LOCATION CROOKEDRUN              MT

Established Series
REV. GFB-KTS-RJS
03/2012

CROOKEDRUN SERIES


The Crookedrun series consists of very deep somewhat poorly drained soils that formed in alluvium or lacustrine deposits. These soils occur on flood plains, stream terraces, alluvial fans, fan remnants, drainageways and lakebeds. Slopes are 0 to 8 percent. Mean annual precipitation is about 400 mm and mean annual temperature is about 4 degrees C.

TAXONOMIC CLASS: Fine-loamy, mixed, superactive Oxyaquic Haplocryolls

TYPICAL PEDON: Crookedrun silt loam, in rangeland on a 1 percent slope at an elevation of 2030 meters (colors are for dry soil unless otherwise noted).

Oi--0 to 3 cm; undecomposed and partially decomposed matted roots; abrupt smooth boundary. (0 to 8 cm thick)

A1--3 to 13 cm; gray (10YR 5/1) silt loam, very dark gray (10YR 3/1) moist; moderate fine and medium granular structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine, fine and medium roots; many very fine irregular pores; finely disseminated calcium carbonate; strongly effervescent; strongly alkaline (pH 8.8); clear wavy boundary.

A2--13 to 38 cm; gray (10YR 5/1) silt loam, very dark gray (10YR 3/1) moist; moderate medium subangular blocky structure parting to weak fine granular; slightly hard, very friable, slightly sticky and slightly plastic; many very fine, fine and medium roots; many very fine irregular pores; finely disseminated calcium carbonate; strongly effervescent; strongly alkaline (pH 8.8); gradual wavy boundary. (combined thickness of A horizons - 18 to 40 cm)

C--38 to 74 cm; light brownish gray (10YR 6/2) silty clay loam, dark gray (10YR 4/1) moist; massive; hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; many very fine tubular and irregular pores; finely disseminated calcium carbonate; violently effervescent; strongly alkaline (pH 8.8); clear smooth boundary. (30 to 70 cm thick)

Cg1--74 to 124 cm; light gray (10YR 7/2) clay loam, grayish brown (10YR 5/2) moist; few medium distinct yellowish brown (10YR 5/4) redox concentrations; massive, hard, friable, moderately sticky and moderately plastic; few very fine and fine roots; many very fine irregular pores; 5 percent gravel; finely disseminated calcium carbonate; violently effervescent; moderately alkaline (pH 8.2); gradual wavy boundary. (30 to 70 cm thick)

2Cg2--124 to 152 cm; pale brown (10YR 6/3) gravelly sandy loam, brown (10YR 5/3) moist; common medium distinct yellowish brown (10YR 5/6) redox concentrations; massive; hard, friable, slightly sticky and slightly plastic; 30 percent gravel; finely disseminated calcium carbonate; strongly effervescent; moderately alkaline (pH 8.2).

TYPE LOCATION: Beaverhead County, Montana; located about 1800 feet east and 2000 feet south of the northwest corner of sec. 31 , T. 14 S., R6 W; Snowline topographic quadrangle; UTM 12T, 390145e, 4936642n, NAD 83.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 1 to 4 degrees C.
Mollic epipedon thickness - 18 to 40 cm
Depth to lithologic discontinuity - greater than 100 cm
Depth to seasonal high water table - 60 to 100 cm

A horizons
Hue: 10YR or 2.5Y; dry or moist
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 1 or 2; dry or moist
Clay content: 15 to 27 percent
Rock fragments: 0 to 15 percent gravel
Calcium Carbonate Equivalent: 10 to 25 percent
Sodium adsorption ratio: 0 to 13
Electrical conductivity: 0 to 4 mmhos/cm
Reaction: pH 7.9 to 9.0

C and Cg1 horizons
Hue: 10YR or 2.5Y; dry or moist
Value: 5 to 7 dry; 4 or 5 moist
Chroma: 1 to 3; dry or moist
Texture: silty clay loam, loam or clay loam
Clay content: 18 to 35 percent
Rock fragments: 0 to 15 percent gravel
Calcium carbonate equivalent: 15 to 35 percent
Sodium adsorption ratio: 0 to 13
Electrical conductivity: 0 to 4 mmhos/cm
Reaction: pH 7.9 to 9.0

2Cg2 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 to 7 dry; 4 or 5 moist
Chroma: 1 to 3; dry or moist
Clay content: 12 to 20 percent
Rock fragments: 15 to 50 percent--15 to 40 percent gravel, 0 to 10 percent cobbles
Calcium Carbonate Equivalent: 10 to 25 percent.
Reaction: pH 7.9 to 8.4

COMPETING SERIES:
Proposal (MT) - have secondary calcium carbonate accumulation

GEOGRAPHIC SETTING:
Landform - flood plains, stream terraces, alluvial fans, fan remnants, drainageways and lakebeds
Elevation - 1980 to 2450 meters
Slope - 0 to 8 percent
Parent material - alluvium or lacustrine deposits
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 380 to 550 mm
Mean annual air temperature - 1 to 4 degrees F.
Frost-free period - 50 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: None listed.

DRAINAGE AND PERMEABILITY: Somewhat poorly drained; moderate permeability.

USE AND VEGETATION: Crookedrun soils are used mainly for rangeland and pastureland. The vegetation is mainly bluegrasses, sedges, Baltic rush, shrubby cinquefoil, Rocky Mountain iris, pussytoes, and other miscellaneous grasses, forbs and shrubs.

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

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

SERIES ESTABLISHED: Horse Prairie-South Valley Area - Part of Beaverhead County, Montana, 2011; proposed in Beaverhead County, Montana, 2009.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - from 3 to 38 cm (A horizons)
Particle-size control section - from 28 to 103 cm (part of A2, C and part of Cg1 horizons)

Crookedrun soils have a cryic temperature regime, an ustic moisture regime and an oxyaquic moisture subclass.


National Cooperative Soil Survey
U.S.A.