LOCATION TOCALOMA CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Typic Haploxerolls
TYPICAL PEDON: Tocaloma loam, on a north facing convex slope of 48 percent under California-laurel, fern, oak poison-oak, and scattered annual grasses at 600 feet elevation. (Colors are for dry soil unless otherwise stated. When described (9/7/76) the soil was dry throughout.)
A11--0 to 4 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; strong fine subangular blocky structure; hard, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine interstitial and common very fine tubular pores; slightly acid (pH 6.5); clear smooth boundary. (0 to 4 inches thick)
A12--4 to 9 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure; hard, very friable, slightly sticky and slightly plastic; many very fine and fine roots; many very fine and fine interstitial and common very fine tubular pores; slightly acid (pH 6.3); clear smooth boundary. (3 to 5 inches thick)
A13--9 to 15 inches; brown (10YR 5/3) loam, dark brown (7.5YR 3/2) moist; moderate fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine and fine roots, few medium roots; many very fine and fine interstitial pores, and few very fine vesicular and tubular pores; moderately acid (pH 6.0); clear smooth boundary. (3 to 6 inches thick)
A14--15 to 19 inches; brown (10YR 5/3) loam, dark brown (7.5YR 3/2) moist; moderate fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots, and few medium and coarse roots; many very fine and fine interstitial pores, and common very fine vesicular and tubular pores; about 10 percent pebbles; moderately acid (pH 6.0); clear smooth boundary. (2 to 5 inches thick)
B2--19 to 39 inches; light yellowish brown (10YR 6/4) very gravelly loam, brown (7.5YR 4/4) moist; weak fine and medium subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; common very fine and fine interstitial pores, and few very fine tubular pores; 40 percent pebbles; moderately acid (pH 6.0); gradual irregular boundary. (12 to 20 inches thick)
Cr--39 to 45 inches; strongly weathered, highly fractured sandstone.
TYPE LOCATION: Marin County, California; Jacobsen property, about 3/4 mile northeast of the intersection of Marshall-Petaluma Road and Wilson Hill Road, 1.7 mile south-southwest of Laguna School, south of pond, Petaluma Quad.
RANGE IN CHARACTERISTICS: Depth to a paralithic contact is 20 to 40 inches. The mean annual soil temperature is 55 degrees to 59 degrees F. The soil is dry throughout from mid-June until sometime in October and is moist the rest of the time. The soil is medium or slightly acid and commonly becomes slightly more acid with increasing depth. Base saturation is 75 to 95 percent throughout the profile. Gravel averages less than 35 percent in the particle-size control section.
The A horizon has dry color of 10YR 5/2 or 5/3 and moist color of 10YR 3/2, 3/3; or 7.5YR 3/2. Gravel is less than 10 percent.
The B horizon has dry color of 10YR 4/2, 5/3, 6/3 or 6/4 and moist color of 10YR 3/2, 4/2; or 7.5YR 4/4. It has weak or moderate subangular blocky structure or it has a slight increase in clay over the A horizon. Gravel averages 35 to 50 percent.
COMPETING SERIES: These are the Crowshaw, Hoover (T), Laki, Lovline, and Yaxon series in the same family and the Saurin series. Crowshaw soils are deeper than 60 inches and have MAST of 48 degrees to 52 degrees F. Hoover soils, see remarks. Laki soils are deeper than 60 inches, formed in alluvium with a component of ash, and have MAST of 48 degrees to 51 degrees F. Lovline soils are 20 to 40 inches deep to a lithic contact and have MAST of 47 degrees to 51 degrees F. Saurin soils have a thermic soil temperature. Yaxon soils formed in material with a high component of loess and has, have MAST of 50 degrees to 55 degrees F., and are dry for only 70 to 90 consecutive days.
GEOGRAPHIC SETTING: Tocaloma soils are on hills. Slopes are 2 to 75 percent. The soils formed in material weathered from strongly weathered highly fractured sandstone and shale. Elevations are from 50 to 1,500 feet. The climate is subhumid mesothermal with warm dry summers and moist cool winters. Mean annual precipitation is 30 to 40 inches. Mean January temperature is about 47 degrees F.; mean July temperature is about 58 degrees F.; mean annual temperature is 55 degrees to 60 degrees F. Frost-free season is 290 to 330 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bonnydoon, Los Osos, McMullin, Olompali, and the competing Saurin soils. Bonnydoon and McMullin soils have a lithic or paralithic contact at a depth of 10 to 20 inches. Los Osos soils have a fine argillic horizon. Olompali soils have a fine particle-size control section and are more than 60 inches deep.
DRAINAGE AND PERMEABILITY: Well drained; slow to very rapid runoff; moderately rapid permeability.
USE AND VEGETATION: Used for watershed and wildlife habitat. Vegetation is California-laurel and oak trees, fern, blackberry bushes, and poison-oak.
DISTRIBUTION AND EXTENT: Central coast of California. The soil is moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Marin county, California, 1979.
REMARKS: Hoover (t-'64) series is not adequately defined. Depth to rock ranges from 30 to 60 inches.
The activity class was added to the classification in March of 2003. Competing series were not checked at that time. - ET