LOCATION COTHA WYEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, frigid Ustic Haplargids
TYPICAL PEDON: Cotha sandy loam, rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 4 inches; pale brown (10YR 6/3) sandy loam, brown (10YR 4/3) moist; weak fine crumb structure; loose, very friable; many very fine, fine, and medium roots; neutral (pH 6.8); clear smooth boundary. (2 to 5 inches thick)
Bt1--4 to 11 inches; brown (10YR 5/3) sandy loam, brown (10YR 4/3) moist; weak medium angular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine, and medium roots; thin discontinuous waxy coatings on some faces of peds; neutral (pH 6.8); clear smooth boundary. (5 to 8 inches thick)
Bt2--11 to 18 inches; brown (10YR 5/3) sandy loam, brown (10YR 4/3) moist; weak medium prismatic parting to moderate medium angular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; thin discontinuous waxy coatings on some faces of peds and clay bridging between sand grains; neutral (pH 7.0); clear smooth boundary. (5 to 8 inches thick)
BCt--18 to 28 inches; yellowish brown (10YR 5/4) sandy loam, dark yellowish brown (10YR 4/4) moist; weak medium angular blocky structure; soft, friable, slightly stick; few fine roots; thin discontinuous waxy coatings in root channels and some clay bridging between sand grains; neutral (pH 7.0); gradual wavy boundary. (5 to 10 inches thick)
C--28 to 34 inches; light yellowish brown (10YR 6/4) sandy loam, yellowish brown (10YR 5/4) moist; massive; soft, very friable; neutral (pH 7.2); gradual wavy boundary. (5 to 10 inches thick)
Cr--34 to 40 inches; light yellowish brown, soft, noncalcareous, fine grained sandstone; contains few seams of calcium carbonate.
TYPE LOCATION: Sublette County, Wyoming; center of sec. 23, T.31N., R.109W.
RANGE IN CHARACTERISTICS: The depth to a paralithic contact is 20 to 40 inches. The solum is 15 to 30 inches thick. Mean annual soil temperature is about 38 degrees to 47 degrees F. Mean summer soil temperature is about 59 degrees to 66 degrees F. Fine sandstone fragments range from 5 to 15 percent throughout the profile.
The A horizon has hue of 2.5Y or 10YR, value of 5 or 6 dry, 3 or 4 moist, and chroma of 2 or 3 and averages 7 to 15 percent clay.. It is neutral or mildly alkaline.
The Bt horizon has hue of 2.5Y through 7.5YR, value of 5 or 6 dry, 4 or 5 moist, and chroma of 2 through 4. It is sandy loam or fine sandy loam, averaging 10 to 18 percent clay. It is neutral or mildly alkaline.
The C horizon has hue of 2.5Y or 10YR. It is sandy loam or fine sandy loam. It is neutral or mildly alkaline.
COMPETING SERIES: These are the Ryan Park, and Ryark series. Ryan Park soils have continuous horizons of secondary calcium carbonate. Also, Ryan Park soils lack bedrock above depth of 40 inches. Ryark soils have loamy sand or gravelly sand C horizons and lack bedrock above depth of 40 inches.
GEOGRAPHIC SETTING: Cotha soils are on rolling uplands. Slopes are 3 to 30 percent. The soils formed in sandy sediments weathered from underlying soft, noncalcareous sandstone. Elevation is 6,000 to 7,300 feet. The mean annual precipitation is about 10 to 14 inches and occurs mainly in the winter and spring. Mean annual temperature is about 37 degrees to 45 degrees F., and the mean summer temperature is about 58 degrees to 65 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bluerim and Crownest soils and the competing Ryark soils. Bluerim soils have more than 18 percent clay in the argillic horizon. Crownest soils have a lithic contact at depths of 10 to 20 inches.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; moderately rapid permeability.
USE AND VEGETATION: These soils are used for range. Native vegetation is needleandthread grass, big sagebrush, and thickspike wheatgrass.
DISTRIBUTION AND EXTENT: Southwestern Wyoming. The series is moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Fremont County, Lander Area, Wyoming, 1975.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon the zone from the soil surface to a depth of 4 inches (A horizon);
Argillic horizon - the zone from 4 to 28 inches (Bt and BCt horizons).
Paralithic contact- the upper boundary of the Cr horizon 34 inches below the soil surface.