LOCATION SANDUN WAEstablished Series
TAXONOMIC CLASS: Sandy-skeletal, magnesic, frigid Typic Haplorthods
TYPICAL PEDON: Sandun very gravelly sandy loam - on a 45 percent north-facing dissected outwash terrace under a coniferous canopy of Douglas-fir and western hemlock at 1,500 feet elevation. (Colors are for moist soil unless otherwise stated. All textures are apparent field textures.
Oi--3 inches to 0; undecomposed leaves, needles, twigs,and wood fragments.
A--0 to 3 inches; dark reddish brown (5YR 3/4) gravelly sandy loam, brown (7.5YR 5/4) dry; moderate fine and medium granular structure; soft, very friable, nonsticky and nonplastic, weakly smeary; common very fine, fine, and few medium roots; common very fine irregular pores; 30 percent pebbles; NaF pH 11.5; strongly acid (pH 5.2); clear wavy boundary. (0 to 4 inches thick)
Bs1--3 to 11 inches; dark brown (7.5YR 3/4) very gravelly sandy loam, strong brown (7.5YR 5/6) dry; weak medium subangular blocky parting to weak medium granular structure; soft, very friable, nonsticky and nonplastic, weakly smeary; few very fine and common fine and medium roots; common very fine irregular pores; 50 percent pebbles; NaF pH 12.0; moderately acid (pH 5.6); abrupt irregular boundary. (3 to 10 inches thick)
Bs2--11 to 24 inches; dark brown (7.5YR 4/4) very gravelly sandy loam, strong brown (7.5YR 5/6) dry; weak coarse subangular blocky structure; soft, very friable, nonsticky and nonplastic, weakly smeary; common very fine, fine, and few medium roots; common very fine irregular pores; 50 percent pebbles; NaF pH 12.0; moderately acid (pH 5.8); clear smooth boundary. (6 to 13 inches thick)
2BC--24 to 32 inches; dark yellowish brown (10YR 4/4) very gravelly loamy sand, brownish yellow (10YR 6/6) dry; massive; very friable, nonsticky and nonplastic, weakly smeary; few very fine and fine roots; common very fine irregular pores; 55 percent pebbles; NaF pH 12.0; moderately acid (pH 5.8); abrupt smooth boundary. (0 to 8 inches thick)
2C1--32 to 36 inches; dark yellowish brown (10YR 4/4) very gravelly loamy sand; light yellowish brown (2.5Y 6/4) dry; massive; hard; firm; nonsticky and nonplastic, weakly smeary; very few very fine roots; many fine irregular pores; 50 percent pebbles; NaF pH 12.0; moderately acid (pH 6.0); abrupt smooth boundary. (4 to 18 inches thick)
2C2--36 to 60 inches; olive brown (2.5Y 4/4) very gravelly loamy sand, light yellowish brown (2.5Y 6/4) dry; single grain; loose; very few very fine roots; many fine irregular pores; 55 percent pebbles; NaF pH 12.0; slightly acid (pH 6.4).
TYPE LOCATION: Whatcom County, Washington; about 6 1/2 miles east of Van Zandt; 1,900 feet north and 1,900 feet east of the southwest corner of sec. 20, T. 38 N., R. 6 E.
RANGE IN CHARACTERISTICS: Mean annual soil temperature is 44 to 47 degrees F. Thickness of the solum ranges from 20 to 36 inches. The weighted average of rock fragments in the control section ranges from 40 to 80 percent. The rock fragments are dominantly dunite. The Mg:Ca ratio in the control section is greater than 10:1.
The A horizon has hue of 5YR through 10YR, value of 3 or 4 moist, 4 or 5 dry, and chroma of 3 or 4 moist and dry. Reaction is very strongly acid or strongly acid.
The Bs horizon has hue of 5YR through 10YR, value of 3 through 5 moist, 5 through 7 dry, and chroma of 3 through 6 moist and 4 through 6 dry. It has 35 to 55 percent pebbles and 0 to 20 percent cobbles. Reaction is strongly acid to slightly acid.
The 2BC and 2C horizons have hue of 10YR or 2.5Y, value of 3 through 5 moist, 4 through 6 dry, and chroma of 3 through 6 moist and dry. It is loamy sand or sand and has 30 to 65 percent pebbles and 0 to 25 percent cobbles. Reaction is strongly acid to slightly acid.
COMPETING SERIES: These are the Etach, Teneriffe, Limking, and Skykomish soils in another family. These soils have mixed mineralogy.
GEOGRAPHIC SETTING: Sandun soils are on outwash terraces, terrace escarpments, and on mountain footslopes at elevations of 1,200 to 2,500 feet. Slopes are 5 to 65 percent. The soils formed in loess, volcanic ash, and glacial outwash and slope alluvium derived from dunite. Sandun soils are in a marine climate with cool, moist summers and cold, wet winters. Snow cover lasts from December through March. Mean annual precipitation is 70 to 90 inches. Mean January temperature is about 32 degrees F, mean July temperature is about 59 degrees F, and mean annual temperature is about 43 degrees F. The frost-free season is 90 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Jackman, Kindy, Montborne, and Rinker soils. Jackman and Kindy soils are cryic. Montborne soils are 20 to 40 inches deep to a paralithic contact with dense compact glacial till. Rinker soils are 20 to 40 inches deep to a lithic contact. Also, Kindy, Montborne, and Rinker soils have mixed mineralogy.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately rapid permeability in the solum and very rapid in the substratum.
USE AND VEGETATION: Used for timber production, wildlife habitat, and watershed. Native vegetation is western hemlock, Douglas-fir, and red alder with an undergrowth of salal, red huckleberry, and western swordfern.
DISTRIBUTION AND EXTENT: Northwestern Washington. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Skagit County Area, Washington, 1981.
REMARKS: This draft reflects a change in classification from sandy-skeletal, serpentinitic, frigid Andic Xerochrepts to sandy-skeletal, serpentinitic, frigid Typic Haplorthods. Diagnostic horizons and features recognized in this pedon are: a cambic horizon from 3 to 24 inches dominated by amorphous material and 40 to 80 percent rock fragments, dominantly dunite in the particle-size control section. The spodic horizon does not meet chemical criteria for a spodic horizon, but does meet micro morphological for a spodic horizon, but does meet micro morphological criteria, i.e. cracked coatings and silt-sized and larger pellets.