LOCATION SEBASTOPOL CATentative Series
TAXONOMIC CLASS: Fine, mixed, semiactive, mesic Typic Haploxerults
TYPICAL PEDON: Sebastopol sandy loam - on an east facing slope of 10 percent under apple trees at 210 feet elevation. (Colors are for dry soil unless otherwise stated).
Ap1--0 to 4 inches; pale brown (10YR 6/3) sandy loam, brown (10YR 4/3) moist; massive; soft, friable, nonsticky and nonplastic; many fine interstitial pores; very strongly acid (pH 5.0); abrupt wavy boundary. (4 to 6 inches thick)
Ap2--4 to 8 inches; very pale brown (10YR 7/4) sandy loam, brown (10YR 5/3) moist; massive; slightly hard, firm, nonsticky and nonplastic; many very fine and fine roots; many very fine tubular pores; moderately acid (pH 5.7); abrupt wavy boundary. (3 to 6 inches thick)
B1--8 to 12 inches; pale brown (10YR 6/3) light sandy clay loam, variegated yellowish red (5YR 5/8) and yellowish brown (10YR 5/4) moist; massive; hard, friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine tubular pores; very strongly acid (pH 4.5); clear wavy boundary. (3 to 6 inches thick)
Bt1--12 to 18 inches; light red (2.5YR 6/6) heavy clay loam, yellowish red (5YR 5/8) moist; massive; hard, firm, slightly sticky and slightly plastic; many very fine and fine roots; many very fine tubular pores; common thin clay films in pores; extremely acid (pH 4.3); abrupt wavy boundary. (5 to 10 inches thick)
Bt2--18 to 43 inches; light red (2.5YR 6/6) clay, red (2.5YR 5/8) moist; massive; hard, firm, sticky and plastic; few very fine, medium, and coarse roots; many very fine tubular pores; many moderately thick clay films as bridges and in pores; extremely acid (pH 4.3); gradual smooth boundary. (20 to 30 inches thick)
Bt3--43 to 54 inches, light reddish brown (2.5YR 6/4) heavy clay loam, yellowish red (5YR 5/8) moist; massive; hard, firm, slightly sticky and plastic; few medium and coarse roots; many very fine tubular pores; many moderately thick clay films as bridges and in pores; extremely acid (pH 4.3); clear smooth boundary. (6 to 10 inches thick)
Bt4--54 to 62 inches; reddish yellow (5YR 7/6) heavy clay loam, yellowish red (5YR 5/8) moist; massive; hard, firm, slightly sticky and plastic; few very fine and coarse roots; few very fine tubular pores and many very fine interstitial pores; many moderately thick and thick clay films as bridges and in pores; extremely acid (pH 4.3); gradual smooth boundary. (6 to 12 inches thick)
C1--62 to 72 inches; mottled light red (2.5YR 6/6) and light gray (10YR 7/2) sandy clay loam, reddish yellow (5YR 6/8) moist; massive, hard, firm, slightly sticky and slightly plastic; a few coarse roots; common very fine tubular and interstitial pores; common moderately thick and thick clay films in pores and as bridges; extremely acid (pH 4.3).
TYPE LOCATION: Sonoma County, California, in the northeast corner of the SW 1/4, SW 1/4, section 22, T.7 N., R.9 W.
RANGE IN CHARACTERISTICS: The solum is 38 to 55 inches thick and depth to semiconsolidated sediments is greater than 60 inches. Between the depths of 6 to 18 inches the soil is dry, in all parts, from December through April in most years. The mean annual soil temperature is 56 to 58 degrees F. There is 0 to 15 percent rounded gravel throughout the profile. Base saturation ranges from 15 to 35 percent throughout.
The A horizon is 10YR 6/3, 6/4, 7/3, 7/4, 7.5YR 6/4 or 7/4. Moist colors are 10YR 4/3, 4/4, 5/3, 5/4, or 7.5YR 4/4 or 5/4. It is sandy loam with 15 to 20 percent clay. It is moderately to very strongly acid.
The Bt horizon is 2.5YR 6/4, 6/6, 6/8, 5YR 6/6, 6/8 or 7/6. Moist colors are 2.5YR 4/6, 4/8, 5/6, 5/8, 5YR 4/6, 4/8, 5/6 or 5/8. It is clay loam or clay with 35 to 50 percent clay. It is very strongly or extremely acid.
The C horizon is variegated 2.5YR 6/4, 6/6, 5YR 5/6, or 10YR 7/2. Moist colors are variegated 5YR 5/8 or 6/8. It is sandy clay loam or clay loam with 25 to 40 percent clay.
COMPETING SERIES: These are the Kilarc and Gube series in the same family and the Cotati, Diamond Springs, Goldridge, and Sites series. Gube soils are less than 40 inches deep. Kilarc soils have hues of 7.5YR or yellower in the argillic horizon. Cotati soils have thermic soil temperatures and base saturation greater than 35 percent. Diamond Springs and Goldridge soils are fine-loamy. Sites soils have kaolinitic mineralogy.
GEOGRAPHIC SETTING: The Sebastopol soils are on old coastal terraces and have slopes of 2 to 30 percent. They formed in old alluvium weathered form soft sandstone at elevations of 100 to 1,000 feet. The climate is subhumid mesothermal with warm dry summers and cool moist winters. Mean annual precipitation ranges from 30 to 50 inches. Mean annual temperature is 55 degrees F, mean January temperature is 45 degrees F, and mean July temperature is 65 degrees F. Frost-free season ranges from 230 to 260 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Cotati and Goldridge soils and the Blucher soils. Blucher soils are fine-loamy and thermic.
DRAINAGE AND PERMEABILITY: Well drained; moderate to rapid runoff; slow permeability.
USE AND VEGETATION: Used for apple orchards, vineyards and some pasture. Native vegetation is open stands of live oak, madrone and conifers with grass in the openings.
DISTRIBUTION AND EXTENT: Northern coastal California. The soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES PROPOSED: Sonoma County, California, 1941.
REMARKS: The activity class was added to the classification in February of 2003. Competing series were not checked at that time. - ET
Diagnostic horizons and features are as follows:
1. Ochric epipedon - 0 to 8 inches (Ap1, Ap2); ranges from 7 to 12 inches thick. Clay content by field estimates is 20 percent.
2. Argillilc horizon - 12 to 62 inches (Bt1, Bt2, Bt3, Bt4); ranges from 37 to 62 inches thick. B.S. is assumed to be less than 35 percent. The textural control section is 12 to 32 inches or the top 20 inches of the argillic horizon. Clay content by field estimates of the textural control section is 35 to 50 percent.
3. The soil temperature is 56 F to 58 degrees F - assumed from similar soils.
4. Soil moisture regime--the moisture control section (6 to 18 inches) is dry in all parts from June 15th through October 15th. It is moist in all parts from December 15th through April and assumed to be moist in some part more than 90 consecutive days when the soil temperature is greater than 46 degrees F.
The soil temperature is always above 41 degrees F.
Month: J F M A M J J A S O N D
Moisture M M M M MD MD D D D MD MD M
M = Moist all parts
MD = Moist some parts
D = Dry all parts