LOCATION TWOBIT ORTentative Series
TAXONOMIC CLASS: Ashy over loamy-skeletal, amorphic over isotic, frigid Typic Udivitrands
TYPICAL PEDON: Twobit gravelly ashy silt loam - woodland, on a 65 percent north-facing slope at an elevation of 5,100 feet. (Colors are for moist soil unless otherwise noted. Soil textures are apparent field textures.)
Oi--0 to 3 inches; needles, leaves, twigs and logs
Oe--3 to 5 inches; moderately decomposed needles, leaves, twigs and logs
A--5 to 7 inches; dark brown (7.5YR 3/3) gravelly ashy silt loam, brown (7.5YR 4/4) dry; weak very fine subangular blocky structure; soft, very friable, nonsticky, nonplastic and weakly smeary; many very fine and fine, and common medium roots; common very fine irregular pores; 15 percent gravel, 5 percent cobbles, and 5 percent stones; neutral (pH 7.0); clear wavy boundary. (2 to 5 inches thick)
Bw1--7 to 15 inches; dark reddish brown (5YR 3/4) cobbly ashy silt loam, brown (7.5YR 5/4) dry; weak fine and very fine subangular blocky structure; soft, very friable, nonsticky, nonplastic and weakly smeary; many very fine, common fine, many medium and common coarse roots; few very fine irregular pores; 15 percent gravel, 10 percent cobbles, and 5 percent stones; neutral (pH 7.0); gradual smooth boundary.
Bw2--15 to 19 inches; strong brown (7.5YR 4/6) cobbly ashy silt loam, strong brown (7.5YR 5/6) dry; weak fine and very fine subangular blocky structure; soft, very friable, nonsticky, nonplastic and weakly smeary; many very fine and common fine, medium and coarse roots; few very fine irregular pores; 10 percent gravel, 15 percent cobbles, and 5 percent stones; neutral (pH 7.0); clear wavy boundary. (Bw horizons combined are 12 to 19 inches thick)
2Eb--19 to 25 inches; brown (7.5YR 4/4) very cobbly loam, brown (7.5YR 5/4) dry; weak fine and very fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; common very fine, fine, medium and coarse roots; few very fine irregular pores; 25 percent gravel, 15 percent cobbles, and 10 percent stones; neutral (pH 7.0); gradual smooth boundary. (4 to 8 inches thick)
2Bwb--25 to 41 inches; brown (7.5YR 4/4) extremely cobbly loam, brown (7.5YR 5/4) dry; weak very fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; common very fine, fine and medium and few coarse roots; few very fine irregular pores; 30 percent gravel, 20 percent cobbles, and 15 percent stones; neutral (pH 7.0); abrupt irregular boundary. (4 to 16 inches thick)
2R--41 inches; metavolcanic bedrock
TYPE LOCATION: Grant County, Oregon
Section 36 (NW , SW , SW ), T. 11 S., R. 33 E.
Latitude: 44 degrees, 33 minutes, 46 seconds N
Longitude: 118 degrees, 41 minutes, 31 seconds W
UTM Coordinates: Zone 11; 4,935,780 northing; 365,630 easting
USGS Quadrangle: Dixie Meadows
RANGE IN CHARACTERISTICS:
Soil Temperature: frigid regime
Mean Annual Soil Temperature: 40 to 45 degrees F
Mean Summer Soil Temperature: 48 to 54 degrees F
Mean Winter Soil Temperature: 32 to 37 degrees F
Soil Moisture: udic regime, dry 30 to 45 days in summer
Particle-size Control Section: mineral soil surface to bedrock
Upper part (ashy): 14 to 24 inches thick
Clay content: 3 to 8 percent
Rock fragment content: 5 to 30 percent
Lower part (loamy-skeletal): 8 to 22 inches thick
Clay content: 18 to 27 percent
Rock fragment content: 55 to 80 percent
Diagnostic Horizons and Features:
andic soil properties: upper boundary at the mineral surface; 14 to 24 inches thick
A1 + 1/2Fe(aox): 1.0 to 3.0 percent
bulk density: 0.65 to 1.0 g/cc
P retention: 40 to 90 percent
0.02-2.0 mm fraction: 40 to 60 percent of fine earth
glass content in the 0.02-2.0 mm fraction: 60 to 90 percent
water content at 1500 kPa (air dried): 5 to 12 percent
8Si + 2Fe (aox): 5 to 12 percent
8Si - 2Fe (aox): 4 to 8 percent
ochric epipedon: 2 to 5 inches thick
cambic horizon:
upper: 12 to 19 inches thick
lower: 4 to 16 inches thick
lithic contact depth: 20 to 40 inches
Major Horizons:
A horizon
color, moist: 5YR 3/2; 7.5YR 3/3, 3/4, 4/4; 10YR 3/2
color, dry: 7.5YR 4/2, 4/4, 5/4, 5/6; 10YR 5/4
texture: ASHY-SIL, GR-ASHY-SIL
clay content: 2 to 10 percent
rock fragment content: 0 to 30 percent
