LOCATION SILEX COEstablished Series
TAXONOMIC CLASS: Loamy, mixed, superactive Lithic Haplocryalfs
TYPICAL PEDON: Silex loam, on a west facing, simple, 15 percent slope in planted lodgepole pine woodland at an elevation of 10,000 feet. (Colors are for dry soil unless otherwise noted.)
Oi--0 to 1 inch; organic layer of roots, leaves, and needles. (0 to 3 inches thick)
E--1 to 4 inches; pinkish gray (7.5YR 6/2) loam, brown (7.5YR 4/2) moist; moderate medium granular structure; soft, friable, slightly sticky and slightly plastic; 5 percent gravel; strongly acid (pH 5.2); clear smooth boundary. (2 to 7 inches thick)
Bt1--4 to 10 inches; brown (7.5YR 5/4) clay loam, brown (7.5YR 4/4) moist; weak medium subangular blocky structure parting to moderate medium granular; slightly hard, friable, moderately sticky and, moderately sticky and moderately plastic; 5 percent gravel and 3 percent cobbles; few distinct clay films on faces of peds; very strongly acid (pH 4.8); clear wavy boundary. (4 to 12 inches thick)
Bt2--10 to 18 inches; light brown (7.5YR 6/4) sandy clay loam, brown (7.5YR 4/4) moist; weak medium subangular blocky structure parting to moderate medium granular; slightly hard, friable, slightly sticky and slightly plastic; 10 percent gravel and 3 percent cobbles; few distinct clay films on faces of peds; very strongly acid (pH 4.8); abrupt wavy boundary. (0 to 10 inches thick)
R--18 inches; hard limestone bedrock, with cracks in the upper part.
TYPE LOCATION: San Juan County, Colorado; about 6 miles south of Silverton, Colorado; located in an unsectionized area, about 1,400 feet south and 400 feet east of the projected northwest corner (in the SW quarter of the NW quarter) of Sec. 23, T. 40 N., R. 8 W.; Snowdon Peak USGS quad.; lat. 37 degrees, 43 minutes, 23 seconds N; long. 107 degrees, 43 minutes, 24 seconds W.; NAD 27
RANGE IN CHARACTERISTICS: (depths given are measured from the mineral soil surface)
Soil moisture regime: udic; dry in some part of the moisture control section for less than 45 cumulative days (typic udic subclass)..
Mean annual soil temperature: 35 to 40 degrees F.
Mean summer soil temperature: 41 to 46 degrees F. with an 0 horizon
Base saturation: 50 to 70 percent (estimated)
Depth to lithic contact: 7 to 20 inches
Particle-size control section:
Clay content: 20 to 35 percent
Rock fragment content: 0 to 25 percent
E horizon:
Hue: 7.5YR or 10YR
Value: 5 to 7 dry, 4 or 5 moist
Chroma: 2 or 3, dry and moist
Rock fragment content: 0 to 15 percent
Reaction: very strongly acid or strongly acid
Bt horizon:
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 3 to 6, dry and moist
Texture, fine earth fraction: CL, L, or SCL
Rock fragment content: 0 to 25 percent
Reaction: very strongly acid or strongly acid
COMPETING SERIES: These are the
Palomino and
Scotch series.
Palomino: are neutral to moderately acid with mean annual temperature of 42 to 45 degrees F.
Scotch: have hue of 5YR or 2.5YR and are formed from redbed sandstone and shale.
GEOGRAPHIC SETTING:
Parent material: slope alluvium derived from limestone and sandstone.
Landform: mountain slopes, mesas, and structural benches.
Slopes: 10 to 20 percent
Elevation: 10,000 to 11,000 feet
Mean annual air temperature: 32 to 36 degrees F.
Mean annual precipitation: 30 to 45 inches.
Wettest months: July and August receive slightly more precipitation than other months.
Driest months: May and June receive the least precipitation, however the soils are often still covered with snow to mid June.
Frost-free period: 40 to 60 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Needleton and Snowdon series. Both are on mountain slopes.
Needleton soils are very deep.
Snowdon soils have more than 35 percent rock fragments in the particle size control section.
DRAINAGE AND PERMEABILITY: Well drained, medium to high runoff, moderately slow permeability.
USE AND VEGETATION: These soils are used for timber production, livestock grazing, and wildlife habitat. Native vegetation consists mostly of Engelmann's spruce, subalpine fir, whortleberry, sedges, mountain brome, Thurber's fescue, and needlegrass.
DISTRIBUTION AND EXTENT: Southwestern Colorado. LRR E, MLRA 48A. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: San Juan County, Colorado, Animas-Dolores Soil Survey Area, 1989. The name is taken from a nearby mountain peak.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: The zone from 1 to 4 inches. (E horizon)
Argillic horizon: The zone from 4 to 18 inches. (Bt1 and Bt2 horizons)
Lithic contact: Hard bedrock at 18 inches.
Particle size control section: The zone from 4 to 18 inches. (Bt1 and Bt2 horizons)
Keys to Soil Taxonomy: Classified according to the Eighth Edition, 1998
Activity class is presumed based on general trend of soils in the area.