LOCATION SEAQUEST WAEstablished Series
TAXONOMIC CLASS: Fine, mixed, active, mesic Xeric Palehumults
TYPICAL PEDON: Seaquest silt loam - clear cut woodland. (Colors for moist conditions unless otherwise noted.)
A--0 to 6 inches; dark brown (10YR 3/3) silt loam, dark brown (10YR 4/3) dry; weak medium subangular blocky structure parting to moderate fine subangular blocky; hard, firm, slightly sticky and slightly plastic; common to many fine to coarse roots; many fine to coarse vesicular and tubular pores; moderately acid (pH 5.6); clear wavy boundary. (5 to 7 inches thick)
BAt--6 to 12 inches; dark brown (7.5YR 4/4) silty clay loam, brown (7.5YR 5/4) dry; weak medium subangular blocky structure parting to moderate fine subangular blocky; hard, firm, sticky and plastic; common patchy distinct dark brown (7.5YR 3/4) clay films on faces of peds; common to many fine to coarse roots; many fine to coarse vesicular and tubular pores; strongly acid (pH 5.2); clear smooth boundary. (5 to 7 inches thick)
Bt1--12 to 24 inches; strong brown (7.5YR 4/6) silty clay loam, brown (7.5YR 5/4) dry; weak medium subangular blocky structure parting to moderate fine subangular blocky; hard, firm, sticky and plastic; common patchy distinct dark brown (7.5YR 3/4) clay film on faces of peds; few to common fine to coarse roots; many fine to coarse vesicular and tubular pores; strongly acid (pH 5.1); clear smooth boundary.
Bt2--24 to 38 inches; dark brown (7.5YR 4/4) silty clay loam, yellowish brown (l0YR 5/4) dry; moderate medium subangular blocky structure parting to strong fine angular blocky; hard, firm, sticky and plastic; many discontinuous distinct reddish brown (5YR 4/4) clay films on faces of peds; few to common fine to coarse roots; many fine to coarse vesicular and tubular pores; common medium irregular soft masses of iron-manganese; very strongly acid (pH 4.9); gradual smooth boundary.
Bt3--38 to 52 inches; strong brown (7.5YR 4/6) silty clay loam, reddish yellow (7.5YR 6/6) dry; moderate medium subangular blocky structure parting to strong fine angular blocky; hard, firm, sticky and plastic; many continuous prominent reddish brown (5YR 4/4) clay films on faces of peds; few to common fine to coarse roots, many fine to coarse vesicular and tubular pores; very strongly acid (pH 5.0); gradual smooth boundary. (Combined thickness of the Bt horizon is 33 to 45 inches)
BCt--52 to 60 inches; yellowish brown (10YR 5/4) silty clay loam, brownish yellow (10YR 6/6) dry; moderate medium subangular blocky structure; hard, firm, sticky and plastic; many continuous prominent reddish brown (5YR 4/4) clay films on faces of peds; very few to few fine and medium roots; very strongly acid (pH 4.9).
TYPE LOCATION: Cowlitz County, Washington. About 5 miles northeast of Castle Rock, Washington, 1,400 feet east and 750 feet south of the northwest corner of sec. 33, T. 10 N., R. 1 W.
RANGE IN CHARACTERISTICS: These soils are usually moist but are dry in the moisture control section for 45 to 60 days following the summer solstice. Average annual soil temperature is 50 to 52 degrees F. Average annual soil temperature is 50 to 52 degrees F. Rock fragments in the particle-size control section average 0 to 5 percent. The ratio of calcium to magnesium is 0.3 to 1.0:1 in the particle-size control section.
The A horizon has value of 2 to 3 moist and chroma of 2 to 4 moist. It is slightly acid to strongly acid.
The ABt and Bt horizons have hue of 10YR, 7.5YR or 5YR, value of 3 to 5 moist and chroma of 3 to 6 moist. It is silty clay loam, clay loam, or clay. Clay content averages 35 to 60 percent. It is strongly acid or very strongly acid.
COMPETING SERIES: These are the Bellpine, Jory, Nekia, and Olympic series. Bellpine soils are 20 to 40 inches deep to a paralithic contact. Jory soils have a ratio of calcium to magnesium of more than 2:1 and a mean annual soil temperature of 52 to 57 degrees F. Nekia soils are 20 to 40 inches deep to a lithic contact. Olympic soils have an umbric epipedon.
GEOGRAPHIC SETTING: Seaquest soils are on hills and terraces at elevations of 400 to 700 feet. Slopes are 0 to 30 percent. They developed in alluvium and sediments from fine-grained non-marine sandstone of the Wilkes formation, miocene age, tuffaceous siltstone, conglomerate, and andesite. The climate is characterized by warm dry summers and cool wet winters. The average January air temperature is 34 degrees F. and in July it is 62 degrees F. The average annual temperature is 48 degrees F. Frost-free season (32 degrees F) is 180 to 220 days. The average growing season at 28 degrees F is 200 to 240 days. The average annual precipitation is 50 to 60 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Olympic soils and the Sara soils. Sara soils have base saturation of more than 35 percent and are mottled.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff. Permeability is moderately slow.
USE AND VEGETATION: Used for timber production, hay, pasture, cropland, and wildlife habitat. Small grains, strawberries, and cane fruit are common crops. The principal native vegetation includes Douglas-fir, bigleaf maple, red alder, and western redcedar with an understory of cascara buckthorn, salmonberry, western swordfern, red elderberry, red huckleberry, vine maple, western hazel, salal, Oregongrape, and Pacific trillium.
DISTRIBUTION AND EXTENT: Puget lowlands in Cowlitz County, Washington. Seaquest soils are of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Cowlitz County, Washington. 1965
REMARKS: Characterization data are available on this pedon. Sample numbers S84-WA-015-007. Diagnostic horizons and features recognized in this pedon are an ochric epipedon from the mineral surface to 6 inches and an argillic horizon from 6 to 60 inches.