LOCATION IRSON WYEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Lithic Haplocryolls
TYPICAL PEDON: Irson very gravelly sandy clay loam--rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 7 inches; dark brown (10YR 4/3) very gravelly sandy clay loam, dark brown (10YR 3/3) moist; moderate fine granular structure; soft, very friable, slightly sticky and slightly plastic; many fine roots; 30 percent angular granite gravel, 15 percent angular granite cobbles; neutral (pH 7.2); clear wavy boundary. (6 to 12 inches thick)
C--7 to 11 inches; dark yellowish brown (10YR 4/4) very cobbly sandy clay loam, dark yellowish brown (10YR 3/4) moist; massive; soft, friable, slightly sticky and slightly plastic; common fine and medium roots; 40 percent angular granite cobbles; 20 percent angular granite gravel; neutral (pH 7.2). (0 to 11 inches thick)
R--11 inches; hard, fractured granite.
TYPE LOCATION: Natrona County, Wyoming; Big Horn Mountains in the northwest corner of the county; 600 feet east and 2,300 feet north of the southwest corner of section 17, T. 40 N., R. 87 W. 43 degrees 26 minutes 9 seconds north latitude and 107 degrees 19 minutes 3 seconds west longitude.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 32 to 35 degrees F., and the mean annual summer soil temperature is 44 to 47 degrees F. Depth to bedrock ranges from 8 to 20 inches. Thickness of the mollic epipedon is 7 to 13 inches. The matrix of the particle-size control section is sandy clay loam or loam with 18 to 27 percent clay and more than 35 percent fine sand or coarser. Igneous rock fragments range from 35 to 85 percent with 10 to 50 percent angular gravel or channers less than 3 inches in diameter, 10 to 40 percent angular cobbles or channers more than 3 inches in diameter, and 0 to 50 percent stones.
The A horizon has hue of 10YR or 7.5YR value of 3 or 4 dry, 2 or 3 moist, and chroma of 2 or 3.
The C horizon has value of 4 or 5 dry, 3 or 4 moist and chroma of 3 or 4.
COMPETING SERIES: These are the Arrowpeak (T), Cheadle, Clamp, Dollarhide Eyre, Irigul, Jonlake (T), Labshaft, Milling (T), Poin, Rogert, Starley, Topeki (T), and Udel series. Arrowpeak, Clamp, Dollarhide, Jonlake, Milling, Poin and Topeki soils have annual soil temperatures higher than 37 degrees F. Cheadle and Starley soils are calcareous. Eyre, Rogert, and Udel soils have less than 18 percent clay in the particle size control section. Irigul soils have less than 35 percent fine sand or coarser. Labshaft soils have a cambic horizon.
GEOGRAPHIC SETTING: Irson soils are on ridges and steep hillsides of granite and basalt mountains and mesa tops. Elevation is 6,500 to 8900 feet. In Colorado elevation is as high as 10,700 feet. Slopes range from 0 to 65 percent. They formed in colluvium and residuum derived dominantly from granite or basalt. The mean annual precipitation is 15 to 40 inches, and the mean annual temperature is 32 to 36 degrees F. The frost-free season is less than 90 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Kezar and competing Starley soils. Kezar soils are moderately deep and have an argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained; rapid runoff; moderate permeability.
USE AND VEGETATION: These soils are used mainly for livestock grazing and wildlife habitat. Native vegetation is mainly bluebunch wheatgrass, Idaho fescue, black sagebrush, and threetip sagebrush.
DISTRIBUTION AND EXTENT: Mountains of central Wyoming and Colorado. 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:
Mollic epipedon - 0 to 7 inches (A)
Lithic contact - 11 inches (R)
SIR- WY0650
LRR- E