LOCATION SIMMONT WYEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Aridic Argiustolls
TYPICAL PEDON: Simmont sandy loam - grassland (Colors are for dry soils unless otherwise noted.)
A--0 to 5 inches; grayish brown (10YR 5/2) extremely stony sandy loam, very dark grayish brown (10YR 3/2) moist; moderate fine crumb and granular structure; soft, very friable; 70 percent stone most of which is more than 10 inches in diameter; neutral (pH 6.8); clear smooth boundary. (4 to 8 inches thick)
AB--5 to 9 inches; brown (10YR 5/3) extremely stony light sandy clay loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure that parts to moderate fine granules; slightly hard, very friable, few faint clay films on faces of peds and discontinuous clay films in root channels; 70 percent coarse fragments most of which are larger that 10 inches in diameter; neutral (pH 7.0); clear smooth boundary. (3 to 6 inches thick)
Bt--9 to 18 inches; brown (10YR 5/3) extremely stony sandy clay loam, brown (10YR 4/3) moist; moderate medium subangular blocky structure; hard, very friable; many faint clay films on faces of peds, faint nearly continuous clay films in root channels, clay films on coarse fragments; 70 percent coarse fragments, most of which is larger than 10 inches in diameter; neutral (pH 7.0); gradual wavy boundary. (5 to 11 inches thick)
BC--18 to 22 inches; yellowish brown (10YR 5/4) extremely stony light sandy clay loam, dark yellowish brown (10YR 4/4) moist; weak medium subangular blocky structure; hard, very friable; few faint clay films and some on coarse fragments and in root channels; 70 percent stone; neutral (pH 7.0); gradual wavy boundary. (3 to 5 inches thick)
C--22 to 30 inches; yellowish brown (10YR 5/4) extremely stony fine sandy loam, dark yellowish brown (10YR 4/4) moist; massive; slightly hard, very friable; 70 percent coarse fragments; neutral (pH 7 0); abrupt wavy boundary. (O to 25 inches thick)
R--30 to 32 inches; hard noncalcareous continuous sandstone bedrock.
TYPE LOCATION: Johnson County, Wyoming; near the center of sec. 3, T.45N., R.83W.
RANGE IN CHARACTERISTICS: The mollic epipedon is 7 to 16 inches thick. The solum is 15 to 30 inches thick and depth to the lithic contact ranges from 20 to 40 inches. The content of organic carbon ranges from 1 to 3 percent in the mollic epipedon and decreases uniformly with depth. The soil is 90 to 100 percent base saturated. The content of coarse fragments ranges from 35 to 80 percent and consists mainly of sandstone fragments more than 10 inches in diameter. The mean annual soil temperature ranges from 40 degrees to 47 degrees F., and the mean summer soil temperature ranges from 60 degrees to 70 degrees F.
The A horizon has hue of 2.5Y through 7.5YR, value of 4 or 5 dry and 2 or 3 moist and chroma of 2 or 3. It typically has granular or crumb primary structure, but has subangular blocky structure in some pedons. This horizon is soft to slightly hard and neutral to slightly alkaline.
The Bt horizon has hue of 2.5Y through 7.5YR, value of 5 or 6 dry and 3 through 5 moist and chroma of 2 through 4. It usually has subangular blocky primary structure but has weak prismatic structure in some pedons. This horizon is typically extremely stony sandy clay loam but clay ranges from 18 to 35 percent, silt from 5 to 30 percent, and sand from 40 to 75 percent with more than 35 percent fine or coarser sand. The content of rock fragments ranges from 35 to 80 percent and consists mainly of sandstone fragments more than 10 inches in diameter. This horizon is neutral to slightly alkaline.
The C horizon, if present, has hue of 2.5Y through 7.5YR. It is neutral to mildly alkaline.
COMPETING SERIES: These are the Badito, Hauz, Ironco, San Isabel, and Zillman series. The Badito, Ironco, San Isabel, and Zillman soils are more than 40 inches deep. The Hauz soils have less than 35 percent fine and coarser sand in the particle-size control section.
GEOGRAPHIC SETTING: The Simmont soils are on moderately to steeply sloping upland hills and ridges. Slopes are usually from 5 to 30 percent. These soils formed in moderately coarse textured, noncalcareous, moderately thick sediments derived principally from the weathering of noncalcareous sandstones. At the type location the average annual precipitation is 16 inches, with peak periods of precipitation in the spring and early summer months. The average annual temperature is 40 degrees F., average summer temperature is 62 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Sunup and Tolman soils. Sunup and Tolman soils have bedrock at depths of 20 inches or less. Tolman and Sunup soils lack an argillic horizon.
DRAINAGE AND PERMEABILITY: Well to excessively drained; rapid runoff; moderate permeability.
USE AND VEGETATION: These soils are used principally as native pastureland. They have a limited value for forestry in some localities and are frequently used for recreational purposes. Principal native plants are Ponderosa pine, Idaho fescue, and species of juniper.
DISTRIBUTION AND EXTENT: North-central Wyoming. The series is of minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Johnson County (Southern Johnson County Area), Wyoming, 1971.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon from the soil surface to 9 inches (A1 and B1 horizons);
Argillic horizon from 5 to 22 inches (B1, B2t and B3 horizons)
Lithic contact at 30 inches (top of R horizon.
The Simmont soils have a frigid temperature regime and an ustic moisture regime.