LOCATION BIGSHEEP MTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Typic Calciustolls
TYPICAL PEDON: Bigsheep very gravelly loam, in rangeland. (Colors are for dry soil unless otherwise noted)
A1--0 to 4 inches; brown (10YR 4/3) very gravelly loam, dark brown (10YR 3/3) moist; weak medium subangular blocky structure parting to moderate fine and medium granular; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots and common fine roots; 55 percent pebbles; slightly alkaline (pH 7.8); clear smooth boundary.
A2--4 to 9 inches; brown (10YR 5/3) very gravelly loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots and common fine roots; 50 percent pebbles; slightly effervescent; slightly alkaline; clear smooth boundary. (Combined A horizons are 7 to 9 inches thick.)
Bk--9 to 24 inches; very pale brown (10YR 7/3) very gravelly loam, yellowish brown (10YR 5/4) moist; massive; soft, very friable, slightly sticky and slightly plastic; few very fine roots; 55 percent pebbles; many distinct lime coatings on pebbles; violently effervescent; moderately alkaline (pH 8.4); gradual smooth boundary. (10 to 30 inches thick)
2C1--24 to 33 inches; very pale brown (10YR 7/3) silt loam, yellowish brown (10YR 5/4) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; strongly effervescent; strongly alkaline (pH 8.6); gradual smooth boundary. (0 to 12 inches thick)
3C2--33 to 60 inches; pale yellow (2.5Y 7/4) very gravelly loam, light olive brown (2.5Y 5/4) moist; massive; soft, very friable, slightly sticky and slightly plastic; 55 percent pebbles; common thin lime coatings on pebbles; strongly effervescent; strongly alkaline (pH 8.6).
TYPE LOCATION: Prairie County, Montana; 2,300 feet south and 1,300 feet west of the NE corner of sec. 32, T. 14 N., R. 47 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Soil moisture control section - between of 4 and 12 inches, dry in all parts between four-tenths and five-tenths of the cumulative days per year when the soil temperature at a depth of 20 inches is 41 degrees or higher.
Mollic epipedon thickness - 7 to 9 inches.
Depth to Bk horizon - 7 to 9 inches.
A bedrock substratum phase is recognized. Weakly consolidated sedimentary beds are at a depth of 40 to 60 inches. They crush to loamy fine sand, silt loam, or loam. Reaction is pH 7.4 to 9.0.
A horizons - Hue 10YR or 2.5Y
Value: 4 or 5 dry
Chroma: 2 or 3
Clay content: 18 to 27 percent
Rock fragments: 0 to 60 percent--0 to 5 percent cobbles; 0 to 55 percent pebbles
Reaction: pH 6.6 to 8.4
Bk horizon - Hue: 10YR or 2.5Y
Value: 6 or 7 dry; 4 or 5 moist
Chroma: 2, 3, 4, or 6
Texture: loam, sandy loam, or sandy clay loam
Clay content: 18 to 27 percent
Rock fragments: 35 to 60 percent--0 to 5 percent cobbles; 35 to 55 percent pebbles
Calcium carbonate equivalent: 15 to 30 percent
Reaction: pH 7.9 to 9.0
2C1 horizon--Hue: 10YR, 2.5Y, or 5Y
Value: 6 or 7 dry; 5 or 6 moist
Chroma: 2, 3, or 4
Texture: silt loam, loam
Clay content: 18 to 27 percent
Rock fragments: 0 to 5 percent pebbles
Calcium carbonate equivalent: 8 to 15 percent
Reaction: pH 7.9 to 9.0
3C2 horizon - Hue: 10YR or 2.5Y
Value: 6 or 7 dry; 4 or 5 moist
Chroma: 2, 3, 4, or 6
Texture: loam, sandy loam, or sandy clay loam
Clay content: 10 to 27 percent
Rock fragments: 35 to 75 percent--0 to 5 percent cobbles; 35 to 70 percent pebbles
Calcium carbonate equivalent: 8 to 15 percent
Reaction: pH 8.5 to 9.0
COMPETING SERIES:
Eagar - has a Bk horizon more than 40 inches thick and occurs above elevations of more than 6900 feet
Saddlehorse - has a paralithic contact at depths of 20 to 40 inches
Tosca - has less than 18 percent clay in the particle-size control section and has a lithic contact at depths of 40 to 60 inches
Winspect - occurs at elevations of more than 3600 feet and have a higher mean annual precipitation.
GEOGRAPHIC SETTING:
Landform - alluvial fans; stream terraces; hills; sedimentary plains.
Elevation - 2,200 to 3,600 feet.
Slope- 0 to 45 percent.
Parent material - alluvium or colluvium.
Climate - cool, with long, cold winters; moist springs; warm summers.
Mean annual precipitation - 12 to 15 inches.
Mean annual temperature - 40 to 45 degrees F.
Frost-free period - 100 to 135 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cambert, Cambeth, Golva and Subwell soils. Cambert, Cambeth and Golva soils do not have rock fragments. In addition, Cambert and Cambeth soils are moderately deep to soft bedrock and do not have a mollic epipedon. Golva and Subwell soils have a cambic horizon and are more than 10 inches to carbonates. These soils are all below the Bigsheep soils on the landscape.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: Bigsheep soils are used mainly as rangeland. A few small areas are used as cropland when in complex with other soils. Potential native vegetation is mainly bluebunch wheatgrass, needleandthread, little bluestem, blue grama, threadleaf sedge, plains muhly and fringed sagewort.
DISTRIBUTION AND EXTENT: Bighsheep soils are of limited extent in southeastern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Prairie County, Montana, 1986; proposed in Prairie County, 1982. Named after a landmark in Prairie County, Montana.
REMARKS: Soil interpretation record: MT0738, MT0739. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the soil surface to 9 inches (A1, A2 horizons); a Bk horizon from 9 to 24 inches (Bk horizon); a particle-size control section from 10 to 40 inches (Bk, 2C1, 3C2 horizons).