LOCATION OBRAST UTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Vertic Haploxerolls
TYPICAL PEDON: Obrast silty clay - rangeland
(Colors are for air dry soils unless otherwise noted.)
A11--0 to 2 inches; very dark grayish brown (10YR 3/2) silt loam, very dark brown (10YR 2/2) moist; moderate medium granular structure; slightly hard, friable, slightly sticky, plastic; few fine, very fine and coarse roots; common very fine pores; neutral (pH 7.0); abrupt smooth boundary. (O to 3 inches thick)
A12--2 to 6 inches; very dark grayish brown (10YR 3/2) silty clay; very dark brown (10YR 2/2) moist; moderate medium subangular blocky structure; very hard, firm, sticky, plastic; few very fine, few coarse roots; few fine and few medium pores; neutral (pH 7.0); gradual smooth boundary. (2 to 6 inches thick)
A13--6 to 10 inches; brown (10YR 4/3) clay, dark brown (10YR 3/3) moist; moderate medium prismatic structure that parts to strong angular blocky; extremely hard, very firm, very sticky, very plastic; few fine and few coarse roots; few very fine pores; few slickensides and wedge structure at 10- to 15-degree angle; neutral (pH 7.0); gradual smooth boundary. (3 to 6 inches thick)
Cl--10 to 15 inches; brown (10YR 5/3) clay; dark brown (10YR 3/3) moist; moderate medium prismatic structure that parts to strong angular blocky; extremely hard, very firm, very sticky, very plastic; few fine and few coarse roots; few very fine pores; common slickensides and wedge structure at 10 to 15 degree angle; neutral (pH 7.0); gradual smooth boundary. (3 to 5 inches thick)
C2--15 to 36 inches; brown (10YR 5/3) clay, brown (10YR 4/3) moist; moderate medium prismatic structure that parts to strong angular block; extremely hard, very firm, very sticky, very plastic; few fine, few coarse roots; few fine pores; common slickensides and wedge structure at 10 to 15 degree angle; 25 to 30 percent of horizon darkened by mixing of dark colored surface layers; slightly calcareous, lime is in fine veins; neutral (pH 7.0); clear smooth boundary. (15 to 25 inches thick)
C3--36 to 46 inches; light gray (10YR 7/2) silty clay loam; light gray brown (10YR 6/2) moist; massive; very hard, very firm, sticky, plastic; strongly calcareous, lime is disseminated and in soft rounded accretions; moderately alkaline (pH 8.0); clear smooth boundary. (0 to 10 inches thick)
C4--46 to 56 inches; very pale brown (l0)YR 7/3) heavy silty clay loam, pale brown (10YR 6/3) moist; massive; very hard, very firm, sticky, plastic; moderately calcareous, lime is disseminated; moderately alkaline (ph 8.2); clear smooth boundary. (5 to 15 inches thick)
C5--56 to 65 inches; white (l0YR 8/2) sandy clay loam; light gray (10YR 7/2) moist; massive; hard, firm, sticky, plastic; strongly calcareous, lime is disseminated and in soft rounded accretions; strongly alkaline (ph 8.8).
TYPE LOCATION: Utah County, Utah; about 1 1/4 miles due west of Thistle, about 1,320 feet west and 660 feet north of the southeast corner of sec. 30, T.95., R.4E.
Range in Characteristics: Shale bedrock occurs in some pedons at depths of 40 to 60 inches. The mollic epipedon is 8 to 20 inches thick. The 10 to 40 inch section is clay or silty clay. The soils are slightly to moderately calcareous at some depth above 30 inches and are moderately or strongly calcareous below 30 inches. Mean annual soil temperature is 43 degrees to 47 inches F. at about 20 inches. Cracks 1/2 inch to 2 inches wide extending to depths of 40 inches or more occur when the soils are dry. The cracks open and close once each year and remain open for 60 consecutive days or more in 7 out of 10 years.
The Al horizon has hue of 10YR or 7.5YR, value of 3 through 5 dry, 2 or 3 moist, and chroma of 2 or 3. It is noncalcareous to moderately calcareous and contains O to 20 percent carbonate content. This horizon is neutral to moderately alkaline.
The C horizon has hue of 5YR, 7.5YR, or 10YR, value of 5 through 8 dry, 3 through 6 moist, and chroma of 1 through 4. It has common to many slickensides. This horizon is neutral to strongly alkaline and contains 3 to 30 percent lime. Cobble and shale fragments content ranges from O to 30 percent.
COMPETING SERIES: These are the Ager, Aikman, Cardon, Climax, Day, Lassen, Marias, Montague, Moroni, Obray and Springerville series. Ager, Aikman, Climax, Day, Lassen, Montague, Moroni and Springerville soils have mean annual soil temperature of more than 47 degrees F. Cardon soils have chroma of less than 1.5 throughout the upper 12 inches, and mean annual soil temperature of more than 47 degrees F. Marias and Moroni soils lack mollic epipedons. Obray soils are noncalcareous to a depth of 30 to 40 inches and are noncalcareous to moderately calcareous below 30 inches.
GEOGRAPHIC SETTING: These soils are on gently to strongly sloping mountain slopes and alluvial fans at elevations of 5,000 to 7,600 feet. The soils formed in alluvium and residuum from shale, limestone and basic igneous rocks. The climate is moist subhumid an the average annual precipitation ranges from 14 to 20 inches. Mean annual temperature ranges from 42 degrees to 45 degrees F., the mean summer temperature is 62 degrees to 65 degrees F. Frost-free period is 85 to 100 days.
GEOGRAPHIC ASSOCIATED SOILS: These are the Ant Flat, Deer Creek, Harkers, Mower and Yeates Hollow soils. Ant Flat, Deer Creek and Harkers soils have clay argillic horizons. Yeates Hollow soils have cobbly clay argillic horizons. Mower soils have more than 40 percent carbonate.
DRAINAGE AND PERMEABILITY: Well-drained; slow to medium runoff; very slow permeability.
USE AND VEGETATION: These soils are used for range and for nonirrigated pasture. The present vegetation is mulesear dock, oakbrush big sagebrush, slender wheatgrass, and native bluegrass.
DISTRIBUTION AND EXTENT: Central Utah. The series is inextensive in the Sanpete Area.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Sanpete Area; Utah, 1971.
REMARKS: In the 1938 classification these soils were classified as Grumosols.
Series scanned by NSSQA. Last revised by state 9/71.