LOCATION CLACKAMAS OREstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Typic Argiaquolls
TYPICAL PEDON: Clackamas gravelly loam - grass. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 6 inches; very dark brown (10YR 2/2) gravelly loam, dark grayish brown (10YR 4/2) dry; moderate medium and fine subangular blocky structure; slightly hard, friable, slightly sticky, slightly plastic; many very fine roots; many very fine and fine irregular pores; medium acid (pH 5.6); abrupt smooth boundary. (5 to 12 inches thick)
AB--6 to 15 inches; very dark grayish brown (10YR 3/2) gravelly loam, dark grayish brown (10YR 4/2) dry; common fine and medium black and reddish brown mottles; moderate medium subangular blocky structure; hard, friable, slightly sticky, slightly plastic; many roots; many very fine and fine tubular pores; common fine (1 millimeter) light colored fragments; medium acid (pH 5.8); clear smooth boundary. (0 to 15 inches thick)
Btg--15 to 24 inches; very dark gray (10YR 3/1) gravelly clay loam, grayish brown (10YR 5/2) dry; many fine prominent dark reddish brown (2.5YR 3/4) mottles; moderate medium subangular blocky structure; hard, friable, sticky, plastic; many roots; many very fine and fine pores; common moderately thick clay films in pores, on surfaces of gravel, and few on surfaces of peds; common fine black stains; medium acid (pH 5.6); abrupt smooth boundary. (8 to 15 inches thick)
2Cg--24 to 60 inches; mottled dark brown (10YR 3/3) and strong brown (7.5YR 5/6) extremely gravelly clay loam, light brownish gray (10YR 6/2), pale brown (10YR 6/3) and light yellowish brown (10YR 6/4) dry; massive; very hard, firm, slightly sticky, slightly plastic; few pores; 80 percent gravel and cobbles; strongly acid (pH 5.4); (many feet thick)
TYPE LOCATION: Marion County, Oregon; 50 feet east of paved road in northeast 1/4 southeast 1/4, sec. 1, T. 8 S., R. 3 W.
RANGE IN CHARACTERISTICS: The mean annual soil temperature ranges from 52 to 55 degrees F. The soils have an aquic moisture regime and are saturated with water during the winter. Rock fragments in the A and B horizons range from 5 to 35 percent. The depth of 2Cg horizon ranges from 13 to 36 inches.
The A horizon is dark brown, black, very dark brown or very dark grayish brown. It is gravelly loam, silt loam or gravelly silt loam.
The Btg horizon has hue of 10YR to 5Y, value of 3 or 4 moist, 5 or 6 dry, chroma of 1 or 2 moist and dry and has common or many, faint or prominent mottles. It is gravelly clay loam, silty clay loam or gravelly silty clay loam with 27 to 35 percent clay. In some pedons the lower part of the horizon has 35 to 50 percent gravel but the argillic horizon averages less than 35 percent. THe 2Cg horizon is highly variegated and prominently mottled. It is loam, clay loam, or silty clay loam with 50 to 70 percent gravel and 5 to 10 percent cobbles. This horizon is very hard or extremely hard and very firm or extremely firm.
COMPETING SERIES: These are the Barry, Berville, Brookston, Buntingville, Cordova, Hamel, Jameston, Marengo, Millgrove, Navan Rensselaer and Westland series. Barry, Berville, Brookston, Jameston and Navan soils are slightly acid to mildly alkaline in the solum. Buntingville soils have secondary lime at depth of 20 inches and lack rock fragments. Marengo soils have a solum over 40 inches thick. Cordova, Hamel and Rensselaer soils are calcareous in the lower part. Millgrove soils are slightly to mildly alkaline in the B horizon. Westland soils are neutral to moderately alkaline in the lower part of the B horizon.
GEOGRAPHIC SETTING: The Clackamas soils are on level to gently rolling terraces at elevations of 175 to 700 feet. Slope gradients range from 0 to 3 percent. The soils formed in gravelly moderately fine textured mixed alluvium. The climate is characterized by having dry, cool summers and cool, wet winters. The mean annual precipitation is 40 to 60 inches. The mean annual temperature is 50 to 54 degrees F, the mean July temperature is about 67 degrees F, the mean January temperature is about 39 degrees F. The frost-free period is 165 to 210 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Courtney, Salem, and Sifton soils. Courtney soils are poorly drained and have a fine textured B horizon. Salem soils are well drained and have contrasting textures within a depth of 40 inches. Sifton soils lack argillic horizons and have contrasting textures within a depth of 40 inches.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; slow runoff; and moderately slow permeability.
USE AND VEGETATION: Used for small grains, corn, pole beans, berries, pasture and hay. Vegetation is mainly Douglas-fir, hazel brush, brackenfern, rose, and grass.
DISTRIBUTION AND EXTENT: Tributary valleys of the Willamette Valley area in western Oregon. The soils are of moderate extent.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Clackamas County, Oregon, Soil Survey, 1921.