LOCATION BOULDERFAN              CA

Established Series
Rev. JBF/TM
12/2022

BOULDERFAN SERIES

The Boulderfan series consists of very deep, well drained soils that formed in glacial till and glacial debris, volcanic ash, alluvium and colluvium derived from andesite and andesitic tuff. Boulderfan soils are on ground moraines and mountain valleys. Slopes are 2 to 8 percent. The mean annual precipitation is about 25 inches and the mean annual temperature is about 44 degrees F.

TAXONOMIC CLASS: Ashy-skeletal, glassy Vitrandic Argicryolls

TYPICAL PEDON: Boulderfan ashy loam - rangeland. (Colors are for dry soil unless otherwise noted.)

A1--0 to 3 inches; brown (10YR 5/3) ashy loam, very dark grayish brown (10YR 3/2) moist; weak very fine and fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many very fine roots; many very fine interstitial pores; 10 percent hard volcanic gravel; moderately acid (pH 6.0); abrupt wavy boundary. (3 to 5 inches thick)

A2--3 to 10 inches; brown (10YR 5/3) ashy loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; slightly hard, very friable, moderately sticky and moderately plastic; many very fine and common fine roots; many very fine tubular pores; 10 percent hard volcanic gravel; moderately acid (pH 6.0); clear wavy boundary. (6 to 15 inches thick)

2Bt1--10 to 26 inches; brown (10YR 5/3) extremely cobbly ashy loam, very dark grayish brown (10YR 3/2) moist; moderate medium subangular blocky structure; slightly hard, very friable, moderately sticky and moderately plastic; many very fine, common fine and few medium and coarse roots; many very fine and fine tubular pores; common distinct clay films on faces of peds and bridging mineral grains; 10 percent stones; 40 percent cobbles and 15 percent hard volcanic gravel; slightly acid (pH 6.4); abrupt wavy boundary. (10 to 18 inches thick)

3Bt2--26 to 35 inches; light yellowish brown (10YR 6/4) ashy loam, brown (10YR 4/3) moist; weak coarse angular blocky structure; hard, very friable, moderately sticky and moderately plastic; few very fine roots; common very fine tubular pores; common distinct clay films on faces of peds and bridging mineral grains; 10 percent hard volcanic gravel; slightly acid (pH 6.4); gradual smooth boundary. (10 to 20 inches thick)

3Bt3--35 to 44 inches; very pale brown (10YR 7/3) ashy clay loam, brown (10YR 4/3) moist; moderate medium and coarse angular blocky structure; hard, very friable, moderately sticky and moderately plastic; few fine roots; common very fine tubular pores; 5 percent 2 to 5 millimeter prominent reddish yellow (7.5YR 6/6) dry, strong brown (7.5YR 4/6) moist masses of iron accumulation in the matrix and lining pores; common distinct clay films on faces of peds and bridging mineral grains; 10 percent hard volcanic gravel; slightly acid (pH 6.4); clear smooth boundary. (6 to 11 inches thick)

3C--44 to 60 inches; very pale brown (10YR 8/2) ashy clay loam, dark yellowish brown (10YR 4/4) moist; weak fine prismatic structure; hard, very friable, moderately sticky and moderately plastic; few very fine roots; common very fine tubular pores; 5 percent 2 to 5 millimeter prominent reddish yellow (7.5YR 6/6) dry, strong brown (7.5YR 4/6) moist masses of iron accumulation in the matrix and lining pores; 10 percent hard volcanic gravel; slightly acid (pH 6.4).

TYPE LOCATION: Modoc County, California; on the Modoc National Forest just south of the Patterson Guard Station road and about a mile north of Camp One Spring; about 500 feet north and 600 feet west of the southeast corner of Section 3, T. 38 N., R. 16 E.; USGS Emerson Peak 7.5 minute topographic quadrangle; 41 degrees 11 minutes 11.5 seconds north latitude and 120 degrees 08 minutes 10.3 seconds west longitude, NAD 27.

RANGE IN CHARACTERISTICS:
Soil moisture -- Usually moist, moist in winter and spring, dry in late summer and fall; completely dry for at least 45 consecutive days between July and October; xeric moisture regime. Endosaturation is present with an apparent seasonal high water table between 3.5 and 5 feet (common deep free water duration and depth class) from January through May.

