LOCATION ROARK OKEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Pachic Argiustolls
TYPICAL PEDON: Roark loam--on 0.5 percent slope in cropland. (Colors are for dry soil unless otherwise stated.)
Ap--0 to 10 inches; brown (7.5YR 4/2) loam, dark brown (7.5YR 3/2) moist; moderate fine and medium granular structure; slightly hard, very friable; few fine roots; few fine pores; noneffervescent; neutral; clear smooth boundary. (8 to 17 inches thick)
Bt--10 to 24 inches; brown (7.5YR 4/2) clay loam, dark brown (7.5YR 3/2) moist; moderate medium and coarse prismatic structure parting to moderate and strong medium subangular blocky; hard, firm; few very fine and fine roots; few fine pores; common distinct clay films on surfaces of peds and in pores; noneffervescent; slightly alkaline; clear smooth boundary. (8 to 44 inches thick)
Btkl--24 to 34 inches; brown (7.5YR 5/3) clay loam, brown (7.5YR 4/3) moist; moderate coarse prismatic structure parting to moderate medium subangular blocky; very hard, firm; few fine roots; few fine pores; many distinct clay films on surfaces of peds and in pores; common fine and medium concretions and few fine and medium masses of calcium carbonate; slightly effervescent; moderately alkaline; gradual smooth boundary.
Btk2--34 to 49 inches; brown (7.5YR 5/4) clay loam, brown (7.5YR 4/4) moist; moderate coarse prismatic structure parting to moderate medium subangular blocky; very hard, firm; few fine roots; few fine pores; common distinct clay films on surfaces of peds; common fine and medium concretions and common fine and medium masses of calcium carbonate; strongly effervescent; moderately alkaline; clear smooth boundary.
Btk3--49 to 67 inches; reddish yellow (7.5YR 7/6) loam, reddish yellow (7.5YR 6/6) moist; weak coarse prismatic structure parting to moderate medium subangular blocky; hard, firm; few fine roots; few fine pores; common faint clay films on surfaces of peds; common fine and medium distinct yellowish red (5YR 5/8) iron concentrations and common fine and medium prominent dark grayish brown (10YR 4/2) iron depletions; common fine and medium concretions and few fine and medium masses of calcium carbonate; strongly effervescent; moderately alkaline; clear smooth boundary. (combined thickness of the Btk is 10 to 50 inches)
2C--67 to 80 inches; yellowish red (5YR 5/6) clay loam, yellowish red (5YR 4/6) moist; massive; very hard, firm; slightly effervescent; moderately alkaline.
TYPE LOCATION: Jackson County, Oklahoma; from the intersection of U. S. Highways 62 and 283 in Altus; 6 miles north on U. S. Highway 283; 2 miles west and 1 mile north on county road; 1,600 feet west on county road; 50 feet south in cropland. (50 feet south and 1600 feet west of the northeast corner of sec. 14, T.3 N., R.21 W). USGS Altus quad; (Latitude: 34N, 44, 22; Longitude: 99W, 22, 29)
RANGE IN CHARACTERISTICS: Solum thickness ranges from 60 to 80 inches. Depth to secondary calcium carbonate ranges from 20 to 40 inches. Depth to redoximorphic features having a chroma of 2 or less ranges from 40 to 60 inches. The mollic epipedon is more than 20 inches thick. Weighted average clay content of the particle-size control section ranges from 35 to 45 percent.
The A horizon has hue of 7.5YR or 10YR, value of 4, and chroma of 2 or 3. Texture is loam or clay loam. Reaction ranges from slightly acid to slightly alkaline.
The Bt horizon has hue of 5YR to 10YR, value of 4 or 5, and chroma of 2 or 3. Texture is clay loam, silty clay loam, or clay. Reaction is slightly alkaline or moderately alkaline.
The Btk, or lower Bt horizons, have hue of 5YR to 10YR, value of 4 to 7, and chroma of 2 to 6. Texture is clay loam, silty clay loam, or clay, and includes sandy clay loam and loam below a depth of 40 inches. Reaction is moderately alkaline. Visible carbonates range from 0 to 5 percent by volume and calcium carbonate equivalent ranges from 1 to 10 percent. Redoximorphic features in the form of reddish concentrations and/or grayish depletions range from 0 to 5 percent.
The BC or BCk horizon, where present, has hue of 5YR to 10YR, value of 5 to 7, and chroma of 2 to 6. Texture is loam, clay loam, sandy clay loam, fine sandy loam, or silty clay loam. Reaction is moderately alkaline. Visible carbonates range up to 10 percent by volume. Redoximorphic features in the form of reddish concentrations and/or grayish depletions range from 0 to 5 percent.
The C horizon has color and reaction similar to the BC horizon. Texture is variable and ranges from silty clay loam to loamy sand and is stratified in some pedons.
COMPETING SERIES: These are the Abilene, Blanket, Dodson, McLain, Tenaga, and Wolco series in the same family. Abilene and Blanket soils have a calcic horizon and do not have redoximorphic features in the lower part of the solum. Dodson soils formed in more silty sediments, are underlain with Permian redbed materials, and do not have redoximorphic features in the lower part of the solum. McLain soils occur on floodplains and are moist for longer periods. Tenaga soils are dry for longer periods. Wolco soils are deep to hard limestone bedrock and are moist for longer periods.
GEOGRAPHIC SETTING: Roark soils are on nearly level to very gently sloping broad terraces of major rivers. These soils formed in alluvial sediments of late Pleistocene age. Slopes range from 0 to 3 percent. Mean annual precipitation ranges from 20 to 28 inches. Mean annual temperature ranges from 59 to 64 degrees F. Frost free days range from 200 to 230 days and elevation ranges from 1,000 to 2,100 feet. Thornthwaite P-E indices ranges from 32 to 44.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Frankirk, Grandfield, Grandmore, Madge, Tipton, and Ozark series. Frankirk soils are on more sloping areas and have a mollic epipedon less than 20 inches thick. Grandfield and Grandmore soils are on higher landscape positions, have an ochric epipedon, and have a fine-loamy particle-size control section. Madge, Tipton, and Ozark soils are on similar landscape positions and have a fine-loamy particle-size control section Also, Madge and Ozark soils have a mollic epipedon less than 20 inches thick.
DRAINAGE AND PERMEABILITY: Roark soils are well drained. Permeability is slow. Runoff is medium on 0 to 1 percent slopes and high on 1 to 3 percent slopes. Depth to a water table ranges from 50 to more than 80 inches from October to May during wet years.
USE AND VEGETATION: Roark soils are used almost entirely for cropland. The major crops are cotton, wheat, and grain sorghum. Native vegetation is a mixed grass prairie.
DISTRIBUTION AND EXTENT: The Central Rolling Red Plains of western Oklahoma and possibly northwestern Texas LRR H (MLRA 78C). The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas.
SERIES ESTABLISHED: Jackson County, Oklahoma; 2000. The name is from a small town.
REMARKS: These soils were formerly included with the Abilene series.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon--0 to 24 inches (A & Bt horizons).
Argillic horizon--10 to 67 inches (Bt & Btk horizons).
The assignment of the cation-exchange activity class is based on lab data from Jackson County, OK.
Range Site: Loamy Prairie - 078CY056OK
ADDITIONAL DATA: NSSL data from Jackson County, OK (S96OK-065-007,008,009,011) (S97OK-065-007,008).
TAXONOMIC VERSION: Soil Taxonomy, Second Edition, 1999.