LOCATION ARROWPEAK               MT

Established Series
Rev. NRS-KTS-RJS
03/2011

ARROWPEAK SERIES

The Arrowpeak series consists of shallow, well drained soils that formed in colluvium or residuum derived from igneous and argillite rocks. These soils are on mountain slopes, ridges and cuestas. Slopes are 4 to 70 percent. Mean annual precipitation is about 24 inches, and mean annual air temperature is about 40 degrees F.

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

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

A--0 to 8 inches; dark grayish brown (10YR 4/2) very cobbly loam, very dark grayish brown (10YR 3/2) moist; strong fine and medium granular structure; soft, very friable, slightly sticky and slightly plastic; many fine and very fine, and few medium roots; 20 percent gravel and 30 percent cobbles, few surface stones; neutral (pH 6.6); clear wavy boundary. (6 to 10 inches thick)

Bw--8 to 17 inches; brown (10YR 5/3) extremely cobbly loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many fine, very fine, and few medium roots; many very fine tubular and irregular pores; 40 percent gravel and 30 percent cobbles; neutral (pH 6.6); clear wavy boundary. (4 to 14 inches thick)

R--17 inches; hard, fractured igneous bedrock.

TYPE LOCATION: Chouteau County, Montana; 700 feet south and 200 feet west of the NE corner of sec. 7, T. 20 N., R. 9 E.

RANGE IN CHARACTERISTICS:
Soil temperature - 36 to 44 degrees F.
Mollic epipedon thickness - 7 to 20 inches
Depth to a lithic contact - 10 to 20 inches

Note: Some pedons may have a BC or C horizon.

A horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 2 or 3; dry or moist
Texture: sandy loam or loam
Clay content: 10 to 27 percent
Rock fragments: 15 to 70 percent--10 to 45 percent gravel or channers, 5 to 30 percent cobbles, 0 to 5 percent stones
Reaction: pH 5.6 to 7.3

Bw horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2 to 4; dry or moist
Texture: loam or sandy loam
Clay content: 10 to 25 percent
Rock fragments: 40 to 80 percent--20 to 50 percent gravel or channers, 15 to 45 percent cobbles, 0 to 5 percent stones
Reaction: pH 5.6 to 7.3

COMPETING SERIES:
Betemer (CO) - have an ustic moisture regime
Cheadle (MT) - have secondary calcium carbonate accumulation
Chokecherry (ID) - have a xeric moisture regime
Clamp (OR) - have a xeric moisture regime
Dalys (MT) - is very shallow to a lithic contact
Dollarhide (ID) - have a xeric moisture regime
Eyre (CO) - have a moisture control section that is dry in some part when the soil temperature is above 41 degrees F.
Irigul (WY) - have an ustic moisture regime
Irson (WY) - have an ustic moisture regime
Jonlake (NV) - have a xeric moisture regime
Labshaft (NV) - have an ustic moisture regime
Mccadden (UT) - have secondary calcium carbonate accumulation
Poin (MT) - have an ustic moisture regime
Rogert (CO) - have more than 35 percent fine and coarser sand most of which is medium to very coarse sand; is at elevations of over 7,500 feet
Schwacheim (CO) - have formed in residuum derived from basalt; is at elevations of over 8,600 feet
Starley (WY) - have secondary calcium carbonate accumulation
Topeki (NV) - have a xeric moisture regime
Trump (CO) - have an ustic moisture regime
Udel (NV) - is very shallow to a lithic contact

GEOGRAPHIC SETTING:
Landform - mountain slopes, ridges and cuestas
Elevation - 4,400 to 8,400 feet
Slope - 4 to 70 percent
Parent material - colluvium or residuum derived from igneous and argillite rocks
Climate - cool with long, cold winters; moist springs; cool summers
Mean annual precipitation - 20 to 35 inches
Mean annual air temperature - 34 to 42 degrees F.
Frost-free period - 30 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: None listed.

DRAINAGE AND PERMEABILITY: Well drained; moderately rapid permeability.

USE AND VEGETATION: Arrowpeak soils are used mainly for rangeland and as wildlife habitat. The potential native vegetation is mainly rough fescue, bluebunch wheatgrass, Columbia needlegrass, Idaho fescue, slender wheatgrass, bearded wheatgrass, big bluegrass, spike trisetum, serviceberry, and common chokecherry. Some areas have sparse stands of limber pine and Douglas fir.

DISTRIBUTION AND EXTENT: Arrowpeak soils are of minor extent in mountain ranges in north-central and southwestern Montana. MLRA 43B.

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

SERIES ESTABLISHED: Chouteau County, Montana, 1992.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 0 to 17 inches (A and Bw horizons);
Lithic contact - at 17 inches (R horizon)
Particle-size control section - from 10 to 17 inches (Bw horizon)

Arrowpeak soils have a cryic temperature regime and an udic moisture regime.

Additional Data: Soil interpretations record - MT1284.

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National Cooperative Soil Survey
U.S.A.