Mean annual soil temperature - 41 to 46 degrees F.
Mean summer soil temperature - 54 to 59 degrees F.
Volcanic glass content - 50 to 80 percent in the coarse silt through fine sand fractions.
Mollic epipedon thickness: 25 to 30 inches.
Other features: Lithology of rock fragments is tuff and andesite.

Control Section
Clay Content: averages 20 to 27 percent.
Rock Fragments: When mixed, averages 35 to 70 percent; 60 to 80 percent in the upper part, dominantly cobbles and stones; 10 to 15 percent gravel in the lower part.

A horizon - Value: 4 or 5 dry, 2 or 3 moist.
Chroma: 2 or 3, dry or moist.
Rock fragments: 10 to 15 percent; mostly gravel and cobbles.
Clay content: 8 to 15 percent.
Structure: Weak or moderate, very fine to medium, subangular blocky.
Consistence: Soft or slightly hard.
Reaction: Moderately acid or slightly acid.


2Bt1 horizon - Hue: 7.5YR or l0YR.
Value: 4 or 5 dry, 3 or 4 moist.
Chroma: 2 or 3.
Texture: Ashy loam.
Rock fragments: 60 to 80 percent, dominantly cobbles and stones.
Reaction: Slightly acid or neutral.

3Bt2 and 3Bt3 horizons Hue: 7.5YR or l0YR.
Value: 6 or 7 dry, 3 or 4 moist.
Chroma: 3 or 4, dry or moist.
Rock fragments: 10 to 15 percent, dominantly gravel.
Reaction: Slightly acid or neutral.

C horizon - Hue: 10YR or 7.5YR.
Value: 6 through 8 dry, 5 or 6 moist.
Chroma: 2 through 4, dry or moist.
Reaction: Slightly acid or neutral.

COMPETING SERIES: These are the Ashflat (T, CA) Cowbell (T, CA), Fendersflat, Paynepeak, Pyropatti, Snag and Tusune series. Ashflat, Cowbell, Fendersflat, Paynepeak, Snag, and Tusune lack a water table within the profile. Pyropatti soils have a mollic epipedon 30 to 60 inches thick.

GEOGRAPHIC SETTING: Boulderfan soils are on ground moraines and mountain valleys. They formed in glacial till and glacial debris, volcanic ash, alluvium and colluvium derived from andesite and andesitic tuff. Slopes are 2 to 8 percent. Elevations range from 6,680 to 8,000 feet. The mean annual precipitation is 20 to 25 inches, mean annual temperature is 43 to 45 degrees F., and the frost-free period is 60 to 80 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Lyonman, Tourn, and Waca soils. Lyonman and Tourn soils are moderately deep to paralithic contacts. soils are ashy-skeletal and are moderately deep to paralithic contacts. Waca soils are medial-skeletal and moderately deep to paralithic contacts.

DRAINAGE AND PERMEABILITY: Well drained; low or medium runoff; moderate permeability; moderately high or high saturated hydraulic conductivity class.

USE AND VEGETATION: These soils are used to provide livestock grazing and wildlife habitat, and for watershed purposes. The vegetation is dominated by mountain silver sagebrush, western needlegrass and bluegrass.

DISTRIBUTION AND EXTENT: Mountainous areas of northeastern California in the Warner Mountains. They are not extensive. MLRA 21.

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

SERIES ESTABLISHED: Surprise Valley-Home Camp Area, California and Nevada, 2004. The name is coined.

REMARKS:
Diagnostic horizons and features recognized in the pedon:

Mollic epipedon - The zone from the soil surface to 26 inches (A1, A2, 2Bt1 horizons).
Argillic horizon - The zone from 10 to 44 inches (2Bt1, 2Bt2 and 2Bt3 horizons).
Particle-size control section - The zone from 10 to 30 inches (2Bt1 and part of the 2Bt2 horizons).
Vitrandic feature and ashy, glassy texture modifier and mineralogy - 50 to 80 percent glass in all horizons.

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National Cooperative Soil Survey
U.S.A.