LOCATION TIBKEY                  MT

Established Series
Rev. DES-JJU-RJS
09/2011

TIBKEY SERIES

The Tibkey series consists of very deep, somewhat poorly drained soils that formed in alluvium, colluvium or alpine till derived from fine grained igneous or metamorphic rocks. These soils are on alluvial fans, drainageways and mountain slopes. Slopes are 1 to 15 percent. Mean annual precipitation is about 18 inches, and mean annual air temperature is about 38 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Fluvaquentic Haplocryolls

TYPICAL PEDON: Tibkey mucky silt loam, bouldery, in rangeland (colors are for dry soil unless otherwise noted).

A1--0 to 2 inches; very dark grayish brown (10YR 3/2) mucky silt loam, very dark brown (10YR 2/2) moist; massive; slightly hard, very friable, nonsticky and nonplastic; many very fine and fine roots; 10 percent gravel; slightly acid (pH 6.2); clear wavy boundary.

A2--2 to 8 inches; very dark gray (10YR 3/1) mucky silt loam, black (10YR 2/1) moist; strong medium prismatic structure parting to moderate fine and medium subangular blocky; hard, firm, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine tubular pores; 10 percent gravel; neutral (pH 6.6); clear wavy boundary. (combined thickness of A1, A2 horizons - 2 to 10 inches).

Bw1--8 to 13 inches; grayish brown (10YR 5/2) very gravelly loam, very dark grayish brown (10YR 3/2) moist; weak coarse prismatic structure parting to moderate medium subangular blocky; slightly hard, firm, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine interstitial pores; 40 percent gravel; neutral (pH 6.6); clear wavy boundary.

Bw2--13 to 25 inches; light brownish gray (10YR 6/2) very gravelly loam, brown (10YR 5/3) moist; moderate medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine interstitial pores; 30 percent gravel and 5 percent cobbles; neutral (pH 6.8); gradual wavy boundary.

Bw3--25 to 32 inches; light gray (10YR 7/2) very gravelly loam, brown (10YR 5/3) moist; few fine distinct yellowish brown (10YR 5/6) redox concentrations; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine interstitial pores; 30 percent gravel and 5 percent cobbles; neutral (pH 6.8); gradual irregular boundary. (combined thickness of Bw1, Bw2, Bw3 horizons - 10 to 40 inches)

BC--32 to 60 inches; very pale brown (10YR 7/3) very gravelly loam, pale brown (10YR 6/3) moist; common fine prominent strong brown (7.5YR 5/6) redox concentrations; massive; slightly hard, very friable, slightly sticky and nonplastic; common very fine and fine roots; common very fine and fine interstitial pores; 40 percent gravel and 5 percent cobbles; slightly alkaline (pH 7.4).

TYPE LOCATION: Jefferson County, Montana; 1700 feet north and 350 feet east of the southwest corner of sec. 1, T. 4N, R. 4W.

RANGE IN CHARACTERISTICS:
Soil Temperature - 36 to 42 degrees F.
Mollic epipedon thickness - 8 to 15 inches
Depth to a seasonally high water table - 24 to 42 inches

A1, A2 horizons
Hue: 10YR or 2.5Y; dry or moist
Value: 2 to 4 dry; 2 or 3 moist
Chroma: 0 to 2; dry or moist
Texture: loam, mucky silt loam or mucky loam
Clay content: 15 to 27 percent
Rock fragments: 10 to 40 percent--10 to 35 percent gravel, 0 to 15 percent cobbles, stones or boulders
Reaction: pH 6.1 to 7.3

Bw1 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2 or 3; dry or moist
Texture: silt loam or loam
Clay content: 18 to 27 percent
Rock fragments: 15 to 50 percent--15 to 40 percent gravel, 0 to 15 percent cobbles, stones or boulders
Reaction: pH 6.6 to 7.3

Bw2 horizon
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 2 or 3; dry or moist
Texture: loam, clay loam or sandy clay loam
Clay content: 18 to 30 percent
Rock fragments: 35 to 60 percent--30 to 50 percent gravel, 0 to 10 percent cobbles and stones
Reaction: pH 6.6 to 7.3

Bw3 horizon
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 2 or 3; dry or moist
Texture: loam, clay loam or sandy clay loam
Clay content: 18 to 30 percent
Rock fragments: 35 to 60 percent--30 to 50 percent gravel, 0 to 10 percent cobbles and stones
Reaction: pH 6.1 to 7.3

BC horizon
Value: 6 or 7 dry; 5 or 6 moist
Chroma: 2 to 4; dry or moist
Texture: loam or sandy clay loam
Clay content: 18 to 27 percent
Rock fragments: 35 to 60 percent--35 to 50 percent gravel, 0 to 10 percent cobbles
Reaction: pH 6.6 to 7.8

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING:
Landform - alluvial fans, drainageways and mountain slopes
Elevation - 5,500 to 7,500 feet
Slope - 1 to 15 percent
Parent material - alluvium, colluvium or alpine till derived from fine grained igneous or metamorphic rocks
Climate - long, cold winters; cool, moist springs; short, cool summers
Mean annual precipitation - 15 to 24 inches
Mean annual air temperature - 36 to 40 degrees F.
Frost-free period - 30 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Foolhen, Marcel, and Sebud soils. Foolhen soils are very poorly drained and fine-loamy on floodplains. Marcel soils have an argillic horizon and are on alluvial fans and mountain slopes. Sebud soils are well drained and are on alluvial fans and mountain slopes.

DRAINAGE AND PERMEABILITY: Somewhat poorly drained; moderate permeability.

USE AND VEGETATION: Tibkey soils are primarily used for rangeland, wildlife habitat and watershed. The potential native vegetation is mainly rough fescue, Idaho fescue, tufted hairgrass, sedges, lupine, iris, ballhead sandwort, shrubby cinquefoil, alder and willows.

DISTRIBUTION AND EXTENT: Tibkey soils are of small extent in southwestern Montana. MLRA - 43B.

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

SERIES ESTABLISHED: Jefferson County, Montana, 1998.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 13 inches (A1, A2, Bw1 horizons)
Cambic horizon - from 13 to 32 inches (Bw2, Bw3 horizons)
Particle-size control section - from 10 to 40 inches (part of Bw1, Bw2, Bw3, part of BC horizons)

Tibkey soils have a cryic temperature regime, an ustic moisture regime, and an aquic moisture subclass.

ADDITIONAL DATA: Soil interpretation record - MT3058.

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National Cooperative Soil Survey
U.S.A.