LOCATION TWINADAMS MT

Established Series
Rev. GFB-JJU-EMM
04/2014

TWINADAMS SERIES

The Twinadams series consists of moderately deep, well drained soils that formed in slope alluvium or colluvium derived from hard sedimentary and igneous rock. They are on cuestas, scarp slopes, hills, mountain slopes and ridges. Slopes are 4 to 60 percent. The mean annual precipitation is about 12 inches, and the mean annual air temperature is about 43 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Calcidic Haplustalfs

TYPICAL PEDON: Twinadams very channery loam, in rangeland (colors are for dry soil unless otherwise noted).

A--0 to 4 inches; light olive brown (2.5Y 5/3) very channery loam, dark olive brown (2.5Y 3/3) moist; weak fine and medium subangular blocky structure parting to weak fine granular; soft, very friable, slightly sticky and slightly plastic; common very fine and few fine roots; 40 percent channers and 15 percent flagstones; neutral (pH 6.8); clear smooth boundary. (3 to 6 inches thick)

Bt--4 to 9 inches; light olive brown (2.5Y 5/4) very channery clay loam, olive brown (2.5Y 4/4) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine and few fine roots; many distinct clay films on faces of peds and on surface of rock fragments; 50 percent channers; neutral (pH 6.8); clear smooth boundary. (4 to 9 inches thick)

Bk1--9 to 17 inches; light gray (2.5Y 7/2) very channery sandy loam, light yellowish brown (2.5Y 6/3) moist; weak fine and medium subangular blocky structure parting to weak fine granular; soft, very friable, slightly sticky and nonplastic; common very fine and few fine roots; 40 percent channers; common soft masses of calcium carbonate; violently effervescent; moderately alkaline (pH 8.0); clear smooth boundary. (7 to 13 inches thick)

Bk2--17 to 28 inches; light yellowish brown (2.5Y 6/3) very channery sandy loam, light olive brown (2.5Y 5/3) moist; weak fine and medium subangular blocky structure parting to weak fine granular; soft, very friable, slightly sticky and nonplastic; few fine roots; 55 percent channers; common soft masses of calcium carbonate, and finely disseminated calcium carbonate; violently effervescent; moderately alkaline (pH 8.3); clear smooth boundary. (6 to 13 inches thick)

Cr--28 to 36 inches; pale yellow (5Y 7/3) semiconsolidated sedimentary beds that crush to sandy loam, olive (5Y 5/4) moist; strongly effervescent; strongly alkaline (pH 8.6); clear smooth boundary. (0 to 16 inches thick)

R--36 inches; sedimentary bedrock.

TYPE LOCATION: Beaverhead County, Montana; 300 feet south and 700 feet west of the northeast corner of sec. 31, T. 4S, R. 9W; Twin Adams Mountain topographic quadrangle; Latitude 45 degrees 27 minutes 5 seconds N.; Longitude 112 degrees 45 minutes 35 seconds W.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 38 to 44 degrees F.
Depth to argillic horizon - 3 to 6 inches
Depth to calcic horizon - 7 to 15 inches
Depth to paralithic contact - 20 to 36 inches
Depth to lithic contact - 24 to 40 inches.

A horizon
Hue: 2.5Y or 10YR; dry or moist
Value: 3 or 4 moist
Chroma: 2 or 3; dry or moist
Texture: loam, sandy clay loam, sandy loam or clay loam
Clay content: 15 to 30 percent
Rock fragments: 20 to 60 percent--20 to 45 percent channers or gravel, 0 to 20 percent flagstones or cobbles
Reaction: pH 6.1 to 7.6

Bt horizon
Hue: 2.5Y or 10YR; dry or moist
Value: 3 or 4 moist
Chroma: 2 to 4; dry or moist
Texture: clay loam, sandy clay loam or loam
Clay content: 22 to 35 percent
Rock fragments: 35 to 70 percent--35 to 55 percent channers or gravel, 0 to 15 percent flagstones or cobbles
Reaction: pH 6.1 to 7.8

Bk1 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 6 or 7 dry; 5 or 6 moist
Chroma: 2 or 3; dry or moist
Texture: sandy loam, sandy clay loam or loam
Clay content: 10 to 30 percent
Rock fragments: 35 to 70 percent--35 to 55 percent channers or gravel, 0 to 15 percent flagstones or cobbles
Calcium carbonate equivalent: 15 to 30 percent
Reaction: pH 7.6 to 8.6

Bk2 horizon
Hue: 10YR, 2.5Y or 5Y; dry or moist
Value: 6 to 8 dry; 5 or 6 moist
Chroma: 2 or 3; dry or moist
Texture: sandy clay loam, loam, silt loam or sandy loam
Clay content: 15 to 25 percent
Rock fragments: 35 to 70 percent--35 to 55 percent channers or gravel, 0 to 20 percent flagstones or cobbles
Calcium carbonate equivalent: 15 to 30 percent
Reaction: pH 7.6 to 8.6

COMPETING SERIES:
Amalia (NM) - are very deep

GEOGRAPHIC SETTING:
Landform - cuestas, scarp slopes, hills, mountain slopes and ridges
Elevation - 4,500 to 6,500 feet
Slope - 4 to 60 percent
Parent material - slope alluvium or colluvium derived from hard sedimentary and igneous rock
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 10 to 14 inches
Mean annual temperature - 39 to 45 degrees F.
Frost-free period - 70 to 90 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Blackleaf and Thunderhead soils. The Blackleaf soils are shallow to lithic contact and loamy-skeletal. The Thunderhead soils are moderately deep and fine-loamy. These soils occur on similar landforms as the Blackleaf soils.

DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.

USE AND VEGETATION: Twinadams soils are used mainly for rangeland. Native vegetation is mainly bluebunch wheatgrass, needleandthread, prairie junegrass, western wheatgrass, fringed sagewort, and big sage.

DISTRIBUTION AND EXTENT: Twinadams soils are of moderate extent in southwestern Montana. MLRAs - 43B, 44B, and 46.

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 4 inches (A horizon)
Argillic horizon - from 4 to 9 inches (Bt horizon
Calcic horizon - from 9 to 28 inches (Bk1, Bk2 horizons)
Paralithic contact - at 28 inches (Cr horizon)
Lithic contact - at 36 inches (R horizon)
Particle-size control section - from 4 to 28 inches (Bt, Bk1, Bk2 horizons)

Twinadams soils have a frigid temperature regime and an ustic moisture regime that borders on aridic.

National Cooperative Soil Survey
U.S.A.