LOCATION SWIFTCURRENT MTEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive Eutric Glossocryalfs
TYPICAL PEDON: Swiftcurrent loam in woodland (colors are for dry soil unless noted otherwise).
Oi--0 to 2 inches; forest litter of pine needles and twigs.
E--2 to 6 inches; very pale brown (10YR 7/3) loam, brown (10YR 5/3) moist; moderate thin platy structure parting to moderate fine and very fine granular; soft, very friable, slightly sticky and nonplastic; many fine and very fine roots, and few medium roots; 5 percent pebbles; neutral (pH 6.6); clear smooth boundary. (3 to 10 inches thick)
E/Bt--6 to 13 inches; E part (80 percent) very pale brown (10YR 7/3) loam, brown (10YR 5/3) moist tongues; Bt part (20 percent) pale brown (10YR 6/3) clay loam, dark brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate medium and fine subangular blocky; slightly hard, very friable, moderately sticky and slightly plastic; many fine and very fine roots, and few medium roots; many very fine tubular and interstitial pores; many faint silt and sand skeletans on faces of peds; few faint clay films on faces of peds; 5 percent pebbles and 5 percent cobbles; neutral (pH 6.8); gradual smooth boundary. (5 to 15 inches thick)
Bt1--13 to 30 inches; pale brown (10YR 6/3) gravelly clay loam, dark yellowish brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate medium and coarse subangular blocky; hard, friable, moderately sticky and slightly plastic; common fine and very fine roots, and few medium roots; many very fine tubular and interstitial pores; many distinct clay films on faces of peds; 15 percent pebbles and 5 percent cobbles; neutral (pH 6.8); gradual smooth boundary. (15 to 25 inches thick)
Bt2--30 to 43 inches; light yellowish brown (10YR 6/4) gravelly clay loam, yellowish brown (10YR 5/4) moist; moderate medium prismatic structure; slightly hard, friable, moderately sticky and slightly plastic; common very fine roots; many very fine tubular and interstitial pores; many distinct clay films on faces of peds; 15 percent pebbles and 5 percent cobbles; slightly alkaline (pH 7.6); gradual smooth boundary. (12 to 25 inches thick)
Bk--43 to 60 inches; very pale brown (10YR 7/3) gravelly loam, brown (10YR 5/3) moist; weak medium and fine subangular blocky structure; slightly hard, very friable, slightly sticky and nonplastic; few very fine roots; common very fine interstitial pores; 25 percent pebbles and 5 percent cobbles; disseminated lime; common distinct lime casts on undersides of fragments; strongly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Lewis and Clark County, Montana; 2,500 feet west and 1,200 feet south of the NE corner of sec. 30 T. 19 N., R. 8 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 37 to 42 degrees F.
Moisture control section - between 4 and 12 inches.
Depth to the top of the Argillic horizon - 8 to 24 inches.
Depth to carbonate - 40 to 60 inches.
Some pedons have a mollic colored A horizon that is 2 to 4 inches thick.
E horizon - Hue: 5YR, 7.5YR, or 10YR
Value: 5, 6, or 7 dry; 4 or 5 moist
Chroma: 2 or 3
Texture: loam or sandy loam
Clay content: 15 to 27 percent
Coarse fragments: 0 to 15 percent pebbles
Reaction: pH 5.6 to 7.3
E/Bt or BtE horizon - Hue: 5YR, 7.5YR, or 10YR
Value: E part 5, 6, or 7, Bt part 4, 5, or 6 dry; E part 4 or 5, Bt part 3, 4, or 5 moist
Chroma: E part 2 or 3; Bt part 3 or 4
Texture: loam, sandy loam, or sandy clay loam
Clay content: 18 to 35 percent
Coarse fragments: 0 to 15 percent--0 to 5 percent cobbles, 0 to 10 percent pebbles
Reaction: pH 5.6 to 7.3
Bt horizons - Hue: 5YR, 7.5YR, or 10YR
Value: 5 or 6 dry; 3, 4, or 5 moist
Chroma: 2, 3, or 4
Texture: clay loam or sandy clay loam
Clay content: 27 to 35 percent
Coarse fragments: 0 to 35 percent--0 to 5 percent cobbles, 0 to 30 percent pebbles
Reaction: pH 6.1 to 7.8
Bk horizon - Hue: 7.5YR or 10YR
Value: 6 or 7 dry; 4 or 5 moist
Chroma: 2 or 3
Texture: loam or sandy clay loam
Clay content: 20 to 27 percent
Coarse fragments: 0 to 35 percent--0 to 5 percent cobbles, 0 to 30 percent pebbles
Calcium carbonate equivalent: 1 to 10 percent
Reaction: pH 7.4 to 8.4
COMPETING SERIES:
Uinta (WY) - does not have horizon of secondary carbonate accumulation.
Warwood (MT) - does not have horizon of secondary carbonate accumulation.
GEOGRAPHIC SETTING:
Landform - mountains.
Elevation - 4,800 to 6,500 feet.
Slope - 8 to 65 percent.
Parent material - colluvium and alluvium from mixed and igneous rocks.
Climate - long, cold winters; moist springs; cool summers.
Mean annual precipitation - 20 to 30 inches, most of which falls as snow and spring rain.
Mean annual air temperature - 35 to 40 degrees F.
Frost-free period - 50 to 70 days.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.
USE AND VEGETATION: Swiftcurrent soils are used mainly for woodland, understory grazing, and wildlife habitat. The potential native vegetation is mainly Douglas fir, lodgepole pine, and subalpine fir trees with an understory of heartleaf arnica, Rocky mountain clematis, dwarf huckleberry, western meadowrue, white spiraea, pinegrass, elk sedge, common snowberry, Engelmann aster, twinflower, and kinnikinnick.
DISTRIBUTION AND EXTENT: Swiftcurrent soils are inextensive in the mountains of western and north central Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Lewis and Clark County, Montana, 1991.
REMARKS: Soil interpretation record: MT1259. Diagnostic horizons and features recognized in this pedon are: an ochric epipedon from 2 to 13 inches (E and E/Bt horizons); an argillic horizon from 13 to 43 inches (Bt1 and Bt2 horizons); a particle-size control section in the upper 20 inches of the argillic horizon (Bt1 and part of Bt2 horizons). Swiftcurrent soils have a cryic temperature regime and a udic moisture regime.