LOCATION BRABAS IDTentative Series
TAXONOMIC CLASS: Fine, smectitic Inceptic Haplocryalfs
TYPICAL PEDON: Brabas very gravelly loam on a 10 percent southwest-facing slope at 7,200 feet elevation in rangeland. (Colors are for dry soil unless otherwise stated. When described on September 15, 1981, the soil was dry throughout.)
A--0 to 3 inches; grayish brown (10YR 5/2) very gravelly loam, dark brown (10YR 3/3) moist; moderate medium platy structure parting to weak fine granular; slightly hard, friable, slightly sticky and slightly plastic; common very fine and few fine roots; many very fine interstitial pores; 35 percent pebbles; slightly effervescent; slightly alkaline (pH 7.6); clear smooth boundary. (1 to 5 inches thick)
Bt--3 to 8 inches; brown (10YR 5/3) gravelly clay loam, dark brown (10YR 4/3) moist; moderate medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine and few fine roots; common very fine interstitial pores; common distinct clay films lining pores and on faces of peds; 20 percent pebbles; strongly effervescent; neutral (pH 7.1); abrupt smooth boundary. (0 to 8 inches thick)
Btk--8 to 17 inches; light yellowish brown (10YR 6/4) silty clay, brown (10YR 5/3) moist; strong medium prismatic structure; extremely hard, extremely firm, very sticky and very plastic; common very fine roots; few very fine interstitial pores; many prominent clay films lining pores and on faces of peds; lime coatings less than 1mm thick on faces of peds; slightly effervescent; slightly alkaline (pH 7.8); abrupt smooth boundary. (6 to 14 inches thick)
2Bkq1--17 to 24 inches; white (10YR 8/1) extremely gravelly loam; light gray (10YR 7/2) moist; massive; hard, firm, slightly sticky and slightly plastic; few very fine roots; common very fine and few fine and medium interstitial pores; 55 percent gravel, 20 percent cobbles; lime and silica coatings less than 1mm thick on undersides of coarse fragments; violently effervescent, moderately alkaline (pH 8.0); abrupt wavy boundary. (0 to 10 inches thick)
2Bkq2--24 to 30 inches; pale brown (10YR 6/3) extremely gravelly loamy sand; very pale brown (10YR 7/3) moist; massive; slightly hard, friable, nonsticky and nonplastic; few very fine roots; many very fine and few fine and medium interstitial pores; 60 percent pebbles, 25 percent cobbles; lime and silica coatings less than 1mm thick on undersides of coarse fragments; violently effervescent; moderately alkaline (pH 8.4); abrupt wavy boundary. (0 to 11 inches thick)
3Btb1--30 to 50 inches; light yellowish brown (10YR 6/4) gravelly silty clay, brown (10YR 5/3) moist; strong medium angular blocky structure; very hard, very firm, very sticky and very plastic; few very fine roots; common very fine tubular and few very fine interstitial pores; many prominent clay film, lining pores and on faces of peds; 15 percent pebbles; slightly effervescent; slightly alkaline (pH 7.7); abrupt smooth boundary. (0 to 28 inches thick)
3Btb2--50 to 60 inches; very pale brown (10YR 7/3) silty clay, pale brown (10YR 6/3) moist; moderate medium angular blocky structure; hard, firm, very sticky and very plastic; common very fine interstitial pores; common distinct clay films lining pores and on faces of peds; violently effervescent; slightly alkaline (pH 7.5).
TYPE LOCATION: Lemhi County, Idaho, about 23 miles southeast of Leadore, Idaho; about 2,600 feet east and 900 feet north of the southwest corner of sec. 8, T. 12 N., R. 28 E. Latitude - 44 degrees, 22 minutes, 56 seconds North; Longitude - 113 degrees, 09 minutes, 40 seconds West.
RANGE IN CHARACTERISTICS:
Soil moisture regime - Xeric
Average annual soil temperature - 37 to 40 degrees F
Average summer soil temperature - 52 to 59 degrees F
Control section - percent clay averages 35 to 50
Coarse fragments - 5 to 20 percent
Depth to secondary lime - 2 to 17 inches
Reaction of profile - neutral through moderately alkaline
Thickness of the argillic horizon - 6 to 14 inches
A horizon
Chroma - 2 or 3 dry and moist
Bt and Btk horizon
Hue - 7.5YR or 10YR
Value - 5 through 7 dry and 4 through 6 moist
Chroma - 2 through 6 dry and 3 through 6 moist
Texture - GR-CL, SIC
2Bkq horizon
Value - 6 through 8 dry and 5 through 7 moist
Chroma - 1 through 4 dry and 2 through 6 moist
Texture - GRX-L and GRX-LS
Coarse fragments - 60 to 85 percent
3Btb horizon
Value - 6 or 7 dry, 5 to 6 moist
Chroma - 3 or 4 dry or moist
Texture - GR-SIC, SIC
Reaction - slightly or moderately alkaline
Rock fragments - 0 to 20 percent
COMPETING SERIES: These are the Chedsey, Cramont (T), Goldhill, Harkness, Hatch, Herd, Pagosa, and Stovho soils. Chedsey, Herd, Pagosa, and Stovho soils lack calcic horizons. Cramont and Harkness soils have O horizons. Goldhill soils are moderately deep to lime. Hatch soils are moderately deep to bedrock.
GEOGRAPHIC SETTING: Brabas soils are on hills and mountains and have slopes of 8 to 30 percent. Elevations are 6,800 to 9,000 feet. The soils formed in lacustrine sediments with glacial till influence. The climate is cold and moist in winter and spring and cool and dry in summer. Average annual precipitation is 14 to 18 inches. Average annual temperature is 35 to 38 degrees F. The frost-free period is 30 to 60 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Escarlo, Geemore, Duckree, Goldhill, Grouseville, and Wiggleton soils. Grouseville soils are on mountains and have mollic epipedons. Geemore and Wiggleton soils are on outwash fans and have mollic epipedons. Escarlo soils are on hills and have mollic epipedons. Duckree soils are on hills and lack an argillic horizon. Goldhill soils are on hills and are moderately deep to lime.
DRAINAGE AND PERMEABILITY: Well drained; medium to very rapid runoff; permeability is slow.
USE AND VEGETATION: Rangeland. Vegetation is mainly low sagebrush and bluebunch wheatgrass.
DISTRIBUTION AND EXTENT: East-central Idaho. These soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES PROPOSED: Lemhi County, Idaho, 1982.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon
Argillic horizon - the zone from 3 to 17 inches (Bt and BtK horizons)
Calcic horizon - 17 to 30 inches
Particle-size control section - the zone from 3 to 17 inches (Bt and Btk horizons)