gravel: 0 to 30 percent
cobbles: 0 to 5 percent
stones: 0 to 5 percent
reaction: slightly acid to neutral; pH: 6.1 to 7.3
organic carbon: 1.0 to 5.0 percent
Bw horizon
color, moist: 5YR 3/4; 7.5YR 4/4, 4/6, 5/6; 10YR 3/4
color, dry: 7.5YR 5/4, 5/6, 6/4, 7/4; 10YR 6/4, 7/4
texture: ASHY-SIL, GR-ASHY-SIL, CB-ASHY-SIL
clay content: 3 to 8 percent
rock fragment content: 5 to 30 percent
gravel: 2 to 25 percent
cobbles: 0 to 15 percent
stones: 0 to 10 percent
reaction: slightly acid to neutral; pH: 6.1 to 7.3
organic carbon: 0.6 to 1.0 percent
2Eb horizon:
color, moist: 7.5YR 4/4, 5/4; 10YR 4/3
color, dry: 7.5YR 5/4; 10YR 6/3, 6/4
texture: CBV-L, GRV-L, GRV-SIL
clay content: 15 to 20 percent
rock fragment content: 50 to 60 percent
gravel: 10 to 40 percent
cobbles: 0 to 20 percent
stones: 0 to 10 percent
reaction: slightly acid to neutral; pH: 6.1 to 7.3
2Bwb horizon:
color, moist: 5YR 4/6; 7.5YR 3/4, 4/4; 10YR 4/3, 4/4
color, dry: 7.5YR 5/4, 5/6; 10YR 5/4, 6/4
texture: GRV-L, CBV-SIL, CBX-L, GRX-L
clay content: 18 to 27 percent
rock fragment content: 50 to 85 percent
gravel: 30 to 70 percent
cobbles: 10 to 30 percent
stones: 0 to 15 percent
reaction: slightly acid to neutral; pH: 6.1 to 7.3
COMPETING SERIES:
Twobit (T) -- moderately deep (20 to 40 inches) to a lithic contact; ashy part of the pscs has 60 to 90 percent glass in the 0.02 to 2.0 mm fraction; loamy-skeletal part of pscs has 18 to 27 percent clay; formed in volcanic ash over colluvium and residuum from metavolcanic rock
Boulderjud -- deep (40 to 60 inches) to a paralithic contact of weathered granite; ashy part of the pscs has 30 to 65 percent glass in the 0.02 to 2.0 mm fraction; has 2Bt horizons below the ash mantle; formed in coarse-silty volcanic ash over colluvium and residuum from granitic rocks
Bulgar (T) -- very deep (>60 inches); ashy part of the pscs has 60 to 90 percent glass in the 0.02 to 2.0 mm fraction; ash mantle with greater than 5 percent rounded rock fragments; has 2EBb, 2Ab, 2AEb, or 2Eb buried surface horizon below the ash mantle; loamy-skeletal throughout the series control section (to 80 inches); glacial rock fragments in lower pscs are rounded; formed in volcanic ash over, mostly granitic, till
Bullroar (T) -- very deep (>60 inches); ashy part of the pscs has 60 to 90 percent glass in the 0.02 to 2.0 mm fraction; ash mantle with less than 5 percent rounded rock fragments; texture in 2BC horizon is loam, sandy loam or loamy sand (loamy-skeletal); has 2EBb, 2ACb, or 2Eb buried surface horizon below the ash mantle; coarse sand and gravel in lower part of series control section (60 to 80 inches); rounded alluvial fragments in lower pscs; formed in volcanic ash over mixed alluvium
Deardorf (T) -- moderately deep (20 to 40 inches) to a lithic contact; ashy part of the pscs has 60 to 90 percent glass in the 0.02 to 2.0 mm fraction; loamy-skeletal part of pscs has 12 to 17 percent clay; formed in volcanic ash over colluvium and residuum from andesitic basalt
Ferguson -- very deep (>60 inches); texture of ash is very fine sandy loam; ashy part of the pscs has 30 to 55 percent glass in the 0.02 to 2.0 mm fraction; has 2Bw horizon; depth to 2C horizon with loamy coarse sand or sand (sandy-skeletal) is 40 to 60 inches; formed in volcanic ash over, mostly granitic, glaciofluvial deposits
Gutridge (T) -- deep (40 to 60 inches) to a lithic contact; ashy part of the pscs has 60 to 90 percent glass in the 0.02 to 2.0 mm fraction; rock fragments in the loamy-skeletal part are subangular; formed in volcanic ash over colluvium from metasedimentary rock
Stalter (T) -- moderately deep (20 to 40 inches) to a paralithic contact of weathered granite; ashy part of the pscs has 60 to 90 percent glass in the 0.02 to 2.0 mm fraction; formed in volcanic ash over colluvium and residuum from granite
Threecent (T) -- moderately deep (20 to 40 inches) to a lithic contact; ashy part of the pscs has 60 to 90 percent glass in the 0.02 to 2.0 mm fraction; loamy-skeletal part of pscs has 4 to 12 percent clay; formed in volcanic ash over colluvium and residuum from metasedimentary rock
Similar soils with mixed mineralogy.
