LOCATION KARNAK IL+KYEstablished Series
TAXONOMIC CLASS: Fine, smectitic, nonacid, mesic Vertic Endoaquepts
TYPICAL PEDON: Karnak silty clay - in a cultivated field. (Colors ar for moist soil unless otherwise stated.)
Ap--0 to 5 inches; very dark grayish brown (10YR 3/2) silty clay; light gray (10YR 6/1) and light brownish gray (10YR 6/2) dry; weak fine granular structure; firm; slightly acid; abrupt smooth boundary. (5 to 10 inches thick)
Bg1--5 to 12 inches; dark gray (5Y 4/1) silty clay; few fine faint olive (5Y 5/4) mottles; weak medium and fine subangular blocky structure; firm; few faint dark gray (5Y 4/1) pressure faces on faces of peds; few prominent yellowish brown (10YR 5/6 and 5/8) stains (iron and manganese oxides) lining root channels; slightly acid; clear smooth boundary.
Bg2--12 to 20 inches; dark gray (5Y 4/1) silty clay; common fine distinct light olive brown (2.5Y 5/6) mottles; weak very fine and fine prismatic structure parting to weak medium and fine subangular blocky; firm; few faint dark gray (5Y 4/1) pressure faces on faces of peds; few faint dark gray (5Y 4/1) clay flows lining root channels; common fine black (N 2/0) and yellowish brown (10YR 5/8) concretions (iron and manganese oxides); slightly acid; clear smooth boundary.
Bg3--20 to 33 inches; dark gray (5Y 4/1) silty clay; common fine distinct light olive brown (2.5Y 5/6) and few fine prominent yellowish brown (10YR 5/6) mottles; moderate medium prismatic structure parting to weak very fine angular blocky; firm; few distinct gray (N 5/0) clay flows in root channels; common fine yellowish brown (10YR 5/8) concretions (iron and manganese oxides); slightly acid; clear smooth boundary.
Bg4--33 to 50 inches; dark gray (N 4/0) silty clay; few fine distinct light olive brown (2.5Y 5/6) and few fine prominent yellowish brown (10YR 5/6) mottles; weak fine prismatic structure parting to weak fine subangular blocky; firm; few distinct gray (N 5/0) pressure faces on faces of peds; slightly acid; clear smooth boundary.
Cg--50 to 60 inches; gray (5Y 5/1) silty clay loam; many fine prominent yellowish brown (10YR 5/6 and 5/8), common fine distinct light olive brown (2.5Y 5/6), and few fine faint light gray (5Y 7/1) mottles; massive; firm; mildly alkaline.
TYPE LOCATION: Massac County, Illinois; about 14 miles northwest of Metropolis; 230 feet north and 2800 feet east of the SE corner of sec. 18, T. 14 S., R. 3 E.
RANGE IN CHARACTERISTICS: The solum typically is 45 to 55 inches in thickness, but ranges from 30 to 60 inches. The control section averages 40 to 60 percent clay.
The Ap or A horizon has hue of 10YR, value of 3 through 6, and chroma of 1 or 2. Pedons that have color value of 3 have dry value of 6 or are less than 10 inches in thickness, or both. The Ap or A horizon typically is silty clay or clay, but some pedons are silty clay loam. Overwash phases include silt loam. The Ap or A horizon typically is slightly acid or medium acid, but some pedons that have been limed are neutral.
The Bg horizon has hue of 10YR, 2.5Y, 5Y, or is neutral; value of 4 through 7; and chroma of 1 or 2. Mottles typically have higher chroma than the matrix, and have hue ranging from 5Y to 5YR. The Bg horizon is silty clay or clay. It is strongly acid to slightly acid. Some pedons have slickensides.
The C horizon has hue of 10YR, 2.5Y, 5Y, or is neutral; value of 4 through 7; and chroma of 0 through 2 and is mottled. Mottles typically have higher chroma than the matrix, and have hue of 7.5YR, 10YR, 2.5Y, or 5Y. The C horizon is silty clay or silty clay loam and some pedons contain strata within a depth of 60 inches. The strata commonly contain more sand or silt than the matrix. The C horizon is medium acid through mildly alkaline.
COMPETING SERIES: This is the only soil in this family. The Albaton, Cape, Carlow, Darwin, Jacob, and Zipp series are in closely related families. Albaton soils are calcareous throughout the solum. Cape soils contain less clay in the upper part of the solum and are strongly acid to extremely acid throughout the control section. Carlow and Darwin soils have mollic epipedons. Jacob soils contain more clay and are more acid in the solum. Zipp soils have mixed mineralogy and lower linear extensibility, therefore, they don't have the deep, wide cracks when the soil is dry.
GEOGRAPHIC SETTING: Karnak soils are on low-lying parts of flood plains, principally along the Mississippi and Ohio Rivers and along their larger tributaries. Slope gradients commonly are less than one percent, but range from 0 to 2 percent. The soils formed in silty clay or clay alluvium. They have high linear extensibility and form deep, wide cracks when the soil is dry. Mean annual temperature varies from 54 to 57 degrees F, and mean annual precipitation varies from about 36 to 48 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Cape, Darwin, and Jacob soils and the Petrolia and Piopolis soils. Cape soils are on similar or slightly higher parts of the flood plains nearby. Darwin and Jacob soils are on similar parts of flood plains nearby. Petrolia and Piopolis soils contain less clay and, in addition, Piopolis soils are more acid in the control section. Petrolia and Piopolis soils are on similar or slightly higher parts of the flood plain nearby.
DRAINAGE AND PERMEABILITY: Poorly drained and very poorly drained. Runoff is slow to very slow. Permeability is very slow or slow.
USE AND VEGETATION: Areas that are drained are cultivated. Soybeans and corn are the principal crops. Areas that are undrained are idle or are used for pasture or woodland. Native vegetation was mostly deciduous hardwoods.
DISTRIBUTION AND EXTENT: Southern Illinois, Kentucky and Missouri. The extent is large; more than 140,000 acres have been correlated.
MLRA OFFICE RESPONSIBLE: Lexington, Kentucky
SERIES ESTABLISHED: Johnson County, Illinois, 1942.
REMARKS: Diagnostic horizons and features recognized in this pedon are: Ochric epipedon - the zone from the surface of the soil to a depth of 5 inches (Ap horizon). Cambic horizon - the zone from approximately 5 to 50 inches (Bg1, Bg2, Bg3, and Bg4 horizons). Vertic subgroup feature - silty clay texture and pressure faces on the faces of peds in the control section. Aquic moisture regime.
ADDITIONAL DATA: Engineering test data for the typical pedon is published in the Soil Survey of Pope, Hardin, and Massac Counties, Illinois, June, 1975.
OSED scanned by NSSQA. Last revised by state on 2/84.
Classification only was changed in 7/94. Competing series and other items will be updated later.