Clayton formation (MSPNac;0)

State	Mississippi
Name	Clayton formation
Geologic age	Paleocene
Original map label	Pac
Comments	Secondary unit desrciption from USGS Lexicon website (MS002) and MS010: In MS Fearn Springs removed from Wilcox Group, reduced to member status, and assigned to the top of the Naheola Formation of the Midway Group. This revision changes the Midway-Wilcox boundary in MS. Boundary now placed at the Fearn Springs-Nanafalia contact (Dockery, 1990). East of Butler Co., AL, name Clayton is used for all of Midway beds. In Butler Co. and westward in AL and MS, it is used only for beds below Porters Creek clay. In Butler and Wilcox Cos., includes McBryde limestone member and Pine Barren member (both new). In western AL and MS, the Clayton is represented by single unit, the Chalybeate limestone member (new). In western AL and east-central MS, the Clayton thins to a few ft and may be overlapped by Porters Creek clay in places. From Chickasaw Co. northward in MS, formation thickens and in northern MS is probably 60 ft thick. At Clayton, AL, section consists of lower zone of about 35 ft of sand and limestone, grading from noncalcareous, HALMENITES-bearing sand at base, through coarse sandy limestone to sand-free hard white limestone at top, and an upper zone of about 15 ft of hackly gray clay. Formation thickens eastward to nearly 130 ft in Chattahoochee River, where upper clay is represented by smooth-textured argillaceous limestone. In northern MS, includes a bed of calcareous siltstone formerly regarded by Mississippi Geological Survey as base of Porters Creek. This revision is made to make base of the clay consistently the base of the Porters Creek in MS and also because this siltstone carries the large nautiloid HERCOGLOSSA ULRICHI, a marker for upper part of Clayton in central AL. Source: GNU records (USGS DDS-6; Reston GNULEX).
Primary rock type	limestone
Secondary rock type	sand
Other rock types	clay or mud; calcarenite
Lithologic constituents	Major Sedimentary > Carbonate > LimestoneLower part, crystalline sandy limestone and loose sand. Minor Unconsolidated > Coarse-detrital > SandUpper part, greenish-gray coarsely glauconitic sandy clay and marl. Lower part, crystalline sandy limestone and loose sand. Unconsolidated > Fine-detrital > ClayUpper part, greenish-gray coarsely glauconitic sandy clay and marl. Incidental Sedimentary > Clastic > Sandstone > Arenite > Calcarenite (Calcareous)Lower part, crystalline sandy limestone and loose sand, represented south of Houston by a discontinuous bed of indurated calcareous sandstone. Unconsolidated > MarlUpper part, greenish-gray coarsely glauconitic sandy clay and marl.
Map references	Moore, William Halsell, 1969, reprinted 1985, Geologic Map of Mississippi, Compiled by Bicker, A. R., Jr., a revision of the geologic map published by the MS Geological Survey in 1945 in cooperation with the USGS, revised from data submitted by Dr. E. E. Russell of MS State University from published reports of the MS Geological Survey and from field revisions, Mercury Maps Inc., Jackson, MS.
Unit references	Moore, William Halsell, 1969, reprinted 1985, Geologic Map of Mississippi, Compiled by Bicker, A. R., Jr., a revision of the geologic map published by the MS Geological Survey in 1945 in cooperation with the USGS, revised from data submitted by Dr. E. E. Russell of MS State University from published reports of the MS Geological Survey and from field revisions, Mercury Maps Inc., Jackson, MS. USGS Geologic Names Lexicon (GEOLEX) [http://ngmdb.usgs.gov/Geolex/] Dockery, D.T., III, 1990, A revision of the Fearn Springs Formation and relocation of the Midway-Wilcox Group boundary in Mississippi, IN Bograd, M.B.E., and Dockery, D.T., III, eds., Geologic mapping in Mississippi; proceedings of the 1989 MISGEOMAP conference: Mississippi Office of Geology Circular, no. 3, p. 21-23.
Geographic coverage	Chickasaw - Clay - Kemper - Noxubee - Oktibbeha - Pontotoc - Tippah - Union - Winston