LOCATION FOURCHE MOEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, active, mesic Glossaquic Paleudalfs
TYPICAL PEDON: Fourche silt loam - on an 8 percent south-facing slope in a grass-legume pasture at an elevation of 920 feet. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 7 inches; brown (10YR 4/3) silt loam; moderate fine granular structure; friable; many very fine roots; neutral; abrupt smooth boundary. (5 to 10 inches thick)
Bt1--7 to 14 inches; yellowish brown (10YR 5/4) silt loam; weak fine and very fine subangular blocky structure; friable; common very fine roots; few faint clay films on faces of peds; few fine dark brown (10YR 3/3) masses of iron and manganese accumulation; slightly acid; clear smooth boundary. (4 to 12 inches thick)
Bt2--14 to 23 inches; brown (7.5YR 5/4) silty clay loam; moderate fine and very fine subangular blocky structure; friable; common very fine roots; common faint clay films on faces of peds; common fine distinct yellowish red (5YR 4/6) masses of iron accumulation; few fine black iron and manganese concretions; strongly acid; clear smooth boundary. (Combined thickness of the Bt horizon is 10 to 30 inches.)
2Bt/E--23 to 33 inches; yellowish red (5YR 4/6) silty clay loam (2Bt); strong brown (7.5YR 5/6) kneaded, moderate fine and medium prismatic structure parting to moderate medium subangular blocky; firm; light yellowish brown (10YR 6/4) silt loam (E) 1 to 5 mm thick covering faces of peds, very pale brown (10YR 8/3) dry; common very fine roots; few faint clay films on surfaces of peds; common fine black masses of iron and manganese accumulation; few fine black iron and manganese concretions; strongly acid; clear wavy boundary. (4 to 23 inches thick)
3Bt1--33 to 52 inches; yellowish red (5YR 4/6) silty clay; moderate fine subangular blocky structure; very firm; few very fine roots; common brown clay films on faces of peds and lining pores; few medium distinct light brownish gray (2.5Y 6/2) iron depletions; many black masses of iron and manganese accumulation; many fine black iron and manganese concretions; slightly acid; gradual smooth boundary.
3Bt2--52 to 80 inches; strong brown (7.5YR 5/6) silty clay; moderate and weak fine subangular blocky structure; firm; brown clay films on faces of peds and line pores; few fine light gray (2.5Y 7/2) iron depletions; neutral; abrupt smooth boundary. (Combined thickness of 3Bt horizon is 25 to more than 50 inches.)
3R--80 inches; dolomite
TYPE LOCATION: St. Francois County, Missouri; one mile north of Farmington; 200 feet south and 150 feet west of northwest corner, sec. 25, T. 36 N., R. 5 E; USGS Farmington quadrangle, lat. 37 degrees 48 minutes 14 seconds N. and long 90 degrees 25 minutes 19 seconds W.
RANGE IN CHARACTERISTICS: Thickness of the solum and depth to bedrock are about 60 to more than 100 inches. The upper solum formed in 18 to 36 inches of loess.
The A horizon has hue of 10YR, value of 4, and chroma of 2 to 4. It is silt loam except for eroded areas which are silty clay loam. It is medium acid to neutral.
The AB (where present) and Bt horizons have hue of 10YR or 7.5YR, value of 4 to 6, and chroma of 3 to 6. Texture is silty clay loam or silt loam. Reaction is very strongly acid to slightly acid.
In the 2Bt/E horizon, the 2Bt portion has hue of 2.5YR to 10YR, value of 3 to 6, and chroma of 4 to 6. Some pedons are mottled with gray colors. It is silty clay loam, silty clay, or clay. The E portion is discontinuous silt loam material that makes up 5 to 20 percent of the horizon and are 1 to 5 mm thick on surfaces of peds. It has hue of 10YR, value of 5 to 7, and chroma of 1 to 4. This horizon is very strongly acid to medium acid. Common to many masses and concretions of iron and manganese accumulations may be present.
The 3Bt horizon has hue of 10YR to 2.5YR, value of 3 to 5, and chroma of 4 to 8, and commonly has mottles with lower chroma. It is silty clay loam, silty clay, or clay. Reaction is very strongly acid to moderately alkaline.
Some pedons have a C horizon.
COMPETING SERIES: There are no other series in this family.
GEOGRAPHIC SETTING: Fourche soils are on upland side slopes with even or slightly concave surfaces and point ridgetops. Slope gradients commonly are 5 to 9 percent but range from 2 to 15 percent. The soils formed in loess and the underlying residuum from dolomite or limestone. The bedrock in some places is glauconitic or interbedded with shale. Mean annual temperature ranges from 55 to 57 degrees F, and the mean annual precipitation is about 40 to 45 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Auxvasse, Caneyville, Crider, Gasconade, and Hildebrecht soils. Auxvasse soils are poorly drained. Caneyville soils are underlain by dolomite between 20 to 40 inches. Crider soils do not have glossic properties and are on similar landscape postions. Gasconade soils are less than 20 inches to bedrock and have a mollic epipedon. Hildebrecht soils have a fragipan and commonly are on higher ridgetops. Auxvasse, Caneyville, and Gasconade soils are on lower landscape positions.
DRAINAGE AND PERMEABILITY: Moderately well drained. Runoff is medium. Permeability is moderately slow. There is a perched water table 1.5 to 3 feet below the surface at sometime from November to May in most years.
USE AND VEGETATION: Mostly used for pasture, hay, and some cultivated crops. Tall fescue is the principal grass and corn, grain sorghum, and wheat are the principal cultivated crops. Native vegetation is mixed hardwoods.
DISTRIBUTION AND EXTENT: The Ozarks Border Region (MLRA 116B) of eastern Missouri. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Morgantown, West Virginia
SERIES ESTABLISHED: St. Francois County, Missouri, 1979.
REMARKS: Fourche soils were originally classified as Glossic Paleudalfs, but additional mapping shows that this soil best classifies as a Glossaquic Paleudalf.
Diagnostic horizons and features recognized in this series are:
ochric epipedon - the zone from the surface of the soil to a depth of 7 inches (Ap horizon);
argillic horizon - the zone from approximately 7 to 80 inches (Bt1, Bt2, 2Bt/E, 3Bt1, and 3Bt2 horizons).
Glossic horizon - the zone from 23 to 33 inches (2Bt/E horizon)