Geologic units in Dickson county, Tennessee

St. Louis Limestone and Warsaw Limestone (Mississippian) at surface, covers 78 % 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 21 % 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)

Tuscaloosa Formation (Cretaceous) at surface, covers 0.3 % of this area

Poorly sorted, light-gray chert gravel in a matrix of silt and sand; locally interbedded with sand and clay lenses. Thickness 0 to 150 feet.

Alluvial deposits (Quaternary) at surface, covers 0.2 % of this area

Sand, silt, clay, and gravel. As much as 60 feet thick in flood plains of Tennessee and Cumberland Rivers; in smaller streams generally less than 20 feet thick.