LOCATION STEINBECK CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Ultic Haplustalfs
TYPICAL PEDON: Steinbeck loam, on a SW facing convex slope of 5 percent under sub-clover, ryegrass, wild barley, Italian thistle, velvet grass and soft chess at 320 feet elevation. (Colors are for dry soil unless otherwise stated. When described (1/20/76) the soil was moist throughout.)
A11--0 to 12 inches; dark grayish brown (10YR 4/2) loam, black (10YR 2/1) moist; weak fine subangular blocky structure parting to moderate medium granular; hard, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine interstitial and vesicular pores; moderately acid (pH 6.0); gradual wavy boundary. (10 to 15 inches thick)
A12--12 to 23 inches; grayish brown (10YR 5/2) loam, very dark gray (10YR 3/1) moist; weak fine subangular blocky structure parting to weak medium granular; hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; many very fine interstitial and vesicular, common fine tubular pores; slightly acid (pH 6.3); clear wavy boundary. (10 to 15 inches thick)
A2--23 to 35 inches; variegated very pale brown and pale brown (10YR 7/4, 10YR 6/3) loam, dark grayish brown (10YR 4/2) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; few very fine and fine roots; many very fine interstitial and common very fine tubular pores; slightly acid (pH 6.3); abrupt wavy boundary. (10 to 15 inches thick)
B21t--35 to 42 inches; variegated grayish brown and light yellowish brown (10YR 5/2, 10YR 6/4) light clay loam, yellowish brown (10YR 5/4) moist; common medium prominent yellowish red and dark grayish brown (5YR 5/8, 10YR 4/2) mottles; massive; slightly hard, firm, sticky and plastic; few very fine roots; common very fine interstitial and few very fine tubular pores; few thin clay films on peds and in pores; slightly acid (pH 6.3); gradual wavy boundary. (5 to 10 inches thick)
B22t--42 to 48 inches; variegated light yellowish brown and brownish yellow (10YR 6/4, 10YR 6/8) light clay loam, yellowish brown (10YR 5/6, 10YR 5/4) moist; common medium prominent dark yellowish brown (10YR 3/6) and brownish yellow (10YR 6/8) mottles; massive; hard, firm, sticky and plastic; few very fine roots; common very fine interstitial pores; few thin dark yellowish brown (10YR 3/6) clay films on peds and in pores; slightly acid (pH 6.5); gradual irregular boundary. (5 to 10 inches thick)
Cr--48 to 64 inches; strongly weathered soft sandstone; moderately acid (pH 6.0).
TYPE LOCATION: Marin County, California; 0.9 miles north of intersection of Highway 1 and Tomales-Dillon Beach Road and 0.5 miles east of Highway 1; 122 degrees 54' 40'' W latitude and 38 degrees 15' 28'' N longitude.
RANGE IN CHARACTERISTICS: Depth to a paralithic contact of sandstone is 40 to 60 inches. The mean annual soil temperature is 54 degrees F. to 59 degrees F. The soil is moist in some or all parts between the depths of 7 to 20 inches from October to August. It is dry in all parts for less than 45 consecutive days in August and September. Moisture in the summer is due, in part, from heavy fog and low evapotranspiration rates.
The A1 horizon has dry color of 10YR 6/3, 7/2, 7/3 or 7/4 and moist color of 10YR 4/2, 4/3, 5/2 or 5/3. It is loam or fine sandy loam. Reaction is medium acid or slightly acid. Base saturation is less than 50 percent.
The A2 horizon has dry color of 10YR 6/3, 7/2, 7/3 or 7/4 and moist color of 10YR 4/2, 4/3, 5/2 or 5.3. It is loam or fine sandy loam. Reaction is medium acid or slightly acid. Base saturation is less than 50 percent.
The B2t horizon has dry color of 10YR 5/2, 6/3, 6/4, 6/6 or 6/8 and moist color of 10YR 4/4, 5/4, 6/4 or 6/8. There are common distinct and prominent 5YR 5/8; 7.5YR 5/8; 10YR 4/2, 3/6, 5/6 or 6/8 moist mottles. This horizon is clay loam or heavy loam and averages 25 to 35 percent clay. Reaction is medium acid to neutral. Base saturation is 35 to 50 percent.
COMPETING SERIES: These are the Inverness and Tomales series in other families. Inverness soils have less than 9 degrees F. difference between mean summer and mean winter soil temperatures. Tomales soils are fine textured in the particle-size control section.
GEOGRAPHIC SETTING: The Steinbeck soils occur on dissected marine terraces of soft weathered sandstone. Elevations are from sea level to 1,500 feet. Slopes are 2 to 50 percent. The climate is subhumid mesothermal with cool, foggy summers and cool, moist winters. Mean annual precipitation is 25 to 35 inches. Mean January temperature is about 49 degrees F.; mean annual July temperature is about 61 degrees F.; and mean annual temperature is about 52 degrees to 57 degrees F. Frost-free season is about 270 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Sobega soils and the competing Tomales soils. Sobega soils lack an argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderate permeability.
USE AND VEGETATION: Used mainly for rangeland. Native vegetation is annual grasses, forbs, shrub and scattered live oak.
DISTRIBUTION AND EXTENT: Coastal areas of central and northern California. The soils are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Marin County, California, 1979.
REMARKS: The activity class was added to the classification in February of 2003. Competing series were not checked at that time. - ET