LOCATION SHOSHONE WYEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, calcareous, mesic Typic Fluvaquents
TYPICAL PEDON: Shoshone loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 4 inches; gray (10YR 5/1) loam, dark gray (10YR 4/1) moist; moderate fine granular structure; soft, very friable, slightly sticky, slightly plastic; few scattered basalt pebbles; dark colored magnetic mineral grains in the silt and sand fractions; calcareous; moderately alkaline (pH 8.3); clear smooth boundary. (3 to 8 inches thick)
Cg--4 to 30 inches; gray (10YR 6/1) sandy loam stratified with thin lenses of loamy sand and loam, dark gray (10YR 4/1) moist; common medium distinct brown (7.5YR 5/4) redox concentrations; massive; slightly hard, very friable; 10 percent basalt gravel and cobbles; dark colored magnetic mineral grains in the silt and sand fractions; calcareous; moderately alkaline (pH 8.3); gradual wavy boundary. (12 to 32 inches thick)
2C--30 to 60 inches; basalt gravel and cobbles in a matrix of sand.
TYPE LOCATION: Big Horn County, Wyoming; approximately 400 feet south and .7 mile east of bridge over the Shoshone River south of Byron, Wyoming, near the center of NW1/4 sec. 36, T.56N., R.97W.
RANGE IN CHARACTERISTICS: Depth to sand, gravel, and cobbles is 25 to 40 inches. The mean annual soil temperature is 48 to 50 degrees F. The mean summer soil temperature is 62 to 68 degrees F. These soils are usually calcareous throughout. Some pedons are leached a few inches. Calcium carbonate equivalent ranges from 0 to 15 percent. The soils are slightly to strongly alkaline. The upper part of the control section (Cg horizon) is highly stratified and averages sandy loam. It has 6 to 18 percent clay, 10 to 40 percent silt, 50 to 80 percent fine sand or coarser and 0 to 35 percent rock fragments, mainly gravel and cobbles. The sand and silt fractions contain 5 to 20 percent or more of dark colored ferromagnesian rich minerals and basalt fragments. Hue is 5Y through 10YR, value is 5 or 6 dry, 4 or 5 moist, and chroma is 1 or 2.
COMPETING SERIES: This is the Las Animas series. Las Animas soils have sand, gravel, and cobble beds below a depth of 40 inches.
GEOGRAPHIC SETTING: Shoshone soils are on floodplains and low terraces at elevations of 3,800 to 5,200 feet. Slope gradients typically range from 0 to 3 percent. These soils formed in highly stratified but predominantly moderately coarse textured sediments derived from basaltic material. At the type location the average annual precipitation is 7 inches with peak periods of precipitation in the spring and early summer months. Mean annual temperature is 45 degrees F. and mean summer temperature is 69 degrees F. The frost-free season is 110 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Glending, Havig, Las Animas, Poganeab, and Willwood soils. Willwood soils are well drained and have more than 35 percent basalt gravel and cobbles throughout.
DRAINAGE AND PERMEABILITY: Somewhat poorly to poorly drained; slow runoff; moderate over rapid permeability.
USE AND VEGETATION: These soils are used principally as rangeland; however, they may be tilled to crops in some locations. Native vegetation is mainly sedges and rushes and some willow and cottonwood.
DISTRIBUTION AND EXTENT: North-central portion of Wyoming. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Big Horn County (Shoshone Area) Wyoming 1926.