LOCATION SHASTACOSTA OREstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Typic Palexerults
TYPICAL PEDON: Shastacosta very gravelly loam - woodland, on a 57 percent south-facing slope at an elevation of 1,800 feet. (When described on August 23, 1993 the soil was dry throughout. Colors are for moist soil unless otherwise noted.)
Oi--1/2 inch to 0; partially decomposed needles, leaves, twigs and woody materials.
A--0 to 2 inches; very dark grayish brown (10YR 3/2) very gravelly loam, dark grayish brown (10YR 4/2) dry; weak very fine and fine subangular blocky structure parting to weak fine granular; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and fine, and few medium and coarse roots; many fine and very fine tubular pores; 40 percent gravel and 5 percent cobbles; moderately acid (pH 5.8); clear smooth boundary. (2 to 5 inches thick)
BA--2 to 10 inches; brown (10YR 4/3) very gravelly loam, pale brown (10YR 6/3) dry; moderate very fine and fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and fine, and few medium and coarse roots; many fine and very fine tubular pores; 45 percent gravel and 5 percent cobbles; moderately acid (pH 5.6); clear smooth boundary. (0 to 9 inches thick)
Bt1--10 to 22 inches; dark yellowish brown (10YR 4/4) very gravelly loam, pale brown (10YR 6/3) dry; moderate very fine and fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; many very fine and fine, and few medium and coarse roots; many fine and very fine tubular pores; few faint clay films on ped faces and in pores; 40 percent gravel and 5 percent cobbles; strongly acid (pH 5.4); clear wavy boundary.
Bt2--22 to 32 inches; dark yellowish brown (10YR 4/4) very gravelly clay loam, light yellowish brown (10YR 6/4) dry; moderate fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; common very fine and fine, and few medium roots; many fine tubular pores; common distinct clay films on ped faces and in pores; 40 percent gravel and 15 percent cobbles; strongly acid (pH 5.4); clear wavy boundary.
Bt3--32 to 41 inches; dark yellowish brown (10YR 4/4) extremely cobbly clay loam, light yellowish brown (10YR 6/4) dry; moderate fine subangular blocky structure; hard, firm, sticky and plastic; few fine and medium roots; common fine tubular pores; common distinct clay films on ped faces and in pores; 40 percent gravel and 25 percent cobbles; strongly acid (pH 5.2); abrupt wavy boundary. (Combined thickness of the Bt1, Bt2, and Bt3 horizons ranges from 25 to 40 inches)
2Bt4--41 to 56 inches; dark brown (10YR 4/3) very cobbly clay, brown (10YR 5/3) dry; strong fine subangular blocky structure; hard, firm, sticky and plastic; few medium and coarse roots; common fine tubular pores; many distinct clay films on ped faces and in pores; 30 percent gravel and 20 percent cobbles; very strongly acid (pH 4.8); gradual wavy boundary. (12 to 24 inches thick)
2Bt5--56 to 72 inches; dark yellowish brown (10YR 4/4) very gravelly clay, light yellowish brown (10YR 6/4) dry; strong fine subangular blocky structure; very hard, very firm, sticky and plastic; few medium and coarse roots; common fine tubular pores; many distinct clay films on ped faces and in pores; 35 percent gravel and 10 percent cobbles; very strongly acid (pH 4.8).
TYPE LOCATION: Curry County, Oregon; located about 2,640 feet south and 2,080 feet west of the northeast corner of section 16, T. 35 S., R. 11 W., W. M. (Latitude 42 degrees, 32 minutes, 57 seconds N, Longitude 124 degrees, 01 minutes, 04 seconds W)
RANGE IN CHARACTERISTICS: The soils are usually moist but are dry in all parts of the moisture control section for 60 to 90 consecutive days or more in the four months following the summer solstice and are moist during the winter. The mean annual soil temperature at a depth of 20 inches is 51 to 57 degrees F. Depth to bedrock and solum thickness is greater than 60 inches. The particle size control section averages 25 to 30 percent clay and has 45 to 75 percent total rock fragments. Depth to the clayey-skeletal 2Bt horizon ranges from 35 to 50 inches. Hue is 10YR or 7.5YR.
The A horizon has value of 2 or 3 moist, 3 to 5 dry and chroma of 2 to 4 moist and dry. It is very gravelly loam with 15 to 20 percent clay. It has 35 to 50 percent gravel and 0 to 5 percent cobbles.
The Bt horizon has value of 4 or 5 moist, 4 to 6 dry and chroma of 3 to 6 moist and dry. It is very gravelly loam, very gravelly clay loam, or extremely cobbly clay loam with 25 to 30 percent clay. It has 40 to 50 percent gravel and 5 to 25 percent cobbles. Soil reaction is strongly acid to moderately acid.
The 2Bt horizon has color similar to the Bt horizon. It is very cobbly clay, very gravelly clay, or extremely gravelly clay averaging 45 to 55 percent clay with 30 to 50 percent gravel and 10 to 20 percent cobbles. Soil reaction is very strongly acid to strongly acid.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: The Shastacosta soils are on broad ridgetops and south-facing side slopes of mountains. Slopes are 2 to 60 percent. The soils formed in colluvium and residuum weathered from mudstone and metasedimentary rock types derived from Tertiary sediments of the Flournoy, Lookingglass, and Roseburg Formations. Elevations are 200 to 2,300 feet. The climate is characterized by warm, wet winters and hot, dry summers. The mean annual precipitation is 80 to 100 inches. The mean annual temperature is 49 to 56 degrees F. The frost-free period is 170 to 200 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Beekman, Colestine, Josephine, Pollard, Speaker and Vermisa soils. Beekman soils are on south-facing side slopes of mountains, and are 20 to 40 inches deep bedrock. Colestine, Josephine, and Speaker soils occur on broad ridgetops, stable benches, or south-facing side slopes of mountains, and are fine-loamy. Colestine and Speaker soils are 20 to 40 inches deep to bedrock. Josephine soils are 40 to 60 inches deep to bedrock. Pollard soils occur on toe slopes, foot slopes, hill slopes, broad ridgetops, stable benches, and south-facing side slopes of mountains, are clayey and have less than 35 percent rock fragments in the soil profile. Vermisa soils occur on broad ridgetops and south-facing side slopes of mountains, and are 10 to 20 inches deep to bedrock.
DRAINAGE AND PERMEABILITY: Well drained; slow permeability.
USE AND VEGETATION: Shastacosta soils are used for timber production, watershed, and wildlife habitat. The native vegetation is Douglas fir, Pacific madrone, canyon live oak, tanoak, Oregon white oak, California black oak, poison oak, California honeysuckle, Whipplevine, mountain sweetroot, western rattlesnake plantain, western swordfern, California fescue, mountain brome, and western fescue.
DISTRIBUTION AND EXTENT: Mountainous areas of southwestern Oregon; MLRA 5. The series is not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Curry County, Oregon, 1996. The source of the name is Shasta Costa Creek east of Agness in the central interior of Curry County.
REMARKS: Diagnostic horizons are features recognized in this pedon include:
Ochric epipedon.
Argillic horizon - from depths of 10 to 72 inches (Bt1, Bt2, Bt3, 2Bt4, 2Bt5 horizons).
Particle-size control section - from 10 to 30 inches (Bt1 horizon and upper 8 inches of the Bt2 horizon).
Palexerults great group - clay distribution in the argillic horizon does not decrease from its maximum amount by more than 20 percent within a depth of 60 inches from the soil surface (Bt1, Bt2, Bt3, 2Bt4, 2Bt5 horizons).