Irregularly bedded sand, locally interbedded with lenses and beds of gray to white clay, silty clay, lignitic clay, and lignite. Thickness more than 400 feet.
Predominantly sand, in places interbedded with silty light-gray clays. Fine-grained sand at base, locally contains heavy minerals. Thickness about 300 feet.
Clayey and sandy silt, gray to brown, massive. Maximum thickness about 100 feet along bluffs of Mississippi River; thins eastward. (Minimum mapped thickness 4 feet.)
Midway Group - includes Porters Creek Clay - Pale-brown to brownish-gray, massive, blocky clay; locally contains glauconitic sand. Thickness 130 to 170 feet. Also includes Clayton Formation- Glauconitic sand, argillaceous and locally fossiliferous; at base in Hardeman County is an impure fossiliferous limestone. Thickness 30 to 70 feet.
Sand, silt, clay, and gravel. In flood plain of Mississippi River more than 100 feet thick; in smaller streams generally less than 20 feet thick.
Iron-stained gravel, sand, silt, and clay; variable in thickness but generally less then 60 feet thick.
Fossiliferous, micaceous sand, silty and glauconitic; locally fossiliferous sandy clay at base. Siderite concretions common in upper part. Thickness about 140 feet.
Loose fine-grained sand, light-gray, sparsely glauconitic, locally interbedded with laminated lignitic clay. Thickness 25 to 200 feet; thins northward.
Fort Payne Formation - Bedded chert and calcereous and dolomitic silicastone; minor coarse-grained limestone and shale. Thin green shale (Maury) at base. Thickness about 200 feet. Chattanooga Shale - Black carbonaceous shale, fissile. Thickness 0 to 70 feet.
Devonian Formations - Characterized by marked north-south facies variations. Because of pre-Chattanooga and/or pre-Cretaceous warping and erosion, the distribution and thickness of Devonian formations is very irregular. Includes Pegram Formation - Thick-bedded, gray limestone and gray sandstone. Thickness 0 to 15 feet; Camden Formation - Light-gray novaculitic chert and tripolitic clay; and minor siliceous limestone. Thickness 0 to about 100 feet; Harriman Formation - Light-gray novaculitic chert and tripolitic clay; and minor siliceous limestone. (Harriman and Camden are differentiated paleontologically.) Thickness 0 to 50 feet; Flat Gap Limestone - Thick-bedded, coarse-grained limestone, gray with red and brown grains. Thickness 0 to 55 feet; Ross Formation - Siliceous limestone; gray and variegated shale; and medium-grained glauconitic limestone. Thickness 0 to 75 feet.
Continental deposits and loess, undifferentiated; West of the Tennessee River
Poorly sorted, light-gray chert gravel in a matrix of silt and sand; locally interbedded with sand and clay lenses. Thickness 0 to 140 feet.
Clayton and McNairy Formations, undivided
Alluvium; includes glacial deposits along the Ohio River and its tributaries west of Cannelton locks
Jackson and Claiborne Formations, undivided; includes some rocks of Oligocene age
Porters Creek Clay
Silurian Formations - A complete section of Silurian formations is not common because of pre-Chattanooga and/or pre- Cretaceous erosion. Where preserved, Silurian formations are remarkably uniform in thickness and are characteristically light olive-gray to greenish-gray with variable reddish-brown color in some area; Decatur Limestone - Thick-bedded, medium- to coarse-grained limestone, gray with reddish-brown grains. Thickness 0 to 70 feet; Brownsport Group which includes 1) Lobelville Formation - Shale with thin beds of limestone. Thickness 0 to 40 feet; 2) Bob Limestone - Thick-bedded, medium-grained limestone, locally oolitic. Thickness 0 to 25 feet; and 3) Beech River Formation - Shale with thin beds of limestone. Thickness 0 to 60 feet; Wayne Group which includes: 1) Dixon Formation - Green and reddish-brown argillaceous limestone, shale, and mudstone. Thickness 0 to 40 feet; 2) Lego Limestone - Even-bedded, olive-gray limestone with scattered reddish-brown grains. Thickness 0 to 30 feet; 3) Waldron Shale - Greenish-gray fossiliferous shale. Thickness 0 to 5 feet; 4) Laurel Limestone - Even-bedded, gray limestone with scattered reddish-brown grains. Thickness 0 to 30 feet; 5) Osgood Formation - Greenish- and reddish-gray shale and argillaceous limestone. Thickness 0 to 15 feet.; and Brassfield Limestone - Thin-bedded cherty limestone, locally glauconitic. Thickness 0 to 20 feet.
Warsaw Limestone; west of Christian County