LOCATION PEPTON WYEstablished Series
TAXONOMIC CLASS: Loamy, mixed, superactive, frigid Lithic Ustic Haplocambids
TYPICAL PEDON: Pepton sandy loam-rangeland. (Colors are for dry soil unless otherwise stated.)
A1--0 to 2 inches; light brownish gray (10YR 6/2) sandy loam, dark brown (10YR 4/3) moist; moderate medium and fine platy structure; soft, very friable, slightly sticky and slightly plastic; few very fine and fine roots; mildly alkaline (pH 7.4); abrupt wavy boundary.
A2--2 to 3 inches; light brownish gray (10YR 6/2) sandy loam, dark brown (10YR 4/3) moist; moderate fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; mildly alkaline (pH 7.4); abrupt wavy boundary. (Combined thickness of A horizon is 2 to 5 inches)
Bw--3 to 11 inches; pale brown (10YR 6/3) sandy loam, dark yellowish brown (10YR 4/4) moist; weak coarse subangular blocky structure parting to moderate fine subangular blocky; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; mildly alkaline (pH 7.4); clear wavy boundary. (6 to 10 inches thick)
Bk--11 to 15 inches; light yellowish brown (2.5Y 6/4) channery sandy loam, light olive brown (2.5Y 5/4) moist; massive; soft, very friable, slightly sticky and slightly plastic; few fine roots; strongly effervescent, lime disseminated and as few thin crusts on underside of some channers; 35 percent channers; moderately alkaline (pH 8.0); abrupt wavy boundary. (0 to 6 inches thick)
R--15 inches; hard, calcareous sandstone.
TYPE LOCATION: Sweetwater County, Wyoming; about 6 miles southwest of Farson in NW1/4, NW1/4 of sec. 21, T. 24 N., R. 107 W.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 43 to 47 degrees F., and the mean summer soil temperature is 59 to 63 degrees F. Depth to lithic contact is 12 to 20 inches. Clay content of the particle size control section ranges from 10 to 18 percent.
The A horizon has hue of 10YR or 2.5Y, value of 5 or 6 dry, 3 or 4 moist, and chroma of 2 or 3. Content of rock fragments is typically less than 5 percent but may range from 0 to 15 percent channers. In some areas this horizon has a 25 percent cover of a fine channer and lag gravel.
The Bw horizon has hue of 10YR or 2.5Y, value of 5 or 6 dry, 3 or 4 moist, and chroma of 3 or 4. Texture is sandy loam or fine sandy loam. Content of rock fragments is typically less than 5 percent but may range from 0 to 15 percent.
The Bk horizon has hue of 10YR or 2.5Y, value of 6 through 8 dry and 4 through 7 moist, and chroma of 2 through 4. Texture is fine sandy loam or channery sandy loam. Content of rock fragments ranges from 0 to 35 percent when averaged. This horizon is absent in some pedons and when present is either too thin or does not contain enough pedogenetic calcium carbonate to be a calcic horizon.
COMPETING SERIES: There are no other soils presently identified in this class. The Quealy and Travelers soils are similar but have over 35 percent coarse fragments throughout the control section.
GEOGRAPHIC SETTING: Pepton soils are on nearly level to undulating upland plains. They formed in residuum and colluvial slopewash derived from sandstone. Slopes are typically 0 to 4 percent but range up to 8 percent. Elevation is 6,500 to 7,200 feet. The mean annual precipitation is 7 to 12 inches, and the mean annual temperature is 35 to 42 degrees F. The frost-free season is about 60 to 90 days depending upon aspect and air drainage.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Edlin and Screggs series. Edlin soils are deep. Screggs soils are moderately deep.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately rapid permeability.
USE AND VEGETATION: Rangeland and wildlife habitat. The native vegetation consists of big sagebrush, low rabbitbrush, shadscale, thickspike wheatgrass, and Indian ricegrass.
DISTRIBUTION AND EXTENT: Southwestern Wyoming. These soils are of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Eden Valley Soil Survey Area, Sweetwater County, Wyoming; 1985.