LOCATION LOBITOS CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Typic Argixerolls
TYPICAL PEDON: Lobitos loam, annual range. (Colors are for dry soil unless otherwise noted.)
01--0.5 to 0 inches; loose, dark colored, fresh and rotting twigs, leaves, and grass; abrupt smooth boundary.
A11--0 to 9 inches; dark grayish brown (10YR 4/2) loam, very dark brown (10YR 2/2) moist; weak medium and fine subangular blocky structure; hard, friable, nonsticky and slightly plastic; many very fine roots; many very fine pores; few wormcasts; moderately acid (pH 5.9); clear wavy boundary. (7 to 10 inches thick)
A12--9 to 18 inches; dark grayish brown (10YR 4/2) heavy loam, very dark grayish brown (10YR 3/2) moist; weak medium and fine subangular blocky structure; hard, friable, nonsticky and slightly plastic; many very fine roots; many very fine pores; few fragments of rock; moderately acid (pH 5.9); clear wavy boundary. (7 to 10 inches thick)
B2t--18 to 29 inches; light olive brown (2.5Y 5/4) shaly clay loam, olive brown (2.5Y 4/4) moist; hard, firm, slightly sticky and plastic; common very fine roots; common very fine pores; common thin discontinuous olive clay films; many weathered angular rock fragments; moderately acid (pH 5.8); clear wavy boundary. (10 to 18 inches thick)
C--29 to 34 inches; light olive brown (2.5Y 5/4) heavy shaly loam, olive brown (2.5Y 4/4) moist; massive; hard, friable, nonsticky and slightly plastic; few very fine roots; many angular weathered fragments of rock; moderately acid (pH 5.8); clear wavy boundary. (4 to 12 inches thick)
R--34 to 38 inches; moderately hard fractured shale and sandstone.
TYPE LOCATION: San Mateo County, California, one mile northeast of Lobitos on Irish Ridge road and 20 feet north into field.
RANGE IN CHARACTERISTICS: Depth to a lithic contact is 24 to 40 inches. The mean annual soil temperature is about 56 degrees to 59 degrees F. The soil between depths of 4 to 12 inches is usually dry all of the time from June until late October or early November and is moist in some or all parts all the rest of the year. Rock fragments of angular pieces of shale and sandstone include up to 30 percent by volume, with horizons below the A containing the greater amounts.
The A horizon is grayish brown, dark grayish brown, dark gray and very dark grayish brown (10YR 5/2, 4/2, 4/1, and 3/2). It is fine sandy loam, loam, silt loam or light clay loam. Angular rock fragments of gravel size range up to 15 percent by volume. Structure is weak or medium granular or subangular blocky. Reaction is slightly or moderately acid.
The Bt horizon is light olive brown, brown or pale brown (2.5Y 5/4, 10YR 5/3, 6/3). It is clay loam or silty clay loam modified by 10 to 35 percent gravel size angular shale fragments.
COMPETING SERIES: These are the Colma, Dragoon, Glenrose, Ladd, Los Gatos, Los Osos, Melhorn, McCoy and Miramar series. Dragoon, Glenrose, Ladd and Melhorn soils have a mean annual soil temperature of less than 56 degrees F. with a difference between mean summer and winter temperatures of more than 15 degrees F. Colma, Los Osos, McCoy and Miramar have paralithic contacts. Colma soils have less than 30 percent clay in their argillic horizons. Los Gatos soils have hue of 7.5YR or 5YR hue in the argillic horizon. Los Osos soils have more than 35 percent clay in their argillic horizon and are thermic. McCoy and Miramar soils are pachic and McCoy soils are thermic.
GEOGRAPHIC SETTING: Lobitos soils are on moderately sloping to very steep uplands at elevations of 200 to 1,000 feet. They formed in residuum from shale and sandstone. The climate is subhumid to mesothermal and has warm dry summers and cool moist winters. Mean annual precipitation is 25 to 35 inches. Average January temperature is about 48 degrees F.; average July temperature is about 60 degrees F.; mean annual temperature is about 56 degrees F. The frost-free season is 270 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Gazos, Pomponio and Santa Lucia soils. Gazos and Santa Lucia soils have mollic epipedons thicker than 20 inches. Gazos soils lack argillic horizons. Santa Lucia soils also have over 35 percent coarse fragments by volume in their control section. Pomponio soils have over 35 percent clay in their argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; medium and rapid runoff; moderately slow permeability.
USE AND VEGETATION: Mostly used for pasture and range. Some areas have been cultivated to grow grain, hay, barley and flax. Vegetation is annual grasses and forbs with some brush including coyote brush, cascara berry, and poison oak.
DISTRIBUTION AND EXTENT: Coast Range of Central California. The soils are of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: San Mateo County, California, 1956.
REMARKS: These soils were formerly classified as Brunizems.
The activity class was added to the classification in February of 2003. Competing series were not checked at that time. - ET
ADDITIONAL DATA: For additional data refer to pedon S-55 Calif. 41-13 in SSI report No. 24, page 463.
OSED scanned by SSQA. Last revised by state on 6/75.