LOCATION OBSKEL             CA
Established Series
IRD: AEC/DWB/DWH
10/2006

OBSKEL SERIES


The Obskel series consists of deep, well drained soils that formed in weathered tephra over residuum and colluvium from coarse grained metamorphic rocks, mainly metadiorite. Obskel soils are on ridge tops and side slopes on metamorphic Sierra Nevada mountains. Slopes range from 15 to 70 percent. The mean annual precipitation is about 75 inches, (1905 mm) and the mean annual temperature is about 51 degrees F, (11 degrees C).

TAXONOMIC CLASS: Loamy-skeletal, isotic, mesic Andic Haploxerults

TYPICAL PEDON: Obskel very gravelly sandy loam on a west southwest-facing 25 percent slope under a cover of mixed conifers at an elevation of 4340 feet, (1323 m). When described on 9/29/97 the soil was dry throughout. (Colors are for dry soil unless otherwise noted)

Oi--0 to 0.2 inches (0 to 1 cm); needles and twigs

Oe--0.2 to 0.5 inches (1 to 2cm); partially decomposed needles and twigs

A--0.5 to 3.5 inches, (2 to 9 cm); light brown (7.5YR 6/4) very gravelly sandy loam, brown (7.5YR 4/3) moist; 12 percent clay; weak fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine and fine roots; many very fine to coarse irregular and tubular pores; 40 percent gravel; slightly acid, pH 6.5 by Hellige-Truog; NaF pH 10.0; clear smooth boundary. (2 to 7 inches, (5 to 18 cm) thick)

Bt1--3.5 to 8.5 inches, (9 to 22 cm); light brown (7.5YR 6/4) very gravelly sandy loam, brown (7.5YR 4/4) moist; 14 percent clay; weak fine and medium granular structure; soft, very friable, nonsticky and nonplastic; many very fine to medium roots; many very fine to coarse irregular and tubular pores; clay bridging between sand grains; 40 percent gravel; slightly acid, pH 6.4 by Hellige-Truog; NaF pH 9.8; clear smooth boundary.

Bt2--8.5 to 18.5 inches, (22 to 47 cm); reddish yellow (7.5YR 7/6) very gravelly sandy loam, brown (7.5YR 4/4) moist; 17 percent clay; moderate fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; many very fine to medium roots and common coarse roots; many very fine to medium irregular and tubular pores; many faint continuous clay films on faces of peds; 35 percent gravel and 5 percent cobbles; slightly acid, pH 6.3 by Hellige-Truog; NaF pH 9.8; clear smooth boundary.

Bt3--18.5 to 30.5 inches, (47 to 77 cm); pink (7.5YR 7/4) very gravelly loam, reddish yellow (7.5YR 6/6) moist; 19 percent clay; moderate fine and medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine to medium roots and few coarse roots; many very fine to medium irregular and tubular pores; many faint continuous clay films on faces of peds; 25 percent gravel and 15 percent cobbles; NaF pH 9.5; slightly acid, pH 6.3 by Hellige-Truog; gradual wavy boundary.

Bt4--30.5 to 55.5 inches, (77 to 141 cm); yellow (10YR 8/6) very gravelly loam, yellow (10YR 7/8) moist; 18 percent clay; moderate fine and medium subangular blocky structure; soft, nonsticky and nonplastic; common very fine to medium roots and few coarse roots; many very fine and fine irregular and tubular pores and common medium irregular and tubular pores; many faint continuous clay films on faces of peds; 30 percent gravel and 10 percent cobbles; NaF pH 9.1; moderately acid, pH 6.0 by Hellige-Truog; abrupt smooth boundary. (Combined thickness of the Bt horizon is 33 to 58 inches, (84 to 147 cm) thick).

Cr--55.5 inches, (141 cm); very weakly cemented metadiorite bedrock; roots are greater than 4 inches, (10 cm) apart, rock fractures are less than 4 inches, (10 cm) apart.

TYPE LOCATION: Butte County, California; about 1 mile southwest of Inskip, approximately 2250 feet south and 600 feet east of the northwest corner of Section 32, Township 25 N., Range 4 E., 39 degrees, 58 minutes, 52.9 seconds north latitude and 121 degrees, 33 minutes, 23.5 seconds west longitude, NAD83. U.S.G.S. Quad: Stirling, California.

