LOCATION HAIRPIN MT

Established Series
REV. GFB-KTS-RJS
04/2011

HAIRPIN SERIES

The Hairpin series consists of very deep, well drained soils that formed in alluvium, colluvium, lacustrine deposits, or slide deposits derived from sedimentary and metamorphic rock. These soils are on alluvial fans, fan remnants, landslides, depressions, hillsides and mountain slopes. Slopes are 2 to 35 percent. Mean annual precipitation is about 22 inches, and mean annual air temperature is about 36 degrees F.

TAXONOMIC CLASS: Fine, smectitic Vertic Argicryolls

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

A1--0 to 4 inches; very dark grayish brown (10YR 3/2) silt loam, very dark brown (10YR 2/2) moist; weak medium subangular blocky structure parting to weak fine and medium granular; soft, very friable, slightly sticky and nonplastic; common very fine and fine roots throughout; 10 percent subangular quartzite gravel; moderately acid (pH 6.0); clear smooth boundary. (3 to 8 inches thick)

A2--4 to 12 inches; dark grayish brown (10YR 4/2) cobbly silt loam, very dark grayish brown (10YR 3/2) moist; weak medium and coarse subangular blocky structure parting to moderate fine and medium subangular blocky; soft, very friable, slightly sticky and slightly plastic; many very fine and few fine roots throughout; 10 percent subangular quartzite gravel and 15 percent subangular cobbles; slightly acid (pH 6.4); clear wavy boundary. (4 to 10 inches thick)

Bt/E1--12 to 18 inches; Bt part (80 percent): brown (10YR 5/3), brown (10YR 4/3) moist; E part (20 percent): light gray (10YR 7/2), light brownish gray (10YR 6/2) moist, clay loam; moderate medium and coarse subangular blocky structure parting to strong fine and medium subangular blocky; very hard, firm, moderately sticky and moderately plastic; common distinct clay films on all faces of peds; common very fine and fine roots throughout; 10 percent subangular quartzite gravel; neutral (pH 6.8); clear wavy boundary.

Bt/E2--18 to 22 inches; Bt part (60 percent): pale brown (10YR 6/3), brown (10YR 5/3) moist; E part (40 percent): light gray (10YR 7/2), light brownish gray (10YR 6/2) moist, clay loam; moderate fine and medium subangular blocky structure; very hard, firm, moderately sticky and moderately plastic; common distinct clay films on all faces of peds; common very fine roots throughout; 10 percent subangular quartzite gravel; neutral (pH 7.0); abrupt wavy boundary. (combined thickness of Bt/E horizons - 6 to 14 inches)

2Btss1--22 to 42 inches; yellowish brown (10YR 5/4) clay, dark yellowish brown (10YR 4/4) moist; strong coarse prismatic structure; extremely hard, very firm, very sticky and very plastic; many prominent clay films on all faces of peds; common prominent slickensides on vertical faces of peds; few very fine roots throughout; 10 percent subangular quartzite gravel and 1 percent subangular cobbles; neutral (pH 7.0); gradual wavy boundary. (11 to 30 inches thick)

2Btss2--42 to 60 inches; light yellowish brown (10YR 6/4) gravelly clay, yellowish brown (10YR 5/4) moist; moderate coarse subangular blocky structure; extremely hard, very firm, very sticky and very plastic; many prominent clay films on all faces of peds; common prominent slickensides on vertical faces of peds; few very fine roots throughout; 20 percent subangular quartzite gravel and 5 percent subangular cobbles; neutral (pH 7.0).

TYPE LOCATION: Beaverhead County, Montana; 3,200 feet west and 1,200 feet south of the NE corner of sec. 19, T. 7 S., R. 14 W. Peterson Lake topographic quadrangle, UTM 12T, 313779e, 5009714n. NAD 83

RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 35 to 40 degrees F.
Mean summer soil temperature: 55 to 59 degrees F.
Depth to top of argillic horizon: 8 to 18 inches
Mollic epipedon thickness: 10 to 15 inches

Note: Some pedons may have a thin E horizon.

