) at surface, covers 3 % of this area

Gray limestone, slightly oolitic and cherty, with some green shale and fine-grained sandstone. Maximum preserved thickness 70 feet. (In Western Highland Rim area only.)

Ste. Genevieve and St. Louis Limestones, undivided (Mississippian) at surface, covers 0.8 % of this area

Ste. Genevieve and St. Louis Limestones, undivided; includes Salem Limestone west of Christian County

Alluvium (Pleistocene to Holocene) at surface, covers < 0.1 % of this area

Alluvium; includes glacial deposits along the Ohio River and its tributaries west of Cannelton locks