LOCATION OKOLONA MS+ALEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Oxyaquic Hapluderts
TYPICAL PEDON: Okolona silty clay on 0 to 2 percent slopes, cultivated.
(Colors are for moist soil unless otherwise stated.)
Ap--0 to 8 inches; very dark grayish brown (2.5Y 3/2) silty clay; moderate medium granular structure; firm, sticky, very plastic; few fine roots; few fine calcium carbonate nodules; noncalcareous; moderately alkaline; abrupt smooth boundary.
A--8 to 18 inches; very dark grayish brown (2.5Y 3/2) silty clay; moderate medium prismatic structure parts to moderate fine angular blocky; firm, very sticky, very plastic; few fine roots; few medium worm casts; few fine black and brown concretions; stress surfaces on faces of peds; few fine and medium calcium carbonate nodules; calcareous, slightly effervescent; moderately alkaline; gradual wavy boundary. (Combined thickness of the A horizon is 14 to 25 inches)
Bw1--18 to 27 inches; olive (5Y 4/3) silty clay; common fine faint light olive brown (2.5Y 5/4) mottles; moderate medium prismatic structure parts to moderate medium and fine angular blocky; firm, very sticky, very plastic; few fine roots; few fine slickensides that intersect; few fine and medium calcium carbonate nodules; few fine black concretions; stress surfaces on faces of peds; calcareous, slightly effervescent; moderately alkaline; gradual wavy boundary.
Bw2--27 to 48 inches; olive (5Y 4/3) silty clay; common fine faint light olive brown (2.5Y 5/4) mottles; intersecting slickensides form wedge-shaped aggregates that part to fine angular blocky structure; firm, very sticky, very plastic; few fine black concretions; few fine and medium calcium carbonate nodules; calcareous, slightly effervescent; moderately alkaline; gradual wavy boundary. (Combined thickness of the Bw horizon is 26 to 45 inches)
C--48 to 65 inches; mottled dark grayish brown (2.5Y 4/2), olive brown (2.5Y 4/4), and yellowish brown (10YR 5/8) clay; intersecting slickensides form wedge-shaped aggregates which part to fine and medium angular blocky structure; very firm, very sticky, very plastic; few fine black concretions; common medium and coarse calcium carbonate nodules; calcareous, strongly effervescent; moderately alkaline; gradual wavy boundary. (12 to 20 inches thick)
R--65 to 82 inches; olive gray (5Y 5/2) platy chalk.
TYPE LOCATION: Monroe County, Mississippi; 0.75 miles southeast of Muldon, and 360 feet south of gravel road and 1,800 feet east of railroad, NW1/4NW1/4 sec. 2, T. 15 S., R. 6 E.
RANGE IN CHARACTERISTICS: The combined thickness of the A and Bw horizon ranges from 40 to more than 65 inches. Depth to chalk ranges from 48 to more than 100 inches. Intersecting slickensides are at a depth ranging from 15 to 33 inches below the surface. Cycles of micro-lows and micro-highs are repeated about every 7 to 20 feet. Thickness of horizons with a color value of less than 3.5 and chroma of 1.5 or more ranges from 16 to 25 inches in the center of the micro-lows and from 8 to 14 inches in the center of the micro-highs. The extremes of amplitude of waviness of the boundary between the A and Bw horizons vary from 8 to 33 inches from the center of the micro-highs to the center of the micro-lows.
The A horizon has in the upper 12 inches of more than half of each pedon a matrix in hue of 10YR, 2.5Y or 5Y, value of 2 or 3, and chroma of 2 or 3; other colors, if present, have hue of 10YR, value of 3 or 4 and chroma of 1 or 2; and hue of 2.5Y and 5Y, with value of 4, and chroma of 2. Texture is silty clay or clay. Some pedons have a silty clay loam Ap horizon. Reaction is neutral to moderately alkaline.
The Bw and C horizons have hue 2.5Y or 5Y, value of 4 or 5, and chroma of 2 to 4; or they are mottled in shades of brown and gray. Texture of the Bw and C horizons is silty clay or clay. The particle size control section, from 10- to 40-inches, has 40 to 55 percent clay. Brown and black concretions range from few to common. The Bw and C horizons are neutral to moderately alkaline.
COMPETING SERIES: There are no competing series in the same family. Closely related soils are the Beaumont, Brooksville, Burleson, Eutaw, Heiden, Houston, Houston Black, Kipling, and Lela series. The Beaumont and Eutaw soils are grayer and have a dominant chroma of less than 1.5 throughout the control section. Brooksville soils have distinct or prominent mottles in shades of red and brown within 20 inches of the surface and are more acid in the upper part of the soil. Burleson, Heiden, and Houston Black soils have an ustic moisture regime. Houston soils have more than 60 percent clay and are less silty in the 10- to 40-inch control section. Kipling soils have a yellowish brown Bt horizon mottled with gray. Lela soils have mixed mineralogy.
GEOGRAPHIC SETTING: Okolona soils are on uplands in the Blackland Prairie Major Land Resource Area. Slopes range from 0 to 5 percent. These are nearly level to gently sloping soils that formed in calcareous clayey material, which is underlain by marly clay and chalk. The climate is warm and humid. Average annual precipitation is about 48 inches and average annual temperature is about 63 degrees Fahrenheit near the type location.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Brooksville and Kipling soils listed in the competing series and the Binnsville, Demopolis, Griffith, and Sumter series. Somewhat poorly drained Brooksville and Kipling soils are on similar landscape positions as the Okolona soils. Well drained Binnsville and Demopolis soils, which have a solum less than 20 inches thick over chalk, commonly are in slightly higher positions on ridgetops and hillsides. Well drained Griffith soils, which have amplitude of waviness between the A and Bw horizons of 6 to 10 inches and have an A horizon 24 to 48 inches thick, are on flood plains. Well drained Sumter soils, which have a solum 20 to 40 inches thick and do not have intersecting slickensides, are mainly in small areas on ridges and hillsides.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; very slow permeability. The seasonal high water table in wet seasons is at a depth of 4 to 6 feet.
USE AND VEGETATION: The Okolona soils are used for growing cotton, soybeans, sorgum, small grain, hay, and pasture. Common trees include eastern redcedar and osage orange.
DISTRIBUTION AND EXTENT: Mississippi. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Auburn, Alabama
SERIES ESTABLISHED: Monroe County, Mississippi; 1969.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from the surface to a depth of about 18 inches (Ap, A horizons).
Typic Chromuderts features - do not have distinct or prominent mottles within 20 inches of the soil surface (Ap, A, Bw1 horizons). Have color value, moist, less than 3.5 throughout the upper 12 inches in more than half of each pedon (Ap, A horizons).
Slickensides that are close enough to intersect (Bw1, Bw2, C horizons).