LOCATION POLARIS MT
Established Series
REV. KTS-JJU-RJS
01/2012
POLARIS SERIES
The Polaris series consists of shallow, well drained soils that formed in colluvium or slide deposits over residuum derived from interbedded shale, siltstone and sandstone. These soils occur on hills, escarpments, ridges, landslides and eroded fan remnants. Slopes are 4 to 45 percent. Mean annual precipitation is about 330 mm, and the mean annual air temperature is about 5 degrees C.
TAXONOMIC CLASS: Loamy, mixed, superactive, frigid, shallow Aridic Calciustepts
TYPICAL PEDON: Polaris cobbly sandy clay loam, in rangeland on a 35 percent slope at an elevation of 1870 meters. (colors are for dry soil unless otherwise noted)
A--0 to 8 cm; grayish brown (10YR 5/2) cobbly sandy clay loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium granular structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; many very fine and fine irregular pores; 10 percent gravel and 10 percent cobbles; slightly effervescent; moderately alkaline (pH 8.0); clear smooth boundary. (5 to 13 cm thick)
Bk1--8 to 30 cm; pale brown (10YR 6/3) cobbly sandy clay loam, brown (10YR 4/3) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; common very fine and fine irregular pores; 10 percent gravel and 10 percent cobbles; finely disseminated calcium carbonate, and 2 percent fine distinct irregular soft masses and threads of calcium carbonate; strongly effervescent; moderately alkaline (pH 8.2); gradual wavy boundary.
Bk2--30 to 46 cm; very pale brown (10YR 7/3) sandy loam, brown (10YR 5/3) moist; weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; few very fine and fine roots; common very fine and fine irregular pores; 5 percent gravel; finely disseminated calcium carbonate, and 25 percent fine and medium distinct irregular soft masses and threads of calcium carbonate; violently effervescent; strongly alkaline (pH 8.8); gradual wavy boundary. (combined thickness of Bk1, Bk2 horizons - 25 to 45 cm)
Cr--46 to 152 cm; light gray (10YR7/2) moderately cemented semi-consolidated sedimentary beds that crush to a loamy sand, brown (10YR5/3) moist.
TYPE LOCATION: Beaverhead County, Montana; located about 1,250 feet west and 1,900 feet south of the northeast corner of sec.5, T. 7S, R. 12W; Polaris topographic quadrangle; UTM 12T, 335616e, 5013823n, NAD 83.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 5 to 8 degrees C.
Depth to calcic horizon - 8 to 36 cm
Depth to paralithic contact - 25 to 50 cm
A horizon
Hue: 7.5YR, 10YR or 2.5Y; dry or moist
Value: 5 or 6 dry; 3 or 4 moist
Chroma: 2 or 3; dry or moist
Texture: loam or sandy clay loam
Clay content: 10 to 30 percent
Rock fragments: 0 to 35 percent--0 to 35 percent gravel, 0 to 20 percent cobbles
Electrical conductivity: 0 to 4 mmhos/cm
Calcium carbonate equivalent: 3 to 10 percent
Reaction: pH 7.8 to 8.4
Bk horizons
Hue: 7.5YR, 10YR or 2.5Y; dry or moist
Value: 6 or 7 dry; 4 or 5 moist
Chroma: 2 to 4; dry or moist
Texture: loam, sandy clay loam or sandy loam
Clay content: 10 to 30 percent
Rock Fragments: 0 to 35 percent--0 to 30 percent gravel, 0 to 15 percent cobbles
Electrical conductivity: 0 to 8 mmhos/cm
Sodium adsorption ratio: 0 to 10
Calcium carbonate equivalent: 5 to 25 percent
Reaction: pH 7.9 to 9.0
Note: Calcium carbonate equivalent of less than 15 percent have a clay content of less 18 percent.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - hills, escarpments, ridges, landslides and eroded fan remnants
Elevation - 1750 to 2075 meters
Slope - 4 to 45 percent
Parent material - colluvium or slide deposits over residuum derived from interbedded shale, siltstone and sandstone
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 250 to 355 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: Well drained; moderate permeability.
USE AND VEGETATION: Polaris soils are used mainly for rangeland and wildlife habitat. Potential native vegetation is mainly big sagebrush, rabbitbrush, bluebunch wheatgrass, Poa (species), Opuntia (species), miscellaneous forbs and half-shrubs.
DISTRIBUTION AND EXTENT: Polaris soils are of small extent in southwestern Montana. MLRAs - 43B, 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:
Ochric epipedon - from 0 to 8 cm (A horizon)
Calcic horizon - from 8 to 46 cm (Bk1, Bk2 horizons)
Paralithic contact - at 46 cm (Cr horizon)
Particle-size control section - from 25 to 46 cm (part of Bk1, Bk2 horizons)
Polaris soils have a frigid temperature regime and an ustic moisture regime bordering on aridic.
National Cooperative Soil Survey
U.S.A.