LOCATION CLAFORK MOEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Aquertic Hapludalfs
TYPICAL PEDON: Clafork silt loam - on a linear summit of 3 percent slope in cropland at an elevation of 910 feet. (Colors are for moist soil unless otherwise stated.)
Ap--0 to 8 inches; very dark grayish brown (10YR 3/2) silt loam, grayish brown (10YR 5/2) dry; weak fine granular structure; friable; many very fine roots; few fine iron and manganese oxide accumulations; neutral; abrupt smooth boundary. (6 to 10 inches thick)
E--8 to 11 inches; brown (10YR 5/3) silt loam, weak medium platy structure parting to weak very fine subangular blocky; friable; many very fine roots; few fine prominent strong brown (7.5YR 5/8) masses of iron accumulation throughout; few fine iron and manganese oxide accumulations; common distinct silt coats on faces of peds; slightly acid; clear smooth boundary. (0 to 6 inches thick)
Bt--11 to 16 inches; dark yellowish brown (10YR 4/4) and grayish brown (10YR 5/2) silty clay loam, moderate very fine subangular blocky structure; firm; common very fine roots; common distinct clay films on faces of peds; common fine prominent red (2.5YR 4/8) masses of iron accumulation throughout; few fine iron and manganese oxide accumulations; the areas with grayish brown are iron depletions; few distinct silt coats on faces of peds; strongly acid; clear smooth boundary. (0 to 8 inches thick)
Btg1--16 to 23 inches; dark grayish brown (10YR 4/2) and dark yellowish brown (10YR 4/4) silty clay; strong very fine subangular blocky structure; very firm; few very fine roots; many prominent clay films on faces of peds; common fine prominent red (2.5YR 4/8) masses of iron accumulation throughout; few fine iron and manganese oxide accumulations; strongly acid; gradual smooth boundary.
Btg2--23 to 31 inches; dark grayish brown (10YR 4/2) and dark yellowish brown (10YR 4/4) silty clay; strong very fine subangular blocky structure; very firm; few very fine roots; many distinct clay films on faces of peds; common fine prominent strong brown (7.5YR 4/6) masses of iron accumulation throughout; few fine iron and manganese oxide accumulations; moderately acid; gradual smooth boundary.
Btg3--31 to 39 inches; grayish brown (10YR 5/2) and dark yellowish brown (10YR 4/4) silty clay loam; moderate fine subangular blocky structure; firm; few very fine roots; common distinct clay films on faces of peds; common fine prominent strong brown (7.5YR 4/8) masses of iron accumulation throughout; common fine iron and manganese oxide accumulations; slightly acid; gradual smooth boundary. (Combined thickness of the Btg horizons is 12 to 24 inches.)
2Btgx1--39 to 49 inches; grayish brown (10YR 5/2) and yellowish brown (10YR 5/4) silty clay loam; moderate medium prismatic structure; very firm; few very fine roots; few distinct clay films on vertical faces of peds; 40 percent weak brittleness; common fine prominent strong brown (7.5YR 5/8) masses of iron accumulation throughout; few fine iron and manganese oxide accumulations; few distinct silt coats on vertical faces of peds; neutral; clear smooth boundary.
2Btgx2--49 to 59 inches; grayish brown (10YR 5/2) silt loam; weak coarse prismatic structure; very firm; few very fine roots; few distinct clay films in root channels and vertical faces of peds; 50 percent weak brittleness; common fine prominent strong brown (7.5YR 4/8) and common fine distinct yellowish brown (10YR 5/4) masses of iron accumulation throughout; few fine iron and manganese oxide accumulations; 4 percent chert gravel; many distinct silt coats on vertical faces of peds; slightly alkaline; clear smooth boundary. (Combined thickness of the 2Btx horizons is 10 to 30 inches.)
3Btgx3--59 to 72 inches; grayish brown (10YR 5/2) very gravelly silt loam; weak fine subangular blocky structure; firm; few very fine roots; few distinct clay films on faces of peds; 40 percent weak brittleness; common fine prominent strong brown (7.5YR 4/8) masses of iron accumulation throughout; few fine iron and manganese oxide accumulations; 50 percent chert gravel, slightly alkaline; clear smooth boundary. (0 to 15 inches thick)
4Bt--72 to 80 inches; red (2.5YR 4/8) and dark red (2.5YR 3/6) very gravelly silty clay; strong very fine subangular blocky structure; very firm; few very fine roots; common pressure faces; many prominent clay films on faces of peds; few fine iron and manganese oxide stains; 50 percent chert gravel; 10 percent chert cobbles; slightly alkaline; gradual smooth boundary.
