LOCATION ROCHER ILEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, calcareous, mesic Typic Udifluvents
TYPICAL PEDON: Rocher loam - near the crest of a broad low natural levee with a 2 percent gradient in a cultivated field at an elevation of about 382 feet above mean sea level. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 5 inches; brown (10YR 4/3) loam, pale brown (10YR 6/3) dry; weak medium and coarse granular structure; very friable; common fine roots; slightly effervescent; slightly alkaline; clear smooth boundary. (4 to 10 inches thick)
C1--5 to 11 inches; brown (10YR 5/3) very fine sandy loam; massive; very friable; common fine roots; slightly effervescent; slightly alkaline; clear smooth boundary.
C2--11 to 32 inches; light yellowish brown (10YR 6/4) loamy very fine sand; single grain; loose; few fine roots; slightly effervescent; slightly alkaline; gradual smooth boundary.
C3--32 to 53 inches; yellowish brown (10YR 5/4) loamy very fine sand; single grain; loose; slightly effervescent; slightly alkaline; gradual smooth boundary.
C4--53 to 62 inches; light yellowish brown (10YR 6/4) loamy fine sand; single grain; loose; slightly effervescent; slightly alkaline.
TYPE LOCATION: Randolph County, Illinois; about 7 miles southeast of Prairie du Rocher; state plane coordinates 484,480 feet north and 540,490 feet east, Illinois West Zone; approximately 5,400 feet southeast along the levee from the intersection of the levee and the Discharge (drainage ditch), and 800 feet southwest perpendicular to the levee; T. 6 S., R. 8 W; USGS Ste. Genevieve, MO.-IL. topographic quadrangle; lat. 37 degrees 59 minutes 47 seconds N. and long. 90 degrees 1 minute 32 seconds W.
RANGE IN CHARACTERISTICS: Depth to the base of soil development is 6 to 20 inches and corresponds to the thickness of the A horizon or the A and AC horizons. Carbonates are at a depth of 10 inches or less. Some pedons do not have carbonates in some strata at depths between 20 and 60 inches. These soils typically are slightly alkaline or moderately alkaline throughout, but some pedons are neutral in the Ap or A horizon, or in some layers of the C horizon below a depth of 20 inches.
The upper part of the series control section (Ap or A) has hue of 10YR, value of 4 or 5 (6 or 7 dry), and chroma of 2 or 3. Texture is very fine sandy loam, fine sandy loam, loamy fine sand, loamy very fine sand, very fine sand, loam, or silt loam. Clay content is 5 to 18 percent.
Some pedons have an AC horizon. It is within the same ranges defined for the Ap or A horizon.
The lower part of the series control section (C) has hue of 10YR or 2.5Y, value of 4 to 6, and chroma of 2 to 4. Some pedons contain redoximorphic features have chroma higher than the matrix. The C horizon commonly is very fine sand, very fine sandy loam, or loamy very fine sand, and contains strata of loamy fine sand, fine sand, fine sandy loam, silt loam, or loam within a depth of 60 inches. Clay content is 5 to 18 percent in the upper part and 2 to 15 percent in the lower part.
COMPETING SERIES: These are the Carr and Stonelick series. Carr soils are dominated by fine sand in the series control section and occur in areas with less than 35 inches of annual precipitation. Stonelick soils are dominated in the series control section with sand coarser than fine sand.
GEOGRAPHIC SETTING: Rocher soils are on natural levees and flood-plain splays on nearly level or gently undulating flood plains. They formed in loamy or sandy stratified calcareous alluvium that is dominated by very fine sand. Slope ranges from 0 to 7 percent. These soils typically are subject to frequent flooding, but some areas are occasional or rare because of levees, locks and dams, or other flood-control structures. Mean annual temperature is 54 to 57 degrees F., mean annual precipitation is 36 to 44 inches, frost-free period is 170 to 210 days, and elevation is 340 to 450 feet above mean sea level.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Blake, Fults, Haynie, and Sarpy soils. The somewhat poorly drained Blake and poorly drained Fults soils contain more clay in the control section and occur in lower-lying areas of the flood plain. The moderately well drained Haynie soils are coarse-silty and occur on similar but slightly lower landform positions. The excessively drained Sarpy soils are sandy and occur on similar but slightly higher landform positions.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained and moderately rapid permeability. The potential for surface water runoff is slow. The water table remains at a depth below 6 feet except during short periods of high stream flow.
USE AND VEGETATION: Most areas are cultivated. Soybeans, wheat, and forage crops for hay are the principal crops. Native vegetation is native grasses and deciduous trees such as cottonwood and silver maple.
DISTRIBUTION AND EXTENT: Southern Illinois on flood plains of the major rivers. Extent is small, and mainly in MLRA 115.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Indianapolis, Indiana
SERIES ESTABLISHED: Randolph County, Illinois, 1983.
REMARKS: These soils were previously mapped as Sarpy or Sarpy Variant. They are prime farmland where irrigated and where they flood less often than once in two years during the growing season.
Diagnostic horizons and features in this pedon include:
Ochric epipedon - from the surface of the soil to a depth of 5 inches (Ap horizon). Udic moisture regime.