LOCATION CORNUTT OREstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, mesic Ultic Haploxeralfs
TYPICAL PEDON: Cornutt cobbly clay loam, forested. (Colors are for moist unless otherwise noted.)
01--1/2 inch to 0; conifer needles and forest litter, loose and partially decomposed in lower part.
A1--0 to 5 inches; dark reddish brown (5YR 3/3) cobbly clay loam, light brown (7.5YR 6/4) dry; moderate very fine subangular blocky structure; slightly hard, friable, sticky and plastic; many fine and medium roots; many very fine tubular pores; 20 percent cobbles, 10 percent pebbles, 5 percent stones; slightly acid (pH 6.4); clear smooth boundary. (3 to 8 inches thick)
B1--5 to 11 inches; dark reddish brown (5YR 3/4) and reddish brown (5YR 4/4) cobbly clay loam, light brown (7.5YR 6/4) dry; moderate fine subangular blocky structure; hard, friable; sticky and plastic; many fine and medium roots; many fine and very fine tubular pores; 15 percent cobbles, 10 percent pebbles; medium acid (pH 6.0); clear smooth boundary. (3 to 8 inches thick)
IIB21t--11 to 21 inches; dark red (2.5YR 3/6) clay, red (2.5YR 5/6) dry; weak medium prismatic structure parting to moderate coarse subangular blocky; extremely hard, very firm, very sticky and very plastic; common medium and large roots; many very fine tubular pores; few black stains; common thin yellowish red (5YR 3/6) clay films; 10 percent partially weathered pebbles and 5 percent partially weathered cobbles; slightly acid (pH 6.4); gradual wavy boundary. (5 to 15 inches thick)
IIB22t--21 to 41 inches; dark reddish brown (5YR 3/4) clay, reddish brown (5YR 5/4) dry; weak medium prismatic structure parting to moderate coarse subangular blocky; extremely hard, very firm, very sticky and very plastic; common medium and large roots; common very fine tubular pores; few black stains; common thin and few moderately thick yellowish red (5YR 3/6) clay films; 10 percent partially weathered pebbles and 5 percent partially weathered cobbles; slightly acid (pH 6.4); clear wavy boundary. (6 to 15 inches thick)
IIC--41 to 45 inches; weathered metavolcanic bedrock; thick dark red (2.5YR 3/6) clay films in fractures.
TYPE LOCATION: Josephine County, Oregon; 1/4 mile off Granite Hill Road along the logging road; approximately 250 feet west and 610 feet north of the southeast corner of section 20, T. 35 S., R. 5 W., Willamette Meridian.
RANGE IN CHARACTERISTICS: These soils are usually moist but are dry throughout the control section for 60 to 80 consecutive days during the summer. The mean annual soil temperature ranges from 47 to 57 degrees F. Depth to bedrock is 40 to 60 inches or more. The calcium/magnesium ratio is about 1 or less.
The A horizon has hue of 5YR of 7.5YR, value of 2 or 3 moist, 4 through 6 dry, and chroma of 3 or 4 moist and 4 through 6 dry. Rock fragments average 10 to 20 percent cobbles and 5 to 15 percent pebbles.
The Bt horizon has hue of 5YR of 2.5YR, value of 3 or 4 moist, 4 through 6 dry, and chroma of 4 through 6 moist and dry. It averages 40 to 55 percent clay and has partially weathered fragments of rock averaging 0 to 20 percent cobbles and 10 to 20 percent pebbles.
COMPETING SERIES: These are the Bateman, Freezener, Jumpoff, Lettia, Manzanita, Melbourne, Munset, Napavine, Oak Grove, Oakland, Rainier, Secata and Veneta series. All of these soils are low in magnesium. Also, Bateman soils have a silty clay loam, or silty clay Bt horizon. Freezener soils are strongly acid or very strongly acid in the B2t horizon and have clay loam, slity clay loam and silty clay textures. Jumpoff soils have hue yellower than 7.5YR throughtout and are moderately well drained. Lettia soils have more than 25 percent medium and coarse sand in the Bt horizon. Manzabita soils are dry for more than 90 consecutive days in the summer and autumn and have distinct high chroma mottles in the lower part of the argillic horizon. Melbourne soils have hue yellower than 5YR throughout and are medium acid or strongly acid. Munset soils are 20 to 40 inches deep to a lithic contact. Napavine and Oakland soils have hue yellower than 5YR in the argillic horizon. Also, Napavine soils have an umbric epipedon and the Oakland soils are 20 to 40 inches deep to a paralithic contact. Oak Grove soils have an umbric epipedon. Rainier soils have an umbric eipipedon and are strongly acid. Secata soils are neutral or mildly alkaline in the argillic horizon and have hue yellower than 5YR in the argillic horizon. Veneta soils have hue yellower than 5YR and have more than 60 percent clay in the lower part of the argillic horizon.
GEOGRAPHIC SETTING: Cornutt soils are on mountain slopes, alluvial fans of high stream terraces, have slopes of 7 to 55 percent and are at elevations of 800 to 5,000 feet. The soils formed in colluvium weathered from mixed ultramafic rocks high in magnesium and altered sedimentary and extrusive igneous rocks. The climate is characteriaed by cool moist winters and warm dry summers with an annual precipitation of 30 to 60 inches. The mean annual temperature is 45 to 54 degrees F., and the frost-free season is 100 to 170 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Brockman, Dubakella, Eightlar, Josephine, Pearsoll and Speaker soils. Brockman, Dubakella, Eightlar, and Pearsoll soils have serpentinitic mineralogy. Brockman and Eightlar soils lack and argillic horizon. Dubakella and Pearsoll soils are skeletal. Josephine and Speaker soils are fine-loamy. Josephine soils have a base saturation of less than 35 percent. Speaker soils are 20 to 40 inches deep.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; slow permeability.
USE AND VEGETATION: Used for timber production, water supply and wildlife habitat. Vegetation is mainly Douglas-fir, ponderosa pine, incesse-cedar, modrone, shrubs and grasses.
DISTRIBUTION AND EXTENT: Southwestern Oregon and northern California. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Mendicino County, California, 1952. Special correlation.
REMARKS: The Cornutt soils were formerly classified as having serpentinitic mineralogy.