TYPE LOCATION: Cooper County, Missouri; about 6 miles west and 8 miles south of Prairie Home; 1600 feet west and 1670 feet south of the northeast corner of sec. 6, T. 45 N., R. 16 W.; USGS Clarksburg quadrangle, lat. 38 degrees, 41 minutes 45 seconds N. and long. 92 degrees 42 minutes 51 seconds W.
RANGE IN CHARACTERISTICS: Depth to the top of the brittle layer is 30 to 40 inches. Depth to the gravelly 3Btgx or 4Bt horizon typically is 40 to 60 inches. In some pedons the 2Btx horizon may extend below 60 inches.
The A horizon has hue of 10YR or 7.5YR, value of 2 or 3, 4 or 5 dry and chroma of 2 or 3. It is silt loam or silty clay loam and strongly acid to neutral.
The E horizon has hue of 10YR or 7.5YR, value of 4 to 7 and chroma of 2 to 4. It is silt loam or silty clay loam. Reaction is strongly acid to neutral. Some eroded pedons do not have an E horizon.
The Bt and Btg horizons have hue of 7.5YR to 2.5Y, value of 4 or 5, and chroma of 2 to 6. They are silty clay loam or silty clay. Reaction is very strongly acid to slightly acid.
The 2Btgx horizon has hue of 10YR or 2.5Y, value of 4 to 6, and chroma of 2 to 4. It is silt loam or silty clay loam. Brittleness ranges from 20 to 60 percent. Reaction is strongly acid to moderately alkaline.
The 3Btgx horizon has hue of 10YR to 2.5YR, value of 3 to 6, and chroma of 1 to 6. It is very gravelly or extremely gravelly analogues of silt loam or silty clay loam. Reaction is moderately acid to moderately alkaline.
The 4Bt horizon has hue of 7.5YR to 2.5YR, value of 3 to 6, and chroma of 1 to 8. It is very gravelly and extremely gravelly analogues of silty clay loam or silty clay. It is moderately acid to moderately alkaline. Some pedons have silty clay or clay horizons or their gravelly analogues on more sloping area.
COMPETING SERIES: These are the Armstrong, Hoyleton, Malmo, Mystic, Pering, and Sunbury series. These soils do not have brittle horizons in the middle part of the series control section. In addition, Armstrong soils have a stone line in the upper part of the sola, Malmo soils have free cartonates at 15 to 40 inches, Mystic soils have a mean annual temperature of 50 to 54 degrees F., and Sunbury soils have free carbonates at 45 to 60 inches and a mean annual temperature of 50 to 54 degrees F..
GEOGRAPHIC SETTING: Clafork soils are on summits and backslopes of upland landforms and formed in loess and the underlying residuum from cherty limestone. Slopes range from 2 to 9 percent. As slope and erosion increases, the gravelly and clayey 4Bt horizons occur within 60 inches. The mean annual temperature ranges from 53 to 58 degrees F, and mean annual precipitation ranges from 38 to 48 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Crestmeade, Maplewood, and Cotton soils. The Crestmeade soils have a mollic epipedon and are on higher more stable summits. The Maplewood soils have gravelly subsoil layers at 20 to 40 inches and are on lower areas of the landform. Cotton soils have a lighter colored surface layer and are on lower more convex areas of the landform.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained. Runoff is medium or high. Permeability is moderately slow. In undisturbed areas, the upper depth of a perched water table is 1.0 to 2.0 feet during November to April in most years.
USE AND VEGETATION: Clafork soils are used for cultivated crops, pasture, or hayland. Native vegetation is mixed grassland and deciduous trees.
DISTRIBUTION AND EXTENT: Ozark border area (MLRA 116B) of central Missouri. The series is of minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Morgantown, West Virginia
SERIES ESTABLISHED: Cooper County, Missouri, 1994.
REMARKS: Diagnostic horizons and features recognized in this series are: ochric epipedon - the zone from the surface of the soil to a depth of 11 inches (Ap and E horizons);
argillic horizon - the zone from approximately 11 to 80 inches (Bt, Btg1, Btg2, Btg3, 2Btgx1, 2Btgx2, 3Btgx3, and 4Bt horizons).
ADDITIONAL DATA: University of Missouri soil characterization Laboratory sample number M9005302,