LOCATION CASTAIC CAEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, thermic Calcic Haploxerepts
TYPICAL PEDON: Castaic silty clay loam - range. (Colors are for dry soil unless otherwise noted).
A1--0 to 10 inches; brown (10YR 5/3) silty clay loam, dark brown (10YR 4/3) moist; strong fine granular structure; hard, friable, sticky, plastic; many very fine roots; many very fine interstitial pores; slightly acid (pH 6.5); clear smooth boundary. (10 to 14 inches thick)
B2--10 to 28 inches; yellowish brown (10YR 5/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; weak fine granular structure; hard, friable, sticky, plastic; common very fine roots; many very fine tubular pores; neutral (pH 7.2); clear smooth boundary. (10 to 18 inches thick)
C1ca--28 to 36 inches; light yellowish brown (10YR 6/4) shaly clay loam, dark yellowish brown (10YR 4/4) moist; massive; hard, friable, sticky, plastic; few very fine roots; many very fine interstitial pores; about 20 percent shale fragments; strongly effervescent, lime mostly disseminated; slightly alkaline (pH 7.8); gradual broken boundary. (6 to 20 inches thick)
C2--36 to 40 inches; shale banded with mudstone. Lime occurs in seams.
TYPE LOCATION: Los Angeles County, California; 2,300 feet west and 1,300 feet north of the southeast corner sec. 1, T. 1 S., R. 18 W., SBBM.
RANGE IN CHARACTERISTICS: Depth to a paralithic contact of shale is 22 to 40 inches. Depth to lime is more than 20 inches. The mean annual soil temperature is about 63 degrees F, and the soil temperature usually is not below 47 degrees at any time. The climate is dry subhumid mesothermal. The soil between depths of 5 and 15 inches is usually dry all of the time from April until December and is moist in some or all parts all the rest of the year.
The Castaic series have brown, slightly acid, silty clay loam A horizons, yellowish brown, neutral, silty clay loam B horizons, light yellowish brown, calcareous shaly clay loam C horizons over shale at a depth of 36 inches.
Rock fragments consist of small pieces of shale. Fragments make up to 15 percent of the A horizon and up to 35 percent of the lowermost 4 to 8 inches of the C horizon just above the paralithic contact. The soil profile is silt loam or silty clay loam throughout.
The A horizon is grayish brown to light yellowish brown (10YR 5/2, 5/3, 6/3, 6/4; 2.5Y 5/2, 6/2). It has weak or moderate granular or subangular blocky structure or it is massive in some part in some pedons. This horizon averages less than 1 percent organic matter and it is slightly acid or neutral.
The B2 horizon is grayish brown to yellowish brown (10YR 6/3, 5/3, 5/4; 2.5Y 5/2, 5/4, 6/4). Chroma is the same as in the A horizon or it is one unit brighter. It has weak to strong subangular blocky structure. It is usually neutral or mildly alkaline. In some pedons the lower part of the B2 horizon or the transition to the lower horizon is moderately alkaline, and is effervescent with disseminated and segregated lime.
The C horizon is light brownish gray to light olive brown (10YR 6/2, 6/3, 6/4, 5/4; 2.5Y 6/2, 6/4, 5/4). Lime is mostly disseminated, but segregation's are few to common and fine white powder is present in some pedons.
COMPETING SERIES: These are the Balcom, Fontana, Kettleman, Nacimiento, San Benito, Vernalis, and Zacharias series. Balcom soils are effervescent throughout and have more than 15 percent fine sand or coarser. Fontana, Nacimiento, and San Benito soils have mollic epipedons. Kettleman soils have an aridic moisture regime. Vernalis and Zacharias soils lack a paralithic contact within 40 inches of the surface.
GEOGRAPHIC SETTING: The Castaic soils are strongly sloping to very steep and are on rounded hills at elevations of 50 to 2,500 feet. They formed in residuum weathered from shale, sandstone, and mudstone. The climate is dry subhumid mesothermal with warm dry summers and cool moist winters. Mean annual precipitation is 12 to 20 inches. Average January temperature is 51 degrees F; average July temperature is 72 degrees F; mean annual temperature is 61 degrees F. The frost-free season is 280 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Balcom, Fontana, and Nacimento soils and the Gaviota and Saugus soils. Gaviota soils have a lithic contact within 20 inches of the surface. Saugus soils are sandy loam with less than 18 percent clay.
DRAINAGE AND PERMEABILITY: Well-drained; medium to very rapid runoff; moderately slow permeability.
USE AND VEGETATION: Used mostly for range. A few areas are used for growing grain and citrus fruits. Vegetation in uncultivated areas is mostly annual grasses and forbs, with scattered brush and a few live oak trees.
DISTRIBUTION AND EXTENT: Western half of south-central California. The soils are moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Los Angeles County, California, 1973.
REMARKS: The Castaic soils were formerly classified as Regosols. There are clear differentia to separate the Balcom series, but management and mapping considerations suggest little benefit is derived.
The classification was updated in February 2001 using the Eighth Edition to Soil Taxonomy. This series was formerly classified as Fine-silty, mixed, thermic Calcixerollic Xerochrepts. Competing series were not checked at that time.
Last major revision by the state on 10/73.