LOCATION OBSERVATION CA+OREstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Typic Argixerolls
TYPICAL PEDON: Observation very stony loam, rangeland, on a 21 percent N facing slope under a cover of big sagebrush and Idaho fescue at 5,900 feet elevation. (When described September 18, 1978 the soil was slightly moist below 12 inches. Colors are for dry soil unless otherwise noted.)
The surface is covered with 12 percent stones, 20 percent cobbles and 15 percent gravel.
A1--0 to 3 inches; dark grayish brown (10YR 4/2) very stony loam, very dark brown (10YR 2/2) moist; moderate medium and fine granular structure; soft, very friable, sticky and plastic; many very fine roots; many very fine interstitial pores; 12 percent stones, 20 percent cobbles. 15 percent pebbles; neutral (pH 7.0); clear smooth boundary.
A2--3 to 9 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; strong medium and fine subangular blocky structure; slightly hard, very friable, sticky and plastic; common very fine and fine, few medium roots; many very fine and fine tubular and interstitial pores; 5 percent cobbles, 5 percent pebbles; neutral (pH 7.0); clear wavy boundary. (The combined thickness of the A horizons is 6 to 11 inches).
BAt--9 to 18 inches; brown (10YR 5/3) clay loam, dark brown (10YR 3/3) moist; strong medium angular blocky structure; hard, friable, very sticky and very plastic; common very fine and fine roots; many very fine tubular pores; 1 percent stones, 5 percent cobbles and 5 percent pebbles; common moderately thick clay films on faces of peds and in pores; neutral (pH 7.0); gradual wavy boundary. (0 to 10 inches thick)
Bt1--18 to 25 inches; light brown (7.5YR 6/4) gravelly clay, dark brown (7.5YR 4/4) moist; moderate medium and coarse prismatic structure parting to strong coarse angular blocky; extremely hard, firm, very sticky and very plastic; common very fine exped roots; common very fine tubular pores; 5 percent cobbles and 15 percent pebbles; many thick clay films on peds and in pores; neutral (pH 7.0); gradual wavy boundary.
Bt2--25 to 35 inches; reddish yellow (7.5YR 6/6) gravelly clay; strong brown (7.5YR 4/6) moist; massive; very hard, friable, very sticky and very plastic; few very fine roots; common very fine tubular pores; 5 percent cobbles and 15 percent pebbles; few moderately thick clay film coatings on soft rock fragments; neutral (pH 7.0); abrupt wavy boundary. (The combined thickness of the Bt horizons is 10 to 32 inches thick)
R--35 inches; hard fractured andesite, fractures filled with soil material from above.
TYPE LOCATION: Lassen County, California; about 3.0 miles east of Horn Ranch on road to Ravendale and 2.5 miles south of this point on the dirt road to Observation Peak and 75 feet east of this road; about 900 feet N and 100 feet W of the SE corner of section 6, T.34 N., R.16 E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature is 44 to 47 degrees F. Thickness of the solum and depth to bedrock is 20 to 40 inches. The moisture control section (10 to 21 inches) is dry from July 15 to November 1 (110 days). It is moist from December 1 to May 15. The soil temperature exceeds 41 degrees F from April 15 to December 1 (229 days) and exceeds 47 degrees F from May 15 to October 15. Rock fragments, mostly cobbles and stones, cover 20 to 50 percent of the surface. The mollic epipedon is 8 to 18 inches thick and in some pedons extends into the upper part of the B horizon.
The A horizon is 10YR 4/2, 4/3, 5/2, 5/3 or 7.5YR 5/2. Moist color is 10YR 2/2, 3/2, 3/3 or 7.5YR 3/2. It is neutral or mildly alkaline.
The Bt horizon is 10YR 5/3, 4/4; 7.5YR 5/2, 5/4, 6/2 or 6/4, 6/6. Moist color is 10YR 3/3, 3/4; 7.5YR 3/2, 3/4, 4/2, 4/4 or 4/6. It is clay loam or clay with 35 to 50 percent clay and 5 to 25 percent rock fragments, mostly gravel and cobbles. Reaction is neutral or mildly alkaline.
COMPETING SERIES: These are the Booford, Manila, Marsden, Ostler, Rob Roy and Shagnasty series: Booford soils have a paralithic contact at 20 to 40 inches. Manila, Ostler soils are greater than 60 inches deep. Marsden soils have a paralithic contact at 40 to 60 inches. Rob Roy soils are dry 50 to 70 consecutive days. Shagnasty soils are 50 to 80 inches deep to weathered bedrock.
GEOGRAPHIC SETTING: Observation soils are on mountain back slopes. Slopes are 2 to 50 percent. These soils formed in residuum and colluvium from basalt and andesite. Elevation is 4,200 to 7,600 feet. The climate is semi-arid with warm, dry summers and cold moist winters. The mean annual precipitation is 12 to 18 inches with 10 to 60 inches of snow.The mean annual temperature varies from 40 to 44 degrees F. Mean July temperature varies from 58 to 63 degrees F., and the mean January temperature varies from 22 to 28 degrees F. The average frost free season is 50 to 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Glean, Searles and Sumine soils. Glean soils are deep and are loamy-skeletal. Searles and Sumine soils are loamy-skeletal.
DRAINAGE AND PERMEABILITY: Well drained, medium to rapid runoff; slow permeability.
USE AND VEGETATION: Used as rangeland. The vegetation is big sagebrush, Idaho fescue and bluebunch wheatgrass.
DISTRIBUTION AND EXTENT: Northeastern California and central Oregon (MLRA 10). The soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Lassen County, California; Susanville Area Soil Survey Area, 1988.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon--Zone from the surface to a depth of 18 inches (A1, A2, BAt and Bt1 horizons).
Argillic horizon--Zone from about 9 to 35 inches (BAt, Bt1 and Bt2 horizons).