LOCATION BROCKMAN OREstablished Series
TAXONOMIC CLASS: Fine, magnesic, mesic Vertic Haploxerepts
TYPICAL PEDON: Brockman cobbly clay loam, on a 11 percent SW facing slope and forested. (Colors are for moist soil unless otherwise noted.)
A1--0 to 4 inches; dark reddish brown (5YR 3/2) cobbly clay loam, reddish brown (5YR 4/3) dry; moderate fine subangular blocky structure; hard, friable, sticky and plastic; many coarse to very fine roots; many very fine interstitial pores; 15 percent hard cobbles and 15 percent hard pebbles; slightly acid (pH 6.4); clear smooth boundary. (2 to 5 inches thick)
A3--4 to 9 inches; dark reddish brown (5YR 3/3) cobbly clay loam, reddish brown (5YR 4/3) dry; moderate fine subangular blocky structure; hard, friable, sticky and plastic; many coarse to very fine roots; many very fine tubular pores; 15 percent cobbles and 10 percent pebbles; slightly acid (pH 6.4); abrupt wavy boundary. (0 to 5 inches thick)
B2--9 to 16 inches; dark reddish brown (5YR 3/4) cobbly clay, reddish brown (5YR 4/4) dry; moderate medium subangular blocky structure; very hard, very firm, very sticky and very plastic; many coarse to very fine roots; common fine tubular pores; 10 percent cobbles and 10 percent pebbles; slightly acid (pH 6.2); abrupt wavy boundary. (7 to 12 inches thick)
IIC1--16 to 34 inches; reddish brown (5YR 4/4) cobbly clay, yellowish red (5YR 4/6) dry; massive; extremely hard, extremely firm, very sticky and very plastic; common intersecting slickensides; few coarse to very fine roots; few very fine tubular pores; 15 percent cobbles and 10 percent pebbles; slightly acid (pH 6.2); clear wavy boundary. (10 to 20 inches thick)
IIIC2--34 to 60 inches; dark brown (7.5YR 3/4) cobbly clay, brown (7.5YR 4/4) dry; massive; extremely hard, extremely firm, very sticky and very plastic; 15 percent partially weathered cobbles and 10 percent partially weathered pebbles; neutral (pH 6.7).
TYPE LOCATION: Josephine County, Oregon; 3 miles north of Grants Pass at the east end of Colonial Valley, about 300 feet east and 30 feet north of the southwest corner of section 20, T.35S., R.5W.
RANGE IN CHARACTERISTICS: The soils are usually moist but are dry in all parts between depths of 4 and 12 inches for 60 to 80 consecutive days in the 4-month period following the summer solstice. The mean annual soil temperature ranges from 50 degrees to 56 degrees F. The thickness of the solum above the nonconforming IIC horizon is 15 to 24 inches. Depth to bedrock is 60 inches or more. Rock fragments are serpentinite and range from 15 to 35 percent in the control section.
The A horizon has hue of 5YR or 7.5YR, value of 2 or 3 moist, 3 through 5 dry, and chroma of 2 through 4 moist and 3 or 4 dry.
The B2 horizon has hue of 2.5YR or 5YR, value of 2 or 3 moist, 3 through 5 dry, and chroma of 4 through 6 moist and 3 or 4 dry. It is clay or clay loam and averages 35 to 45 percent clay. Cobbles range from 10 to 20 percent and pebbles from 5 to 10 percent. The IIC horizon is 50 to 65 percent clay, 10 to 15 percent cobbles and 5 to 10 percent pebbles. It is massive when moist and has a medium to coarse prismatic structure when dry.
The IIIC2 horizon has 15 to 35 percent partially weathered cobbles and 10 to 25 percent partially weathered pebbles and averages 50 to 65 percent clay.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Brockman soils on alluvial fans at elevations of 800 to 4,000 feet. Slope gradients are 2 to 20 percent. The soils formed in cobbly clay alluvium weathered from serpentinite. Summers are warm and dry and winters are cool and moist with an annual precipitation of 30 to 60 inches. The mean annual temperature is 45 to 54 degrees F., the average January temperature is 38 degrees F.; and the average July temperature is 70 degrees F. The frost-free period is 100 to 170 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Copsey, Cornutt, Dubakella, Eightlar and Pearsoll soils. Copsey soils are poorly drained and have a mollic epipedon. Cornutt soils have an argillic horizon and mixed mineralogy. Dubakella, Eightlar, and Pearsoll soils are skeletal. Also Dubakella soils are moderately deep and Pearsoll soils are shallow.
DRAINAGE AND PERMEABILITY: Moderately well drained; medium runoff; very slow permeability.
USE AND VEGETATION: Brockman soils are used for pasture, hay, wildlife habitat and urban development. The native vegetation is scattered Douglas-fir, ponderosa pine, black oak, whiteleaf manzanita, madrone, wedgeleaf, ceanothus, and grasses.
DISTRIBUTION AND EXTENT: Southwestern Oregon. The series is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Josephine County, Oregon, 1979.