LOCATION CUESTA CATentative Series
TAXONOMIC CLASS: Clayey-skeletal, magnesic, thermic Typic Argixerolls
TYPICAL PEDON: Cuesta cobbly loam - on a north facing convex slope of 60 percent, under Sargent Cypress and manzanita at 2,250 feet elevation. (Colors are for dry soil unless otherwise stated).
A1--0 to 2 inches; dark grayish brown (10YR 4/2) cobbly loam, very dark brown (10YR 2/2) moist; strong medium granular structure, soft, friable, slightly sticky and slightly plastic; common very fine, fine, and medium roots; few, very fine and fine discontinuous irregular pores; 12 percent pebbles, 10 percent cobbles, 5 percent stones; neutral (pH 6.7); abrupt smooth boundary. (2 to 9 inches thick)
B21t--2 to 6 inches; dark brown (7.5YR 3/4) gravelly clay loam, dark reddish brown (5YR 3/2) moist; weak medium subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; common fine and medium roots; few very fine and fine continuous interstitial pores; common moderately thick clay films on peds and in pores; 12 percent pebbles; 5 percent cobbles; neutral (pH 6.7); clear smooth boundary. (3 to 8 inches thick)
B22t--6 to 11 inches; mixed yellowish brown (10YR 5/4) and reddish brown (5YR 4/3) gravelly clay, dark brown (10YR 3/3) and dark reddish brown (5YR 3/3) moist; moderate fine subangular blocky structure; slightly hard, firm, sticky and plastic; few very fine and fine, common medium roots; few fine continuous interstitial pores; common moderately thick clay films on peds and in pores; 20 percent pebbles; 5 percent cobbles; neutral (pH 6.7); clear smooth boundary. (5 to 13 inches thick)
B23t--11 to 24 inches; mixed dark yellowish brown (10YR 4/4) and yellowish brown (10YR 5/6) extremely stony clay loam, dark yellowish brown (10YR 3/4) moist; strong coarse subangular blocky structure; very hard, firm, sticky and plastic; few fine and common medium roots; few fine continuous tubular pores; many thick clay films on peds and in pores; 15 percent pebbles, 5 percent cobbles and 50 percent stones, neutral (pH 7.0); clear wavy boundary. (3 to 13 inches thick)
Cr--24 to 34 inches; soft weathered greenish serpentinitic rock. (0 to 20 inches thick)
R--34 to 37 inches; hard greenish serpentinitic rock.
TYPE LOCATION: San Luis Obispo County, California; about 2.5 miles west of Cuesta Pass on Cuest Ridge Road; about 50 feet north of the road on a north aspect with 60 percent slope in the NW 1/4, NW 1/4, sec. 35, T. 29 S., R. 12 E., MDB&M.
RANGE IN CHARACTERISTICS: Depth to a paralithic or a lithic contact is from 25 to 40 inches. The mean annual soil temperature is estimated to be between 59 degrees and 64 degrees F. The soil moisture control section is estimated to usually be dry in all parts from June to October and usually moist in some or all parts the rest of the year. Surface rock fragments range from 5 to 10 percent.
The A horizon has dry color of 10YR 4/2, 3/3; 7.5YR 4/4, 5/4; 5YR 4/3, 4/2 or 3/3; and moist color of 10YR 2/2; 7.5YR 3/3, 4/3; 5YR 3/3, 3/2; 2.5/2 or 2.5Y 3/2. It is a cobbly, gravelly loam or very gravelly loam. It has weak to strong granular or subangular blocky structure. Rock fragments range from 5 to 35 percent gravel, 5 to 15 percent cobbles, and 0 to 5 percent stones. It is neutral to moderately alkaline. Base saturation is estimated about 85 to 95 percent.
The B2t horizon has dry color of 10YR 4/4, 5/4, 5/6; 7.5YR 5/4, 4/4, 3/4; 5YR 4/4, 4/3, 3/4, 3/3, 3/2 or 2.5/2; and moist color of 10YR 3/4, 3/3, 3/2; 7.5YR 4/4, 3/4; 5YR 3/4, 3/3, 3/2; 2.5Y 4/4 or 4/2. It is gravelly clay, very gravelly clay, gravelly clay loam, very gravelly clay loam, very stoney or extremely stony clay or clay loam. It has weak to strong subangular blocky structure. Rock fragments average more than 35 percent and range from 10 to 55 percent gravel, 5 to 35 percent cobbles, and 5 to 60 percent stones. It is neutral to moderately alkaline. Clay films may occur in cracks between the rock fragments and adhere to cobbles. Base saturation is estimated about 75 to 95 percent.
A B3, C or Cr horizon may occur between the B2t horizon and hard bedrock.
COMPETING SERIES: These are the Dellpiedra, Dubakella, Henneke, Huse, Montara, Obispo and Stony ford series in other families. Delpiedra, Dubakella and Huse soils lack a mollic epipedon and Huse soils also lack an argillic horizon. Henneke, Montara, Obispo and Stonyford soils have a lithic contact within 20 inches of the soil surface. Montara soils also lack an argillic horizon.
GEOGRAPHIC SETTING: Cuesta soils are on mountainsides and ridge tops. Elevations are 600 to 3,000 feet. Slopes are 15 to 70 percent. The soils formed in material weathered from serpentinitic rocks. The climate is dry, subhumid mesothermal with warm, dry summers and cool, wet winters. The mean annual precipitation is 20 to 30 inches. The average January temperature is 54 degrees F; the average July temperature is about 68 degrees F; the average annual temperature is 58 to 65 degrees F. The frost-free season is 270 to 345 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Henneke and Montara series and the Diablo, Lodo, and Los Osos series. Diablo soils are Vertisols with montmorillonitic mineralogy. Lodo soils have mixed mineralogy and a lithic contact within 20 inches. Los Osos soils have montmorillonitic mineralogy.
DRAINAGE AND PERMEABILITY: Well-drained; moderate to rapid runoff; slow permeability.
USE AND VEGETATION: Used for watershed, grazing, wildlife and recreation. Dominant vegetation is Sargent cypress, manzanita, and other mixed hard chaparral species, Digger pine and annual grasses.
DISTRIBUTION AND EXTENT: Coast and Transverse Range of California. The soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: San Luis Obispo, California, 1981.
REMARKS:
Last revised by the state on 5/81.