Geologic units in Clay county, Tennessee

Fort Payne Formation and Chattanooga Shale (Mississippian) at surface, covers 29 % 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)

Fort Payne Formation and Chattanooga Shale (Mississippian) at surface, covers 26 % of this area

Fort Payne Formation - Calcareous and dolomitic silicastone; contains bedded chert, cherty limestone, and shale; scattered crinoidal limestone lenses. Thin green shale (Maury) at base. Thickness 100 to 275 feet.; and Chattanooga Shale - Black carbonaceous shale, fissile. Thickness 20 to 30 feet in most areas. (Mapped as MDc in Flynn Creek structure, where it is about 200 feet thick.) (Also mapped as MDc on the East Sheet)

St. Louis Limestone and Warsaw Limestone (Mississippian) at surface, covers 22 % of this area

St. Louis Limestone - Fine-grained, brownish-gray limestone, dolomitic and cherty. Thickness 80 to 160 feet.; and Warsaw Limestone - Mainly medium- to coarse-grained, gray limestone, crossbedded. Includes much calcareous sandstone and shale to the north. Thickness 100 to 130 feet.

Sequatchie Formation, Leipers Formation, Inman Formation and Catheys Formation (Ordovician) at surface, covers 11 % of this area

Sequatchie Formation - Greenish-gray calcareous shale, mudstone, and argillaceous limestone; dolomitic, laminated, and sandy. Thickness 0 to 165 feet; Leipers Formation - Nodular, shaly limestone and fine- to coarse-grained limestone. Thickness 0 to 150 feet; Inman Formation - Thin-bedded to laminated, fine-grained, greenish-gray limestone interbedded with red and green calcareous shale beds. Thickness 0 to 50 feet. (Present only in Sequatchie Valley.); and Catheys Formation - Nodular, shaly, thin- to medium-bedded limestone and fine- to coarse-grained limestone. Thickness 125 to 400 feet.

Ordovician [units] including Richmond Group (which includes Mannie Shale, Fernvale Limestone, Sequatchie Formation, and Arnheim Formation), the Maysville Group (which includes Leipers Formation), the Eden Group (which includes Inman Formation), and the Nashville Group (which includes Catheys Formation). (Ordovician) at surface, covers 8 % of this area

Ordovician [units] including Richmond Group (which includes Mannie Shale - Olive-gray shale. Thickness 0 to 20 feet; Fernvale Limestone - Massive, coarsely crystalline, gray limestone with varicolored grains. Thickness 0 to 50 feet; Sequatchie Formation - Olive-gray and greenish-gray shale, mudstone, and argillaceous limestone; dolomitic, laminated, and sandy. Thickness 0 to 100 feet; and Arnheim Formation Nodular, shaly, gray limestone. Thickness 0 to 20 feet; the Maysville Group (which includes Leipers Formation - Nodular, shaly limestone; fine- to coarse-grained limestone; and phosphatic calcarenite locally. Thickness 0 to 150 feet); the Eden Group (which includes the Inman Formation - Thin-bedded to laminated, fine-grained, gray limestone with shale partings. Thickness 0 to 50 feet); and the Nashville Group (which includes Catheys Formation - Nodular, shaly limestone; fine- to coarse-grained limestone; phosphatic calcarenite; and light-gray cryptograined limestone. Thickness 50 to 175 feet.)

Alluvial deposits (Quaternary) at surface, covers 3 % of this area

Sand, silt, clay and gravel. Mapped only in valley of Cumberland River and in Elk Valley. Thickness generally less than 30 feet.

Renfro and Muldraugh Members of Borden Formation and Fort Payne Formation, undivided (Mississippian) at surface, covers 0.5 % of this area

Renfro and Muldraugh Members of Borden Formation and Fort Payne Formation, undivided

Monteagle Limestone (Mississippian) at surface, covers 0.2 % of this area

Mainly fragmental and oolitic, light-gray limestone; blocky bryozoan chert weathers from base. Thickness 180 to 300 feet.

Salem, Warsaw, and Harrodsburg Limestones, undivided (Mississippian) at surface, covers 0.2 % of this area

Salem, Warsaw, and Harrodsburg Limestones, undivided

Ste. Genevieve and St. Louis Limestones, undivided (Mississippian) at surface, covers 0.1 % of this area

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

Cumberland Formation and Leipers and Catheys (?) Limestones, undivided (Ordovician) at surface, covers < 0.1 % of this area

Cumberland Formation and Leipers and Catheys (?) Limestones, undivided; in southernmost Kentucky

New Albany, Chattanooga, and Ohio Shales, Boyle Dolomite (Limestone), and Sellersburg Limestone, undivided (Devonian to Mississippian) at surface, covers < 0.1 % of this area

New Albany, Chattanooga, and Ohio Shales, Boyle Dolomite (Limestone), and Sellersburg Limestone, undivided

Crooked Fork Group, including Wartburg Sandstone, Glenmary Shale, Coalfield Sandstone, Burnt Mill Shale, Crossville Sandstone, Dorton Shale (Pennsylvanian) at surface, covers < 0.1 % of this area

Crooked Fork Group - Shale, sandstone, conglomerate, siltstone, and coal; from Poplar Creek coal to top of Rockcastle Conglomerate. Thickness 320 to 455 feet; Wartburg Sandstone - Sandstone, gray to brown, fine- to medium-grained, locally conglomeratic. Poplar Creek coal and thin shale at top. Thickness 0 to 50 feet; Glenmary Shale - Mostly dark-gray to light-brown shale with minor siltstone and sandstone. Thin coal near base locally. Thickness 50 to 150 feet; Coalfield Sandstone - Sandstone, gray to brown, fine- to medium-grained. Thickness 0 to 80 feet; Burnt Mill Shale - Mostly dark-gray to light-brown shale, with minor siltstone. Thin sandstone locally present near base. Hooper coal just above base. Thickness as much as 110 feet; Crossville Sandstone - Sandstone, gray to brown or pink, fine- to medium-grained, thinly and evenly bedded. Thickness 30 to 70 feet; Dorton Shale - Mostly dark-gray to light-brown shale, with minor siltstone and sandstone. Thin coal near top. Rex coal as much as 70 feet above base. Thickness as much as 150 feet.

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