LOCATION SNOWDON CO+WY
Established Series
Rev. JPP/TWH/KLS
03/2018
SNOWDON SERIES
The Snowdon series consists of shallow, well drained soils that formed in slope alluvium or colluvium derived from rhyolite, sandstone, and limestone. Snowdon soils are on mountain slopes, structural benches, mesas, and ridges. Slopes range from 5 to 90 percent. Mean annual precipitation is about 889 mm and the mean annual temperature is about 2.2 degrees C.
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Lithic Haplocryalfs
TYPICAL PEDON: Snowdon very stony loam, on a west facing, simple, 30 percent slope in spruce-fir woodland at an elevation of 3,109 meters. (Colors are for dry soil unless otherwise noted.) When described on August 11, 1983 the soil was moist from 0 to 46 cm.
Oi--0 to 5 cm; organic layer of needles, twigs, and leaves.
A--5 to 15 cm; light reddish brown (5YR 6/3) very stony loam, reddish brown (5YR 4/3) moist; moderate medium granular structure; soft, friable, slightly sticky and nonplastic; 15 percent gravel, 20 percent cobble, 20 percent stones; very strongly acid (pH 4.8); clear smooth boundary. (0 to 13 cm thick)
E--15 to 33 cm; pinkish gray (7.5YR 6/2) very stony sandy loam, brown (7.5YR 5/3) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; 15 percent gravel, 20 percent cobble, 20 percent stones; very strongly acid; (pH 4.6); clear wavy boundary. (8 to 20 cm thick)
Bt--33 to 50 cm; reddish brown (5YR 5/4) extremely stony sandy clay loam,, reddish brown (5YR 4/4) moist; weak medium subangular blocky structure parting to moderate medium granular; soft, very friable, slightly sticky and slightly plastic; common distinct clay films on the faces of peds; 10 percent gravel, 25 percent cobble, and 25 percent stones; very strongly acid (pH 5.0); abrupt wavy boundary. (13 to 30 cm thick)
R--50 cm; hard rhyolite bedrock
TYPE LOCATION: San Juan County, Colorado; Kendall Gulch road, about 3.0 kilometers south of Silverton. Along old mine road off of the main road; located about 671 meters east and 320 meters south of the northwest corner of Sec. 29, T. 41 N., R. 7 W.; Silverton USGS quad; Lat. 37 degrees, 47 minutes, 12 seconds, N. and Long. 107 degrees, 39 minutes, 38 seconds, W., NAD 27.
RANGE IN CHARACTERISTICS: (depths given are measured from the mineral soil surface)
Soil moisture regime: Typic udic
Mean annual soil temperature: 1.1 to 3.3 degrees C.
Mean summer soil temperature: 4.4 to 7.8 degrees C., with an O horizon
Surface rock fragments: 0 to 20 percent
Base saturation: 50 to 70 percent (NH4OAc) (estimated)
Depth to lithic contact: 25 to 50 cm
Particle-size control section:
Clay content: 18 to 35 percent
Rock fragment content: 35 to 75 percent rhyolite gravel, cobbles, or stone
Reaction (pH): 4.5 to 6.5 (slightly acid to very strongly acid)
A horizon
Hue: 5YR to 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 1 to 3, dry or moist
Texture, fine earth fraction: loam, sandy loam
Rock fragment content: 5 to 65 percent
Reaction (pH): 4.5 to 6.5
E horizon
Hue: 5YR to 10YR
Value: 6 or 7 dry, 4 or 5 moist
Chroma: 2 to 4, dry or moist
Texture, fine earth fraction: sandy loam, loam
Rock fragment content: 5 to 65 percent
Reaction (pH): 4.5 to 6.5
Bt horizon
Hue: 5YR or 7.5YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 to 6, dry and moist
Texture, fine earth fraction: sandy clay loam, loam, or clay loam
Rock fragment content: 35 to 75 percent
Reaction (pH): 4.5 to 6.5
COMPETING SERIES:
Hapjack (WY) - have granite rock fragments
Herakle (CO) - have horizons of calcium carbonate accumulation and an ustic moisture regime
Redfern (MT) - have an ustic moisture regime
Whiteman (UT) - have neutral or moderately alkaline reaction
GEOGRAPHIC SETTING:
Landform - mountain slopes, structural benches, mesas, and ridges
Elevation - 2,500 to 3,510 meters
Slopes - 5 to 90 percent
Parent material - slope alluvium or colluvium derived from rhyolite, sandstone, and limestone
Mean annual air temperature - -1.1 to 3.3 degrees C.
Mean annual precipitation - 635 to 1,143 mm
Precipitation pattern - wettest months are July and August receive slightly more precipitation than other months; while May and June receive the least precipitation and are driest, however the soils are still moist from snowmelt and are often covered with snow through May.
Frost-free period - 40 to 75 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: well drained, medium to high runoff, moderate permeability.
USE AND VEGETATION: These soils are used for wildlife habitat, recreation, woodland, and livestock grazing. The principal native vegetation is Engelmann's spruce, Rocky Mountain Douglas Fir, subalpine fir, and quaking aspen. Grasses include Thurber's fescue, mountain brome and bluegrass.
DISTRIBUTION AND EXTENT: Western Colorado and parts of Wyoming. LRR E, MLRA 43B, 48A; large extent.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Ouray Soil Survey Area, Colorado, 1998. Series proposed in the Animas-Dolores Survey Area, 1984.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Albic horizon - 15 to 33 cm (E horizon)
Argillic horizon - 33 to 50 cm (Bt horizon)
Lithic contact - 50 cm to hard bedrock (R layer)
Particle size control section - 33 to 50 cm (Bt horizon)
This soil is presumed to have greater than 35 percent base saturation (sum of cations) at the lithic contact, hence meets the requirement for Alfisols. This needs to be confirmed by further study.
Snowdon soils have a cryic temperature regime and are in a udic soil moisture regime with a typic subclass.
National Cooperative Soil Survey
U.S.A.