LOCATION SWANTOWN WAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, isotic, acid, mesic Typic Petraquepts
TYPICAL PEDON: Swantown gravelly sandy loam, forested. (Colors are for moist soil unless otherwise noted.)
Oi--0 to 2 inches; leaves, needles, and twigs.
Oa--2 to 3 inches; dark reddish brown (5YR 2/2) highly decomposed leaves, needles and twigs; very strongly acid (pH 5.0).
A--3 to 8 inches; very dark grayish brown (10YR 3/2) very gravelly sandy loam, grayish brown (10YR 5/2) dry; moderate fine and medium granular structure; soft, very friable,; many fine, medium, and coarse roots; 35 percent gravel; strongly acid (pH 5.4); clear smooth boundary. (4 to 6 inches thick)
Bw--8 to 16 inches; brown (10YR 5/3) very gravelly sandy loam, very pale brown (10YR 7/3) dry; common medium distinct strong brown (7.5YR 5/6) redox concentrations; weak medium and coarse subangular blocky structure; slightly hard, firm; many fine and medium tubular pores; 35 percent gravel; many dark concretions; strongly acid (pH 5.5); gradual wavy boundary. (7 to 12 inches thick)
BC--16 to 25 inches; gray (10YR 5/1) very gravelly sandy loam, light gray (10YR 7/1) dry; common medium distinct yellowish brown (10YR 5/6) and yellowish red (5YR 5/6) redox concentrations; massive; compact, hard, very firm,; common fine and medium roots, root mat at base of horizon; common medium and coarse pores; 40 percent gravel; moderately acid (pH 5.8); gradual wavy boundary. (6 to 12 inches thick)
Bsm--25 to 35 inches; gray (10YR 5/1) pan that breaks to very gravelly sandy loam, light gray (10YR 7/1) dry; common medium distinct brown (10YR 5/3) redox concentrations; massive; cemented, extremely hard, extremely firm; 60 percent gravel; moderately acid (pH 5.8). (Several feet thick)
TYPE LOCATION: Jefferson County, Washington; 120 yards east of West Chimicum Valley Road; NE1/4 NW1/4 NE1/4 section 27, T.29N., R.1W.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is estimated to range from 47 to about 53 degrees F. These soils are usually moist and are not dry in all parts between 8 and 24 inches for as much as 45 consecutive days or in some part for as much as 90 cumulative days. The particle-size control section is 35 to 60 percent coarse fragments by volume and 5 to 15 percent clay by weight. Depth to the Bsm horizon ranges from 20 to 30 inches.
The A horizon has value of 3 through 5 moist, and chroma of 2 or 3. It has weak to moderate granular structure. Reaction is strongly acid or moderately acid.
The Bw horizon has value of 4 or 5 moist, and chroma of 2 through 4 moist, and is mottled. It is gravelly loam or gravelly sandy loam and has weak to moderate blocky structure. Reaction is strongly acid or moderately acid.
The BC horizon has hue of 10YR or 2.5Y, value of 4 through 6 moist, and chroma of 1 or 2, and it is mottled. Reaction is moderately acid or slightly acid.
The Bsm horizon has hue of 10YR through 5Y, value of 4 through 6 moist, and chroma of 1 or 2, and it is mottled. It ranges from gravelly sandy loam to very gravelly sandy loam and is moderately to weakly cemented.
COMPETING SERIES: These are the Tukey and Whidbey series. Tukey and Whidbey soils have a xeric moisture regime.
GEOGRAPHIC SETTING: Swantown soils are on till plains at elevations from near sea level to about 600 feet. The soil formed in ablation till underlain by compact basal till. These soils are in a mild marine climate. The average precipitation ranges from 18 to 35 inches. The mean January temperature is 39 degrees F.; the mean July temperature is 59 degrees F.; and the mean annual temperature is about 50 degrees F. The growing season is about 220 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Whidbey soils.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; runoff is slow; permeability is moderately rapid in the solum and very slow in the cemented till. A perched water table is as high as 6 inches to 2 feet at times from November to March.
USE AND VEGETATION: Used for woodland and pasture. Natural vegetation is Douglas-fir, red alder, western redcedar, and grand fir, with an understory of salmonberry, sedge, stinging nettle, skunkcabbage, western swordfern, vine maple, salal, evergreen huckleberry, and red huckleberry.
DISTRIBUTION AND EXTENT: Northwestern Washington. Series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Island County, Washington, 1950.
REMARKS: Classification only changed 4/94 because of recent amendments to Soil Taxonomy.
This draft is an update in format only of a 1970 series description. The "pan" in similar soils is cemented by iron, aluminum and organic matter and the soils classified as Spodisols. This soil has a udic moisture regime.
Diagnostic horizons and features recognized in this pedon are an ochric epipedon from 3 to 8 inches, a cambic horizon from 8 to 25 inches, and a cemented pan at 25 to 35 inches.
Classification changed 1/00 from mixed, mesic Vitrandic Durochrepts to isotic, mesic Tyhpic Petraquepts based on revisions to Soil Taxonomy.
Depth to diagnostic horizons and features are measured from the to of the first mineral horizon.