LOCATION ARBUS IDEstablished Series
TAXONOMIC CLASS: Sandy-skeletal, carbonatic Xeric Calcicryids
TYPICAL PEDON: Arbus gravelly loam--on a 3 percent northeast-facing slope at 7,050 feet elevation in rangeland. (Colors are for dry soil unless otherwise stated. When described on June 16, 1981, the soil was moist to 12 inches and dry below this depth.)
A--0 to 4 inches; brown (10YR 5/3) gravelly loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure; slightly hard, friable, nonsticky and slightly plastic; many very fine and fine and few medium roots; common very fine and fine interstitial and few fine tubular pores; 15 percent pebbles; strongly effervescent; moderately alkaline (pH 8.2); clear smooth boundary. (3 to 6 inches thick)
Bk--4 to 12 inches; pale brown (10YR 6/3) very gravelly loam, brown (10YR 4/3) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine roots; common very fine and fine interstitial and few fine tubular pores; 35 percent pebbles; lime coatings less than 1 mm thick on undersides of coarse fragments; violently effervescent (65 percent calcium carbonate); moderately alkaline (pH 8.1); abrupt wavy boundary. (4 to 12 inches thick)
Bkq1--12 to 16 inches; pale brown (10YR 6/3) very gravelly loam, brown (10YR 5/3) moist; weak fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; few very fine and fine roots; common very fine and fine tubular and interstitial pores; 45 percent pebbles and 1 percent cobbles; lime and silica coatings and pendants less than 2 mm thick on undersides of coarse fragments; violently effervescent (greater than 70 percent calcium carbonate); strongly alkaline (pH 9.0); clear wavy boundary. (3 to 7 inches thick)
Bkq2--16 to 21 inches; very pale brown (10YR 7/3) extremely gravelly loam, brown (10YR 5/3) moist; massive; slightly hard, friable, nonsticky and nonplastic; few fine dead roots, root mat at upper boundary of horizon; few very fine and fine tubular pores; 60 percent pebbles and 5 percent cobbles; lime and silica coatings and pendants 1 to 3 mm thick on undersides of coarse fragments; violently effervescent (60 percent calcium carbonate); very strongly alkaline (pH 9.3); clear wavy boundary. (2 to 8 inches thick)
2Bkq3--21 to 25 inches; grayish brown (10YR 5/2) extremely gravelly loamy sand, very dark grayish brown (10YR 3/2) moist; single grain; loose; few very fine roots; many very fine and fine and common medium and coarse interstitial pores; 80 percent pebbles; silica and lime pendants 2 to 5 mm thick on undersides and some sides of coarse fragments; violently effervescent (60 percent calcium carbonate); very strongly alkaline (pH 9.4); clear wavy boundary. (2 to 6 inches thick)
2Bkq4--25 to 60 inches; grayish brown (10YR 5/2) and dark gray (10YR 4/1) extremely gravelly loamy coarse sand, black (10YR 2/1) moist; single grain; loose; few very fine and fine dead roots; many very fine and fine and common medium interstitial pores; 80 percent pebbles; lime and silica coatings less than 2 mm thick on undersides of coarse fragments; violently effervescent (65 percent calcium carbonate); strongly alkaline (pH 8.8).
TYPE LOCATION: Lemhi County, Idaho; about 1,500 feet west and 500 feet north from the southeast corner of sec. 33, T. 12 N., R. 28 E. Latitude - 44 degrees, 20 minutes, 12 seconds North; Longitude - 113 degrees, 07 minutes, 22 seconds West.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 37 to 40 degrees F
Average summer soil temperature - 55 to 59 degrees F
Depth to calcic horizon - 3 to 6 inches
Reaction of profile - moderately alkaline through very strongly
alkaline.
Control section - percent clay 3 to 20 and averages 5 to 15 percent
Coarse fragments - 50 to 80 percent
Calcium carbonate equivalent - 40 to 80 percent
A horizon
Value - 5 or 6 dry
Bk and Bkq horizons
Value - 6 or 7 dry, 4 through 6 moist
Chroma - 2 or 3 dry and 3 or 4 moist
Texture - GRV-L, GRX-L, GRX-SL, or GRV-SL
Rock fragments - 45 to 70 percent
Clay content - 12 to 20 percent
Calcium carbonate equivalent - 40 to 80 percent
2Bkq horizon
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 1 or 2 dry or moist
Texture - GRX-LS or GRX-LCOS
Rock fragments - 65 to 85 percent
Exchangeable sodium percentage - 25 to 50 percent
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Arbus soils are on outwash fans and fan terraces and have slopes of 1 to 6 percent. Elevations range from 6,400 to 7,100 feet. The soils formed in alluvium dominantly from limestone. The climate is cold and moist in winter and spring and cool and dry in summer. Average annual precipitation is 8 to 11 inches, and average annual temperature is 35 to 38 degrees F. The frost-free period is 30 to 60 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Fandow, Leatherman, Mountainboy, Paint, Simeroi, Bluedome, Sparmo, and Wiggleton soils. Bluedome, Fandow, Leatherman, Mountainboy, and Paint soils are on fan terraces and have duripans. Wiggleton soils are on fan terraces and have mollic epipedons. Simeroi soils are on fan terraces and have loamy-skeletal control sections. Sparmo soils are on fan terraces and have coarse-loamy control sections.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; runoff is slow; permeability is moderate in the upper part and rapid in the lower part.
USE AND VEGETATION: Rangeland. Vegetation is mainly low sagebrush and bluebunch wheatgrass.
DISTRIBUTION AND EXTENT: East-central Idaho. These soils are moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Lemhi County, Idaho, 1999.
REMARKS: Diagnostic features recognized in this pedon are:
Ochric epipedon
Calcic horizon - The zone from 4 to 25 inches (Bk, Bkq1, Bkq2, and 2Bkq1 horizons).
Particle-size control section - The zone from 10 to 40 inches (part of Bk, the Bkq1, Bkq2, 2Bkq1, part of 2Bkq2).