LOCATION RODEO CAEstablished Series
TAXONOMIC CLASS: Fine, smectitic, isomesic Aquic Paleustolls
TYPICAL PEDON: Rodeo clay loam, on a southwest facing concave slope of 5 percent under California oatgrass, foxtail fescue, soft chess, ripgut brome, dock, wiregrass, ryegrass, hemlock and willow at 100 feet elevation. (Colors are for dry soil unless otherwise stated. When described on 9/16/75 the soil was moist below 20 inches.
Ap--0 to 6 inches; very dark grayish brown (10YR 3/2) clay loam, very dark gray (10YR 3/1) moist; moderate fine and medium subangular blocky structure; hard, very friable, sticky and plastic; many very fine and fine roots; many very fine and fine interstitial and common very fine tubular pores; medium acid (pH 6.0); clear smooth boundary. (5 to 10 inches thick)
A12--6 to 14 inches; very dark grayish brown (10YR 3/2) clay loam, very dark grayish brown (10YR 3/2) moist; weak fine and medium subangular blocky structure; hard, very friable, sticky and plastic; many very fine and fine roots; many very fine interstitial and tubular pores; medium acid (pH 5.8); clear wavy boundary. (4 to 10 inches thick)
A2--14 to 20 inches; pale brown (10YR 6/3) clay loam, brown (10YR 5/3) moist; common medium fine brownish yellow (10YR 6/8), and common medium distinct yellowish brown and brownish yellow (10YR 5/8, 6/8) moist mottles; massive; hard, very friable, sticky and plastic; common very fine roots; many very fine subangular pores; medium acid (pH 5.8); abrupt smooth boundary. (5 to 12 inches thick)
B21t--20 to 29 inches; variegated pale brown, light yellowish brown, and brownish yellow (10YR 6/3, 6/4, 6/8) clay, yellowish brown (10YR 5/4) moist; many medium and large prominent yellowish red (5YR 4/8) moist mottles; moderate fine subangular blocky structure; hard, firm, sticky and plastic; few very fine roots; common very fine tubular pores; many moderately thick clay films in pores and on peds; many pressure faces; many pressure faces; few fine concretions; medium acid (pH 5.8); clear wavy boundary. (7 to 11 inches thick)
B22t--29 to 40 inches; variegated pale brown and brownish yellow (10YR 6/3, 6/8) clay, strong brown and yellowish red (7.5YR 5/8; 5YR 5/8) moist; many medium prominent gray and light gray (5Y 5/1, 6/1) moist mottles; weak fine subangular blocky structure; hard, firm, sticky and plastic; few very fine roots; few very fine interstitial pores; many moderately thick clay films in pores and peds; many pressure faces; common fine concretions; very strongly acid (pH 5.0); gradual wavy boundary. (9 to 13 inches thick)
B23t--40 to 58 inches; variegated light gray, brownish yellow and yellowish brown (10YR 7/2, 6/6, 6/8) clay, yellowish brown and pale brown (10YR 5/6, 6/3) moist; weak medium subangular blocky structure; hard, firm, sticky and plastic; few very fine pores; many moderately thick clay films in pores and on peds; common fine concretions, common pressure faces; very strongly acid (pH 4.8) clear wavy boundary. (10 to 18 inches thick)
B24t--58 to 75 inches; variegated light gray and brownish yellow (10YR 7/2, 6/8) clay, pale brown and brown (10YR 6/3; 7.5YR 4/4) moist; massive; hard, very firm, sticky and plastic; few very fine roots; common thin clay films in pores and on peds; common fine concretions; very strongly acid (pH 4.8).
TYPE LOCATION: Marin County, California; about 1,400 feet north on light duty road from old dairy barn and 200 feet west of light duty road at Fort Barry, Golden Gate National Recreational Area.
RANGE IN CHARACTERISTICS: The solum is 60 to 90 inches thick. Mean annual soil temperature ranges from 54 degrees to 59 degrees F. Difference between mean winter and mean summer temperature is 5 degrees to 8 degrees F. The soil moisture control section is usually moist in all parts for 45 consecutive days. The particle-size control section commonly becomes more acid as depth increases.
The A horizon has dry color of 10YR 3/1, 3/2, 4/1 or 4/2 and moist color of 10YR 2/1, 2/2, 3/1, 3/2. This horizon has moderate or strong subangular blocky or granular structure.
The A2 horizon has dry color of 10YR 6/3, 6/4, 7/3, with common 10YR 5/6, 6/6 or 6/8 mottles, and 10YR 5/3, 5/8, 6/3 or 6/8 mottles moist. It has weak subangular blocky structure or is massive.
The B2t horizon has dry color of 10YR 6/3, 6/4, 6/6, 6/8, 7/2 or 7/3 and moist color of 10YR 5/3, 5/4, 5/6, 6/2, 6/3; 7.5YR 4/4, 5/8; or 5Y 5/8. Moist mottles are 5YR 4/8; 10YR 5/6, 5/8, 6/6, 6/8; 5Y 5/1 or 6/1. Some part of the B2t horizon, within 60 inches of the soil surface, has hue redder than 10YR and chroma greater than 4 in the matrix, and/or common coarse mottles that have hue of 7.5YR or redder or chroma greater than 5. It is clay or heavy clay loam. It has weak or moderate subangular blocky structure or is massive. Two to 15 percent of rounded concretions are present throughout the argillic horizon.
COMPETING SERIES: These are the Cole and Cronkhite series in other families. Cole soils have a xeric moisture regime and a thermic soil temperature. Cronkhite soils have a mollic epipedon more than 20 inches thick, are moderately well drained, and have a paralithic contact at a depth of 20 to 40 inches.
GEOGRAPHIC SETTING: Rodeo soils are in narrow coastal valleys and drainages adjacent to the Pacific Ocean. Slopes are 2 to 15 percent. The soils formed in alluvium from chert, sandstone, and granite. Elevations are 20 to 200 feet. The climate is subhumid mesothermal with cool foggy summers and cool moist winters. Mean annual precipitation is 25 to 30 inches. Mean January temperature is about 50 degrees F.; mean July temperature is about 55 degrees F.; mean annual temperature is about 50 degrees to 56 degrees F. Frost-free season is about 300 to 365 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Tamalpais soils, and the competing Cronkhite soils. Tamalpais soils have a lithic contact at a depth of 20 to 40 inches.
DRAINAGE AND PERMEABILITY: Poorly drained; very slow runoff; slow permeability. a water table occurs at a depth of 18 to 36 inches from December through April. During the rest of the year the water table ranges in depth from 36 to over 60 inches.
USE AND VEGETATION: The soil is used for range, recreation and wildlife habitat. Natural vegetation is wiregrass, hemlock, annual grasses and forbs.
DISTRIBUTION AND EXTENT: Narrow valleys of central coastal California. The soils are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Marin County, California, 1979.