LOCATION CHEWAUCAN OREstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Argiduridic Argixerolls
TYPICAL PEDON: Chewaucan very cobbly silty clay loam--rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 5 inches; dark grayish brown (10YR 4/2) very cobbly silty clay loam, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure; hard, firm, moderately sticky and very plastic; many fine, many very fine, few medium, and few coarse roots; many very fine pores; 5 percent stones, 20 percent cobbles, 15 percent coarse gravel, and 10 percent fine gravel; moderately alkaline (pH 8.0); gradual smooth boundary. (4 to 10 inches thick)
Bt1--5 to 10 inches; yellowish brown (10YR 5/4) silty clay loam, dark brown (10YR 3/3) moist; moderate medium prismatic structure parting to moderate medium subangular blocky; hard, firm, moderately sticky and very plastic; many very fine, many fine, few medium, and few coarse roots; few very fine tubular pores; common distinct clay films on faces of peds; 5 percent stones, 5 percent cobbles, 1 percent coarse gravel, and 1 percent fine gravel; slightly alkaline (pH 7.6); gradual smooth boundary. (4 to 10 inches thick)
Bt2--10 to 24 inches; light yellowish brown (10YR 6/4) silty clay loam, dark yellowish brown (10YR 4/4) moist; weak medium prismatic structure parting to moderate medium subangular blocky; hard, firm, moderately sticky and very plastic; common very fine and common fine roots; few very fine tubular pores; common distinct clay films on faces of peds; 5 percent stones, 5 percent cobbles, 2 percent coarse gravel, and 2 percent fine gravel; slightly alkaline (pH 7.6); abrupt smooth boundary. (12 to 18 inches thick)
Bkq--24 to 44 inches; very pale brown (10YR 7/4) loam, dark yellowish brown (10YR 4/4) moist; very hard, firm and brittle, slightly sticky and slightly plastic; few fine roots in the upper 2 inches; strongly effervescent; secondary carbonates segregated in common fine filaments; 5 percent stones and 5 percent cobbles; moderately alkaline (pH 8.4) abrupt smooth boundary. (18 to 24 inches thick)
2R--44 inches; basalt.
TYPE LOCATION: Lake County, Oregon; about 3 miles northwest of Valley Falls between Willow Creek and Juniper Creek; in the SW 1/4 of the NE 1/4 of the NE 1/4 of section 34, T. 35 S., R. 20 E.; USGS Valley Falls 7.5 minute topographic quadrangle.
RANGE IN CHARACTERISTICS:
Soil moisture - The soils are dry in all parts more than half the time when the soil temperature is above 41 degrees F.; aridic moisture regime that borders on xeric.
Mean annual soil temperature - 48 to 50 degrees F.
Mollic epipedon thickness - 10 to 15 inches; includes the Bt1 horizon.
Depth to base of argillic horizon - 20 to 40 inches.
Depth to horizon with firm, brittle matrix - 20 to 40 inches.
Depth to bedrock - 40 to 60 inches to a lithic contact.
Particle-size control section - Clay content: 35 to 45 percent; Rock fragments: 0 to 25 percent, mainly gravel and cobbles. Lithology of fragments are volcanic rocks such as basalt.
A horizon - Value: 4 or 5 dry.
Chroma: 2 or 3, dry or moist.
Rock fragments: Total range from 35 to 60 percent; 0 to 10 percent stones, 15 to 25 percent cobbles, 10 to 35 percent gravel.
Structure: Commonly has weak thin platy structure in the surface 1 inch.
Organic matter content: 1 to 3 percent.
Reaction: Slightly alkaline or moderately alkaline.
Bt1 horizon - Texture: Silty clay loam, silty clay, gravelly silty clay, or cobbly silty clay.
Clay content: 35 to 45 percent.
Rock fragments: Total range from 0 to 25 percent; 0 to 10 percent stones, 0 to 15 percent cobbles, and 0 to 25 percent gravel.
Organic matter content: 1 or 2 percent.
Reaction: Slightly alkaline or moderately alkaline.
Bt2 horizon - Value: 5 or 6 dry, 3 or 4 moist.
Chroma: 3 or 4, dry or moist.
Texture: Silty clay loam, silty clay, gravelly silty clay, or cobbly silty clay.
Clay content: 35 to 45 percent.
Rock fragments: Total range from 0 to 25 percent; 0 to 10 percent stones, 0 to 15 percent cobbles, and 0 to 25 percent gravel.
Reaction: Slightly alkaline or moderately alkaline.
Bkq horizon - Texture: Loam or clay loam.
Clay content: 20 to 35 percent.
Consistence: Firm or extremely firm when moist with a brittle manner of failure.
Rock fragments: Total range from 0 to 15 percent; 0 to 10 percent stones, 0 to 10 percent cobbles, and 0 to 10 percent gravel.
Calcium carbonate equivalent: 4 to 8 percent.
COMPETING SERIES: There are currently no other series in this family.
GEOGRAPHIC SETTING: Chewaucan soils are on lake terraces or structural benches below the high-water mark of Pleistocene lakes. These soils formed in lacustrine deposits derived from volcanic rocks such as basalt, tuff, and andesite. Slopes are 2 to 15 percent. Elevations range from 4,200 to 4,800 feet. The climate is semiarid and characterized by cool, moist winters and warm, dry summers. The mean annual precipitation is 12 to 14 inches, the mean annual temperature is 45 to 48 degrees F., and the frost-free period is 70 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Booth, McConnel, and Redcanyon soils. Booth soils are moderately deep to paralithic contacts, have 45 to 60 percent clay in the particle-size control section, and have a frigid temperature regime. McConnel soils are sandy-skeletal and are on lower lake terraces. Redcanyon soils are loamy-skeletal, moderately deep to lithic contacts, and are on adjacent hills.
DRAINAGE AND PERMEABILITY: Well drained; high surface runoff; moderately slow permeability.
USE AND VEGETATION: Chewaucan soils are used for livestock grazing and wildlife habitat. The potential vegetation is Wyoming big sagebrush, bluebunch wheatgrass, Thurber's needlegrass, and bottlebrush squirreltail.
DISTRIBUTION AND EXTENT: South-central Oregon. These soils are not extensive. MLRA 21.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.
SERIES ESTABLISHED: Lake County (Southern Part), Oregon, 1991.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the soil surface to 10 inches (A and Bt1 horizons).
Argillic horizon - The zone from 5 to 24 inches (Bt1 and Bt2 horizons).
Duric feature - The zone from 24 to 44 inches (Bkq horizon).
Identifiable secondary carbonates - The zone from 24 to 44 inches (Bkq horizon).
Lithic contact - The boundary at 44 inches to underlying hard, unweathered bedrock (2R layer).
Particle-size control section - The zone from 5 to 24 inches (Bt1 and Bt2 horizons).