LOCATION HORSESHOE CAEstablished Series
TAXONOMIC CLASS: Fine-loamy, parasesquic, mesic Xeric Haplohumults
TYPICAL PEDON: Horseshoe gravelly loam - on a 9 to 15 percent slope at about 2850 feet elevation under second growth timber. (Colors are for dry soil unless otherwise stated.)
0--3 to 0 inches; Litter, duff, leaves and twigs.
A--0 to 2 inches; reddish brown (5YR 4/4) gravelly loam, dark reddish brown (5YR 3/3) moist; weak fine and medium granular structure; soft, very friable, nonsticky and nonplastic; common very fine and few fine roots; many very fine interstitial pores; medium acid (pH 6.0); clear smooth boundary. (2 to 5 inches thick)
AB--2 to 10 inches; yellowish red (5YR 4/6) gravelly loam, dark reddish brown (2.5YR 3/4) moist; weak fine and medium granular structure; soft, very friable, slightly sticky and slightly plastic; common very fine, fine, medium and coarse roots; many very fine interstitial pores; medium acid (pH 5.8); gradual smooth boundary. (0 to 8 inches thick)
Bt1--10 to 17 inches; yellowish red (5YR 4/8) gravelly light clay loam, dark red (2.5YR 3/6) moist; weak medium and coarse granular structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine and fine and common medium and coarse roots; many very fine interstitial pores; medium acid (pH 5.6); gradual smooth boundary. (6 to 14 inches thick)
Bt2--17 to 32 inches; yellowish red (5YR 4/8) gravelly clay loam, dark red (2.5YR 3/6) moist; massive; slightly hard, friable, sticky and plastic; few very fine and fine, and common medium and coarse roots; many very fine interstitial pores; few thin clay films as bridges and staining mineral grains, many moderately thick clay films line pores; strongly acid (pH 5.5); gradual smooth boundary. (13 to 20 inches thick)
Bt3--32 to 43 inches; red (2.5YR 4/8) gravelly clay loam, dark red (2.5YR 3/6) moist; massive; slightly hard, firm, sticky and plastic; few very fine, medium and coarse roots; common very fine pores; common moderately thick clay films as bridges and stains on mineral grains and lining pores; very strongly acid (pH 5.0); gradual wavy boundary. (10 to 30 inches thick)
BCt--43 to 50 inches; yellowish red (5YR 5/8) light gravelly clay loam, red (2.5YR 4/8) moist; massive; slightly hard, firm, slightly sticky and slightly plastic; few fine, medium and coarse roots; few very fine pores; common moderately thick clay films as bridges and stains on mineral grains and lining pores; very strongly acid (pH 5.0); gradual wavy boundary. (6 to 24 inches thick)
2BCt--50 to 59 inches; strong brown (7.5YR 5/8) very gravelly loam, strong brown (7.5YR 5/8) moist; massive; slightly hard, firm, slightly sticky and slightly plastic; few medium and coarse roots; common moderately thick clay films as bridges, clay nearly fills pores; very strongly acid (pH 4.8); gradual wavy boundary. (6 to 15 inches thick)
3C--59 to 65 inches; stratified sands and gravel.
TYPE LOCATION: Nevada County, California; about 1.5 miles southwest of North Columbia on the southeast face of the hydraulic digging; 1,320 feet west and 300 feet north of the E 1/4 corner section 7, T.17 N., R.9 E. Nevada City Quad.
RANGE IN CHARACTERISTICS: The solum is 40 to 80 inches thick. Weathered bedrock is at more than 60 inches. The mean annual soil temperature is 47 to 59 degrees F. The soils between a depth of about 4 to 16 inches are usually moist, but become dry sometime in June and remain dry until sometime in October. Organic matter content is 4 to 10 percent in the A horizon; it is 1.5 to 2.5 percent in the upper 40 inches, or in the upper 6 to 10 inches of the Bt horizons, or both.
The A horizon has dry colors of 7.5YR 5/4, 5/2, 4/4, 4/2; 5YR 5/8, 5/6, 5/4, 5/3, 4/6, 4/4 or 4/3. The surface few inches in some pedons are 7.5YR 6/4 or 10YR 6/2. Moist colors are 7.5YR 3/4; 5YR 3/4, 3/3; or 2.5YR 3/4. Below a depth of 0 to 5 inches moist chroma is 4, 6 or 8. Chroma is commonly less than 4 above these depths. It is loam, gravelly sandy loam or gravelly loam with 10 to 25 percent clay and 0 to 35 percent coarse fragments. Reaction is medium to slightly acid.
The B horizon has dry colors of 7.5YR 6/6, 6/4, 5/6, 5/4, 4/6, 4/4; 5YR 6/6, 5/8, 5/6, 5/4, 4/8, 4/6; 2.5YR 4/8, 4/6 or 3/6 and moist colors of 7.5YR 5/8, 4/6, 4/4; 5YR 4/6, 4/4; 2.5YR 4/8 or 3/6. It is loam, clay loam, gravelly loam, gravelly sandy clay loam or gravelly clay loam with 20 to 35 percent clay and 0 to 35 percent coarse fragments. Base saturation is 15 to 45 percent, but less than 35 percent below a depth of 60 inches. Reaction is medium to very strongly acid and is more acid with depth.
The 2B and 3C horizons are very gravelly loam, very gravelly clay loam or stratified sands and gravel with 15 to 65 percent coarse fragments.
COMPETING SERIES: These are the Mieruf soils. Mieruf soils are...
GEOGRAPHIC SETTING: These soils are on broad tabular ridges and sideslopes. Slope ranges from 2 to 50 percent. Elevation ranges from 1,500 to 4,125 feet. They formed in materials from gravelly Tertiary terrace remnants and basic volcanic rocks, principally tuff breccia. Climate has warm dry summers and cool wet winters. Mean annual precipitation is 30 to 85 inches, some of which falls as snow. Mean annual temperature is 50 to 57 degrees F; average January temperature is about 40 degrees F; average July temperature is about 70 degrees F. Frost-free season is 140 to 230 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Aiken, Cohasset, Holland, Jocal and Mariposa soils. Aiken soils have more than 35 percent clay in the Bt horizon. Cohasset and Holland soils have more than 35 percent base saturation in the argillic horizon. Jocal and Mariposa soils have less than 0.9 percent organic carbon in the upper Bt horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow to rapid runoff; moderate permeability.
USE AND VEGETATION: Used mainly for timber production. A few areas are mined for gold. Native vegetation is mainly ponderosa pine, sugar pine, Douglas-fir, California black oak, tanoak and whiteleaf manzanita.
DISTRIBUTION AND EXTENT: Northern and central Sierra Nevada in California. The series is moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Nevada County, California 1970.
REMARKS: Horseshoe soils were formerly classified as having mixed mineralogy. Based on age of the material it formed from, and data on surrounding soils, mineralogy was changed to Oxidic.
Last revised by the state on 4/92.