LOCATION BIGTOM UTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, siliceous, superactive, frigid Pachic Argiustolls
TYPICAL PEDON: Bigtom extremely bouldery loam, on a northwest facing, 50 percent slope in curlleaf mountainmahogony rangeland at an elevation of 7,200 feet. (Colors are for dry soil unless otherwise noted.)
The surface is covered by 5 percent boulders, 15 percent stones, 15 percent cobbles, and 5 percent gravel.
Oi--0 inch to 1; slightly decomposed leaves, twigs, grass, and stems; abrupt smooth boundary. (0 to 3 inches thick)
A1--1 to 7 inches; very dark gray (5YR 3/1) extremely bouldery loam, black (5YR 2.5/1) moist; moderate very fine granular structure; soft, very friable, nonsticky and slightly plastic; many very fine, common medium and fine, and few coarse roots; common fine and very fine and few medium tubular pores; 5 percent boulders, 15 percent stones, 20 percent cobbles, 10 percent gravel; slightly alkaline (pH 7.5); clear smooth boundary.
A2--7 to 12 inches; dark reddish brown (5YR 3/2) extremely stony loam, black (5YR 2.5/1) moist; weak coarse and medium subangular blocky structure parting to moderate fine and very fine subangular blocky; soft, friable, slightly sticky and slightly plastic; many medium, fine, and very fine and common coarse roots; many very fine, common fine, and few medium tubular pores; 20 percent stones, 30 percent cobbles, and 20 percent gravel; neutral (pH 7.2); gradual smooth boundary. (combined thickness of A horizons range from 8 to 17 inches)
Bt1--12 to 23 inches; dark reddish brown (5YR 3/3) extremely stony clay loam, dark reddish brown (5YR 3/2) moist; moderate very fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many medium, fine and very fine, and common coarse roots; common fine and very fine and few medium tubular pores; few faint clay films on faces of peds and rock
fragments; 20 percent stones, 45 percent cobbles, and 15 percent gravel; neutral (pH 7.2); gradual wavy boundary.
Bt2--23 to 31 inches; reddish brown (5YR 4/4) extremely stony clay loam, dark reddish brown (5YR 3/3) moist; moderate fine and very fine subangular blocky structure; slightly hard, firm, moderately sticky and moderately plastic; common coarse, medium, fine and very fine roots; common fine and very fine tubular pores; common distinct clay films on faces of peds and rock fragments; 20 percent stones, 40 percent cobbles, and 20 percent gravel; slightly alkaline (pH 7.4); clear wavy boundary.
Bt3--31 to 41 inches; reddish brown (5YR 4/4) extremely stony clay loam, dark reddish brown (2.5YR 3/4) moist; moderate coarse subangular blocky structure parting to moderate fine and very fine subangular blocky; hard, firm, moderately sticky and moderately plastic; common coarse, medium, fine, and very fine roots; common fine and very fine tubular pores; common distinct clay films on faces of peds and rock fragments; 20 percent stones, 35 percent cobbles, and 25 percent gravel; slightly alkaline (pH 7.4); gradual wavy boundary.
Bt4--41 to 61 inches; reddish brown (5YR 4/4) extremely cobbly sandy clay loam, dark red (2.5YR 3/6) moist; weak medium and fine subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few coarse and common medium, fine, and very fine roots; common fine and very fine tubular pores; common distinct clay films on faces of peds and rock fragments; 10 percent stones, 30 percent cobbles, and 40 percent gravel; slightly alkaline (pH 7.4).
TYPE LOCATION: Uintah County, Utah; about 2.5 miles east of Crouse Reservoir; located about 2,200 feet west and 2,500 feet south of the northeast corner of sec. 20, T. 1 S., R. 25 E., SLBM; Crouse Reservoir, Utah USGS quad; lat. 40 degrees 43 minutes 14 seconds N. and long. 109 degrees 07 minutes 49 seconds W., NAD 27.
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is affected by precipitation that falls evenly through the year with a slight increase in late summer and early fall. Ustic moisture regime.
Mean annual soil temperature: 42 to 45 degrees F.
Thickness of the mollic epipedon: 16 to 30 inches
Particle-size control section: 28 to 35 percent clay and 45 to 90 percent rock fragments of sandstone and quartzite origin
A horizon:
Value: 3 or 4 dry, 2 or 3 moist
Chroma: 1 to 4 dry, 1 or 3 moist
Reaction: neutral or slightly alkaline
Bt horizon:
Hue: 10R to 5YR
Value: 4 to 6 dry, 3 or 4 moist
Chroma: 3 to 6 dry or moist
Texture: extremely stony clay loam, extremely cobbly sandy clay loam, and very stony clay loam
Reaction: neutral or slightly alkaline
COMPETING SERIES: These are no competing series in this family.
GEOGRAPHIC SETTING:
Parent material: slope alluvium and colluvium derived from sandstone and quartzite
Landform: mountain slopes
Slopes: 15 to 50 percent
Elevation: 7,000 to 8,700 feet
Mean annual air temperature: 40 to 43 degrees F.
Mean annual precipitation: 16 to 22 inches
Frost-free period: 70 to 90 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cortyzack, Diagulch, Dokie, Flynncove, Hoymount, Ironco, and Namlot series.
Cortyzack and Diagulch soils occur on plateau summits and shoulders and have fine-loamy particle-size control section.
Dokie soils have an ochric epipedon.
Flynncove soils are not pachic.
Hoymount soils have an ochric epipedon and are deep to bedrock.
Ironco soils occur on dissected plateaus, are not pachic, and are drier.
Namlot soils are shallow.
DRAINAGE AND PERMEABILITY: Well drained, high runoff, moderately slow permeability.
USE AND VEGETATION: The major uses are rangeland, wildlife habitat, and recreation. Potential native vegetation consists of curlleaf mountainmahogany, bluebunch wheatgrass, mountain snowberry, and Utah serviceberry. These soils have been correlated to the Mountain Stony Loam (Curlleaf Mountainmahogany) - 047CY461UT range site in Utah.
DISTRIBUTION AND EXTENT: Northeastern Utah. LRR E, MLRA 47. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Uintah County, Uintah Area Soil Survey, Utah. 1998. The name is taken from a nearby geographic location.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Particle-size control section: The zone from 12 to 32 inches. (Bt1, Bt2, and Bt3 horizons)
Mollic epipedon: The zone from 1 to 31 inches. (A1, A2, Bt1, and Bt2 horizons)
Argillic horizon: The zone from 12 to 61 inches. (Bt1, Bt2, Bt3, and Bt4 horizons)
Siliceous mineralogy: Determined from laboratory samples on similar geologic material and landscapes in the area.
The cation exchange activity class was inferred from laboratory data from similar soils in the Uintah Area Soil Survey.
Classification was changed from Pachic Argiborolls to frigid Pachic Argiustolls 11/98.
Taxonomic version: Eighth Edition, 1998.
The surface texture modifier was determined following the guidelines outlined in the Utah document, "Procedures for Distributing Rock Fragments on the Surface Layer into the Upper 6 inches of Soil and Subsequent Naming of Map Units, April 1979."