LOCATION BORKY MTEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, mixed, superactive, frigid Typic Argiustolls
TYPICAL PEDON: Borky very stony loam, in rangeland (colors are for dry soil unless otherwise noted).
A--0 to 4 inches; dark grayish brown (10YR 4/2) very stony loam, very dark grayish brown (10YR 3/2) moist; moderate very fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; many fine and very fine roots; many fine and very fine pores; 25 percent stones, 5 percent cobbles, 15 percent pebbles; neutral (pH 6.8); clear wavy boundary. (2 to 5 inches thick)
Bt1--4 to 8 inches; brown (10YR 4/3) very stony clay, dark brown (10YR 3/3) moist; moderate medium prismatic structure parting to strong fine subangular blocky; very hard, friable, moderately sticky and very plastic; many fine and very fine roots; many fine and very fine pores; many distinct clay films on faces of peds; 30 percent stones, 15 percent pebbles; neutral (pH 7.0); clear wavy boundary.
Bt2--8 to 14 inches; brown (10YR 5/3) very stony clay, brown (10YR 4/3) moist; moderate medium prismatic structure parting to strong fine subangular blocky; very hard, firm, moderately sticky and very plastic; many fine and very fine roots; many fine and very fine pores; many distinct clay film on faces of peds; 35 percent stones, 15 percent pebbles; slightly alkaline (pH 7.4); clear irregular boundary. (Combined thickness of the Bt horizons is 9 to 18 inches)
Bk--14 to 32 inches; pale yellow (2.5Y 8/4) very stony silty clay, pale yellow (2.5Y 7/4) moist; moderate medium prismatic structure parting to moderate fine and very fine subangular blocky structure; very hard, firm, moderately sticky and moderately plastic; common fine and very fine roots; many fine and very fine pores; 35 percent stones, 20 percent pebbles; common threads and masses of lime; strongly effervescent; moderately alkaline (pH 8.4); gradual wavy boundary. (9 to 22 inches thick)
Cr--32 inches; pale yellow (2.5Y 8/4) shale interbedded with thin lenses of sandstone.
TYPE LOCATION: Cascade County, Montana; 1,600 feet west and 1,700 feet north of the SE corner of sec. 11, T. 18 N., R. 6 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Moisture control section - between 4 and 12 inches.
Mollic epipedon thickness - 7 to 14 inches.
Control section - 35 to 50 percent clay; 35 to 60 percent rock fragments.
Rock fragments - mainly sandstone.
Depth to Bk horizon - 11 to 20 inches.
Depth to Cr horizon - 20 to 40 inches.
A horizon - Value: 4 or 5 dry; 2 or 3 moist
Chroma: 2 or 3
Texture: loam or clay loam
Clay content: 20 to 35 percent
Rock fragments: 15 to 60 percent--0 to 30 percent flagstones, stones, or cobbles; 15 to 30 percent pebbles or channers
Reaction: pH 6.6 to 7.8
Bt1, Bt2 horizons - Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2 or 3
Texture: clay or clay loam
Clay content: 35 to 50 percent
Rock fragments: 35 to 60 percent--20 to 40 percent flagstones, stones, and cobbles; 15 to 30 percent pebbles or channers
Reaction: pH 6.6 to 7.8
Bk horizon - Hue: 10YR or 2.5Y
Value: 6, 7, or 8 dry; 5, 6, or 7 moist
Chroma: 2, 3, or 4
Texture: clay loam, clay, silty clay loam, or silty clay
Clay content: 35 to 45 percent
Rock fragments: 35 to 60 percent--20 to 40 percent stones and cobbles; 15 to 30 percent pebbles or channers
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 8.4
COMPETING SERIES:
Cebolleta (NM) - has a lithic contact at 20 to 40 inches.
Rionutria (NM) - has a lithic contact at 20 to 40 inches.
Roy (MT) - does not have a paralithic contact above a depth of 60 inches.
Shanley (MT) - does not have a paralithic contact; does not have horizons of carbonate accumulation.
Storyhill (MT) - is very deep; has a calcic horizon.
GEOGRAPHIC SETTING:
Landform - sedimentary plains; hills.
Elevation - 3,500 to 5,000 feet.
Slope - 2 to 45 percent.
Parent material - residuum from semiconsolidated interbedded shale and sandstone.
Climate - cold winters; moist springs; warm summers.
Mean annual precipitation - 15 to 19 inches.
Mean annual air temperature - 40 to 45 degrees F.
Frost-free period - 105 to 135 days.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability.
USE AND VEGETATION: Borky soils are used for rangeland. Potential native vegetation is western wheatgrass, bluebunch wheatgrass, needleandthread, and green needlegrass.
DISTRIBUTION AND EXTENT: Borky soils are of small extent in north-central Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Cascade County, Montana, 1975.
REMARKS: Soil interpretations record: MT0031. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the surface to 8 inches (A, Bt1 horizons); an argillic horizon and particle-size control section from 4 to 14 inches (Bt1, Bt2 horizons); a horizon of lime accumulation from 14 to 32 inches (Bk horizon); and a paralithic contact at 32 inches (Cr horizon). Borky soils have a frigid temperature regime and an ustic moisture regime.