LOCATION COTEAU LA
Established Series
Rev. JDS
04/2019
COTEAU SERIES
The Coteau series consists of somewhat poorly drained, moderately slowly permeable soils that formed under grassland vegetation in loess deposits more than 4 feet thick. These soils are on slightly convex interfluve positions. Slopes range from 0 to 3 percent.
TAXONOMIC CLASS: Fine-silty, mixed, active, hyperthermic Glossaquic Hapludalfs
TYPICAL PEDON: Coteau silt loam--pasture. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 5 inches; dark grayish brown (10YR 4/2) silt loam; few fine faint light brownish gray (10YR 6/2) mottles; weak fine granular structure; friable; many fine roots; few fine soft black organic masses; strongly acid; abrupt wavy boundary. (3 to 12 inches thick)
Bt--5 to 12 inches; dark yellowish brown (10YR 3/4) silty clay loam; common medium faint dark brown (10YR 4/3 and 7.5YR 4/4) masses of iron accumulation; weak medium prismatic structure that parts to moderate medium subangular blocky; firm; common fine roots throughout; common fine pores; faint clay films on faces of peds; common fine black and brown iron/manganese concretions; moderately acid; clear irregular boundary. (2 to 11 inches thick)
Bt/E--12 to 22 inches; brown (10YR 5/3) silty clay loam; moderate coarse and medium prismatic structure that parts to moderate medium subangular blocky; firm; about 20 percent brittle peds; few fine roots throughout; faint clay films on faces of peds and in pores; about 15 percent interfingerings of grayish brown (10YR 5/2) silt loam (E) 2 to 8 mm wide between prisms; few medium dark brown iron/manganese concretions; common medium faint dark yellowish brown (10YR 3/4) masses of iron accumulation; few fine faint grayish brown (10YR 5/2) iron depletions; moderately acid; clear irregular boundary. (5 to 15 inches thick)
Bt'--22 to 43 inches; dark yellowish brown (10YR 4/4) silty clay loam (70 percent) with light brownish gray (10YR 6/2) silty clay loam iron depletions in vertical streaks 1 to 3 cm. wide (30 percent); moderate medium and coarse prismatic structure that parts to moderate medium subangular blocky; firm; about 25 percent brittle peds; few fine roots mainly concentrated between peds; common fine and medium pores; distinct clay films on faces of peds and in pores; thin patchy black manganese stains on faces of peds; common medium distinct strong brown (7.5YR 5/6) masses of iron accumulation throughout; moderately acid; clear irregular boundary. (10 to 30 inches thick)
BC--43 to 70 inches; dark yellowish brown (10YR 4/4) silt loam; common medium distinct light brownish gray (10YR 6/2) continuous vertical streaks of silty clay loam iron depletions 5 to 13 mm wide; weak coarse prismatic structure that parts to weak coarse subangular blocky; friable; few fine roots throughout; many fine and medium pores and voids; faint gray (10YR 5/1) clay films in pores and voids; thin patchy silt coatings on faces of peds; moderately acid; gradual wavy boundary. (10 to 30 inches thick)
C--70 to 100 inches; dark yellowish brown (10YR 4/4) silt loam; massive; friable; common fine and medium pores and voids; few faint clay films lining some pores; common fine distinct pale brown (10YR 6/3) and gray (10YR 6/1) iron depletions around pores and voids; moderately acid.
TYPE LOCATION: Iberia Parish, Louisiana; 1 1/2 miles northwest of Coteau school and church; 70 feet east of U. S. Highway 90 right-of-way; 50 feet north of crossfence, near western edge of SE1/4 SE1/4 NW1/4, sec, 36, T. 11 S., R. 5 E.; lat. 30 degrees 2 minutes 53.08 seconds N. and long. 91 degrees 55 minutes 16.39 seconds W., WGS84.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 48 to 100 inches. Typically these soils have less than 3 percent total sand in the solum, but sand content in the solum ranges up to 10 percent.
The Ap horizon has hue of 10YR, value of 4 or 5, and chroma of 2 to 4. The A horizon, where present has hue of 10YR, value of 3 to 5, and chroma of 1 to 3. Where value is 3 thickness is 7 inches or less. Texture is silt or silt loam. Reaction ranges from very strongly acid to slightly acid.
The E horizon, where present, has hue of 10YR, value of 4 to 6, and chroma of 2 or 3. Texture is silt or silt loam. Reaction ranges from very strongly acid to slightly acid.
