Geologic units in Henry county, Tennessee

Additional scientific data in this geographic area

Claiborne and Wilcox Formation (Tertiary) at surface, covers 32 % of this area

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.

McNairy Sand (Cretaceous) at surface, covers 20 % of this area

Predominantly sand, in places interbedded with silty light-gray clays. Fine-grained sand at base, locally contains heavy minerals. Thickness about 300 feet.

Loess (Quaternary) at surface, covers 17 % of this area

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 including Porters Creek Clay and Clayton Formation (Tertiary) at surface, covers 11 % of this area

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.

Alluvial deposits (Quaternary) at surface, covers 9 % of this area

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.

High-level alluvial deposits (Quaternary-Tertiary) at surface, covers 5 % of this area

Iron-stained gravel, sand, silt, and clay; variable in thickness but generally less then 60 feet thick.

Coon Creek Formation (Cretaceous) at surface, covers 2 % of this area

Fossiliferous, micaceous sand, silty and glauconitic; locally fossiliferous sandy clay at base. Siderite concretions common in upper part. Thickness about 140 feet.

Coffee Sand (Cretaceous) at surface, covers 2 % of this area

Loose fine-grained sand, light-gray, sparsely glauconitic, locally interbedded with laminated lignitic clay. Thickness 25 to 200 feet; thins northward.

Fort Payne Formation and Chattanooga Shale (Mississippian) at surface, covers 1 % of this area

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, includes Pegram Formation, Camden Formation, Harriman Formation, Flat Gap Limestone, and Ross Formation (Devonian) at surface, covers 0.6 % of this area

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 (Tertiary to Quaternary) at surface, covers 0.1 % of this area

Continental deposits and loess, undifferentiated; West of the Tennessee River

Tuscaloosa Formation (Cretaceous) at surface, covers < 0.1 % 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 140 feet.

Clayton and McNairy Formations, undivided (Paleocene to Upper Cretaceous) at surface, covers < 0.1 % of this area

Clayton and McNairy Formations, undivided

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

Jackson and Claiborne Formations, undivided (Tertiary) at surface, covers < 0.1 % of this area

Jackson and Claiborne Formations, undivided; includes some rocks of Oligocene age

Porters Creek Clay (Paleocene) at surface, covers < 0.1 % of this area

Porters Creek Clay

Silurian Formations, including Decatur Limestone, Brownsport Group (Lobelville Formation, Bob Limestone, Beech River Formation), Wayne Group (Dixon Formation, Lego Formation, Waldron Shale, Laurel Limestone, Osgood Formation) and Brassfield Limestone (Silurian) at surface, covers < 0.1 % of this area

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 (Mississippian) at surface, covers < 0.1 % of this area

Warsaw Limestone; west of Christian County