LOCATION TWELVEMILE              OR

Established Series
Rev. RHB/RWL/CEG
11/2023

TWELVEMILE SERIES

Landform-mountain slopes, hills, scarpslopes
Slope--0 to 60 percent
Parent material--volcanic ash mixed with colluvium and residuum, primarily from rhyolite
Mean annual precipitation--about 760 mm
Mean annual air temperature--about 7 degrees C
Depth class--very deep
Drainage class--somewhat excessively drained
Soil moisture regime--xeric
Soil temperature regime--frigid
Soil moisture subclass--typic

TAXONOMIC CLASS: Ashy-skeletal, glassy, frigid Typic Vitrixerands

TYPICAL PEDON: Twelvemile very gravelly ashy fine sandy loam, in forest on an 18 percent northwest facing slope at elevation of about 2086 m

Oi--0 to 3 cm; partially decomposed conifer needles

A1--3 to 8 cm; very gravelly ashy fine sandy loam, brown (10YR 5/3) dry, dark brown (10YR 3/3) moist; moderate fine granular structure; slightly hard, very friable, nonsticky and nonplastic; many roots; many irregular pores; 10 percent cobbles, 25 percent gravel; slightly acid (pH 6.3); clear smooth boundary. (3 to 15 cm thick)

A2--8 to 31 cm; very gravelly ashy fine sandy loam, pale brown (10YR 6/3) dry, brown (10YR 4/3) moist; weak fine and medium subangular blocky structure parting to moderate fine granular; slightly hard, friable, nonsticky and nonplastic; many roots; common very fine and fine irregular pores; 10 percent cobbles, 25 percent gravel; slightly acid (pH 6.1); gradual wavy boundary. (18 to 36 cm thick)

Bw--31 to 64 cm; very gravelly ashy fine sandy loam, pale brown (10YR 6/3) dry, dark yellowish brown (10YR 4/4) moist; weak fine and medium subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; many roots; many irregular pores; 40 percent gravel; slightly acid (pH 6.1); clear wavy boundary. (25 to 76 cm thick)

Bt--64 to 97 cm; very cobbly ashy fine sandy loam, light yellowish brown (10YR 6/4) dry, brown (10YR 5/3) moist; moderate fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and nonplastic; many roots; few very fine tubular pores; few faint clay films on peds and in pores; 20 percent cobbles, 35 percent gravel; slightly acid (pH 6.1); gradual wavy boundary. (0 to 43 cm thick)

C--97 to 155 cm; very cobbly ashy sandy loam, very pale brown (10YR 7/3) dry, brown (10YR 5/3) moist; massive; slightly hard, friable, slightly sticky and nonplastic; common very fine and fine roots and few medium and coarse; few very fine and fine tubular pores; 20 percent cobbles, 25 percent gravel; slightly acid (pH 6.1).

TYPE LOCATION: Lake County, Oregon, about 7 miles north and 8 miles east of the town of Lakeview, OR; SE1/4, NE1/4 of section 12 T. 38 S., R. 21 E., Willamette Meridian; Crook Peak, Oregon USGS quadrangle; latitude 42.2905950 degrees north, longitude 120.1818590 degrees west, datum WGS84 (coordinates estimated from PLSS details)

RANGE IN CHARACTERISTICS:

Soil Temperature: frigid regime
Mean annual soil temperature--6 to 8 degrees C
Moisture control section--20 to 60 cm; xeric regime; moist in the winter and spring; dry in all parts for 60 to 100 consecutive days after the summer solstice

Particle-size control section
*Clay content--7 to 18 percent
*Sand content--55 to 90 percent
*Total Rock fragment content--35 to 60 percent, mainly rhyolite
*Gravel content--25 to 40 percent
*Cobble and stone content--5 to 20 percent
*Reaction--moderately to slightly acid (pH 5.6 to 6.5)

Estimated andic properties, from the mineral soil surface to the C horizon:
*Medium to very coarse sand in the .02 to 2.0 mm fraction--less than 50 percent
*Volcanic glass content--50 to 70 percent in the very fine sand fraction
*1/3-bar bulk density--0.85 to 1.10 g/cm3

A horizon
Value--3 or 4 moist, 5 or 6 dry
Chroma--2 to 4, moist or dry
Fine-earth texture--ashy fine sandy loam, ashy loamy sand
Total content of rock fragments--30 to 50 percent
Gravel content--25 to 40 percent
Cobble and stone content--0 to 8 percent

