LOCATION BEAVROCK MT
Established Series
Rev. GFB-KTS-RJS
03/2011
BEAVROCK SERIES
The Beavrock series consists of very deep, poorly drained soils that formed in alluvium. These soils are on flood plains, flood plain steps, and sloughs. Slopes are 0 to 4 percent. Mean annual precipitation is about 12 inches, and mean annual air temperature is about 42 degrees F.
TAXONOMIC CLASS: Fine-loamy over sandy or sandy-skeletal, mixed, superactive, calcareous, frigid Typic Fluvaquents
TYPICAL PEDON: Beavrock silt loam, in rangeland. (Colors are for moist soil unless otherwise noted)
Oe--0 to 3 inches; mat of roots and partially decomposed sedges and grasses; clear smooth boundary. (0 to 5 inches thick)
A--3 to 8 inches; dark grayish brown (10YR 4/2) silt loam, light brownish gray (10YR 6/2) dry; moderate fine and medium platy structure; very hard, firm, very sticky and very plastic; many very fine, fine, medium, and coarse roots; many very fine and few fine interstitial pores; disseminated calcium carbonate; violently effervescent; moderately alkaline (pH 8.4); clear wavy boundary. (3 to 10 inches thick)
C1--8 to 15 inches; dark grayish brown (2.5Y 4/2) clay loam consisting of thin strata of silty clay loam, loam, and sandy loam, grayish brown (2.5Y 5/2) dry; massive; very hard, firm, very sticky and very plastic; common very fine, fine, medium, and coarse roots; many fine and very fine tubular and interstitial pores; disseminated calcium carbonate; strongly effervescent; moderately alkaline (pH 8.2); clear wavy boundary.
C2--15 to 20 inches; dark grayish brown (2.5Y 4/2) clay loam consisting of thin strata of silty clay loam and sandy loam, light brownish gray (2.5Y 6/2) dry; few fine and medium distinct brownish yellow (10YR 6/6) redox concentrations; massive; very hard, firm, very sticky and very plastic; common very fine and fine roots; few very fine tubular and interstitial pores; disseminated calcium carbonate; strongly effervescent; moderately alkaline (pH 8.0); abrupt smooth boundary. (combined thickness of C1 and C2 horizons is 10 to 14 inches)
C3--20 to 23 inches; light olive brown (2.5Y 5/3) sandy loam, light yellowish brown (2.5Y 6/3) dry; common fine, medium, and coarse prominent brownish yellow (10YR 6/6) redox concentrations; massive; soft, very friable, nonsticky and nonplastic; few very fine roots; disseminated calcium carbonate; strongly effervescent; slightly alkaline (pH 7.8); abrupt smooth boundary. (0 to 5 inches thick)
Cg1--23 to 28 inches; dark gray (N 4/) silty clay loam, light greenish gray (10Y 7/1) dry; many medium and coarse prominent brownish yellow (10YR 6/6) redox concentrations; massive; extremely hard, firm, very sticky and very plastic; disseminated calcium carbonate; strongly effervescent; slightly alkaline (pH 7.8); clear smooth boundary. (0 to 10 inches thick)
2Cg2--28 to 60 inches; dark gray (N 4/) extremely gravelly sand, light greenish gray (10Y 7/1) dry; massive; loose, nonsticky and nonplastic; 65 percent gravel, 10 percent cobbles; disseminated calcium carbonate; slightly effervescent; slightly alkaline (pH 7.8).
TYPE LOCATION: Beaverhead County, Montana; 200 feet west and 1800 feet north of the SE corner of sec. 21, T. 6 S., R. 7 W. Beaverhead Rock topographic quadrangle. lat. 45 degrees 23 minutes 2 seconds N. and long. 112 degrees 27 minutes 45 seconds W.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 38 to 43 degrees F.
Depth to lithologic discontinuity - 16 to 40 inches
Depth to seasonal high water table - 12 to 24 inches
A horizon
Hue: 10YR, 2.5Y or 5Y; dry or moist
Value: 4 to 6 dry; 3 to 5 moist
Chroma: 1 or 2; dry or moist
Texture: loam or silt loam
Clay content: 15 to 27 percent
Rock fragments: 0 to 10 percent gravel
Calcium carbonate equivalent: 10 to 30 percent
Reaction: pH 7.4 to 8.4
Note: When mixed to 6 inches the epipedon has moist value of 4.
C horizons
Hue: 2.5Y or 5Y; dry or moist
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 1 to 3; dry or moist
Texture: loam, sandy loam, sandy clay loam or clay loam
Clay content: 18 to 35 percent
Rock fragments: 0 to 10 percent gravel
Calcium carbonate equivalent: 10 to 25 percent
Reaction: 7.4 to 8.4
Cg1 horizon
Hue: N, 10Y, or 10YR; dry or moist
Value: 5 to 7 dry; 4 or 5 moist
Chroma: 1 or 2; dry or moist
Texture: sandy loam, loam or silty clay loam
Clay content: 18 to 35 percent
Rock fragments: 0 to 10 percent gravel
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 8.4
2Cg2 horizon
Hue: N, 10Y, or 10YR; dry or moist
Value: 5 to 7 dry, 4 or 5 moist
Texture: loamy sand, loamy coarse sand, sand or coarse sand
Clay content: 0 to 10 percent
Rock fragments: 35 to 85 percent--35 to 65 percent gravel, 0 to 20 percent cobbles
Reaction: pH 7.4 to 8.4
COMPETING SERIES:
Threeriv (MT) - has a seasonal high water table at depths less than 12 inches
GEOGRAPHIC SETTING:
Landform - flood plains, flood plain steps and sloughs
Elevation - 4,500 to 6,500 feet
Slope - 0 to 4 percent
Parent material - alluvium
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 10 to 14 inches
Mean annual air temperature - 39 to 45 degrees F.
Frost-free period - 70 to 105 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Poorly drained; moderate permeability above the 2Cg2 horizon and rapid permeability in the 2Cg2 horizon.
USE AND VEGETATION: Beavrock soils are used mainly for range. Potential native vegetation is mainly Nebraska sedge, wire grass, iris, and willows.
DISTRIBUTION AND EXTENT: Beavrock soils are of small extent in southwest Montana. MLRA 44B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Beaverhead County, Montana, 2001.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - from 0 to 8 inches (Oe and A horizons)
Particle-size control section - from 10 to 40 inches (part of C1, C2, C3, Cg1, and part of 2Cg2 horizons)
Beavrock soils have a frigid temperature regime and an aquic moisture regime.
National Cooperative Soil Survey
U.S.A.