LOCATION THOMPSONCABIN OR

Established Series
Rev. CWL-MPK-JVC-JBF
06/2011

THOMPSONCABIN SERIES

The Thompsoncabin series consists of shallow, well drained soils that formed in eolian deposits derived from mixed rocks over colluvium and residuum derived from basalt. Thompsoncabin soils are on hills and plateaus. Slopes are 15 to 70 percent. The mean annual precipitation is about 230 mm and the mean annual temperature is about 9 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Lithic Natrargids

TYPICAL PEDON: Thompsoncabin extremely stony sandy loam--on a 50 percent west-facing slope of a plateau at an elevation of 1,555 meters--rangeland. (Colors are for dry soil unless otherwise noted)

An--0 to 8 cm; pale brown (10YR 6/3) extremely stony sandy loam, dark grayish brown (10YR 4/2) moist; moderate medium granular structure; soft, friable, nonsticky and nonplastic; few very fine and fine roots; common fine and medium interstitial and tubular pores; 30 percent gravel, 20 percent cobbles, 20 percent stones, and 5 percent boulders; strongly effervescent; very strongly alkaline (pH 9.4); clear smooth boundary. (5 to 10 cm thick)

Btkn1--8 to 18 cm; pale brown (10YR 6/3) extremely cobbly sandy clay loam; brown (10YR 4/3) moist; moderate fine columnar structure parting to weak fine subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; common very fine and few fine and medium roots; common fine and medium interstitial and tubular pores; common faint clay films on faces of peds; 30 percent gravel, 20 percent cobbles, and 10 percent stones; secondary carbonates segregated as few fine coats on bottoms of gravel; strongly effervescent; very strongly alkaline (pH 9.6); clear irregular boundary.

Btkn2--18 to 25 cm; light brown (7.5YR 6/3) extremely cobbly clay loam, brown (7.5YR 4/3) moist; moderate fine subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine and few fine and medium roots; common fine and medium interstitial and tubular pores; common distinct clay films on faces of peds; 35 percent gravel, 30 percent cobbles, and 10 percent stones; secondary carbonates segregated as few fine coats on faces of peds and bottoms of gravel; violently effervescent; very strongly alkaline (pH 9.6); clear irregular boundary.

Btkn3--25 to 36 cm; light brown (7.5YR 6/4) extremely cobbly clay loam, brown (7.5YR 4/4) moist; moderate fine subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few very fine and fine roots; common distinct clay films on faces of peds; 35 percent gravel, 30 percent cobbles, and 10 percent stones; secondary carbonates segregated as few fine coats on faces of peds and bottoms of gravel; violently effervescent; very strongly alkaline (pH 9.6); abrupt smooth boundary. (Combined thickness of the Btkn horizons is 20 to 46 cm)

R--36 cm; fractured basalt.

TYPE LOCATION: Lake County, Oregon; below the west side of Diablo Rim and above the mouth of Cat Camp Draw; approximately 2,600 feet east and 1,800 feet south of the northwest corner of section 9, T. 30 S., R. 18 E.; USGS Diablo Peak 7.5 minute topographic quadrangle; latitude 42 degrees 59 minutes 10 seconds N and longitude 120 degrees 35 minutes 38 seconds W; NAD 83.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually moist in the moisture control section in winter and spring, dry in summer and fall; aridic moisture regime that borders on xeric.
Mean annual soil temperature: 9 to 11 degrees C.
Ochric epipedon thickness: 5 to 10 cm.
Depth to base of natric horizon: 25 to 50 cm.
Depth to bedrock: 25 to 50 cm to a lithic contact.
Reaction: Strongly alkaline or very strongly alkaline.

Particle-size control section - Clay content: Averages 25 to 35 percent.
Rock fragments: 60 to 80 percent, mainly cobbles. Lithology of fragments are basalt.

An horizon
Value: 6 or 7 dry.
Chroma: 2 or 3, dry or moist.
Salinity (EC): 4 to 8 mmhos/cm.
Sodicity (SAR): 13 to 30.

Btkn horizons
Hue: 10YR or 7.5YR.
Value: 6 or 7 dry.
Chroma: 3 or 4, dry or moist.
Texture: Extremely cobbly sandy clay loam or extremely cobbly clay loam.
Clay content: 25 to 35 percent.
Rock fragments: 60 to 80 percent.
Salinity (EC): 4 to 16 mmhos/cm.
Sodicity (SAR): 13 to 45.
Identifiable secondary carbonates: Occurs as few fine coats on faces of peds, on bottoms of rock fragments, or as filaments in the matrix.
Calcium carbonate equivalent: 2 to 8 percent.

COMPETING SERIES: This is the Labou series. Labou soils have albic horizons, are dominated by gravel, and average 35 to 60 percent rock fragments in the particle-size control section.

GEOGRAPHIC SETTING: Thompsoncabin soils are on hills and plateaus. They typically occur on backslope positions. They formed in eolian deposits derived from mixed rocks over colluvium and residuum derived from basalt. These soils occur downwind of a salty playa (Summer Lake) and frequently receive new deposits of loess high in sodium salts. Slopes are 15 to 70 percent. Elevations range from 1,345 to 1,800 meters. The climate is arid with cool, moist winters and warm, dry summers. The mean annual precipitation is 200 to 250 mm, the mean annual temperature is 8 to 9 degrees C, and the frost-free period is 70 to 100 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Diablopeak and Wildhill soils. Wildhill soils are moderately deep to lithic contacts and have sodium affected argillic horizons. Diablopeak soils are clayey.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; very high surface runoff; moderately high saturated hydraulic conductivity.

USE AND VEGETATION: Thompsoncabin soils are used for livestock grazing and wildlife habitat. The present vegetation is shadscale, bud sagebrush, Indian ricegrass, and bottlebrush squirreltail.

DISTRIBUTION AND EXTENT: South-central Oregon. These soils are not extensive with about 3,600 acres of the series mapped to date. MLRA 23.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.

SERIES ESTABLISHED: Lake County (Northern Part), Oregon, 2006. The name is from Thompson Cabin, a local historic site.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 8 cm (An horizon).
Natric horizon - The zone from 8 to 36 cm (Btnk1, Btkn2, and Btkn3 horizons).
Identifiable secondary carbonates - The zone from 8 to 36 cm (Btnk1, Btkn2, and Btkn3 horizons).
Lithic contact - The boundary at 36 cm to underlying hard, unweathered bedrock (R layer).
Particle-size control section - The zone from the soil surface to 36 cm (An, Btkn1, Btkn2, and Btkn3 horizons).

National Cooperative Soil Survey
U.S.A.