LOCATION TOPANGA CAEstablished Series
TAXONOMIC CLASS: Loamy, mixed, superactive, thermic, shallow Typic Argixerolls
TYPICAL PEDON: Topanga loam, on the side of a mountain at an elevation of 1210 feet. (Colors are for dry soil unless otherwise noted).
A1--0 to 2 inches (0 to 5 centimeters); grayish brown (10YR 5/2) gravelly loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine through medium roots; few fine interstitial pores; 25 percent fine and medium subangular gravel; 10 percent fine subangular pararock fragments; slightly acid (pH 6.5); clear wavy boundary.
A2--2 to 15 inches (5 to 38 centimeters); grayish brown (10YR 5/2) gravelly loam; very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; few very fine through medium roots; few fine interstitial pores; 20 percent fine and medium subangular gravel; 10 percent fine subangular pararock fragments; slightly acid (pH 6.5); clear wavy boundary. (Combined thickness of A horizons is 8 to 18 inches thick)
Bt--15 to 18 inches (38 to 45 centimeters); yellowish brown (10YR 5/4) gravelly clay loam, dark yellowish brown (10YR 3/4) moist; moderate fine subangular blocky structure; slightly hard, very friable, slightly sticky and plastic; common very fine through medium roots; few fine tubular pores; 20 percent fine and medium subangular gravel; 10 percent fine subangular pararock fragments; slightly acid (pH 6.5); abrupt wavy boundary. (2 to 7 inches thick)
Cr--18 to 30 inches (45 to 75 centimeters); highly fractured, bedded shale with fractures 1 to 3 inches apart, and with about 10 to 15 percent soil in fractures with few very fine roots.
TYPE LOCATION: Ventura County, California; about one mile north of the junction of Highway 1 and Highway 23; 750 feet south and 10 feet west of the northwest corner of section 29, T. 1 S., R. 21 W.; Latitude 34 degrees, 3 minutes, 26 seconds north and Longitude 118 degrees, 53 minutes, 38 seconds west; Triunfo Pass 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 May.
Depth to paralithic contact: 10 to 20 inches.
Reaction: Neutral to slightly acid.
Organic matter content: 2 to 4 percent.
A horizon--10YR 5/2, 5/3, 4/2, 4/3 and 10YR 3/2, 3/3 moist.
Clay percentage--12 to 27 percent.
Coarse fragments--15 to 30 percent.
Bt horizon--10YR 5/2, 5/3, 5/4 and 10YR 3/2, 3/3, 3/4, 4/3, 4/4 moist.
Texture--Loam, gravelly loam, gravelly clay loam or clay loam.
Clay percentage--18 to 35 percent.
Coarse fragments--10 to 30 percent.
COMPETING SERIES: This is the Talepop(T) soils. Talepop soils have Cr horizons comprised of meta-volcanic rock at depths of 4 to 14 inches.
GEOGRAPHIC SETTING: Topanga soils are on side slopes of hills and mountains. These soils formed in residuum and colluvium derived from bedded shale and sandstone. Slopes are 30 to 75 percent. Elevations are 400 to 2510 feet. The climate is characterized by warm, dry summers and cool, moist winters. The mean annual precipitation is 18 to 24 inches, the mean annual temperature is 60 to 64 degrees F., and the frost free season is 290 to 350 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Mipolomol (T) and Kayiwish (T) soils. Mipolomol soils are on the side slopes of hills and mountains and lack argillic horizons. Kayiwish soils are on the toe slopes of hills and have more than 35 percent clay in the solum.
DRAINAGE AND PERMEABILITY: Well drained; high runoff; moderate to moderately slow permeability.
USE AND VEGETATION: Wildlife habitat, recreation and building site development. Vegetation is Big pod Ceonothus, lupine, Mulberry, Coffeberry and chamise.
DISTRIBUTION AND EXTENT: Ventura County and Los Angeles County, California. The soil is not extensive. MLRA 20.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES PROPOSED: Los Angeles County, California, 1999.
REMARKS: The series name is from a local town. Diagnostic horizons and features recognized in this pedon:
Mollic epipedon--The zone from the soil surface to a depth of about 15 inches (A1 and A2 horizons).
Argillic horizon--The zone from a depth of 15 inches to a depth of about 18 inches (Bt horizon).
Paralithic material--The zone from a depth of 18 inches to about 30 inches (Cr horizon)