A horizons
Value: 3 or 4 dry; 2 or 3 moist
Chroma: 1 or 2; dry or moist
Texture: loam or silt loam
Clay content: 15 to 27 percent
Content of rock fragments: 0 to 30 percent--0 to 25 percent gravel, 0 to 15 percent cobbles
Reaction: pH 5.6 to 7.3

Bt/E horizons
Hue: 10YR or 7.5YR; dry or moist
Value: Bt part: 5 or 6 dry; 4 or 5 moist;
E part: 6 or 7 dry; 5 or 6 moist;
Chroma: 2 to 4; dry or moist
Clay content: 27 to 35 percent
Content of rock fragments: 0 to 15 percent--0 to 15 percent gravel, 0 to 5 percent cobbles
Reaction: 6.1 to 7.3

2Btss horizons
Hue: 10YR or 7.5YR; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 3 or 4; dry or moist
Texture: silty clay or clay
Clay content: 40 to 60 percent
Rock fragments: 0 to 30 percent--0 to 20 percent gravel, 0 to 10 percent cobbles
Reaction: pH 6.1 to 7.3

COMPETING SERIES:
Beaverdam (ID) - do not have Bt/E horizons
Buckskin (ID) - do not have Bt/E horizons
Chicken (MT) - is moderately deep to a paralithic contact
Cimarron (CO) - do not have Bt/E horizons
Cooperwash (NV) - do not have Bt/E horizons
Cucharas (CO) - is moderately deep to a paralithic contact
Gourley (CO) - have secondary calcium carbonate accumulation
Heathcoat (ID) - have secondary calcium carbonate accumulation
Helmet (CO) - do not have Bt/E horizons
Savar (WY) - have secondary calcium carbonate accumulation
Slights (ID) - have a xeric moisture regime
Sudduth (CO) - have an udic moisture regime
Sudpeak (ID) - have a seasonally high water table at 3 to 6 feet
Toponce (ID) - have an udic moisture regime
Wetopa (CO) - have an udic moisture regime
Youman (CO) - do not have Bt/E horizons

GEOGRAPHIC SETTING:
Landform - alluvial fans, fan remnants, landslides, depressions, hillsides and mountain slopes
Elevation - 6,100 to 8,300 feet
Slope- 2 to 35 percent
Parent material - alluvium, colluvium, lacustrine deposits, or slide deposits derived from sedimentary and metamorphic rock
Climate - long, cold winters; cool, moist springs; short summers
Mean annual precipitation - 16 to 24 inches
Mean annual air temperature - 34 to 39 degrees
Frost-free season - 30 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Libeg, Bearmouth, and Garlet soils. Libeg is loamy-skeletal and found on foothills. The Bearmouth soil is sandy-skeletal, does not have an argillic horizon, and is found on terraces. The Garlet soils are loamy-skeletal, lack a mollic epipedon, and formed under forest cover.

DRAINAGE AND PERMEABILITY: Well drained; slow permeability

USE AND VEGETATION: Hairpin soils are used mainly for rangeland grazing and as wildlife habitat. The potential native vegetation is mainly timber danthonia, tufted hairgrass, meadow foxtail, bearded wheatgrass, and Richardson needlegrass.

DISTRIBUTION AND EXTENT: Hairpin soils are of small extent in southwestern Montana. MLRAs - 43B, 44B.

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

SERIES ESTABLISHED: Beaverhead County, Montana, Big Hole Valley Area, 2005.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 12 inches (A1, A2 horizons)
Argillic horizon - from 12 to 60 inches (Bt/E1, Bt/E2, 2Btss1, 2Btss2 horizons)
Particle-size control section - from 12 to 32 inches (Bt/E1, Bt/E2, part of 2Btss1 horizons)

Hairpin soils have a cryic soil temperature regime and an ustic moisture regime bordering on udic.

National Cooperative Soil Survey
U.S.A.