LOCATION RAWLINS WYEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, frigid Ustic Calciargids
TYPICAL PEDON: Rawlins gravelly loamy sand-rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 2 inches; pale brown (10YR 6/3) gravelly loamy sand, dark brown (10YR 3/3) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; common fine and medium roots; 15 percent very fine and fine rounded pebbles, many of which are imbedded in the surface half inch; neutral (pH 7.0); clear smooth boundary. (1 to 3 inches thick)
Bt--2 to 9 inches; brown (7.5YR 5/4) sandy clay loam, dark brown (7.5YR 4/4) moist; moderate medium prismatic structure parting to moderate fine subangular blocky; slightly hard, friable, sticky and plastic; common fine and medium roots; continuous thin clay films on vertical faces of peds; moderately alkaline (pH 8.0); clear wavy boundary. (3 to 8 inches thick)
Bk1--9 to 12 inches; brown (7.5YR 5/4) sandy loam, dark brown (7.5YR 4/4) moist; weak medium subangular blocky structure; soft, friable, slightly sticky and nonplastic; common fine and medium roots; strongly effervescent, lime as common fine soft masses and filaments; moderately alkaline (pH 8.2); clear smooth boundary. (2 to 5 inches thick)
Bk2--12 to 18 inches; white (10YR 8/1) sandy loam, light yellowish brown (10YR 6/4) moist; massive; slightly hard, very friable, slightly sticky and nonplastic; very few fine roots; violently effervescent, lime as common soft masses, threads, and filaments; moderately alkaline (pH 8.4); clear wavy boundary. (6 to 12 inches thick)
Bk3--18 to 52 inches; yellowish brown (10YR 6/4) sandy loam, yellowish brown (10YR 5/4) moist; massive; slightly hard, very friable, slightly sticky and nonplastic; strongly effervescent, lime as common soft masses, filaments, and threads; strongly alkaline (pH 8.6); clear wavy boundary. (20 to 50 inches thick)
C--52 to 60 inches; yellowish brown (10YR 6/4) gravelly sandy loam, yellowish brown (10YR 5/4) moist; massive; slightly hard, very friable, nonsticky and nonplastic; strongly effervescent, lime disseminated and as few soft, irregular masses; strongly alkaline (pH 8.8)
TYPE LOCATION: Carbon County, Wyoming; approximately 2,600 feet north and 550 feet east of the SW corner of sec. 33, T. 22 N., R. 87 W.
RANGE IN CHARACTERISTICS: The mean annual soil temperature ranges from 42 to 47 degrees F., and the mean summer soil temperature ranges from 59 to 63 degrees F. Depth to the base of the argillic horizon and continuous horizons of carbonate accumulation ranges from 4 to 10 inches. The particle-size control section from the top of the argillic horizon to 40 inches, when averaged, has less than 18 percent noncarbonate clay and from 5 to 25 percent rock fragments, mostly pebbles with a few semirounded cobbles. EC ranges from 0 to 4 mmhos through the Bk and C horizons.
The A horizon has hue of 2.5Y or 10YR, value of 5 or 6 dry, 3 or 4 moist, and chroma of 2 through 4. Textures are loamy sand or sandy loam and may have gravelly modifiers. It is neutral or mildly alkaline.
The Bt horizon has hue of 10YR or 7.5YR, value of 4 through 6 dry, 3 or 4 moist, and chroma of 1 through 4. It is sandy clay loam, sandy loam, gravelly sandy clay loam, or gravelly sandy loam with 18 to 28 percent clay and 0 to 20 percent coarse fragments, mainly pebbles. It is mildly alkaline or moderately alkaline.
The Bk horizon has hue of 2.5Y through 7.5YR, value of 6 through 8 dry, 4 through 7 moist, and chroma of 1 through 4. It is typically sandy loam, fine sandy loam, very fine sandy loam or gravelly sandy loam with 5 to 18 percent clay but is sandy clay loam or gravelly sandy clay loam where carbonate clay is present and raises total clay to about 24 percent. Coarse fragments range from 5 to 30 percent pebbles with a few stones. The calcium carbonate equivalent ranges from 8 to 25 percent with inconsistent pockets ranging up to 35 percent. It is mildly through strongly alkaline.
The C horizon has hue of 2.5Y through 7.5YR, value of 5 through 7 dry, 4 through 6 moist, and chroma of 1 through 4. It is sandy loam or gravelly sandy loam with 5 to 18 percent clay and 5 to 20 percent pebbles with a few cobbles. Most carbonates are authigenic and disseminated with few soft masses. It is moderately alkaline or strongly alkaline.
COMPETING SERIES: These are the Canwall Cotha, Elk Mountain, Farson, Joemre, Means, Rohonda, Ryan Park, and Ryark series. All of these soils have 18 percent or less clay in the Bt horizon, and the base of the argillic horizon is below 10 inches. Also, Canwall, Cotha, Elk Mountain, Means, and Rohonda soils have bedrock at 20 to 40 inches. Ryan Park soils do not have a calcic horizon. Ryark soils are noncalcareous throughout.
GEOGRAPHIC SETTING: Rawlins soils are on relict fan aprons, terraces, fan pediments, and toeslopes along valley margins. These soils formed in mixed, calcareous alluvium. Slopes are 0 to 20 percent. Elevations are 6,000 to 7,800 feet. The mean annual precipitation ranges from 9 to 14 inches of which about half falls as snow and less commonly as rain in April, May, and early June. The mean annual temperature is about 39 to 44 degrees F. The frost-free season is estimated to range from 75 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Brownsto, McFadden, and the competing Ryan Park soils. Brownsto soils are loamy-skeletal. McFadden soils do not have an argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow or medium runoff; moderate permeability.
USE AND VEGETATION: Rangeland and wildlife habitat. Native vegetation consists of needleandthread, Indian ricegrass, bluebunch wheatgrass, bottlebrush squirreltail, black sagebrush, and threadleaf sedge.
DISTRIBUTION AND EXTENT: South central Wyoming. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Natrona County, Wyoming; 1985.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon--0 to 2 inches (A)
Argillic horizon--2 to 9 inches (Bt)
Calcic horizon--9 to 52 inches (Bk1,Bk2,Bk3)
Borollic feature--.84% organic carbon in the A horizon and a frigid temperature regime meet the requirements for the Borollic subgroup.