Bonnash -- very deep (>60 inches); ashy part of the pscs has 5 to 30 percent glass in the 0.02 to 2.0 mm fraction; has 2E/Bw horizon; depth to 2C horizon with loamy coarse sand (sandy-skeletal) is 25 to 45 inches, formed in volcanic ash over mixed alluvium or glaciofluvial deposits
Bouldercreek -- very deep (>60 inches); ashy part of the pscs has 15 to 65 percent glass in the 0.02 to 2.0 mm fraction; Bw horizon has 0 to 25 percent subangular rock fragments; has 2BC and 2C horizons below the ash mantle that contain mica flakes; formed in volcanic ash and loess over colluvium from schist, gneiss, granitic or quartzite bedrock
Dewberry -- very deep (>60 inches); ashy part of the pscs has 12 to 20 percent glass in the 0.02 to 2.0 mm fraction; texture in 2C horizon is sandy loam (loamy-skeletal), does not have 2EBb, 2ACb, or 2Eb buried surface horizon below the ash mantle; formed in volcanic ash over mixed alluvium
Stevie -- very deep (>60 inches); ashy part of the pscs has 12 to 20 percent glass in the 0.02 to 2.0 mm fraction; Bw horizon has 15 to 30 percent rock fragments; has 2E/Bw horizon below the ash mantle, excessively drained; formed in volcanic ash over colluvium
GEOGRAPHIC SETTING:
Landform: volcaniclastic depositional and relatively stable backslopes of metavolcanic mountains, on convex lower backslopes, planer mid to upper backslopes and concave shoulder slopes
Slope gradient: 0 to 90 percent
Parent material: volcaniclastic volcanic ash overlying colluvium
Lithology: Mazama ash over metavolcanic rocks
Elevation: 4,200 to 6,000 feet
Climate: cold, wet winters and warm, dry summers
Mean annual precipitation: 26 to 41 inches
Mean annual air temperature: 37 to 42 degrees F
Frost-free period: 30 to 80 days
GEOGRAPHICALLY ASSOCIATED SOILS:
Carbeleek (T): occur on backslopes; >60 inches to bedrock; <14 inches volcanic ash mantle; 18 to 31 percent clay in pscs
Honeymooncan (T): occur on backslopes; 40 to 60 inches to a lithic contact; has an argillic horizon
DRAINAGE AND PERMEABILITY:
Drainage: well drained
Permeability: moderately rapid over moderate
USE AND VEGETATION:
Use: timber production, wildlife habitat, recreation, watershed, and livestock grazing
Native vegetation: Grand fir, western larch, lodgepole pine, Douglas fir, ponderosa pine, big huckleberry, grouse huckleberry; common princes pine, longtube twinflower, white hawkweed, sidebells pyrola, bigleaf sandwort, pinegrass, western fescue, northwest sedge and elk sedge.
Ecological site: Dominant: ABGR/LIBOL2; Others may include: ABGR/VAME, PICO(ABGR)/VAME/CARU and ABGR/VASC0
DISTRIBUTION AND EXTENT:
MLRA - E43c
Distribution: South Central Blue Mountains of Eastern Oregon
Extent: moderate
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES PROPOSED: Grant County, Oregon, 2003. The name is coined.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
ochric epipedon: 5 to 7 inches (A horizon)
cambic horizons:
upper: 7 to 19 inches (Bw1 and Bw2 horizons)
lower: 25 to 41 inches (2Bwb horizon)
particle-size control section:
ashy part: 5 to 19 inches (A, Bw1, and Bwb2 horizons)
loamy-skeletal part: 19 to 41 inches (2Eb and 2Bwb horizons)
lithic contact: 41 inches (2R layer)