LOCATION BIGBUTTE MTEstablished Series
TAXONOMIC CLASS: Ashy, glassy Vitrandic Haplocryolls
TYPICAL PEDON: Bigbutte gravelly ashy sandy loam, in rangeland on a 12 percent slope at 1,896 meters elevation (colors are for dry soil unless otherwise indicated).
A--0 to 25 cm; dark grayish brown (10YR 4/2) gravelly ashy sandy loam, very dark brown (10YR 2/2) moist; weak fine granular structure; very friable, soft, nonsticky and nonplastic; many very fine and fine roots; many fine interstitial and irregular pores; 15 percent gravel; slightly acid (pH 6.2); clear smooth boundary. (18 to 30 cm thick)
Bw--25 to 46 cm; brown (10YR 5/3) gravelly ashy sandy loam, brown (10YR 4/3) moist; weak medium subangular blocky structure; very friable, soft, nonsticky and nonplastic; common fine roots; common fine irregular pores; 20 percent gravel; neutral (pH 6.6); gradual wavy boundary. (15 to 70 cm thick)
BC--46 to 69 cm; light brownish gray (10YR 6/2) gravelly ashy coarse sandy loam, grayish brown (10YR 5/2) moist; weak medium subangular blocky structure; friable, slightly hard, nonsticky and nonplastic; few fine roots; common fine irregular pores; 30 percent gravel; neutral (pH 7.0); abrupt smooth boundary. (10 to 50 cm thick)
Cr--69 to 81 cm; weakly cemented tuffaceous rhyolite.
R--81 cm; indurated tuffaceous rhyolite.
TYPE LOCATION: Butte North topographic quadrangle, Silver Bow County, Montana; 100 meters south and 215 meters east of the NW corner of section 3, T. 3 N., R. 8 W. UTM Zone 12: 377082e, 5100448n, NAD 83.
RANGE IN CHARACTERISTICS:
Soil temperature - 2 to 6 degrees C
Moisture control section - 20 to 60 cm
Thickness of the mollic epipedon - 18 to 30 cm
Depth to bedrock - 50 to 100 cm
Volcanic glass - 30 to 50 percent in the coarse silt and sand fraction.
Acid oxalate Al + 1/2 Fe - .12 to .20 percent
A horizon
Hue: 10YR or 2.5Y
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 2 or 3, dry or moist
Clay content: 12 to 22 percent
Rock fragments: 5 to 20 percent--0 to 15 percent gravel, 0 to 5 percent cobbles Reaction: pH 5.6 to 7.3
Bw horizon
Hue: 10YR or 2.5Y
Value: 4 to 6 dry; 3 to 5 moist
Chroma: 3 or 4, dry or moist
Texture: ashy sandy loam or ashy coarse sandy loam
Clay content: 12 to 22 percent
Rock fragments: 15 to 35 percent--5 to 30 percent gravel, 0 to 10 percent cobbles
Reaction: pH 5.6 to 7.2
BC horizon
Hue: 10YR or 2.5Y
Value: 5 to 7 dry; 4 or 5 moist
Chroma: 2 to 4, dry or moist
Texture: ashy coarse sandy loam or ashy sandy loam
Clay content: 10 to 22 percent
Rock fragments: 15 to 35 percent--15 to 35 percent gravel, 0 to 10 percent cobbles
Reaction: pH 5.6 to 7.2
COMPETING SERIES:
Anniecreek (OR) - has Bg horizons.
Brownsbowl (NV) - has a mollic epipedon 100 to 115 centimeters thick.
Cadero (ID) - is moderately deep to a paralithic contact.
GEOGRAPHIC SETTING:
Landform - mountain, hills and benches
Elevation - 1,585 to 2,220 meters
Slope - 6 to 50 percent
Parent material - volcanic ash influenced colluvium over rhyolite, rhyodacite, or rhyolitic tuff
Climate - long, cold winters; cold, moist springs; short, cool summers
Mean annual precipitation - 355 to 483 millimeters, much of which falls as snow and as spring rain
Mean annual air temperature - 1 to 5 degrees centigrade
Frost-free period - 50 to 70 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Poin, Euell and Hungryhill soils which occur on similar landforms. Poin soils are in the loamy-skeletal particle-size family. Euell soils are very deep. Hungryhill soils have an argillic horizon.
DRAINAGE AND PERMEABILITY: well drained; moderate permeability.
USE AND VEGETATION: Bigbutte soils are used mainly for grazing. Native vegetation is Idaho fescue, bluebunch wheatgrass, rough fescue, prairie junegrass, big sagebrush and widely spaced Rocky Mountain juniper.
DISTRIBUTION AND EXTENT: Bigbutte soils are of small extent in the intermontane basins of central Montana. MLRA 43B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Silver Bow County, Montana, 2006.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 25 cm (A horizon)
Cambic horizon - from 25 to 46 cm (Bw horizon)
Particle-size control section - from 25 to 69 cm
Bigbutte soils have a cryic temperature regime and an ustic moisture regime.