LOCATION OKLARK OKEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, thermic Aridic Calciustolls
TYPICAL PEDON: Oklark loam--on a 14 percent slope--rangeland.
(Colors are for dry soil unless otherwise stated.)
A--0 to 10 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium granular structure; slightly hard, friable; many fine and common medium roots; many wormcasts; few fine calcium carbonate concretions; strongly effervescent; moderately alkaline; gradual smooth boundary. (7 to 13 inches thick)
Bk--10 to 16 inches; brown (10YR 5/3) loam, dark brown (10YR 4/3) moist; weak medium prismatic structure parting to weak fine and medium subangular blocky; slightly hard, friable; many fine and medium roots; common wormcasts; common fine and medium calcium carbonate concretions; few fine soft masses of calcium carbonate; violently effervescent; moderately alkaline; clear wavy boundary. (0 to 17 inches thick)
BCk--16 to 28 inches; pink (7.5YR 7/4) loam, light brown (7.5YR 6/4) moist; moderate coarse prismatic structure; slightly hard, friable; few fine and medium roots mainly between peds; in the upper 6 inches the prisms are surrounded with brown material, similar to the Bk, that is 1 to 3 inches wide at the tops of the prisms and thins with depth; many threads of calcium carbonate; many fine and few coarse calcium carbonate concretions; about 25 percent by volume of soft masses of calcium carbonate; the masses of calcium carbonate are platy and slightly brittle; violently effervescent; moderately alkaline; abrupt wavy boundary. (0 to 14 inches thick)
Ck--28 to 80 inches; reddish yellow (7.5YR 8/6) loam, reddish yellow (7.5YR 7/6) moist; massive; slightly hard, friable; thick strata of coarser and finer material occurs below 40 inches; common films and soft masses of calcium carbonate; violently effervescent; moderately alkaline.
TYPE LOCATION: Woods County, Oklahoma; about 25 miles west and 10 miles north of Alva, Oklahoma; about 1,710 feet north and 1,500 feet west of the southeast corner of sec. 35, T. 29 N., R. 18 W.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 20 to 40 inches. Between the base of the A horizon and depth of 40 inches the soil contains a zone of accumulation of calcium carbonate that is greater than 5 percent visible carbonates and has a calcium carbonate equivalent of 15 percent or more. Depth to the calcic horizon ranges from 8 to 28 inches. Below a depth of 24 inches, some pedons have a layer of calcium carbonate that is partially indurated, but do not contain a petrocalcic horizon. The average clay content of the 10 to 40 inch section ranges from 10 to 18 percent. Thickness of the mollic epipedon ranges from 7 to 13 inches. Coarse pebbles less than 76 mm in diameter make up 0 to 5 percent of all horizons.
The A horizon has hue of 7.5YR or 10YR, value of 4 or 5, and chroma of 2 or 3. Texture is loam, clay loam, sandy loam, or fine sandy loam. Reaction is slightly or moderately alkaline.
The Bk horizon has hue of 7.5YR or 10YR, value of 4 to 6, and chroma of 2 to 6. Texture is loam, sandy loam, or fine sandy loam. Some pedons lack Bk horizons. Reaction is slightly or moderately alkaline.
The BCk horizon has hue of 7.5YR or 10YR, value of 5 to 8, and chroma of 3 to 6. Texture is loam, sandy loam, or fine sandy loam.
The Ck horizon has hue of 7.5YR or 10YR, value of 5 to 8, and chroma of 3 to 6. Texture is loam, sandy loam, or fine sandy loam. Some pedons contain strata of clay loam.
COMPETING SERIES: This is the Pyeatt (AZ) series in the same family. Soils in similar families are the Clark, Engle, Mansic, and Portales series. Pyeatt soils occur at elevations above 4500 feet and have fewer frost free days. Clark, Engle, Mansic, and Portales soils have a fine-loamy control section. In addition, Clark soils have a mesic temperature regime and Portales soils are dry for longer periods of time. Engle soils have a Cr horizon and are moderately deep over calcareous sandstone.
GEOGRAPHIC SETTING: Oklark soils are on very gently sloping to steep side slopes and foot slopes of uplands in the Southern High Plains Breaks (MLRA 77E). Slopes range from 1 to 30 percent. They formed in calcareous alluvium of the Ogallala formation of Tertiary age. Climate is subhumid dry. Mean annual precipitation ranges from 20 to 26 inches. Mean annual temperature ranges from 57 to 61 degrees F. Thornthwaite annual P-E indices ranges from 32 to 40. Frost free days range from 190 to 210.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Abbie,
Case,
Farry,
Fortyone,
Irene,
Mansic,
Teagard,
Wellsford, and
Woods series. Mansic soils occur on similar landscapes. Abbie soils occur on slightly higher landscapes and have argillic horizons and have a fine-loamy control section. Case soils do not have mollic surfaces and occur on slightly higher landscapes. Fortyone soils occur on slightly higher landscapes and have argillic horizons and do not have calcic horizons. Irene soils occur on slightly higher landscapes and have argillic horizons, have fine-silty control section, and do not have a calcic horizon. Farry soils occur on slightly higher landscapes and have argillic horizons, have a fine-loamy control section, and do not have a calcic horizon.
Teagard, Wellsford and Woods soils have clayey textural control sections and occur at lower positions on the landscape.
DRAINAGE AND PERMEABILITY: Oklark soils are well drained; runoff is very low to high; permeability is moderate to moderately rapid.
USE AND VEGETATION: Used mainly for rangeland. Some of the less sloping areas are cultivated to small grains. Native vegetation is mid and tall grasses.
DISTRIBUTION AND EXTENT: Southern High Plains Breaks (MLRA 77E) of Oklahoma and possibly Kansas and Texas. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Woods County, Oklahoma; 1995.
REMARKS: Oklark soils were formerly included in the Potter series in the earlier soil survey of Woods County, Oklahoma; 1939 series.
Soil Interpretation Record: Series OK0339
Diagnostic horizons and features recognized in this pedon:
Mollic epipedon - the zone from the surface of the soil to a depth of approximately 13 inches (A horizon.)
Cambic horizon - the zone from approximately 10 to 16 inches (Bw horizon).
Calcic horizon - the zone from approximately 16 to 28 inches (BCk horizon).
Moisture Regime: Aridic-Ustic.
ADDITIONAL DATA: Oklahoma State University; lab sample 82-OK-151-5.