LOCATION TIMBUCTOO CAEstablished Series
TAXONOMIC CLASS: Fine, parasesquic, thermic Typic Rhodoxeralfs
TYPICAL PEDON: Timbuctoo gravelly loam - on a northeast facing slope of 22 percent under blue oak, liveoak, Digger pine and annual grasses at an elevation of 480 feet. (Colors are for dry soil unless otherwise stated. When described on September 26, 1984, the soil was dry throughout).
A--0 to 4 inches; yellowish red (5YR 4/6) gravelly loam, dark reddish brown (5YR 3/4) moist; moderate fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots; common very fine interstitial and tubular pores; 20 percent pebbles, 5 percent cobbles, 1 percent stones; slightly acid (pH 6.5); clear smooth boundary. (2 to 5 inches thick)
Bt1--4 to 9 inches; red (2.5YR 4/6) gravelly clay loam, dark red (2.5YR 3/6) moist; strong medium subangular blocky structure; hard, very friable, slightly sticky and plastic; few very fine, fine and medium roots; common very fine interstitial pores and common fine tubular pores; few thin clay films on ped faces and lining pores; 20 percent pebbles, 5 percent cobbles; neutral (pH 7.0); clear wavy boundary. (3 to 6 inches thick)
Bt2--9 to 18 inches; dark red (2.5YR 3/6) gravelly clay, dark red (2.5YR 3/6) moist; strong medium subangular blocky structure; hard, very friable, sticky and plastic; few very fine and fine roots; common very fine interstitial and fine tubular pores; common moderately thick clay films on ped faces and lining pores; 20 percent pebbles, 5 percent cobbles; neutral (pH 7.0); clear wavy boundary. (4 to 12 inches thick)
Bt3--18 to 26 inches; dark red (2.5YR 3/6) gravelly clay, dark red (2.5YR 3/6) moist; strong medium subangular blocky structure; hard, friable, sticky and plastic; few very fine and fine common coarse roots; common fine tubular pores; many moderately thick clay films on peds and in pores; 20 percent pebbles 2 percent cobbles; neutral (pH 7.0); clear wavy boundary. (4 to 12 inches thick)
BCt--26 to 38 inches; dark red (2.5YR 3/6) gravelly sandy clay loam, dark red (2.5YR 3/6) moist; moderate medium subangular blocky structure; hard, friable, sticky and plastic; few very fine and common coarse roots; few fine tubular pores; many moderately thick clay films on peds; 20 percent pebbles, 2 percent cobbles; neutral (pH 7.0); abrupt wavy boundary. (4 to 15 inches thick)
Cr--38 to 45 inches; mixed black (N 2/0) and olive (5Y 4/3) weathered diabase.
R--45 inches; hard diabase.
TYPE LOCATION: Yuba County, California; about 1,900 feet southeast of Long Bar Road, along Sicard Flat Ditch, then 30 feet west up slope, University of California Sierra Field Station; about 2,200 feet east and 2,500 feet north of the southwest corner of section 17, T.16 N., R.6 E.
RANGE IN CHARACTERISTICS: Depth to a paralithic contact ranges from 20 to 40 inches. The mean annual soil temperature is 59 degrees to 63 degrees F. The soil temperature is above 47 degrees F the entire year. The soil moisture control section is dry in all parts from June 1 to October 31 and is moist in some or all parts from November 1 to May 31. Rock fragments range from 15 to 35 percent. Reaction is slightly acid to neutral.
The A horizon has dry color of 5YR 5/6 or 4/6 and moist color of 5YR 4/6 or 3/4. Clay content ranges from 18 to 27 percent. Stones range from 0 to 3 percent, cobbles from 0 to 10 percent and gravel from 15 to 25 percent.
The Bt and BCt horizons have dry color of 2.5YR 3/6 or 4/6 and moist color of 2.5YR 3/6 or 4/6. Texture is gravelly clay loam or gravelly clay in the Bt horizon and gravelly sandy clay loam in the BCt horizon. Clay content ranges from 35 to 45 percent in the upper 20 inches. Cobbles range from 0 to 10 percent and gravel from 15 to 25 percent.
COMPETING SERIES: There are no other series in this family.
GEOGRAPHIC SETTING: Timbuctoo soils are on foothills generally on north or east facing slopes. Slopes range from 3 to 50 percent. The soils formed in material weathered from basic metavolcanic rock. Elevations are 300 to 1,900 feet. The climate has hot, dry summers and cool, moist winters. The average annual precipitation is 26 to 35 inches. The average January temperature is 45 degrees F; the average July temperature is 76 degrees F; mean annual temperature is 58 to 61 degrees F. The frost-free season is 230 to 250 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Argonaut, Auburn and Sobrante soils. Argonaut soils are in similar sideslope and footslope landscape positions and they lack 2.5YR colors in the argillic horizon. Auburn soils are on ridgetops and have a lithic contact at 10 to 25 inches. Sobrante soils are in similar landscape positions and have less than 35 percent clay in the argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained, slow to rapid runoff; slow permeability.
USE AND VEGETATION: Mainly for livestock grazing, wildlife habitat and watershed. Natural vegetation is blue oak, interior live oak, Digger pine and ponderosa pine with an understory of brush, forbs and annual grasses.
DISTRIBUTION AND EXTENT: Foothills of the Sierra Nevada Range in California. The series is not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Yuba County, California, 1992.
REMARKS: Sampled as S84CA-115-5 for complete characterization 9/84 by NSSL. Sampled a Las Posas Variant. Base Saturation by Hach Kit is 80-100 percent throughout.
Mineralogy is oxidic based on NSSL lab.
d.ta.
e.tractable Fe(1.4) + gibbsite/clay% =.24
The classification was updated in January of 2003 to reflect lab data. Competing series were not checked at that time. - ET
Last revised by the state on 7/92.