LOCATION BIGARM MTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Typic Haploxerolls
TYPICAL PEDON: Bigarm very gravelly loam, native grassland. (Colors are for dry soil unless otherwise noted.)
A--0 to 12 inches; dark grayish brown (10YR 4/2) very gravelly loam, very dark grayish brown (10YR 3/2) moist; moderate fine and very fine granular structure; soft, very friable, nonsticky and nonplastic; many fine and very fine roots; many fine and very fine pores; 45 percent angular gravel; neutral (pH 6.7); gradual wavy boundary. (8 to 20 inches thick)
Bw--12 to 18 inches; brown (10YR 5/3) very gravelly loam, brown (10YR 4/3) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic; common fine and very fine roots; common fine and very fine pores; 50 percent angular gravel; neutral (pH 7.0); gradual wavy boundary. (6 to 21 inches thick)
BC--18 to 38 inches; very pale brown (10YR 7/3) very gravelly fine sandy loam, brown (10YR 5/3) moist; massive; slightly hard, very friable, nonsticky and nonplastic; few fine and very fine roots in upper part; 50 percent angular gravel; neutral (pH 7.0); gradual wavy boundary. (0 to 30 inches thick)
C--38 to 60 inches; very pale brown (10YR 7/3) extremely gravelly sandy loam, brown (10YR 5/3) moist; massive; soft, very friable, nonsticky and nonplastic; 55 percent angular gravel, 10 percent angular cobbles; neutral (pH 7.2).
TYPE LOCATION: Lake County, Montana; near Ravalli; approximately 250 feet east and 1,400 feet south of the NW corner of sec. 32, T. 18 N., R. 20 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 43 to 47 degrees F.
Moisture control section - between 8 and 24 inches.
Mollic epipedon thickness - 8 to 20 inches.
Rock fragments are mainly argillite and quartzite. In some pedons, calcareous material is below a depth of 40 inches.
A horizon - Hue: 7.5YR or 10YR
Value: 3, 4, or 5 dry; 2 or 3 moist
Chroma: 1 or 2
Texture: loam, fine sandy loam, or sandy loam
Clay content: 7 to 18 percent
Rock fragments: 15 to 60 percent--0 to 25 percent cobbles and stones; 10 to 50 percent gravel
Reaction: pH 6.6 to 7.3
Bw horizon - Hue: 7.5YR or 10YR
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: loam, fine sandy loam, or sandy loam
Clay content: 5 to 18 percent
Rock fragments: 35 to 60 percent--0 to 30 percent cobbles and stones; 15 to 50 percent gravel
Reaction: pH 6.6 to 7.3
BC horizon - Value: 6 or 7 dry; 4 or 5 moist
Chroma: 2 or 3
Texture: loam, fine sandy loam, or sandy loam
Clay content: 5 to 18 percent
Rock fragments: 35 to 60 percent--0 to 30 percent cobbles and stones; 15 to 50 percent gravel
Reaction: pH 6.6 to 7.3
C horizon - Value: 6 or 7 dry; 4 or 5 moist
Chroma: 2 or 3
Texture: loam, sandy loam, or loamy sand
Clay content: 5 to 18 percent
Rock fragments: 40 to 85 percent--5 to 40 percent cobbles and stones, 20 to 60 percent gravel
Reaction: pH 6.6 to 7.3
COMPETING SERIES:
Bergquist (ID) - have bedrock at 20 to 40 inches.
Bradshaw (UT) - calcareous above a depth of 40 inches.
Brunzell (ID) - averages more than 18 percent clay in the particle size control section.
Cupine (ID) - have bedrock at 20 to 40 inches.
Fuego (OR) - have bedrock at 20 to 40 inches.
Mud Springs (UT) - have bedrock at 20 to 40 inches.
Potamus (OR) - have 28 to 35 percent clay in the particle size control section.
St. Marys (UT) - have hue of 5YR and 2.5YR in the B horizon.
Warshod (ID) have paralithic contact at 40 to 60 inches.
GEOGRAPHIC SETTING:
Landform: alluvial fans, stream terraces, foothills, moraines, and mountain.
Elevation - 2,500 to 5,500 feet.
Slope - 0 to 70 percent.
Parent material - colluvium, alluvium, or glacial till.
Climate - long, cold winters; moist springs; and warm, dry summers.
Mean annual precipitation - 14 to 24 inches, much of which falls as snow and as spring rain.
Mean annual temperature - 41 to 45 degrees F.
Frost-free period - 80 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS:
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; moderately rapid permeability.
USE AND VEGETATION: Bigarm soils are used mainly as rangeland. The potential native vegetation is rough fescue, Idaho fescue, bluebunch wheatgrass, Sandberg bluegrass, prairie junegrass, perennial forbs, and woody shrubs.
DISTRIBUTION AND EXTENT: Bigarm soils are of moderate extent in mountain valleys in western Montana. MLRA 43A, 44A, 46
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Missoula County, Montana, 1985.
REMARKS: Soil Interpretations Record: MT0420. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the soil surface to 12 inches (A horizon); a cambic horizon from 12 to 18 inches (Bw horizon); a particle-size control section from 10 to 40 inches (A, Bw, BC, C horizons). Bigarm soils have a xeric moisture regime and a frigid temperature regime.