The Bt horizon, has hue of 10YR or 7.5YR, value of 3 to 5, and chroma of 3 or 4. Texture is silt loam or silty clay loam. Iron depletions are in shades of gray and iron accumulations are in shades of brown. Reaction ranges from very strongly acid to slightly acid.
The Bt part of the Bt/E horizon has hue of 10YR or 7.5YR, value of 4 or 5, and chroma of 3 or 4. The E part of the Bt/E horizon is vertically oriented and occurs as interfingers of albic material 2 to 20 mm. wide between prisms, and silt coatings on faces of prisms. The E parts have hue of 10YR or 2.5Y, value of 5 to 7, and chroma of 2 or 3, and make up 1 to 15 percent of the horizon. Texture is silt loam or silty clay loam in the Bt parts, and silt or silt loam in the E parts. The E parts typically become more clayey with depth and grade into vertically oriented streaks of low chroma B materials in the lower part of the solum. Iron depletions are in shades of gray and iron accumulations are in shades of brown. Reaction ranges from very strongly acid to slightly acid. Typically, about 20 to 30 percent of the peds in the horizon are firm and brittle.
The Bt' horizon has hue of 10YR or 7.5YR, value of 4 or 5, and chroma of 3 or 4. Texture is silt loam or silty clay loam. Typically, the horizon has vertical, iron depleted streaks of material with similar texture, but with hue of 10YR or 2.5Y, value of 5 to 7, and chroma of 2 or 3, however these streaks are not present in all pedons. Iron depletions are in shades of gray and iron accumulations are in shades of brown. Reaction ranges from very strongly acid to slightly acid. Typically, about 20 to 30 percent of the peds in the horizon are firm and brittle.
The BC and C horizons have hue of 10YR or 7.5YR, value of 3 to 5, and chroma of 3 or 4. Iron depletions in shades of gray and iron accumulations in shades of brown, range from few to many. Reaction ranges from strongly acid to neutral.
COMPETING SERIES: There are no other series in the same family. The
Duson series is in a closely related family but has a discontinuity to loamy and clayey Pleistocene age alluvium within a depth of 40 inches and does not have interfingerings of albic materials in the subsoil.
GEOGRAPHIC SETTING: Coteau soils are on broad nearly level interfluves on convex, gently undulating areas and very gently sloping sideslopes. Slopes range from 0 to 3 percent. These soils formed under grass vegetation in loess deposits 4 to 20 feet thick. The mean annual temperature is about 68 degrees F., and the average annual rainfall is about 58 inches near the type location. Thornthwaite P-E index is about 70.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Calhoun,
Frost,
Jeanerette, Klienpeter, and
Patoutville series. Calhoun and Frost soils are on lower, flatter positions. They are poorly drained with aquic conditions in the upper part of the subsoil.
Kleinpeter soils are on higher interfluve positions and are well drained. Patoutville soils are on lower, flatter positions. They are poorly drained with aquic conditions in the upper part of the subsoil and have red or reddish iron accumulations in the subsoil. Jeanerette soils are on lower, flat or concave positions. They have aquic conditions in the upper part of the subsoil and have a mollic epipedon.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; low to medium runoff; permeability is moderately slow. A saturated zone is at 1.5 to 3.0 feet of the surface for up to one month duration during winter and spring in normal years.
USE AND VEGETATION: Cultivated row crops and pasture. Native vegetation is tall prairie grasses with some areas encroached by pine and mixed hardwoods
DISTRIBUTION AND EXTENT: Southern Mississippi Valley Silty Uplands (134) in Southern Louisiana, mainly west of the Mississippi River Valley. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: AUBURN, ALABAMA
SERIES ESTABLISHED: Iberia Parish, Louisiana; 1973.
REMARKS: Coteau soils formerly were included in the Olivier series. Diagnostic horizons and other features recognized include:
Ochric epipedon: 0 to 5 inches (Ap horizon).
Argillic horizon: 5 to 43 inches (Bt, Bt/E amd Bt' horizon).
Interfingering of albic material into the argillic horizon: 12 to 22 inches (Bt/E horizon)
Iron depletions with chroma 2 or less: 12 to 22 inches (Bt/E horizon).
LAB DATA: Laboratory analyses were run on samples from 2 pedons in St. Landry Parish, Louisiana (S79LA-097-003 and S79LA-097-003).
National Cooperative Soil Survey
U.S.A.