LOCATION COLHILL WYEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, calcareous, frigid Ustic Torriorthents
TYPICAL PEDON: Colhill gravelly loam-on an east facing 12 percent slope utilized as rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 6 inches; light brownish gray (10YR 6/2) gravelly loam, dark grayish brown (10YR 4/2) moist; soft, very friable, nonsticky, nonplastic; common fine roots; 20 percent gravel; slightly effervescent, lime segregated in few fine irregularly shaped soft masses; mildly alkaline; (pH 7.4), clear smooth boundary. (4 to 7 inches thick)
C--6 to 60 inches; light gray (10YR 7/2) very gravelly loam, grayish brown (10YR 5/2) moist; massive; slightly hard, very friable, nonsticky, nonplastic; few fine roots; 40 percent gravel and 10 percent stones; strongly effervescent, lime as few fine irregularly shaped masses; moderately alkaline (pH 8.4).
TYPE LOCATION: Weston County, Wyoming, 5 miles northeast of Newcastle, 2,890 feet south and 175 feet west of the NE corner of sec. 19, T. 45 N., R. 60 W.
RANGE IN CHARACTERISTICS: Calcium carbonate equivalent ranges from 2 to 10 percent. The control section contains 30 to 70 percent gravel and 10 to 20 percent stones. The mean annual soil temperature is 41 to 47 degrees F., and the mean summer soil temperature is greater than 59 degrees F.
The A horizon has hue of 10YR or 2.5Y, value of 5 or 6 dry, 4 or 5 moist, and chroma of 2 or 3. Lime occurs in seams. Texture is gravelly loam but may be very gravelly loam. It is neutral or mildly alkaline.
The C horizon has hue of 10YR or 2.5Y, value of 6 or 7 dry, 4 or 5 moist, and chroma of 2 through 4. Texture is very gravelly loam, extremely gravelly loam, or very stony loam. Lime occurs in seams. It is mildly to moderately alkaline (pH 7.4-8.4).
COMPETING SERIES: These are the Armells, Southace, and Grobutte series. Armells soils formed in materials weathered from baked shales and have Bk horizons. Southace soils have hue of 7.5YR or 5YR in the C horizon and have shorter growing seasons. Grobutte soils have cooler average temperatures, shorter growing seasons, and occur at higher elevations.
GEOGRAPHIC SETTING: The Colhill soils occupy convex slopes on fans, hill crests, and terraces. They formed in gravelly alluvium and outwash material of mixed origin. The average annual precipitation is 15 to 19 inches, and the average annual temperature is 40 to 45 degrees F. Elevation ranges from 4,700 to 6,000 feet. The frost-free season is 90 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Corpening soils. Corpening soils have a mollic epipedon and lithic contact at less than 20 inches.
DRAINAGE AND PERMEABILITY: Excessively drained; runoff is rapid on higher slopes; moderately rapid permeability.
USE AND VEGETATION: These soils are used for rangeland. Native vegetation is blue grama, needleandthread, western wheatgrass, and green needlegrass.
DISTRIBUTION AND EXTENT: Black Hills area of Wyoming. The soil is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Weston County, Wyoming; 1983.