LOCATION SOMA UTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Lithic Xeric Haplocalcids
TYPICAL PEDON: Soma very cobbly loam in an area of Rock Outcrop-Soma complex, 30 to 70 percent slopes, on a southeast-facing, convex, 42 percent slope under black sagebrush and grasses. (Colors are for air-dry soil unless otherwise stated.)
A1--0 to 2 inches; dark brown (10YR 4/3) very cobbly loam, pale brown (10YR 6/3) dry; moderate medium platy structure; slightly hard, friable, slightly sticky, slightly plastic; few very fine roots; common very fine vesicular pores; 20 percent gravel, 20 percent cobbles; slightly effervescent, 5 percent calcium carbonate equivalent, strongly alkalaline (ph 8.6); abrupt smooth boundary. (2 to 4 inches thick)
Bw--2 to 6 inches; dark brown (10YR 4/3) very cobbly loam, pale brown (10YR 6/3) dry; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic; few fine and medium roots; few very fine tubular pores; 30 percent gravel, 20 percent cobbles; strongly effervescent, 7 percent calcium carbonate equivalent; strongly alkaline (ph 8.6): clear smooth boundary. (4 to 8 inches thick)
Bk1--6 to 14 inches; dark brown (10YR 4/3) extremely cobbly loam, light yellowish brown (10YR 6/4 dry; moderate medium subangular blocky structure; hard, friable, slightly sticky, slightly plastic; few very fine, fine, and medium roots; few very fine tubular pores; 30 percent gravel, 35 percent cobbles, strongly effervescent, 22 percent calcium carbonate equivalent, calcium carbonate is segregated as masses and on the lower sides of rock fragments; strongly alkaline (pH 8.8); gradual wavy boundary (6 to 10 inches thick).
Bk2--14 to 18 inches; dark brown (10YR 4/3) extremely cobbly loam, light yellowish brown (10RY 6/4) dry; weak medium subangular blocky structure; hard, friable, slightly sticky, slightly plastic; few very fine roots; 10 percent gravel, 60 percent cobbles; violently effervescent, 30 percent calcium carbonate equivalent, calcium carbonate is segregated as masses and on the lower sides of rock fragments; strongly alkaline.
R--18 inches; sandstone bedrock.
TYPE LOCATION: Millard County, Utah; about 2 miles north-northeast of Leamington; 2100 feet south and 200 feet east of the northwest corner of Section 1, T. 15 S., R. 4 W. Lynndyl USGS topographic Quadrangle; lat. 39 degrees 32 minutes 54 seconds N. and long. 112 degrees 15 minutes 10 seconds W.
RANGE IN CHARACTERISTICS: The depth to bedrock ranges from 15 to 20 inches. Depth to the calcic horizon ranges from 6 to 10 inches. The particle-size control section ranges from 10 to 18 percent clay and 35 to 75 percent rock fragments which are mostly cobbles.
Average annual soil temperature is 47 to 52 degrees F. The soil moisture regime is Aridic bordering on Xeric.
The A horizon has hue of 10YR, value of 6 or 7 dry, 3 or 4 moist, and chroma of 2 or 3. Rock fragment content is 35 to 60 percent of which 20 to 35 percent are cobbles and 15 to 30 percent are pebbles. Calcium carbonate equivalent is 5 to 15 percent and reaction is moderately alkaline to strongly alkaline.
The Bw horizon has hue of 10YR, value of 6 or 7 dry, 3 or 4 moist, and chroma of 3 or 4. Rock fragment content is 35 to 65 percent of which 20 to 35 percent are cobbles and 15 to 30 percent are pebbles. Calcium carbonate equivalent is 5 to 15 percent and reaction is moderately alkaline to strongly alkaline. The base of this horizon is less than 10 inches and is not deep enough to met the criteria for a cambic horizon.
The Bk horizon has hue of 10YR, value of 6 to 8 dry, 4 or 5 moist, and chroma of 3 or 4. Texture is very cobbly loam or extremely cobbly loam. Rock fragment content is 35 to 75 percent of which 25 to 65 percent are cobbles and 10 to 30 percent are pebbles. Calcium carbonate equivalent is 20 to 40 percent and is disseminated, in soft masses and in coatings on rock fragments.
COMPETING SERIES: These are the Kinghorn (T UT), Samor (NV), Saxby (UT), and Tarnach (UT) series. Kinghorn soils have dominant hue of 5YR and are underlain by conglomerate. Samor soils have a thin calcium carbonate cemented pan above the bedrock. Saxby soils have a cambic horizon. Tarnach soils are 18 to 27 percent clay and are dominated by pebbles in the particle-size control section.
GEOGRAPHIC SETTING: Soma soils are on hillslopes and mountainslopes at elevations of 4800 to 6400 feet. The soils formed in colluvium and residuum from sandstone, limestone, and quartzite. Slopes are 30 to 60 percent. The climate is semiarid. Average annual precipitation is 8 to 12 inches, average annual temperature is 45 to 51 degrees F., and the frost free period is 120 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Hiko Peak and Heist soils. The Hiko Peak and Heist soils are on lake terraces, alluvial fans, and lower parts of hillsides and are very deep.
DRAINAGE AND PERMEABILITY: Well drained; very rapid runoff; moderate permeability
USE AND VEGETATION: Used for rangeland. Potential natural vegetation is black sagebrush, Douglas rabbitbrush, Indian ricegrass and shadscale. This series is correlated with the Semidesert Shallow Loam (Black Sagebrush) range site.
DISTRIBUTION AND EXTENT: South central Utah; MLRA 28A. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Millard County, Utah; Millard County, Eastern Part Soil Survey, 1995.
REMARKS: Diagnostic horizons and other features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 2 inches (A horizon).
Calcic horizon - the zone from 6 to 18 inches (Bk horizons).
Lithic contact - the zone at a depth of 18 inches (R layer).
The classification is based on the "Keys to Soil Taxonomy, Eighth Edition, 1998".