LOCATION CUPPLES WAEstablished Series
TAXONOMIC CLASS: Medial-skeletal, amorphic, frigid Oxyaquic Haplorthods
TYPICAL PEDON: Cupples gravelly silt loam; on a 40 percent convex southwest-facing slope under a conifer canopy. (Colors are for moist soil unless otherwise stated. All textures are apparent field textures.)
0i--7 to 4 inches; undecomposed forest litter. (2 to 5 inches thick)
0a--4 inches to 0; decomposed forest litter. (2 to 6 inches thick)
E--0 to 2 inches; dark brown (7.5YR 4/2) gravelly silt loam, pinkish gray (7.5YR 6/2) dry; massive; slightly hard, friable, slightly sticky and slightly plastic; many very fine and common fine roots; common very fine irregular pores; 20 percent rounded pebbles; NaF pH less than 9.4; strongly acid (pH 5.2); abrupt smooth boundary. (0 to 3 inches thick)
Bs1--2 to 8 inches; dark reddish brown (5YR 3/4) gravelly silt loam, strong brown (7.5YR 5/6) dry; weak coarse subangular blocky structure; slightly hard, friable, nonsticky, nonplastic and weakly smeary; very few fine roots; common very fine irregular pores; 20 percent rounded pebbles; NaF pH 10.0; strongly acid (pH 5.4); abrupt irregular boundary. (2 to 6 inches thick)
Bs2--8 to 18 inches; strong brown (7.5YR 5/6) very gravelly loam, brownish yellow (10YR 6/6) dry, weak medium subangular blocky structure; slightly hard, friable, nonsticky, nonplastic and weakly smeary; very few very fine roots; common very fine irregular pores; 50 percent rounded pebbles; 10 percent cobbles; NaF pH 11.5; medium acid (pH 5.6); clear smooth boundary. (6 to 14 inches thick)
BC--18 to 34 inches; dark yellowish brown (10YR 4/4) very gravelly sandy loam, olive yellow (2.5Y 6/6) dry; weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common fine irregular pores; 45 percent rounded pebbles, 15 percent cobbles; NaF pH 10.6; medium acid (pH 5.6); abrupt smooth boundary. (14 to 25 inches thick)
2Cd--34 to 60 inches; dark grayish brown (2.5Y 4/2) dense glacial till, that breaks to very gravelly sandy loam, light brownish gray (2.5Y 6/2) dry; massive; very hard, firm, nonsticky, nonplastic; 45 percent rounded pebbles; medium acid (pH 5.6).
TYPE LOCATION: Skagit County, Washington; 820 feet south and 920 feet east of the northwest corner of sec. 16, T. 36 N., R. 8 E.
RANGE IN CHARACTERISTICS: These soils are dry less than 45 consecutive days following summer solstice. The mean annual soil temperature ranges from 45 to 47 degrees F. Depth to dense glacial till ranges from 20 to 40 inches. Reaction is strongly acid or medium acid throughout. Content of rock fragments in the particle-size control section averages 35 to 45 percent unweathered pebbles, 0 to 25 percent weathered pebbles, and 0 to 5 percent cobbles.
The E horizon has hue of 7.5YR or 10YR; value of 3 through 5 moist, 5 through 7 dry; and chroma of 1 through 3 moist and dry.
The Bs horizon has hue of 5YR, 7.5YR, or 10YR; value of 3 through 5 moist, 4 through 7 dry; and chroma of 3 through 6 moist and dry. It is gravelly silt loam, very gravelly silt loam, or very gravelly loam.
The BC horizon has hue of 10YR or 2.5Y, value of 4 or 5 moist, 5 or 6 dry, and chroma of 4 through 6 moist and dry. It is very gravelly loam or very gravelly sandy loam.
The 2Cd horizon has hue of 2.5Y or 5Y; value of 4 or 5 moist, 6 or 7 dry; and chroma of 2 through 4 moist and dry. It is dense glacial till that breaks to very gravelly loam or very gravelly sandy loam.
COMPETING SERIES: These are the Danforth, Montborne, Oakes, Olomount, Rinker, Sorensen, and Winnecook series and the Olomount soils in another family. Danforth, Oakes, and Sorensen soils are deep. Montborne soils are 40 to 70 percent hard phyllite in the particle-size control section. Olomount, Rinker, and Winnecook soils have a lithic contact at 20 to 40 inches.
GEOGRAPHIC SETTING: Cupples soils are on till plains and mountain sides at elevations ranging from 1,000 to 2,000 feet. The soils formed in volcanic ash and glacial till. Average annual precipitation is 70 to 90 inches. The mean annual air temperature ranges from 43 to 45 degrees F, mean January temperature is 32 degrees F; and mean July temperature is 59 degrees F. The frost-free season is about 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Montborne and Oakes sols and the Illabot, Jug, Kindy, and Saxon series. Illabot soils lack a spodic horizon. Jug soils are sandy-skeletal. Kindy soils are cryic. Saxon soils are in a fine-silty family.
DRAINAGE AND PERMEABILITY: Moderately well drained; runoff is slow or medium. Permeability is moderate in the subsoil to the dense glacial till and very slow through it. A perched water table is as high as 2 to 3.5 feet from December through April.
USE AND VEGETATION: Used for woodland and wildlife habitat. Native vegetation includes western hemlock, Douglas-fir, western redcedar, red alder, and bigleaf maple, with an undergrowth of western swordfern, deer fern, red huckleberry, longtube twinflower, western brackenfern, salmonberry and vine maple.
DISTRIBUTION AND EXTENT: West slopes of the Cascade Mountains in northwestern Washington. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Skagit County area, Washington, 198l.
REMARKS: Classification only changed 4/94 because of recent amendments to Soil Taxonomy, and in addition the Cr horizon was changed to Cd. The previous draft reflected a change in classification from medial-skeletal, frigid Typic Haplorthods to loamy-skeletal, mixed, frigid Typic Haplorthods. Diagnostic horizons and features recognized in this pedon are andic soil properties from 0 to 34 inches, an albic horizon from the mineral surface to 2 inches, and a spodic horizon from 2 to 18 inches. The spodic horizon meets chemical criteria.