LOCATION CORNELIUS OREstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, mesic Mollic Fragixeralfs
TYPICAL PEDON: Cornelius silt loam, cultivated walnut orchard. (Colors are for moist soil unless otherwise noted.)
Ap--0 to 6 inches; dark brown (10YR 3/3) silt loam, grayish brown (10YR 5/2) dry; moderate fine subangular blocky structure; friable, slightly sticky and slightly plastic; common fine and few medium roots; many very fine irregular pores; many fine concretions; moderately acid (pH 5.6); abrupt smooth boundary. (5 to 6 inches thick)
BA--6 to 11 inches; brown (10YR 4/3) silt loam, pale brown (10YR 6/3) dry; thin silt coatings on some surfaces of peds; moderate fine subangular blocky structure; hard, firm, slightly sticky and slightly plastic; common fine and few medium roots; many very fine irregular pores; 2 percent fine concretions; moderately acid (pH 5.9); clear smooth boundary. (4 to 6 inches thick)
Bw--11 to 17 inches; brown (10YR 4/3) silt loam, light yellowish brown (10YR 6/4) dry; moderate fine and medium subangular blocky structure; hard, firm, sticky and plastic; few very fine, fine and medium roots; many very fine tubular pores; moderately acid (pH 5.7); clear smooth boundary. (6 to 9 inches thick)
Bt1--17 to 28 inches; brown (10YR 4/3) silty clay loam, light yellowish brown (10YR 6/4) dry; moderate fine and medium subangular blocky, structure; very hard, firm, moderately sticky and moderately plastic; few very fine, fine and medium roots; many very fine tubular pores; common distinct clay films; strongly acid (pH 5.2); gradual wavy boundary. (8 to 13 inches thick)
Bt2--28 to 38 inches; brown (10YR 4/3) silt loam, light yellowish brown (10YR 6/4) dry; moderate medium subangular blocky structure; very hard, firm, moderately sticky and moderately plastic; few very fine, fine and medium roots; many very fine tubular pores; common distinct clay films; strongly acid (pH 5.4); clear smooth boundary. (7 to 11 inches thick)
2Btx1--38 to 52 inches; brown (10YR 4/3) silt loam, light yellowish brown (10YR 6/4) dry; grayish brown (10YR 5/2) tongues and coatings in fractures, light gray (10YR 7/2) dry; yellowish brown (10YR 5/6) redox concentrations in fracture margins; weak coarse prismatic; brittle, very firm, moderately sticky and moderately plastic; few fine roots; many very fine tubular pores; common distinct and prominent clay films; common fine black stains; strongly acid (pH 5.3); clear wavy boundary. (12 to 15 inches thick)
2Btx2--52 to 58 inches; brown (10YR 4/3) silt loam, light yellowish brown (10YR 6/4) and very pale brown (10YR 8/3) dry; grayish brown (10YR 5/2) redox depletions; yellowish brown (10YR 5/6) redox concentrations in margins; massive with some vertical fractures; brittle, firm, moderately sticky and moderately plastic; many very fine tubular pores; common distinct clay films; common fine black stains; strongly acid (pH 5.4).
TYPE LOCATION: Washington county, Oregon; about 1 mile west of Scholls, Oregon; 2,000 feet east and 300 feet south of Midway-Vanderschuere Road Junction; NW1/4 NE1/4 SE1/4 section 17, T.2S., R.2W.
RANGE IN CHARACTERISTICS: The soils are usually moist but are dry throughout between depths of 4 and 12 inches for 45 to 60 consecutive days. The mean annual soil temperature is 52 degrees to 56 degrees F. The depth to the fragipan ranges from 30 to 40 inches. The soil is more than 60 inches deep to bedrock.
The A horizon has value of 2 or 3 moist and chroma of 2 or 3 moist.
The Bw and Bt horizon has hue of 10YR or 7.5YR, value of 3 or 4 moist, 5 through 7 dry, and chroma of 3 or 4 moist and dry. It is dominantly silty clay loam and has 27 to 35 percent clay and less than 15 percent coarser than very fine sand. Few faint redox concentrations with hue of 5YR or 7.5YR and chroma of 3 or 4 are near the boundary with the fragipan in some pedons. Clay films are common to nearly continuous and faint to distinct on most peds.
The 2Btx horizon has matrix colors similar to the horizon above it, but it has faint to prominent redox concentrations with chroma of more than 2 and has tongues with chroma of 2 or less. It is silt loam or silty clay loam and commonly is 2 or more feet thick. This horizon is firm and brittle and has few to many faint to distinct clay films on many peds. It overlies a dark reddish brown (2.5YR 3/4) clay soil in some areas.
COMPETING SERIES: There are no other series in this family. Similar soils include the Kinton series. Kinton soils lack argillic horizons.
GEOGRAPHIC SETTING: The Cornelius soils are on gently sloping to rolling low hills and steep hill slopes with convex, long slopes and ridgetops at elevations of 350 to 800 feet. The soils formed in loess-like material over mixed, fine-silty old alluvium of mixed origin. The soils formed in a cool moist winter and a warm dry summer climate. Average July temperature is 66 degrees F., average January temperature is 39 degrees F., average annual temperature is 52 degrees to 54 degrees F., and average annual precipitation is 40 to 60 inches. Frost-free period is 165 to 210 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cascade, Helvetia and Saum soils and the competing Kinton and Laurelwood soils. Cascade soils lack argillic horizons above the fragipan. Helvetia and Saum soils lack fragipans.
DRAINAGE AND PERMEABILITY: Moderately well drained; slow to medium runoff; moderate over slow permeability.
USE AND VEGETATION: Used to produce berries, orchards, small grain and seed crops, hay, pasture, and for woodland. Native vegetation is mainly Douglas-fir, big leaf maple, western red cedar, hazelbrush and grasses.
DISTRIBUTION AND EXTENT: Northwest Oregon. The soils is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Washington County, Oregon, 1975.
REMARKS: Diagnostic horizons and other features:
Ochric epipedon
Cambic horizon - from 11 to 17 inches
Argillic horizon - from 17 to 38 inches
Fragipan - from 38 to 52 inches
ADDITIONAL DATA: Characterization data on one profile (S70 Ore. 34-2) reported in Riverside soil survey printout for soils sampled in Washington County, Oregon, 1970.