B horizons
Value--3 to 5 moist; 5 to 7 dry
Chroma--3 to 5 moist; 2 to 5 dry
Fine-earth texture-ashy loamy sand, ashy sandy loam, ashy fine sandy loam, ashy loam
Total content of rock fragments--35 to 60 percent
Gravel content--25 to 40 percent
Cobble and stone content--0 to 20 percent

C horizon
Value--4 to 6 moist, 6 to 8 dry
Chroma--3 or 4 moist, 2 to 4 dry
Fine-earth texture--ashy sandy loam, ashy fine sandy loam, ashy loamy sand
Total content of rock fragments--35 to 60 percent
Gravel content--25 to 35 percent
Cobble content--10 to 25 percent

COMPETING SERIES:
Doe--greater than 18 percent clay in the particle size control section; volcanic ash mantel 50 to 89 cm thick; formed in granitic colluvium over glacial outwash or ablation till, at elevations of 850 to 1430 m; 95 to 120 frost free days
Grenet--20 to 40 inches to a paralithic contact; dry 45 to 60 days after the summer solstice
Kusu--40 to 60 inches to a lithic contact; 18 to 25 percent clay in the particle-size control section
Natkim--dry 45 to 60 days after the summer solstice; mean annual precip 1015 to 1525 mm; formed in gladial till, at elevations of 670 to 1340 m
Pettijohn--greater than 18 percent clay in the particle size control section; volcanic ash mantel 75 to 115 cm thick; formed in volcanic ash and granitic colluvium, at elevations of 850 to 1430 m; 90 to 120 frost free days
Roundknoll--dry 100 to 120 days after the summer solstice; slightly alkaline to moderately alkaline throughout; has secondary accumulation of calcium carbonate on cinders in Bk horizons
Stices--dry 45 to 60 days after the summer solstice; volcanic ash mantel 35 to 75 cm thick;
Yallani--greater than 18 percent clay in the particle size control section; less than 50 percent volcanic glass; mean annual precip 1015 to 1525 mm; elevations of 550 to 915 m

GEOGRAPHIC SETTING:
Elevation--1475 to 2200 m
Climate--cool moist winters, warm dry summers
Mean annual air temperature-4.4 to 7.2 degrees C
Mean annual precipitation--390 to 900 mm
Frost-free period--30 to 80 days

GEOGRAPHICALLY ASSOCIATED SOILS:
Drakespeak--loamy-skeletal in the particle-size control section; umbric epipedon
Longjohn--cryic soil temperature regime
Rogger--mollic epipedon
Woodchopper--mollic epipedon
Mound--mollic epipedon
Polander--ashy in the particle-size control section

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY:
Drainage class--Somewhat excessively drained
Saturated hydraulic conductivity (Ksat)--high

USE AND VEGETATION:
Use--timber production, watershed, wildlife habitat, recreation, and grazing by livestock
Vegetation--white fir, ponderosa pine, common snowberry, heartleaf arnica, Wheeler's bluegrass

DISTRIBUTION AND EXTENT: Klamath and Shasta Valleys and Basins, Oregon; MLRA 21; small extent

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Davis, California

SERIES ESTABLISHED:
Lake County, Oregon; Southern Part; 1991.

REMARKS:
Diagnostic horizons and features in this pedon
*Ochric epipedon
*Cambic horizon--31 to 97 cm
*Andic soil properties--3 to 155 cm
*Particle-size control section--3 to 103 cm

The 15 bar water on air-dried samples is 5 to 8 percent for the profile. Phosphorous retention is assumed to be greater than 25 percent and the Al-Ox plus Fe-Ox is assumed to be greater than 0.4 percent.

9/19/2023 - This official series description was updated according to SSR01 Technical Note-Content and Format of Official Series Descriptions (revised 11/2017). Most of the changes were in formatting. Also added ashy modifiers and volcanic ash parent materials, added ashy loamy sand textures to the RIC, expanded ranges of elevation, precipitation, and temperature, and updated competing series section (see trip report from May 2015 field review from OR683 Soil Survey Area Project)

ADDITIONAL DATA:
Laboratory data is available for three horizons, (A2, Bw, Bt) S87OR-037-004.

Forest Service vegetative site CW-C4-11 for the white fir-ponderosa pine community.

NASIS SITE ID--S1987OR037004
NASIS PEDON ID--87OR037004

---

National Cooperative Soil Survey
U.S.A.