LOCATION COURTOIS MOEstablished Series
TAXONOMIC CLASS: Fine, mixed, active, mesic Typic Paleudalfs
TYPICAL PEDON: Courtois silt loam - on a 6 percent east-facing slope in an alfalfa field at an elevation of 945 feet. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 4 inches; brown (10YR 4/3) silt loam, brown (10YR 5/3) dry; moderate fine subangular blocky structure; friable; many very fine and fine roots; many very fine and fine interstitial and tubular pores; moderately acid; clear smooth boundary. (2 to 10 inches thick)
Bt1--4 to 8 inches; brown (7.5YR 4/4) silty clay loam; weak very fine prismatic structure parting to moderate fine subangular blocky; friable; common very fine and fine roots; many fine and medium interstitial and tubular pores; few distinct clay films on faces of peds; moderately acid; clear smooth boundary.
Bt2--8 to 13 inches; reddish brown (5YR 4/4) silty clay loam; moderate fine prismatic structure parting to moderate very fine subangular blocky; firm; common very fine and fine roots; common very fine and fine interstitial and tubular pores; few distinct clay films on faces of peds; moderately acid; gradual smooth boundary. (Combined thickness of the Bt horizon is 6 to 20 inches)
2Bt3--13 to 19 inches; dark red (2.5YR 3/6) silty clay loam; strong fine prismatic structure parting to moderate very fine subangular blocky; firm; common very fine and fine roots; common very fine and fine interstitial and tubular pores; many distinct clay films on faces of peds; few prominent black (10YR 2/1) manganese stains on faces of peds; few masses of black (10YR 2/1) manganese oxide accumulations; moderately acid; clear smooth boundary.
2Bt4--19 to 29 inches; red (2.5YR 4/6) silty clay loam; moderate fine prismatic structure parting to moderate fine angular blocky; firm; common very fine and fine roots; few very fine and fine interstitial and tubular pores; many distinct clay films on faces of peds; common prominent black (10YR 2/1) manganese stains on faces of peds; many masses of black (10YR 2/1) manganese oxide accumulations; strongly acid; gradual smooth boundary.
2Bt5--29 to 40 inches; dark red (2.5YR 3/6) silty clay loam; moderate fine prismatic structure parting to moderate fine angular blocky; firm; common very fine and fine roots; few very fine and fine interstitial and tubular pores; many distinct clay films on faces of peds; many prominent black (10YR 2/1) manganese stains on faces of peds; common masses of black (10YR 2/1) manganese oxide accumulations; very strongly acid; gradual smooth boundary.
2Bt6--40 to 48 inches; dark red (2.5YR 3/6) silty clay; moderate fine prismatic structure parting to moderate fine angular blocky; very firm; common very fine and fine roots; few very fine and fine interstitial and tubular pores; many distinct clay films on faces of peds; many prominent black (10YR 2/1) manganese stains on faces of peds; many masses of black (10YR 2/1) manganese oxide accumulations; strongly acid; gradual smooth boundary.
2Bt7--48 to 68 inches; dark red (2.5YR 3/6) silty clay; moderate fine prismatic structure parting to moderate fine angular blocky; very firm; few very fine and fine interstitial and tubular pores; common distinct clay films on faces of peds; few distinct silt coats on faces of peds; common prominent black (10YR 2/1) manganese stains on faces of peds; common masses of black (10YR 2/1) manganese oxide accumulations; strongly acid; gradual smooth boundary.
2Bt8--68 to 80 inches; dark reddish brown (2.5YR 3/4) silty clay; moderate fine prismatic structure parting to moderate fine subangular blocky; very firm; few very fine and fine interstitial and tubular pores; common distinct clay films on faces of peds; common prominent black (10YR 2/1) manganese stains on faces of peds; many masses of black (10YR 2/1) manganese oxide accumulations; strongly acid.
TYPE LOCATION: Washington County, Missouri; about 1 mile northeast of Caledonia; USGS Belgrade quadrangle, UTM zone 15, Easting 697,376, Northing 4,184,494.
