LOCATION ELKPEAK MT
Established Series
Rev. EAW-RJS
07/2012
ELKPEAK SERIES
The Elkpeak series consists of very deep, well drained soils that formed in colluvium derived from sedimentary, metamorphic, or igneous rock. These soils are on escarpments, mountain slopes or landslides. Slopes range from 8 to 60 percent. Mean annual precipitation is about 760 millimeters and the mean annual air temperature is about 3 degrees C.
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Typic Argicryolls
TYPICAL PEDON: Elkpeak gravelly fine sandy loam in shrubland on a 12 percent slope at about 2317 meters elevation (colors are for air-dry soil unless otherwise stated).
A--0 to 22 cm; dark grayish brown (10YR 4/2) gravelly fine sandy loam, very dark brown (10YR 2/2) moist; weak, very fine and fine granular structure; soft, very friable, slightly sticky and nonplastic; many very fine, fine, and medium roots; many very fine and fine irregular pores; 25 percent gravel; neutral (pH 6.8); clear smooth boundary. (15 to 40 cm thick)
Bt1--22 to 37 cm; dark grayish brown (10YR 4/2) very gravelly loam, very dark grayish brown (10YR 3/2) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine, fine, and medium roots; many very fine and fine irregular pores; 25 percent faint clay films on faces of peds and on rock fragments; 30 percent gravel and 10 percent cobbles; neutral (pH 6.6); clear wavy boundary.
Bt2--37 to 63 cm; brown (10YR 5/3) very gravelly clay loam, brown (10YR 4/3) moist; weak medium subangular blocky structure; slightly hard, very friable, moderately sticky and moderately plastic; common very fine and fine roots; common very fine and fine irregular pores; 45 percent distinct clay films on faces of peds and on rock fragments; 35 percent gravel and 5 percent cobbles; neutral (pH 6.6); gradual wavy boundary.
Bt3--63 to 87 cm; brown (10YR 5/3) very gravelly clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; few very fine and fine irregular pores; 60 percent distinct clay films on faces of peds and on rock fragments; 35 percent gravel and 10 percent cobbles; neutral (pH 7.2); gradual wavy boundary. (combined thickness of Bt horizons is 40 to 100 cm thick)
BC--87 to 152 cm; yellowish brown (10YR 5/4) very gravelly loam, dark yellowish brown (10YR 4/4) moist; weak medium angular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; few very fine and fine irregular pores; 35 percent gravel and 20 percent cobbles; slightly alkaline (pH 7.4).
TYPE LOCATION: Beaverhead County, Montana; located about 320 meters south and 630 meters east of the northwest corner of sec. 1, T. 14S., R. 1E; Hidden Lake Bench topographic quadrangle; UTM 12T, 456375e., 4943905n. NAD 83.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 2 to 5 degrees C.
Mollic epipedon thickness - 25 to 40 cm
Depth to argillic horizon - 15 to 40 cm
Particle-size control section - averages 20 to 35 percent clay
A horizon:
Hue: 7.5YR or 10YR
Value: 2 to 4 dry; 2 or 3 moist
Chroma: 2 or 3; dry or moist
Texture: sandy loam, fine sandy loam or loam
Clay content: 16 to 25 percent
Rock fragments: 15 to 35 percent--15 to 35 percent gravel; 0 to 10 percent cobbles
Reaction: pH 6.1 to 7.3
Bt horizons:
Hue: 7.5YR or 10YR
Value: 4 to 6 dry; 3 to 5 moist
Chroma: 2 to 4; dry or moist
Texture: clay loam or loam
Clay content: 20 to 35 percent
Rock fragments: 35 to 60 percent--25 to 55 percent gravel, 0 to 15 percent cobbles, 0 to 5 percent stones
Reaction: pH 6.1 to 7.3
BC horizon:
Hue: 7.5YR or 10YR
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 to 4; dry or moist
Texture: sandy loam, sandy clay loam or loam
Clay content: 18 to 27 percent
Rock fragments: 35 to 60 percent--25 to 50 percent gravel, 10 to 25 percent cobbles, 0 to 10 percent stones
Reaction: pH 6.6 to 7.6
COMPETING SERIES:
Elwood (UT) - is moderately deep to lithic contact
Ezbin (ID) - has an O horizon at the surface.
Quazar (CO) - has a lithologic discontinuity
Tahquats (ID) - has pH values of less than 6.1 in the Bt horizons
Wander (CO) - receives most of its precipitation in July and August
GEOGRAPHIC SETTING:
Landform - escarpments, mountain slopes or landslides
Elevation - 1980 to 2900 meters
Slope - 8 to 60 percent
Parent material - colluvium derived from sedimentary, metamorphic or igneous rock
Climate - long, cold winters; moist springs; short warm summers with May and June receiving the most precipitation
Mean annual precipitation - 600 to 920 mm
Mean annual air temperature - 1 to 4 degrees C.
Frost-free period - 30 to 70 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: These soils are used mainly for recreation and wildlife. The vegetation is mainly mountain big sagebrush, mountain brome, nodding oniongrass, bearded wheatgrass, poa species, upland sedges, snowberry, mule's ears, columbine, lupine, nettleleaf horsemint, tall ragwort, tall larkspur, arnica species, and other grasses and forbs. May have a canopy cover of less than 15% aspen and/or conifers.
DISTRIBUTION AND EXTENT: Elkpeak soils are of limited extent in southwestern Montana. MLRA 43B.
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, 2011.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 37 cm (A and Bt1 horizons)
Argillic horizon - from 22 to 87 cm (Bt1, Bt2 and Bt3 horizons)
Particle-size control section - from 22 to 72 cm (Bt1, Bt2 and part of Bt3 horizons).
Elkpeak soils have a cryic temperature regime and an udic moisture regime.
Taxonomic version: Eleventh Edition, 2010.
National Cooperative Soil Survey
U.S.A.