LOCATION MILLPOINT MT
Established Series
REV. KTS-GFB-RJS
01/2012
MILLPOINT SERIES
The Millpoint series consists of very deep, excessively drained soils that formed in alluvium. These soils occur on stream terraces and fan remnants. Slopes are 0 to 4 percent. Mean annual precipitation is about 250 mm, and the mean annual air temperature is about 6 degrees C.
TAXONOMIC CLASS: Sandy-skeletal, mixed, frigid Aridic Haplustolls
TYPICAL PEDON: Millpoint gravelly sandy loam, in pastureland on a 2 percent slope at an elevation of 1865 meters (colors are for dry soil unless otherwise noted).
A--0 to 13 cm; grayish brown (10YR 5/2) gravelly sandy loam, very dark grayish brown (10YR 3/2) moist; weak medium and fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine dendritic tubular pores; 20 percent gravel and 5 percent cobbles; neutral (pH 6.8); clear smooth boundary. (8 to 18 cm thick)
Bw--13 to 30 cm; brown (10YR 5/3) very gravelly sandy loam, dark brown (10YR 3/3) moist; weak fine and medium subangular blocky structure; soft, very friable, nonsticky and slightly plastic; many very fine and fine roots; common very fine and fine dendritic tubular pores; 30 percent gravel and 15 percent cobbles; neutral (pH 6.8); gradual wavy boundary. (13 to 25 cm thick)
BC--30 to 46 cm; brown (7.5YR 5/3) very gravelly loamy sand, brown (7.5YR 4/3) moist; weak fine subangular blocky; soft, very friable, nonsticky and nonplastic; few very fine and fine roots; common very fine and fine irregular pores; 35 percent gravel and 20 percent cobbles; neutral (pH 7.0); gradual wavy boundary. (0 to 25 cm thick)
C--46 to 152 cm; light brown (7.5YR 6/3) extremely cobbly sand, brown (7.5YR 4/3) moist; single grain; loose, nonsticky and nonplastic; few very fine roots in the upper part; common fine interstitial pores; 40 percent gravel and 30 percent cobbles; neutral (pH 7.0).
TYPE LOCATION: Beaverhead County, Montana; located about 500 feet south and 1950 feet east of the northwest corner of sec. 21, T. 7S, R 12W; Mill Point topographic quadrangle; UTM 12T, 336491e, 5009379n, NAD 83.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 5 to 8 degrees C.
Mollic epipedon thickness - 18 to 38 cm
Depth to sandy-skeletal material - 30 to 50 cm
A horizon
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 2 or 3; dry or moist
Texture: loam or sandy loam
Clay content: 15 to 22 percent
Rock fragments: 10 to 35 percent--10 to 30 percent gravel, 0 to 20 percent cobbles
Reaction: pH 6.6 to 7.3
Bw horizon
Value: 3 to 5 dry; 2 to 4 moist
Chroma: 2 or 3; dry or moist
Texture: loam or sandy loam
Clay content: 15 to 23 percent
Rock fragments: 35 to 65 percent--20 to 50 percent gravel, 15 to 40 percent cobbles and stones
Reaction: pH 6.6 to 7.3
BC horizon
Hue: 10YR or 7.5YR; dry or moist
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2 to 4; dry or moist
Texture: sandy loam or loamy sand
Clay content: 5 to 18 percent
Rock fragments: 40 to 65 percent--20 to 50 percent gravel, 15 to 40 percent cobbles and stones
Reaction: pH 6.6 to 7.3
C horizon
Hue: 10YR or 7.5YR; dry or moist
Value: 4 to 6 dry; 3 or 4 moist
Chroma: 2 to 4; dry or moist
Texture: sand or loamy sand
Clay content: 0 to 10 percent
Rock Fragments: 50 to 80 percent--30 to 50 percent gravel, 20 to 40 percent cobbles and stones
Reaction: pH 6.6 to 7.3
COMPETING SERIES:
Dominson (CO) - are calcareous below the A horizon
Drygulch (MT) - are dominated by 2 to 10 millimeter sized rock fragments in the control section
Tiechute (MT) - does not have a Bw horizon
Vendome (MT) - have secondary calcium carbonate accumulation
GEOGRAPHIC SETTING:
Landform - stream terraces and fan remnants
Elevation - 1820 to 1980 meters
Slope - 0 to 4 percent
Parent material - alluvium
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 230 to 360 mm
Mean annual air temperature - 4 to 7 degrees C.
Frost-free period - 70 to 90 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Excessively drained; moderate permeability above the BC horizon and very rapid below.
USE AND VEGETATION: Millpoint soils are used mainly for pastureland, rangeland and wildlife habitat. Potential native vegetation is mainly bluebunch wheatgrass, western wheatgrass, prairie junegrass, Poa (species), big sagebrush, and other grasses and forbs.
DISTRIBUTION AND EXTENT: Millpoint soils are of small extent in southwestern Montana. MLRA - 44B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Horse Prairie-South Valley Area - Part of Beaverhead County, Montana, 2011; proposed in Beaverhead County, Montana, 2008.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 30 cm (A, Bw horizons)
Particle-size control section - from 25 to 100 cm (part of Bw, BC, part of C horizons)
Millpoint soils have a frigid temperature regime and an ustic moisture regime bordering on aridic.
National Cooperative Soil Survey
U.S.A.