LOCATION FATHOM IDEstablished Series
TAXONOMIC CLASS: Sandy, mixed, mesic Xeric Haplocalcids
TYPICAL PEDON: Fathom loamy fine sand - rangeland vegetation. (Colors are for dry soil unless otherwise noted.)
A--0 to 9 inches; brown (10YR 5/3) loamy fine sand, very dark grayish brown (10YR 3/2) moist; weak medium platy structure; soft, very friable; many very fine and common fine roots; moderately alkaline (pH 8.0); abrupt smooth boundary. (3 to 14 inches thick)
Bw--9 to 26 inches; pale brown (10YR 6/3) loamy fine sand, very dark grayish brown (10YR 4/2) moist; weak coarse subangular blocky structure; soft, very friable; common very fine roots; moderately alkaline (pH 8.2); abrupt wavy boundary. (7 to 26 inches thick)
Bk--26 to 60 inches; pale brown (10YR 6/3) loamy fine sand, dark grayish brown (10YR 4/2) moist; massive; soft, very friable; common very fine roots; strongly effervescent (8 percent calcium carbonate); common filaments and seams of calcium carbonate; strongly alkaline (pH 8.6).
TYPE LOCATION: Twin Falls County, Idaho; in seeded sand dune; 3.5 miles north of Kimberly; southwest 1/4, southeast 1/4, northwest 1/4 section of section 4, T. 10 S., R. 18 E.
RANGE IN CHARACTERISTICS:
Depth to bedrock - 60 inches or more
Average annual soil temperature - 50 to 54 degrees F.
Organic matter of the surface to 15 inches - .5 to 1 percent
Depth to Bk horizon - 15 to 27 inches
Clay percent in control section - 0 to 5
A horizon
Color value, dry - 5 or 6, moist - 3 or 4
Chroma, dry or moist - 2 to 4
Reaction - neutral to moderately alkaline
Dark colors in the ochric epipedon are due mostly to dark sand grains from basalt. In places, large boulders (2 to 6 feet in diameter) cover 3 to 10 percent of the soil area.
Bw horizons
Color value, dry - 5 through 7
Value, moist - 4 to 6
Chroma - 2 to 4 dry or moist
Texture - LFS, LS, FS
Reaction - mildly or moderately alkaline
Bk horizons
Value - 6 to 8 dry, 4 to 7 moist
Chroma - 2 to 4 dry or moist
Texture - LFS, FSL, SL
Reaction - mildly or moderately alkaline
Calcium carbonate equivalent - 5 to 30 percent
Bkqm horizons are present in some pedons below 40 inches
COMPETING SERIES: This is the Sugarloaf series. Sugarloaf soils are sandy loam in the upper part of the profile and are calcareous to the surface.
GEOGRAPHIC SETTING: These soils are on basalt plains and buttes and terraces, breaks and alluvial fans. Slopes range from 0 to 60 percent. Elevations range from 2,700 to 3,700 feet. The soils formed in wind modified alluvium from mixed sources. The average annual precipitation ranges from 7 to 11 inches. The average annual air temperature is 49 to 52 degrees F. The frost free season is 110 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Banbury soils. Banbury soils are loamy, occur on higher terraces, and are shallow over bedrock.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; very slow or slow runoff; rapid permeability.
USE AND VEGETATION: Fathom soils are used for rangeland. Some areas are seeded to grass primarily for stabilization. Native vegetation is basin big sagebrush, needleandthread, and Indian ricegrass.
DISTRIBUTION AND EXTENT: These soils are of small extent along the flood plain just above the Snake River and in the Mellon Valley area northwest of Buhl, Idaho. They also occur on low terraces in small areas above the Snake River.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Twin Falls County, Idaho, 1992.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - 0 to 9 inches (A horizon)
Calcic horizon - 26 to 60 inches (Bk horizon)