LOCATION THIESSEN WA+OREstablished Series
TAXONOMIC CLASS: Clayey-skeletal, smectitic, mesic Pachic Argixerolls
TYPICAL PEDON: Thiessen very stony silt loam- rangeland, on a 70 percent southeast-facing slope at an elevation 1,880 feet. (Colors are for dry soil unless otherwise noted)
A--0 to 3 inches; brown (10YR 4/3) very stony silt loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium granular structure; hard, friable, moderately sticky and moderately plastic; many very fine and few medium roots; many very fine irregular pores; 25 percent gravel, 15 percent cobbles; and 10 percent stones; neutral (pH 7.2); clear wavy boundary. (2 to 6 inches thick)
Bt1--3 to 9 inches; brown (10YR 4/3) very cobbly clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; many very fine and few medium roots; many very fine irregular pores; many faint stress cutans and clay films on faces of peds; 20 percent gravel, 25 percent cobbles and 5 percent stones; neutral (pH 7.2); clear wavy boundary.
Bt2--9 to 17 inches; brown (10YR 5/3) very cobbly clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine roots; common very fine irregular pores; many faint stress cutans and clay films on faces of peds; 20 percent gravel, 25 percent cobbles and 5 percent stones; slightly alkaline (pH 7.5); clear wavy boundary.
Bt3--17 to 22 inches; brown (10YR 5/3) extremely cobbly clay loam, dark brown (10YR 3/3) moist; moderate fine and medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine roots; common very fine irregular pores; continuous faint stress cutans and clay films on faces of peds; 30 percent gravel, 30 percent cobbles and 5 percent stones; slightly alkaline (pH 7.5); abrupt irregular boundary. (Combined thickness of the Bt horizon is 17 to 35 inches)
2R--22 inches; basalt.
TYPE LOCATION: Asotin County, Washington; about 5 miles northeast of Anatone; 250 feet north and 2,600 feet west of southeast corner of section 2, T. 8 N., R. 46E.
RANGE IN CHARACTERISTICS: The solum thickness and depth to a lithic contact is 20 to 40 inches. The mean annual soil temperature is 47 to 52 degrees F. These soils are usually moist, but are dry in all parts between 4 and 12 inches for 75 to 90 consecutive days following summer solstice. The particle-size control section averages 40 to 65 percent angular basalt fragments by volume and is 35 to 45 percent clay in the fine earth fraction. The mollic epipedon is 20 to 35 inches thick and includes all or part of the argillic horizon. The argillic horizon is 18 to 35 inches thick.
The A horizon has hue of 7.5YR or 10YR, value of 3 to 5 dry, 2 or 3 moist and chroma of 1 to 3 dry or moist. Texture is loam or silt loam. It has 18 to 27 percent clay.
An AB horizon is present in some pedons with color similar to the A horizon.
The Bt1 and Bt2 horizons have hue of 7.5YR or 10YR, value of 3 to 5 dry, 2 or 3 moist and chroma of 1 to 3 dry or moist. Texture is very cobbly clay loam, very gravelly clay loam, very gravelly silty clay loam, or very gravelly clay. It has 35 to 45 percent clay. Reaction is neutral or slightly alkaline.
The Bt3 horizon, when present, has hue of 5YR, 7.5YR, or 10YR, value of 3 to 5 dry, 2 or 3 moist and chroma of 2 or 3 dry or moist. Texture is very cobbly clay, extremely cobbly clay loam, extremely gravelly clay loam, very gravelly clay loam, very cobbly clay loam or extremely cobbly clay. It has 35 to 45 percent clay. Reaction is neutral or slightly alkaline.
A BCt horizon is present in some pedons. It has hue of 7.5YR or 10YR, value of 4 or 5 dry, 3 or 4 moist and chroma of 3 or 4 dry or moist. Texture is very cobbly clay, very gravelly clay loam, extremely cobbly clay loam, or very cobbly clay loam. Reaction is slightly acid to slightly alkaline.
COMPETING SERIES: These are the
Dosie,
Drakce (T),
Gurdane,
Kishwalk,
Mallory,
Tablerock, and
Zweygardt (T) series.
Dosie soils 40 to 60 inches to a lithic contact (basalt); dry for more than 90 consecutive days following the summer solstice (aridic bordering xeric)
Drakce soils 40 to 60 inches to a lithic contact (basalt)
Gurdane soils dry for 60 to 75 consecutive days following the summer solstice; argillic horizon 5 to 13 inches thick; have a Bw horizon
Kishwalk soils particle-size control section containing 15 to 50 percent stones and lack stress oriented fabric
Mallory soils dry for 60 to 75 consecutive days following the summer solstice
Tablerock soils greater than 60 inches to a paralithic contact (sandstone); dry for 80 to 110 consecutive days following the summer solstice
Zweygardt soils greater than 60 inches to bedrock; particle-size control section with 35 to 50 percent rounded rock fragments of alluvial origin
GEOGRAPHIC SETTING: Theissen soils are on summits, structural benches, hillslopes, and canyon slopes at elevations of 900 to 4,000 feet. These soils formed in colluvium derived from basalt mixed with loess. Slopes are 2 to 90 percent. The summers are hot and dry and the winters are cool and moist. The mean annual precipitation is 13 to 19 inches. The mean annual temperature is 45 to 50 degrees F. The frost-free season is 100 to 150 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Laufer, Matheny, Pataha, and Stember soils. Laufer soils are on canyon walls and have a lithic contact at a depth of 10 to 20 inches. Pataha and Stember soils are on plateaus and have less than 35 percent clay in particle-size control section. Matheny soils are on canyon walls and are more than 40 inches deep.
DRAINAGE AND PERMEABILITY: Well drained, medium to rapid runoff, moderately slow to slow permeability.
USE AND VEGETATION: These soils are used for livestock grazing and wildlife habitat. Native vegetation is bluebunch wheatgrass and western yarrow.
DISTRIBUTION AND EXTENT: Southeastern Washington and northeastern Oregon. MLRA 8, 9. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Asotin County, Washington, 1984.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from 0 to 22 inches
Argillic horizon - the zone from 3 to 22 inches
Lithic contact - the zone beginning at 22 inches
Particle-size control section - the zone from 3 to 22 inches