LOCATION DILWORTH OKEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Udertic Argiustolls
TYPICAL PEDON: Dilworth silty clay loam - on 3 percent slope in native rangeland. (Colors are dry soil unless otherwise stated.)
A--0 to 7 inches; dark grayish brown (10YR 4/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; strong medium granular structure; hard, firm; common fine roots; few gravels of siltstone; mildly alkaline (pH 7.5); clear smooth boundary. (7 to 10 inches thick)
Bt--7 to 13 inches; brown (10YR 5/3) silty clay, dark brown (10YR 4/3) moist; moderate very fine subangular blocky structure, very hard, very firm; common fine roots; few distinct clay films on faces of peds; few worm casts; common very fine rounded carbonate concretions; few very fine rounded masses of calcium carbonate; few gravels of siltstone; few slightly effervescent spots (HCL, unspecified); moderately alkaline (pH 8.0); clear smooth boundary. (0 to 13 inches thick)
Btk1--13 to 18 inches; grayish brown (2.5Y 5/2) silty clay, dark grayish brown (2.5Y 4/2) moist; moderate medium and fine subangular blocky structure; very hard, very firm; few fine roots; few very fine discontinuous tubular pores; many distinct clay films on faces of peds; common fine irregular masses of calcium carbonate; few gravels of siltstone; few strongly effervescent spots (HCL, unspecified); moderately alkaline (pH 8.0); gradual smooth boundary. (4 to 23 inches thick)
Btk2--18 to 28 inches; grayish brown (2.5Y 5/2) silty clay, dark grayish brown (2.5Y 4/2) moist; moderate medium prismatic structure parting to strong medium and fine subangular blocky; very hard, very firm; few fine roots; few very fine discontinuous tubular pores; common slickensides; many distinct clay films on faces of peds; few very fine rounded carbonate concretions; common medium rounded masses of calcium carbonate; few strongly effervescent spots (HCL, unspecified); moderately alkaline (pH 8.0); clear smooth boundary. (0 to 21 inches thick)
BCk--28 to 36 inches; light brownish gray (2.5Y 6/2) silty clay, grayish brown (2.5Y 5/2) moist; moderate medium subangular blocky structure; very hard, very firm; few fine roots; few very fine discontinuous tubular pores; common coarse irregular masses of calcium carbonate; few slightly effervescent spots (HCL, unspecified); moderately alkaline (pH 8.0); clear smooth boundary. (0 to 15 inches thick)
Cr--36 to 43 inches; light brownish gray (2.5Y 6/2) weathered shale, grayish brown (2.5Y 5/2) moist; common films of calcium carbonate in cracks; moderately alkaline (pH 8.0).
TYPE LOCATION: Noble County, Oklahoma; about 7 miles East and 2 miles South of Billings; 700 ft south and 1250 ft east of the northwest corner, section 33, T. 24 N., R. 1 W.
RANGE IN CHARACTERISTICS: The thickness of the solum and the depth to shale range from 20 to 40 inches. Depth to secondary carbonates ranges from 7 to 17 inches.
The Ap or A horizon has hue of 7.5YR to 2.5Y, value 3 to 5, and chroma of 1 to 3. Some pedons have hue of 5YR in this horizon where colluvial surface is influenced by red sandstone and shale. Texture is silty clay loam or gravelly silty clay loam. Reaction ranges from neutral to moderately alkaline.
The Bt horizon has hue of 7.5YR to 5Y, value 4 to 6, and chroma of 1 to 3. Texture is silty clay loam or silty clay.
The Btk1 horizon has hue of 10YR to 5Y, value 5 or 6, and chroma of 1 to 4. Texture is silty clay or gravelly silty clay.
The Btk2 horizon has hue of 2.5Y or 5Y, value 5 or 6, and chroma of 1 or 2.
The BCk horizon has hue of 2.5Y or 5Y, value 5 to 7, and chroma of 1 or 2.
The Cr horizon has hue of 2.5Y or 5Y, value 5 to 7, and chroma of 1 to 4. It is weathered shale but some pedons have thin strata of red sandstone.
COMPETING SERIES: These are the Brewer, Brewless, Piedmont, Renthin, Westsum, and Wetbeth series in the same family. Brewer and Brewless soils are on floodplains. Piedmont and Renthin soils have hue of 5YR or redder throughout. Also, Renthin soils have depth to shale greater than 40 inches. Westsum soils have depth to shale greater than 60 inches. Wetbeth soils are developed in alluvium, and are very deep.
GEOGRAPHIC SETTING: Dilworth soils are on gently sloping to strongly sloping shoulder slopes and backslopes of hills on uplands in the Central Rolling Red Prairies (MLRA 80A). Slopes range from 3 to 12 percent. The soil formed in colluvial over residual material weathered from clayey, gray Permian shale. Mean annual temperature ranges from 57 to 61 degrees F. The mean annual precipitation is 30 to 36 inches. Thornthwaite annual P-E indices range from 48 to 60.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Grainola series, and the Highview, Lucien, and Westsum series. The Grainola soils are on similar positions where the shales are redder. The Highview soils are on adjacent steep backslopes. The Lucien soils are on summits or shoulder slopes above the Dilworth soils. The Westsum soils are on very gently sloping or gently sloping lower foot slopes and back slopes.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; slow permeability.
USE AND VEGETATION: The principal use is rangeland. Some areas are cultivated to small grains or grain sorghums. Native vegetation is little bluestem, sideoats grama, dropseed, silver bluestem, hairy grama, blue grama, and buffalograss.
DISTRIBUTION AND EXTENT: Central Rolling Red Prairies of Oklahoma and possibly Kansas. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES PROPOSED: Noble County, Oklahoma; 1991.
REMARKS: Dilworth soils were formerly included in the Owens series in the earlier soil survey of Noble County and Kay County, Oklahoma.
Diagnostic horizons and features recognized in this pedon: Mollic Epipedon - the zone from the surface to 7 inches (A horizon). Argillic horizon - the zone from 7 to 28 inches (Bt horizon).
Soil Interpretation Record: OK0390 Dilworth Series