LOCATION DATOM CAEstablished Series
TAXONOMIC CLASS: Clayey, isotic, mesic, shallow Typic Argixerolls
TYPICAL PEDON: Datom ashy clay loam--on a west facing 2 percent slope under a cover of mountain big sagebrush and perennial grasses at an elevation of 4,245 feet--rangeland. (Colors are for dry soil unless otherwise noted. When described July 6, 1984, the soil was dry throughout.)
A--0 to 3 inches; grayish brown (10YR 5/2) ashy clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; common very fine tubular pores; 5 percent gravel; neutral (pH 6.6); abrupt smooth boundary. (2 to 4 inches thick)
Bw1--3 to 8 inches; grayish brown (10YR 5/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots throughout and few medium roots; few very fine tubular pores; 5 percent gravel; neutral (pH 6.8); clear smooth boundary.
Bw2--8 to 12 inches; grayish brown (10YR 5/2) silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few fine roots throughout and few medium roots; common very fine tubular pores; 5 percent gravel; neutral (pH 6.8); abrupt smooth boundary. (Combined thickness of the Bw horizons is 6 to 12 inches)
Bt1--12 to 14 inches; light brownish gray (10YR 6/2) silty clay, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few fine and few medium roots; common very fine tubular pores; few faint clay films lining pores; 5 percent gravel; neutral (pH 6.8); abrupt wavy boundary.
Bt2--14 to 16 inches; light brownish gray (10YR 6/2) silty clay, very dark grayish brown (10YR 3/2) moist; moderate fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; common very fine tubular pores; few faint clay films lining pores; 5 percent diatomite paragravel; neutral (pH 6.8); abrupt wavy boundary. (Combined thickness of the Bt horizons is 2 to 4 inches)
Crt--16 inches; weathered diatomite; common thin clay films on upper surfaces of fractures; fractures 30 to 60 cm apart with soil filling 0.5 cm cracks.
TYPE LOCATION: Lassen County, California; about 5.2 miles east of Bieber; about 800 feet north and 900 feet east from the southwest corner of section 22, T. 38 N., R. 8 E.; USGS Hog Valley 7.5 minute topographic quadrangle; 41 degrees 06 minutes 57 seconds north latitude and 121 degrees 02 minutes 38 seconds west longitude, NAD 27.
RANGE IN CHARACTERISTICS:
Soil moisture - The soil moisture control section (9 to 16 inches) is dry in all parts from early July to November (115 to 130 days); xeric moisture regime that borders on aridic.
Mean annual soil temperature - 47 to 50 degrees F.; The soil temperature exceeds 41 degrees F. from mid March to mid November (260 days) and exceeds 47 degrees F. from mid May to early November (170 days).
Mollic epipedon thickness - 8 to 14 inches.
Depth to bedrock - 10 to 20 inches to a paralithic contact. The paralithic materials below the contact are diatomite or tuff.
Particle-size control section - Clay content: Averages 40 to 45 percent; Fine sand or coarser content: 5 to 15 percent.
Volcanic glass content - 25 to 60 percent in the coarse silt through fine sand fractions. Total content of all particles between coarse silt and very coarse sand is less than 30 percent in the Bw and Bt horizons.
Other features - Values for oxalate extractable aluminum plus one half the oxalate extractable iron are less than 0.4 percent.
A horizon - Dry color: 10YR 5/2 or 5/3.
Moist color: 10YR 3/1 or 3/2.
Clay content: 27 to 35 percent.
Rock fragments: 0 to 5 percent.
Organic matter content: 4 to 9 percent.
Bw horizons - Dry color: 10YR 5/2 or 5/3.
Moist color: 10YR 3/1 or 3/2.
Clay content: 35 to 40 percent.
Rock fragments: 0 to 5 percent.
Organic matter content: 2 to 4 percent.
Bt horizons - Dry color: 10YR 6/2 or 6/4.
Moist color: 10YR 3/2 or 3/3.
Clay content: 40 to 50 percent.
Rock fragments: 5 to 15 percent.
Organic matter content: 1 or 2 percent.
COMPETING SERIES: At present, there are no other series in this family.
GEOGRAPHIC SETTING: Datom soils are on knolls. These soils formed in residuum derived from diatomite and vitric tuff. Slopes are 2 to 9 percent. Elevation ranges from 4,100 to 4,400 feet. The climate is semiarid with cold, moist winters and warm, dry summers. The mean annual precipitation is 14 to 16 inches and average snowfall depths are 12 to 24 inches. The mean annual temperature is 48 to 50 degrees F., mean January temperature is about 32 degrees F., and mean July temperature is about 67 degrees F. The frost-free period is 80 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Adinot, Bieber, and Oxendine soils. Adinot soils are loamy, shallow to lithic contacts, and are on hills and pediments. Bieber soils are clayey, shallow to duripans, and are on terraces. Oxendine soils are loamy, shallow to duripans, and are on terraces.
DRAINAGE AND PERMEABILITY: Well drained; very high surface runoff; slow permeability.
USE AND VEGETATION: Datom soils are used for irrigated cropland and for livestock grazing. Common crops are alfalfa and small grains. Small areas are used as home sites. The vegetation in rangeland is mountain big sagebrush, antelope bitterbrush, basin wildrye, Lemmon needlegrass, bluebunch wheatgrass, and scattered western juniper.
DISTRIBUTION AND EXTENT: Northeastern California. These soils are not extensive with about 2,400 acres of the series mapped to date. MLRA 21.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Lassen County (Intermountain Soil Survey Area), California 1994.
REMARKS: This revision of May 2001 updates the taxonomic class from Clayey, mixed, mesic, shallow Vitrandic Argixerolls.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 12 inches (A, Bw1, and Bw2 horizons).
Argillic horizon - The zone from 3 to 16 inches (Bw1, Bw2, Bt1, and Bt2 horizons).
Paralithic contact - The boundary at 16 inches to underlying soft, weathered bedrock (Crt layer).
Particle-size control section - The zone from 3 to 16 inches (Bw1, Bw2, Bt1, and Bt2 horizons).
ADDITIONAL DATA: The typical pedon at the series type location has full characterization by the Soil Survey Laboratory (SSL), Lincoln, NE, as soil survey sample number S84CA-035-009 (pedon # 84P0738).