LOCATION TONGVA CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, thermic Pachic Argixerolls
TYPICAL PEDON: Tongva loam, on the side of a hill at an elevation of 700 feet (213 meters). (Colors are for dry soil unless otherwise noted).
Oe--0 to 2 inches (0 to 5 centimeters); oak leaves and dead grass. (0 to 4 inches thick, 0 to 10 centimeters)
A--2 to 4 inches (5 to 10 centimeters); very dark gray (10YR 3/1) loam, black (10YR 2/1) moist; weak very fine subangular blocky structure; soft, very friable, slightly sticky and nonplastic; few very fine roots; few interstitial pores; 5 percent gravel; neutral (pH 6.6); clear smooth boundary. (1 to 6 inches thick, 2 to 15 centimeters)
Bt1--4 to 15 inches (10 to 36 centimeters); dark grayish brown (10YR 4/2) loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine through very coarse roots; common very fine through medium tubular pores; common very thin clay films on ped faces and lining pores; 5 percent gravel; neutral (pH 6.7); clear wavy boundary.
Bt2--15 to 30 inches (36 to 75 centimeters); brown (10YR 4/3) loam, dark brown (10YR 3/3) moist; weak fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine through very coarse roots; common very fine through medium tubular pores; common very thin clay films on ped faces and lining pores; 5 percent gravel; neutral (pH 6.8); abrupt smooth boundary. (Combined thickness of the Bt horizons is 19 to 34 inches thick, 48 to 86 centimeters)
Crt--30 to 52 inches (75 to 130 centimeters); highly fractured and weathered andesite that is easily diggable with a spade and augerable. Breaks out as very fine very weak angular blocky pieces. Few very coarse roots. Many very thin clay films on soft rock pieces.
TYPE LOCATION: Los Angeles, California; about one mile south of the junction of Mulholland Highway and Las Virgenes Road; 600 feet north and 900 feet west of the southeast corner of section 12, T. 1 S., R. 18 W.; Latitude 34 degrees, 5 minutes, 30 seconds north and Longitude 118 degrees, 44 minutes, 43 seconds west; Malibu Beach Quadrangle.
RANGE IN CHARACTERISTICS: Mean annual soil temperature: 62 to 66 degrees F.
Soil moisture: Soil is moist in middle to late November to late June or early July.
Depth to paralithic bedrock: 20 to 40 inches (50 to 100 centimeters).
Organic matter content: 2 to 4 percent.
A horizon--10YR 5/2, 5/3, 4/2, 4/3, 3/2, 3/1 and 7.5YR 4/4; 10YR 3/3, 3/2, 2/2, 2/1 and 7.5YR 3/2 moist.
Clay percentage--12 to 27 percent.
Coarse fragments--5 to 15 percent. Some pedons have 15 to 30 percent coarse fragments in the lower part of the horizon.
Bt horizon--10YR 5/2, 5/3, 4/2, 4/3 and 7.5YR 5/2; 10YR 3/3, 3/2, 2/2, and 7.5YR 3/2 and 3/3 moist.
Texture--Clay loam, loam, gravelly loam or gravelly clay loam.
Clay percentage--18 to 35 percent.
Coarse fragments--5 to 30 percent, dominantly gravel.
COMPETING SERIES: These are the Arujo, Botella, Chico, Corona, Elkhorn, Havala, Lockwood, McCoy, Saltcanyon and Sapwi soils. Arujo soils are 40 to 60 inches deep to granitic paralithic material, and have a mean summer temperature that differs by greater than 25 degrees F. from the mean winter temperature. Botella, Chico, Corona, Elkhorn, Havala, Lockwood, and Saltcanyon soils are all greater than 60 inches to rock. McCoy soils are 25 to 40 inches to granitic paralithic material and have Bt horizons that are slightly to moderately alkaline. Sapwi soils have very gravelly, very cobbly or very stony textures in the lower part of the argillic horizon, and they lack paralithic horizons.
GEOGRAPHIC SETTING: Tongva soils are on northerly and easterly facing, concave, side slopes of hills and mountains. These soils formed in alluvium and colluvium derived from weathered andesite and basalt. Slopes are 5 to 75 percent. Elevations are 500 to 3100 feet (152 to 945 meters). The climate is characterized by warm, dry summers and cool, moist winters. The mean annual precipitation is 13 to 24 inches (457 to 610 millimeters), the mean annual temperature is 60 to 73 degrees F. (16 to 23 degrees C.), and the frost free season is to 290 to 365 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cotharin and Talepop soils. Both these soils are shallow to weathered rock on side slopes of hills and mountains.
DRAINAGE AND PERMEABILITY: Well drained; low to very high runoff; moderate to moderately slow permeability.
USE AND VEGETATION: Wildlife habitat, recreation and building site development. Vegetation is Coast Live oak, poison oak, and miscellaneous forbs and grasses. Where these soils occur on Santa Cruz Island the Coast Live oak has been replaced by a Coastal Sage-Buckwheat plant community.
DISTRIBUTION AND EXTENT: Ventura, Santa Barbara and Los Angeles Counties, California. The soil is not extensive. MLRA 20.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Los Angeles County, California, 2000.
REMARKS: Diagnostic horizons and features recognized in this pedon:
Mollic epipedon--The zone from the soil surface to a depth of about 30 inches.
Argillic horizon--The zone from a depth of 4 inches to a depth of about 30 inches.
Paralithic material--The zone from a depth of 30 inches to about 52 inches.