LOCATION OKATON SDEstablished Series
TAXONOMIC CLASS: Clayey, smectitic, calcareous, mesic, shallow Typic Ustorthents
TYPICAL PEDON: Okaton clay - on a northwest-facing slope of 15 percent in native grassland. When described the soil was moist to 15 inches. (Colors are for dry soil unless otherwise stated.)
A--0 to 2 inches; grayish brown (2.5Y 5/2) clay, dark grayish brown (2.5Y 4/2) moist; moderate fine and very fine granular structure; slightly hard, friable, slightly sticky; many roots; strong effervescence; slightly alkaline; gradual smooth boundary. (1 to 4 inches thick)
AC--2 to 8 inches; grayish brown (2.5Y 5/2) silty clay, dark grayish brown (2.5Y 4/2) moist; weak coarse subangular blocky and weak coarse granular structure; hard, friable, sticky and slightly plastic; common fine fragments of shale; many fine roots; strong effervescence; slightly alkaline; gradual wavy boundary. (0 to 12 inches thick)
C--8 to 14 inches; grayish brown (2.5Y 5/2) clay, dark grayish brown (2.5Y 4/2) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; 70 percent by volume fragments of shale; few fine accumulations of carbonate; many fine roots; strong effervescence; slightly alkaline; clear smooth boundary. (4 to 8 inches thick)
Cr1--14 to 21 inches; grayish brown (2.5Y 5/2) fractured shale, dark grayish brown (2.5Y 4/2) moist; thin seams of yellowish brown (10YR 5/6) between shale plates, dark yellowish brown (10YR 4/6) moist; rock structure evident; easily dug with spade; common fine and medium roots; slight effervescence; slightly alkaline; clear smooth boundary.
Cr2--21 to 30 inches; light brownish gray (2.5Y 6/2) bedded shale, dark grayish brown (2.5Y 4/2) moist; thin seams of light yellowish brown (10YR 6/4) between shale plates, yellowish brown (10YR 5/4) moist; rock structure evident; easily dug with spade; common fine nests of gypsum in seams; slight effervescence; slightly alkaline; gradual smooth boundary.
Cr3--30 to 60 inches; light brownish gray (2.5Y 6/2) bedded shale, dark grayish brown (2.5Y 4/2) moist; thin seams of light yellowish brown (2.5Y 6/4) between shale plates, olive brown (2.5Y 4/4) moist; easily dug with spade; slight effervescence; moderately alkaline.
TYPE LOCATION: Jones County, South Dakota; about 14 miles north of Murdo; 1,620 feet north and 50 feet west of the southeast corner of sec. 26, T. 2 N., R. 28 E.
RANGE IN CHARACTERISTICS: The depth to bedrock ranges from 8 to 20 inches; The soil typically is slightly hard and friable and ranges from soft to hard and from friable to firm. The soil is slightly or moderately alkaline throughout and has a calcium carbonate equivalent ranging from 5 to 15 percent. COLE ranges from 0.05 to 0.10. The underlying shale contains varying amounts of gypsum and other salts. Plant roots are few to many and extend into the upper part of the underlying shale. Some pedons have stones and boulders on the surface.
The A1 horizon has hue of 10YR or 2.5Y, value of 5 to 7 and 3 to 5 moist, and chroma of 2 to 4. It is silty clay or clay.
The AC horizon has hue of 10YR or 2.5Y, value of 5 to 7 and 4 to 6 moist, and chroma of 2 to 4. It is silty clay or clay averaging between 45 and 55 percent clay and 35 and 50 percent silt. Some pedons have accumulations of gypsum.
The C horizon has the same color as the AC horizon and is clay or silty clay that contains from 35 to 90 percent by volume of shale fragments. Some pedons have accumulations of gypsum.
The Cr horizon has hue of 10YR or 2.5Y, value of 5 to 7 and 4 to 6 moist, and chroma of 2 to 4. The shale chips are brittle, noncohesive and are loose. Calcium carbonate, calcium sulfate, and other salts are in cracks and along cleavage planes of the shale. The shale is mildly or moderately alkaline.
COMPETING SERIES: This is the Sansarc series. Sansarc soils have less carbonates, contain more clay, and have a COLE of more than 0.10.
GEOGRAPHIC SETTING: The Okaton soils are on moderately sloping to steep breaks of the dissected shale plains. Slope gradients range from 6 to 65 percent. The Okaton soils formed in residuum weathered from oxidized clay shales. Mean annual temperature ranges from 45 to 50 degrees F, and mean annual precipitation ranges from 15 to 24 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Lakoma, Murdo, Sansarc, and Schamber soils. Lakoma soils have shale between depths of 20 and 40 inches and are on more stable landscapes above or below the the Okaton soils in the landscape. Murdo soils are on similar topography above the Okaton soils and have sand and gravel between depths of 12 and 20 inches. Sansarc soils have less carbonates, contain more clay, and are on similar topography below the Okaton soils. Schamber soils are sandy-skeletal and are on ridges and terrace fronts above the Okaton soils.
DRAINAGE AND PERMEABILITY: Well drained. Runoff is very high. Permeability is slow.
USE AND VEGETATION: Mostly in native grassland. Native vegetation is mainly sideoats grama, little bluestem, sedges, western wheatgrass, and yucca.
DISTRIBUTION AND EXTENT: Central and south-central South Dakota. This series is extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Tripp County, South Dakota, 1975.
REMARKS: The Okaton soils were included in the Samsil and Sansarc series in soil surveys made prior to 1975. Diagnostic horizons and features recognized are: ochric epipedon - the zone from the surface to about 8 inches.
ADDITIONAL DATA: Reference: Soil No. S73SD-037-1, Lincoln Soil Survey Lab. No. 73L1373-73L1378.