LOCATION MAHAFFEY IDEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Typic Cryaquolls
TYPICAL PEDON: Mahaffey loam--on a 1 percent slope at 5,207 feet elevation in pasture. (Colors are for dry soil unless otherwise noted. When described on July 30, 1991, the soil was dry from the surface to 4 inches, moist from 4 to 34 inches and saturated below 34 inches. A water table was present at 54 inches).
A1--0 to 4 inches; dark grayish brown (10YR 4/2) loam, black (10YR 2/1) moist; strong medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine and fine and few medium roots; many very fine and fine irregular pores; neutral (pH 7.0); clear smooth boundary. (3 to 9 inches thick)
A2--4 to 12 inches; dark grayish brown (10YR 4/2) loam, black (10YR 2/1) moist; common fine distinct strong brown (7.5YR 5/6) redox concentrations and few fine prominent black (N 2/0) redox depletions; moderate fine and medium subangular blocky structure; soft, friable, slightly sticky and slightly plastic; many very fine, fine and medium roots; many very fine and fine irregular pores, slightly acid (pH 6.2); clear wavy boundary. (5 to 10 inches thick)
Bg--12 to 23 inches; light brownish gray (10YR 6/2) loam, very dark grayish brown (10YR 3/2) moist; many medium distinct dark grayish brown (10YR 4/2) and common medium prominent yellowish brown (10YR 5/8) redox concentrations; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine roots; many very fine and fine irregular pores; slightly acid (pH 6.5); clear wavy boundary. (11 to 15 inches thick)
2Cg1--23 to 34 inches; gray (10YR 5/1) extremely gravelly sandy loam, dark grayish brown (10YR 4/2) moist; many medium prominent reddish yellow (7.5YR 6/8) redox concentrations; weak fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots; common fine and medium irregular pores; 45 percent gravel, 20 percent cobbles; neutral (pH 6.7); gradual wavy boundary. (10 to 20 inches thick)
2Cg2--34 to 61 inches; multicolored extremely cobbly loamy coarse sand; many large prominent light brown (7.5YR 6/3) redox concentrations; single grain; loose; few very fine and fine roots; few fine and medium irregular pores; 30 percent gravel, 35 percent cobbles, 15 percent stones; slightly acid (pH 6.5).
TYPE LOCATION: Lemhi County, Idaho; about 1 mile northwest of Lemhi, Idaho; about 2,300 feet south and 900 feet east from the northwest corner of section 29, T.18N., R.24E. Latitude - 44 degrees, 52 minutes, 8 seconds North; Longitude - 113 degrees, 37 minutes, 32 seconds West.
RANGE IN CHARACTERISTICS:
Average annual soil temperature - 40 to 45 degrees F.
Average summer soil temperature - 49 to 54 degrees F.
Mollic epipedon thickness - 10 to 14 inches.
Organic carbon - decreases irregularly with depth.
Control section - averages 8 to 14 percent clay
Depth to sand and gravel - 30 to 40 inches
Coarse fragments - 45 to 65 percent (average)
Depth of high water table - 24 to 42 inches (April through June)
A horizons
Value - 4 or 5 dry, 2 or 3 moist
Chroma - 1 or 2 dry or moist
Bg horizon
Chroma - 1 or 2 dry or moist
Texture - L or SIL
2Cg1 horizon
Value - 5 or 6 dry
Chroma - 1 or 2 dry or moist
Texture - GRX-SL or GRX-COSL
Coarse fragments - 65 to 85 percent
2Cg2 horizon
Texture - CBX-LCOS or GRX-LS
Rock fragments - 65 to 90 percent
COMPETING SERIES: These are the Finn and Lemroi series. Finn soils average over 18 percent clay in the particle-size control section. Lemroi soils have sand and gravel at depths of 20 to 30 inches and a high water table at depths of 6 to 12 inches.
GEOGRAPHIC SETTING: Mahaffey soils are on flood plains. These soils formed in mixed alluvium. Slopes are 0 to 2 percent. Elevations are 4,500 to 6,000 feet. The climate is cold and moist in the winter and spring and cool in summer. The average annual precipitation is 10 to 14 inches. Average annual air temperature is 38 to 42 degrees F. Frost free period is 50 to 70 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Copperbasin and Wiskisprings soils. Wiskisprings soils are on flood plains and stream terraces and have mollic epipedons that are 16 to 30 inches thick and have fine loamy particle-size control sections. Copperbasin soils are sandy-skeletal.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; slow runoff; moderate permeability in the upper part and rapid in the lower part. Occasional flooding for brief periods from January through June.
USE AND VEGETATION: Pasture. The natural vegetation is sedges, cottonwoods, willows and streambank wheatgrass.
DISTRIBUTION AND EXTENT: East-central Idaho. These soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Lemhi County, Idaho, 1999.
REMARKS: Water tables were monitored by piezometers.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from 0 to 12 inches (the A1 and A2 horizons)
Cambic horizon - The zone form 12 to 23 inches (Bg horizon)
Particle-size control section - The zone from 10 to 40 inches (part of the A2, the Bg, 2Cg1 and part of the 2Cg2 horizons).