RANGE IN CHARACTERISTICS: Depth to paralithic bedrock is 40 to 60 inches, (102 to 152 cm). The mean annual soil temperature is 52 to 54 degrees F, (11 to 12 degrees C). The soil moisture control section is dry in all parts from about July to about October (about 90 days). The particle-size control section averages 12 to 18 percent clay and 35 to 65 percent rock fragments, mostly gravel. Mineralogy is isotic. Rock fragments on the surface range from 15 to 35 percent gravel, 0 to 25 percent cobbles, 0 to 20 percent stones and 0 to 10 percent boulders. Some pedons have Bw and C horizons.

The A horizon dry color is 5YR 5/3, 7.5YR 5/4, 6/3, 6/4 or 7/3. Moist color is 5YR 3/3, 7.5YR 4/2, 4/3 or 4/4. Texture is very gravelly sandy loam or gravelly sandy loam. Clay content ranges from 8 to 16 percent. Rock fragments range from 15 to 40 percent gravel, 0 to 10 percent cobbles, and 0 to 5 percent stones. NaF pH ranges from 9.8 to 11.0. Reaction ranges from moderately acid to slightly acid.

The Bt horizon dry color is 5YR 4/6, 5/6, 6/6, 7.5YR 6/3, 6/4, 7/4, 7/6, 10YR 5/6, 6/4, 6/6, 7/4, 7/6, 7/8 or 8/6. Moist color is 5YR 3/4, 4/4, 4/6, 7.5YR 3/4, 4/2, 4/3, 4/4, 4/6, 5/4, 5/6, 6/6, 6/8 10YR 4/4, 4/6, 5/4, 5/6, 5/8 or 7/8. Texture is sandy loam, gravelly sandy loam, very gravelly sandy loam, very cobbly sandy loam, very gravelly loam, very cobbly loam, gravelly sandy clay loam or very gravelly sandy clay loam. Clay content ranges from 10 to 24 percent. Rock fragments range from 10 to 45 percent gravel, 0 to 20 percent cobbles and 0 to 10 percent stones. NaF pH ranges from 9.0 to 11.0. Reaction ranges from very strongly acid to slightly acid.

COMPETING SERIES: There are no other series in this family.

GEOGRAPHIC SETTING: Obskel soils are on ridge tops and side slopes on metamorphic Sierra Nevada mountains. Slopes range from 15 to 70 percent. These soils formed in weathered tephra over residuum and colluvium weathered from coarse grained metamorphic rocks, mainly metadiorite. Elevation is 3400 to 5200 feet, (853 to 1682 m). The mean annual precipitation is 66 to 78 inches, (1626 to 1981 mm). The mean annual temperature is 50 to 54 degrees F, (10 to 12 degrees C). Frost free season is 100 to 175 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Powellton and Obstruction soils. Powellton soils are on ridge tops and side slopes, are very deep and average 27 to 35 percent clay in the particle-size control section. Obstruction soils are on ridge tops and side slopes and are very deep.

DRAINAGE AND PERMEABILITY: Well drained; high runoff; moderately rapid saturated hydraulic conductivity in the A horizon and moderate to moderately rapid in the Bt horizon.

USE AND VEGETATION: This soil is used for timber production, wildlife habitat, and watershed. Vegetation is ponderosa pine, Douglas-fir, white fir, sugar pine, incense cedar, tanoak, California black oak, broadleaf starflower, Pacific dogwood, brackenfern, California hazel and Sierra chinquapin.

DISTRIBUTION AND EXTENT: Butte County, California. MLRA 22A Sierra Nevada Range. The soils are not extensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California

SERIES ESTABLISHED: Butte County, California 2005. Source of name is coined.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - zone from 0.5 to 4 inches, (1.27 to 10 cm) (A).
Argillic horizon - zone from 9 to 56 inches, (23 to 142 cm) (Bt2, Bt3, Bt4).
Paralithic contact at 56 inches, (142 cm).
Particle-size control section - zone from 9 to 28 inches, (23 to 71 cm).
Soil moisture control section - zone from 12 to 36 inches, (31 to 91 cm).
Bulk density is assumed to be 1 g/cc or less in the upper 9 inches, (23 cm).
Acid Oxalate extractable Al + 1/2 Fe is assumed to be greater than 1.0 in the upper 9 inches, (23 cm).

ADDITIONAL DATA: Lab data from nearby profile S95CA-007-019, (correlated as Obstruction) NSSL, Lincoln, NE 11/97.


National Cooperative Soil Survey
U.S.A.