LOCATION THORTON                 WA

Established Series
Rev. CAB/SBC
06/2011

THORTON SERIES

The Thorton series consists of very deep, well drained soils formed in mixed volcanic ash and glacial drift over glacial drift on debris aprons, valley walls, and bedrock benches. Slopes are 5 to 40 percent. The mean annual precipitation is about 1,700 millimeters. The mean annual temperature is about 7 degrees C.

TAXONOMIC CLASS: Ashy over loamy-skeletal, amorphic over isotic, frigid Typic Udivitrands

TYPICAL PEDON: Thorton ashy sandy loam, on a debris apron landform with a SW facing slope of 35 percent at 549 meters elevation under coniferous forest vegetation. When described on June 7, 2007 the soil was slightly moist throughout. (Colors are for moist soil unless otherwise noted.)

Oi--0 to 4 cm; slightly decomposed plant material; abrupt wavy boundary.

Oe--4 to 8 cm; moderately decomposed plant material; few very fine roots; abrupt wavy boundary.

E--8 to 12 cm; brown (10YR 4/3) ashy sandy loam, brown (10YR 5/3) dry; weak fine subangular blocky structure; soft, very friable, nonsticky, nonplastic; few very fine, fine, medium, and coarse roots; very strongly acid (pH 5.0); clear irregular boundary.

Bw1--12 to 30 cm; brown (7.5YR 4/4) gravelly ashy sandy loam, brown (7.5YR 5/4) dry; weak medium subangular blocky structure; soft, very friable, nonsticky, nonplastic; common very fine and fine and few medium and coarse roots; 10 percent fine gravel, 10 percent medium and coarse gravel, and 5 percent mixed cobbles; strongly acid (pH 5.5); clear irregular boundary.

Bw2--30 to 46 cm; dark yellowish brown (10YR 4/4) gravelly ashy sandy loam, yellowish brown (10YR 5/4) dry; weak medium subangular blocky structure; soft, very friable, nonsticky, nonplastic; few very fine, fine, medium, and coarse roots; 15 percent fine gravel, 10 percent medium and coarse gravel, and 5 percent cobbles; strongly acid (pH 5.5); clear irregular boundary.

2BC1--46 to 60 cm; olive brown (2.5Y 4/4) very gravelly sandy loam, light olive brown (2.5Y 5/4) dry; weak fine subangular blocky structure; soft, very friable, nonsticky, nonplastic; few very fine and fine roots; 15 percent fine gravel, 25 percent medium and coarse gravel, and 10 percent cobbles; moderately acid (pH 6.0); clear irregular boundary.

2BC2--60 to 150 cm; olive brown (2.5Y 4/3) very gravelly sandy loam, light olive brown (2.5Y 5/3) dry; weak fine subangular blocky structure; soft, very friable, nonsticky, nonplastic; few very fine and fine roots; 10 percent fine gravel, 20 percent medium and coarse gravel, and 10 percent cobbles; moderately acid (pH 6.0).

TYPE LOCATION: North Cascades National Park, Whatcom County, Washington; Section 19, T38N, R14E Willamette Meridian; Pumpkin Mountain, Washington USGS quadrangle; 48 degrees, 46 minutes, 15 seconds north latitude and 121 degrees, 1 minutes, 59 seconds west longitude; NAD83; UTM 644516 meters E, 5403848 meters N, zone 10N.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 6 to 8 degrees C. Frigid soil temperature regime.
Soil moisture control section: dry for less than 45 consecutive days from June to October. Udic soil moisture regime.
Thickness of volcanic ash mantle: 38 to 75 centimeters
The particle-size control section in this soil is contrasting. Most characteristics are listed by horizon.

A horizons are sometimes present with thickness ranging from 0 to 12 centimeters, textures of SL or COSL, reaction of very strongly acid or strongly acid, hue of 7.5YR or 10YR, moist value of 2 or 3, and moist chroma of 1or 2.

E horizon:
Hue - 10YR or 7.5YR
Value - 3 or 4 moist, 5 or 6 dry
Chroma - 2 or 3 moist or dry
Fine earth texture - ashy FSL or ashy SL
Rock fragments - 0 to 35 percent total
0 to 20 percent gravel
0 to 10 percent cobbles
Clay content - 1 to 6 percent
Volcanic glass - 15 to 50 percent
Reaction - extremely acid to strongly acid
Thickness - 0 to 7 centimeters

Bw horizons:
Hue - 10YR or 7.5YR
Value - 3 to 5 moist, 4 to 6 dry
Chroma - 3 to 6 moist or dry
Fine earth texture - ashy FSL, ashy SL or ashy COSL
Rock fragments - 10 to 35 percent total
10 to 30 percent gravel
0 to 10 percent cobbles
0 to 10 percent stones
Clay content - 2 to 10 percent
Volcanic glass - 20 to 50 percent
Reaction - strongly acid to moderately acid
Thickness - 34 to 95 centimeters

2BC horizons:
Hue - 2.5Y or 5Y
Value - 3 to 5 moist, 4 to 6 dry
Chroma - 2 to 4 moist or dry
Fine earth texture - SL, LS, COS
Rock fragments - 35 to 80 percent total
20 to 50 percent gravel
5 to 30 percent cobbles
0 to 10 percent stones
Clay content - 0 to 6 percent
Volcanic glass - 0 to 15 percent
Reaction - strongly acid to slightly acid

COMPETING SERIES: These are the Boulderjud, Bulgar, Bullroar, Deardorf, Ferguson, Gutridge, Honeyjones, Huckle, Stalter, Threecent and Twobit series. All these soils are ashy silt loam in the upper part of the particle-size control section. In addition, Deardorf, Gutridge, and Threecent soils are deep to bedrock. Boulderjud and Huckle soils are deep to a paralithic contact. Stalter soils are moderately deep to a paralithic contact.

GEOGRAPHIC SETTING: The Thorton soils are on debris aprons, valley walls, and bedrock benches at elevations of 400 to 1,000 meters. Slopes are 5 to 40 percent. These soils formed in volcanic ash mixed with reworked glacial drift over glacial drift. The climate consists of cool, dry summers and cold, wet winters. Mean annual precipitation ranges from 1,500 to 2,300 millimeters, and mean annual air temperature ranges from 5 to 8 degrees C. Frost-free season is 60 to 90 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cosho (T), Easy (T), and Tricouni (T) soils. Easy soils have albic and spodic horizons and form on more stable portions of the same landforms. Cosho soils have coarser textures at depth and form on lower slopes. Tricouni soils have andic soil properties to a depth of less than 36 centimeters and form on the more active portions of each landform.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained soils, high to very high saturated hydraulic conductivity.

USE AND VEGETATION: Used for watershed, recreation, woodland and wildlife habitat. Native vegetation is western hemlock, Douglas-fir and western redcedar with an understory of Cascade Oregongrape, vine maple, prince's pine, baldhip rose, pachistima, western rattlesnake plantain, broadleaf star flower, orange honeysuckle, red elderberry, serviceberry, twinflower, and white-veined wintergreen

DISTRIBUTION AND EXTENT: Western slopes of the North Cascade Mountains, Washington. MLRA 3. Series is of moderate extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon

SERIES ESTABLISHED: North Cascades National Park Service Complex, 2011.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: 0 to 18 centimeters (Oi, Oe, E, and upper 6 centimeters of the Bw1 horizon)
Cambic horizon: 12 to 46 centimeters (Bw1 and Bw2 horizons)
Andic soil properties: 8 to 46 centimeters (E, Bw1, and Bw2 horizons)

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National Cooperative Soil Survey
U.S.A.