RANGE IN CHARACTERISTICS: Solum thickness and depth to bedrock ranges from 60 to more than 100 inches. Depth to the 2Bt horizon is 16 to 33 inches.
Ap or A horizon
Hue: 10YR or 7.5YR (5YR where eroded)
Value: 3 or 4
Chroma: 2 to 4
Fine-earth: silt loam
Total Rock Fragments: 0 to 30 percent gravel
Reaction: neutral to strongly acid
E and BE horizon: (Where present)
Hue: 10YR to 5YR
Value: 4 or 5
Chroma: 2 to 6
Fine-earth: silt loam
Total Rock Fragments: 0 to 30 percent gravel
Reaction: neutral to strongly acid
Bt horizon
Hue: 2.5YR to 7.5YR
Value: 3 or 4
Chroma: 4 to 6
Fine-earth: silty clay loam, silty clay, or silt loam
Total Rock Fragments: 0 to 10 percent gravel
Reaction: neutral to strongly acid
2Bt horizon
Hue: 7.5YR to 10R
Value: 3 to 5
Chroma: 4 to 8
Fine-earth: silty clay loam, silty clay, clay loam, or clay
Total Rock fragments: 0 to 60 percent: 0 to 60 percent gravel;
0 to 10 percent cobbles
Reaction: neutral to strongly acid
3Bt horizon: (Where present)
Hue: 5YR to 10R
Value: 3 to 5
Chroma: 3 to 8
Fine-earth: silty clay or clay
Total Rock fragments: 0 to 70 percent: 0 to 65 percent gravel;
0 to 10 percent cobbles
Reaction: neutral to strongly acid
COMPETING SERIES: There are no other series in this family.
GEOGRAPHIC SETTING: Courtois soils are on ridgetop and side slope positions in the larger valleys or mountain basins. Slopes are 2 to 25 percent. The soils have had a complicated geomorphic history. The upper 13 inches is loess or possibly paleosediment (old valley fill) in some pedons. A stone line (where present) represents a prior period of surface erosion and accumulation of rounded, water-worn chert gravel and cobbles. The red clay is probably lacustrine or paleosediment deposites, over residuum from dolostone. Average annual temperature ranges from 54 to 57 degrees F, and average annual precipitation ranges from 40 to 45 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Caneyville, Clarksville, Fourche, Goss, Killarney, Lowell, Useful, and Wilderness soils. Caneyville soils are moderately deep to bedrock and are on lower slopes. Clarksville, Goss, Killarney, and Wilderness soils are skeletal and on steeper slopes above the Courtois soils. Fourche soils are fine silty and have a water table, and Lowell and Useful soils are deep to bedrock and are on similar landscape positions.
DRAINAGE AND PERMEABILITY: Well drained. Runoff is low to high. Permeability is moderate. The saturated hydraulic conductivity is moderately high.
USE AND VEGETATION: Most areas have been cleared and are used for pasture and hayland. Other areas are in brushy regrowth or timber. Native vegetation is mixed hardwoods.
DISTRIBUTION AND EXTENT: The St. Francois Knobs and Basins Region (MLRA 116C) and the Ozark Highlands Region (MLRA 116A) of southern Missouri. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Morgantown, West Virginia
SERIES ESTABLISHED: Iron County, Missouri, 1988.
REMARKS: The update of November, 2002 moved the typical pedon in Washington County, Missouri. The original pedon was in an area that has been mined for barite and no longer exists.
Diagnostic horizons and features recognized in this series are:
ochric epipedon - the zone from the surface of the soil to a depth of 4 inches (Ap horizon);
argillic horizon - the zone from approximately 4 to 80 inches (Bt1, Bt2, 2Bt3, 2Bt4, 2Bt5, 2Bt6, 2Bt7, and 2Bt8
horizons);
udic moisture regime.
ADDITIONAL DATA: Missouri University soil characterization lab reference number is MO9822147. NASIS pedon ID is 98MO221177