LOCATION SEARVAR CAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Aridic Argixerolls
TYPICAL PEDON: Searvar gravelly loam--on a southwest facing slope under mountain big sagebrush, perennial grasses, and scattered western juniper, at an elevation of 5,480 feet--rangeland. (Colors are for dry soil unless otherwise noted. When described on November 20, 1979, the soil was moist to 10 inches).
A1--0 to 3 inches; grayish brown (10YR 5/2) gravelly loam, very dark grayish brown (10YR 3/2) moist; weak thin platy structure parting to moderate fine subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine and few medium roots; common very fine and fine, and few medium tubular pores; 15 percent pebbles; neutral (pH 7.0); clear smooth boundary.
A2--3 to 6 inches; grayish brown (10YR 5/2) gravelly loam, very dark grayish brown (10YR 3/2) moist; moderate thin platy parting to moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine and few medium roots; common very fine and fine tubular, and few medium interstitial pores; 15 percent pebbles; neutral (pH 7.0); clear smooth boundary. (Combined thickness of the A horizons is 4 to 8 inches)
Bt1--6 to 18 inches; brown (10YR 5/3) very cobbly loam, dark brown (10YR 3/3) moist; moderate medium and coarse subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine and few fine and medium roots; common very fine and few fine and medium tubular pores; very few faint clay films on faces of peds; 25 percent cobbles and 15 percent pebbles; neutral (pH 7.0); abrupt wavy boundary. (6 to 20 inches thick)
Bt2--18 to 28 inches; pale brown (10YR 6/3) very cobbly loam, brown (10YR 4/3) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and few fine and medium roots; few very fine and fine tubular pores; very few faint clay films on faces of peds; 25 percent cobbles and 15 percent pebbles; neutral (pH 7.0); abrupt smooth boundary. (8 to 14 inches thick)
Cr--28 to 53 inches; very pale brown (10YR 7/3) weathered tuff-breccia, yellowish brown (10YR 5/4) moist; very weak rupture resistance, brittle by silica; few very fine and fine roots in cracks; disoriented rock fragments in a soft weathered matrix; 20 percent pebbles and 60 percent cobbles; clear smooth boundary. (20 to 45 inches thick)
R--53 inches; tuff-breccia; continuous, dense rock matrix that contains subrounded and angular fragments of andesite and basalt; difficult to chip with a shovel.
TYPE LOCATION: Lassen County, California; about 15 miles south of Adin, 1.5 miles northeast of Silva Flat Reservoir, and 60 feet west of dirt road; 775 feet east and 400 feet south of the center of section 7, T. 36 N., R. 10 E.; USGS Said Valley 7.5 minute topographic quadrangle.
RANGE IN CHARACTERISTICS:
Soil moisture - The soil moisture control section is dry in all parts from mid June to early November (about 120 to 140 days) and is moist in all parts from early December to early May. The soil temperature exceeds 41 degrees F. from mid March to mid November (225 days) and exceeds 47 degrees F. from mid May to early November; aridic moisture regime that borders on xeric.
Mean annual soil temperature - 47 to 51 degrees F.
Mollic epipedon thickness - 10 to 20 inches, includes the Bt1 horizon.
Depth to base of argillic horizon - 20 to 40 inches.
Depth to bedrock - 20 to 40 inches to a paralithic contact. The paralithic materials below the contact are weathered tuff-breccia or similar rocks. Hard, unweathered bedrock is typically within 60 inches.
Control section - Clay content: 18 to 25 percent; Rock fragments: 35 to 50 percent, mostly cobbles. Lithology of fragments are volcanic rocks such as andesite.
Other features - Clay minerals are mainly montmorillonite and halloysite.
A horizons - Hue: 7.5YR or 10YR.
Value: 4 or 5 dry.
Chroma: 2 through 4 dry.
Clay content: 10 to 15 percent.
Rock fragments: 15 to 25 percent, mainly pebbles.
Organic matter content: 2 to 6 percent.
Reaction: slightly acid or neutral.
Base saturation by ammonium acetate: 90 to 100 percent.
Other features: Surface rock fragments range from 5 to 20 percent and are mostly pebbles.
Bt1 horizon - Hue: 5YR through 10YR.
Clay content: 12 to 18 percent.
Rock fragments: 35 to 60 percent.
Organic matter content: 1 or 2 percent.
Base saturation by ammonium acetate: 95 to 100 percent.
Bt2 horizon - Hue: 5YR through 10YR.
Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 3 or 4 dry, 2 through 4 moist.
Clay content: 18 to 25 percent.
Rock fragments: 35 to 60 percent.
Organic matter content: 0.5 to 1 percent.
Base saturation by ammonium acetate: 95 to 100 percent.
COMPETING SERIES: These are the Ashue, Badena (T), Badenaugh, Eaglerock, Gitabyte (T), Grinrod, Ister, Lemm, Leviathan, Nosrac, Oest, Searles, Shawmount (T), Shree, Shroe, Trid, and Tristan series.
Ashue, Badena, Badenaugh, Lemm, Leviathan, Nosrac, Oest, Shawmount, Shree, and Shroe soils are very deep. Eaglerock soils have mainly fine pebbles in the particle-size control section and have paralithic materials of weathered granitic rock in the series control section. Gitabyte, Grinrod, Ister, and Searles soils are moderately deep to lithic contacts. Trid soils have 25 to 35 percent clay and 55 to 75 percent pebbles in the particle-size control section and have paralithic materials of weathered granitic rock in the series control section. Tristan soils are deep.
GEOGRAPHIC SETTING: Searvar soils are on plateaus and hills. These soils formed in slope alluvium and residuum derived from volcanic rocks such as tuff-breccia. They typically occur on summit positions. Slopes are 2 to 15 percent. Elevation ranges from 4,800 to 6,500 feet. The climate is semiarid with cold, moist winters and warm, dry summers. The mean annual precipitation is 12 to 16 inches. Total snowfall is 12 to 30 inches. The mean annual temperature is 45 to 48 degrees F. The mean January temperature is about 27 degrees F. and the mean July temperature is about 66 degrees F. The frost-free period is 80 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Trojan, Erig, Jellycamp, and Longcreek soils. Trojan soils are fine-loamy. Erig soils are frigid and have mollic epipedons more than 20 inches thick. Jellycamp soils are clayey, shallow to duripans, and occur on summit positions of plateaus. Longcreek soils are clayey-skeletal, shallow to lithic contacts, and occur on ridges.
DRAINAGE AND PERMEABILITY: Well drained; medium surface runoff; moderate permeability.
USE AND VEGETATION: Searvar soils are used for livestock grazing. The vegetation is mountain big sagebrush, Idaho fescue, bluebunch wheatgrass, antelope bitterbrush, and scattered western juniper.
DISTRIBUTION AND EXTENT: Northeastern California. These soils are not extensive with about 1,500 acres of the series mapped to date. MLRA 21.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Lassen County (Intermountain Area Soil Survey), California, 1994.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 18 inches (A1, A2, and Bt1 horizons).
Argillic horizon - The zone from 6 to 28 inches (Bt1 and Bt2 horizons).
Paralithic contact - The boundary at 28 inches to underlying weathered bedrock (Cr layer)
Particle-size control section - The zone from 6 to 26 inches (Bt1 horizon and part of the Bt2 horizon).
ADDITIONAL DATA: Reference samples were sent to the Bureau of Land Management in 1980 for mineralogy determination.