LOCATION BEARMOUTH               MT+WY

Established Series
Rev. BDD-KTS-RJS
03/2011

BEARMOUTH SERIES

The Bearmouth series consists of very deep, excessively drained soils that formed in alluvium, colluvium, outwash or till derived from mixed sources. These soils are on flood plains, stream terraces, outwash plains, moraines, fan remnants, alluvial fans and mountain slopes. Slopes are 0 to 40 percent. Mean annual precipitation is about 19 inches, and mean annual air temperature is about 42 degrees F

TAXONOMIC CLASS: Sandy-skeletal, mixed Ustic Haplocryolls

TYPICAL PEDON: Bearmouth cobbly loam, grassland (colors are for dry soil unless otherwise noted).

A--0 to 4 inches; dark gray (10YR 4/1) cobbly loam, very dark brown (10YR 2/2) moist; moderate fine granular structure; soft, very friable, nonsticky and nonplastic; 5 percent gravel and 20 percent cobbles; neutral (pH 6.8); clear wavy boundary. (3 to 8 inches thick)

Bw1--4 to 9 inches; brown (10YR 4/3) very gravelly loam, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; 40 percent gravel and 15 percent cobbles; neutral (pH 6.8); gradual wavy boundary.

Bw2--9 to 14 inches; brown (10YR 4/3) very gravelly loam, dark brown (10YR 3/3) moist; weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; 40 percent gravel and 15 percent cobbles; neutral (pH 6.8); gradual wavy boundary. (Combined thickness of Bw horizons is 6 to 17 inches)

2C--14 to 60 inches; brown (10YR 5/3) extremely cobbly sand, dark grayish brown (10YR 4/2) moist; single grain; loose; 50 percent cobbles and 20 percent gravel; few lime coatings on underside of some rock fragments at depths greater than 22 inches; slightly alkaline (pH 7.8).

TYPE LOCATION: Granite County, Montana; 660 feet east and 300 feet south of the N 1/4 corner of sec. 30, T. 16 N., R. 15 W.

RANGE IN CHARACTERISTICS:
Soil temperature - 35 to 47 degrees F.
Mollic epipedon thickness - 7 to 15 inches
Depth to lithologic discontinuity - 10 to 20 inches

A horizon
Hue: 10YR or 7.5YR; dry or moist
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 1 to 3; dry or moist
Texture: loam or sandy loam
Clay content: 10 to 25 percent
Rock fragments: 10 to 80 percent--5 to 60 percent gravel, 0 to 75 percent stones or cobbles
Reaction: pH 6.4 to 7.3

Bw1 horizon
Hue: 10YR or 7.5YR; dry or moist
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 2 or 3; dry or moist
Texture: loam or sandy loam
Clay content: 10 to 25 percent
Rock fragments: 10 to 60 percent--5 to 60 percent gravel, 5 to 30 percent stones or cobbles
Reaction: pH 6.4 to 7.8

Bw2 horizon
Hue: 10YR or 7.5YR; dry or moist
Value: 3 to 6 dry; 3 to 5 moist
Chroma: 2 to 4; dry or moist
Texture: loam, sandy loam or sandy clay loam
Clay content: 10 to 25 percent
Rock fragments: 35 to 80 percent--20 to 60 percent gravel, 10 to 40 stones or cobbles
Reaction: pH 6.6 to 7.8

2C horizon
Hue: 7.5YR, 10YR or 2.5Y; dry or moist
Value: 4 to 6 dry; 3 to 5 moist
Chroma: 2 to 4; dry or moist
Texture: sand or loamy sand
Clay content: 0 to 10 percent
Rock fragments: 60 to 90 percent--20 to 65 percent gravel, 20 to 50 percent stones or cobbles
CaCO3 equivalent: 0 to 5 percent
Reaction: pH 6.6 to 7.8

COMPETING SERIES:
Pierian (CO) - do not have a lithologic discontinuity
Temdille (CO) - do not have a lithologic discontinuity
Tine (CO) - do not have a Bw horizon

GEOGRAPHIC SETTING:
Landform - flood plains, stream terraces, outwash plains, moraines, fan remnants, alluvial fans and mountain slopes
Elevation - 4800 to 7500 feet
Slope - 0 to 40 percent
Parent material - alluvium, colluvium, outwash or till
Climate - long, cold winter; moist springs; cool summers; and moist falls
Mean annual precipitation - 14 to 24 inches
Mean annual temperature - 34 to 45 degrees F.
Frost-free period - 30 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Lolon and Slocum series. Lolon soils are loamy-skeletal and pachic. Slocum soils are somewhat poorly drained. These soils are on similar landform positions.

DRAINAGE AND PERMEABILITY: Excessively drained; moderate permeability above the 2C horizon and rapid in the 2C horizon.

USE AND VEGETATION: Bearmouth soils are used mainly for rangeland. Potential native vegetation is mainly rough fescue, Idaho fescue, Columbia needlegrass, bluebunch wheatgrass, forbs, and shrubs.

DISTRIBUTION AND EXTENT: Bearmouth soils are moderately extensive in mountain valleys of western Montana and western Wyoming. MLRAs 43B, 44B and 46.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.

SERIES ESTABLISHED: Granite County, Montana, 1969.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 14 inches (A, Bw1 and Bw2 horizons)
Lithologic discontinuity - at 14 inches (2C horizon)
Particle-size control section - from 10 to 40 inches (Bw2 and 2C horizons)

Bearmouth soils have an ustic moisture regime and a cryic temperature regime.

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National Cooperative Soil Survey
U.S.A.