LOCATION BRAZON MTEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, mixed, superactive, frigid Typic Calciustolls
TYPICAL PEDON: Brazon very stony clay loam, rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 8 inches; very dark gray (10YR 3/1) very stony clay loam, black (10YR 2/1) moist; moderate fine and medium granular structure; hard, very friable, moderately sticky and moderately plastic; many fine and very fine roots and common medium roots; 20 percent stones, 10 percent cobbles, 10 percent pebbles; slightly effervescent; slightly alkaline (pH 7.4); clear irregular boundary. (6 to 9 inches thick)
Bw--8 to 17 inches; light brownish gray (10YR 6/2) very stony heavy clay loam, dark grayish brown (10YR 4/2) moist; moderate medium and fine subangu- lar blocky structure; hard, friable, moderately sticky and moderately plastic; many fine and very fine roots and pores and common medium roots and pores; 35 percent stones, 10 percent cobbles, 5 percent pebbles; violently effervescent; moderately alkaline (pH 8.2); clear irregular boundary. (6 to 14 inches thick)
Bk1--17 to 25 inches; light brownish gray (2.5Y 6/2) very cobbly light clay, dark grayish brown (2.5Y 4/2) moist; weak fine and very fine subangular blocky structure; hard, friable, moderately sticky and moderately plastic; common very fine, fine, and medium roots; many very fine and fine pores; 35 percent cobbles, 10 percent stones, 5 percent pebbles; common fine threads and common fine and medium soft masses of lime; violently effervescent; moderately alkaline (pH 8.4); gradual irregular boundary. (6 to 15 inches thick)
Bk2--25 to 40 inches; light brownish gray (2.5Y 6/2) very cobbly clay, grayish brown (2.5Y 5/2) moist; massive; very hard, friable, very sticky and very plastic; common fine and very fine roots and few medium roots; many fine and very fine pores; 40 percent cobbles, 5 percent stones, 10 percent pebbles; many fine distinct threads and many medium and coarse soft masses of lime; violently effervescent; moderately alkaline (pH 8.2); gradual irregular boundary. (10 to 20 inches thick)
2Bk3--40 to 46 inches; light yellowish brown (2.5Y 6/4) clay, light olive brown (2.5Y 5/4) moist; massive; extremely hard, very firm, very sticky and very plastic; common fine and very fine roots and few medium roots; common fine and very fine pores; less than 5 percent cobbles, 5 percent pebbles; many fine and medium distinct threads and common medium and coarse soft masses of lime; violently effervescent; moderately alkaline (pH 8.4); gradual wavy boundary. (6 to 12 inches thick)
2Cr--46 to 60 inches; brownish yellow (10YR 6/6) weathered clay shale beds that rub to a clay texture; yellowish brown (10YR 5/6) moist; extremely hard, very firm, moderately sticky and very plastic; few very fine roots in the upper few inches and in all fracture plains in the shale; common fine and very fine pores; common fine and medium distinct threads and soft masses of lime; strongly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Fergus County, Montana; about 262 feet east and 1800 feet north of the center of sec. 12, T.17N., R.17 E.
RANGE IN CHARACTERISTICS:
Soil temperature: 42 to 45 degrees F.
Mollic epipedon thickness: 7 to 9 inches
Rock fragments: mainly limestone
Depth to Bk horizon: 12 to 19 inches
Depth to bedrock: 40 to 60 inches to clay shale
A horizon: Hue: 10YR or 2.5Y
Value, dry: 3 to 5
Value, moist: 2 or 3
Chroma: 1 or 2
Texture: clay loam, silty clay loam
Clay content: 30 to 40 percent
Rock fragments: 0 to 50 percent
Stones or boulders: 0 to 20 percent
Cobbles: 0 to 20 percent
Pebbles: 0 to 10 percent
Reaction: pH 6.6 to 7.8
Bw horizon:
Hue: 10YR or 2.5Y
Value, dry: 5 or 6
Value, moist: 4 or 5
Chroma: 2 or 3
Texture: clay loam, clay
Clay content: 35 to 50 percent
Rock fragments: 35 to 60 percent
Stones: 25 to 35 percent
Cobbles: 5 to 10 percent
Pebbles: 5 to 15 percent
Reaction: pH 7.4 to 8.4
Bk1 horizon:
Hue: 10YR or 2.5Y
Value, dry: 6
Value, moist: 4 or 5
Chroma: 2 or 3
Texture: clay loam or clay
Non-carbonate clay content: 35 to 50 percent
Rock fragments: 35 to 75 percent
Stones: 10 to 20 percent
Cobbles: 20 to 35 percent
Pebbles: 5 to 20 percent
Calcium carbonate equivalent: 15 to 30 percent
Reaction: pH 7.9 to 8.4
Bk2 horizon:
Hue: 10YR or 2.5Y
Value, dry: 6 or 7
Value, moist: 4 or 5
Chroma: 2 through 6
Texture: clay loam or clay
Non-carbonate clay content: 35 to 50 percent
Rock fragments: 35 to 65 percent
Stones: 5 to 10 percent
Cobbles: 25 to 40 percent
Pebbles: 5 to 15 percent
Calcium carbonate equivalent: 15 to 30 percent
Reaction: pH 7.9 to 8.4
2Bk3 horizons: Hue: 10YR or 2.5Y
Value, dry: 6 or 7
Value, moist: 4 or 5
Chroma: 2 to 6
Texture: clay loam or clay
Clay content: 35 to 50 percent
Rock fragments: 5 to 20 percent
Cobbles: 0 to 5 percent
Pebbles: 5 to 15 percent
Reaction: pH 7.9 to 8.4
Cr horizon: Weathered clay shale
Reaction: pH 7.9 to 8.4
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Brazon soils are on uplands, mountain foot slopes, and fans and have gradients of 2 to 45 percent. Elevations are 4000 to 5020 feet. Brazon soils formed in clayey alluvium and colluvium derived from limestone and calcareous shales. The climate is cool with long cold winters and moist springs and summers. Mean annual precipitation is 19 to 24 inches. Mean annual temperature is 40 to 45 degrees F. The growing season is 90 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: The associated Loken and Winifred soils have less than 35 percent rock fragments in the control section.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; slow permeability.
USE AND VEGETATION: Brazon soil are used mainly for rangeland. To a lesser extent they are used for cropland and pasture. The potential native vegetation is mainly rough fescue, bluebunch wheatgrass, Columbia needlegrass, western wheatgrass, Idaho fescue, forbs, and shrubs.
DISTRIBUTION AND EXTENT: Brazon soils are of limited extent in the foothills area of central Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Fergus County, Montana, 1979.
REMARKS: Diagnostic horizons and feature recognized in this pedon are:
Mollic epipedon, the zone from 0 to 8 inches; (A horizon)
Cambic horizon, the zone from 8 to 17 inches; (Bw horizon)
Calcic horizon, the zone from 17 to 46 inches; (Bk1, Bk2, and 2Bk3 horizons)
Paralithic contact at 46 inches (boundary between the 2Bk3 and Cr horizons)
Particle-size control section 10 to 40 inches.