LOCATION HORSETHIEF COEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Typic Palecryalfs
TYPICAL PEDON: Horsethief loam, on a simple, NW facing slope of 60 percent, in spruce-fir woodland at an elevation of 11,300 feet. (Colors are for dry soil unless otherwise noted). Described on August 6, 1980.
Oi--0 to 2 inches; litter, needles, and partially decomposed organic material.
A--2 to 5 inches; pale brown (10YR 6/3) loam, dark brown (10YR 3/3) moist; moderate fine granular structure; soft, very friable, slightly sticky and slightly plastic; 3 percent gravel, 1 percent cobbles and 1 percent stones; strongly acid (pH 5.2); clear smooth boundary. (0 to 4 inches thick)
E1--5 to 16 inches; pale brown (10YR 6/3) fine sandy loam, brown (10YR 4/3) moist; weak medium subangular blocky structure that parts to weak fine granular; soft, very friable, nonsticky and nonplastic; 3 percent gravel, 1 percent cobbles and 1 percent stone; strongly acid (pH 5.2); clear wavy boundary.
E2--16 to 24 inches; light yellowish brown (10YR 6/4) fine sandy loam, dark yellowish brown (10YR 4/4) moist; weak medium subangular blocky structure that parts to weak fine granular; soft very friable, nonsticky and nonplastic; 5 percent gravel, 3 percent cobble, 1 percent stones; strongly acid (pH 5.2); clear wavy boundary. (Combined thickness of the E horizons is 12 to 20 inches)
E/B--24 to 32 inches; (60 percent E) very pale brown (10YR 7/3) fine sandy loam, brown (10YR 4/3) moist; weak medium subangular blocky structure parting to moderate fine granular; slightly hard, very friable, slightly sticky and slightly plastic; (40 percent B) brown (10YR 5/3) sandy clay loam, dark grayish brown (10YR 4/2) moist; moderate medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; very few distinct clay films on faces of peds of B part; this horizon consists of intermixed blotches of fine sandy loam E material and sandy clay loam B material; 10 percent gravel, 2 percent cobbles, 2 percent stones; strongly acid (pH 5.2); gradual wavy boundary. (8 to 12 inches thick)
Bt--32 to 49 inches; brown (10YR 5/3) very stony clay loam, dark grayish brown (10YR 4/2) moist; moderate medium subangular blocky structure; hard, friable, moderately sticky and moderately plastic; common distinct clay films on faces of peds; 15 percent gravel, 10 percent cobbles, and 15 percent stones; moderately acid (pH 5.6); gradual wavy boundary. (6 to 36 inches thick)
BC--49 to 62 inches; brown (7.5YR 5/2) very stony clay loam, dark brown (7.5YR 3/2) moist; moderate coarse subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; 15 percent gravel, 15 percent cobbles, and 15 percent stones; neutral (pH 6.8).
TYPE LOCATION: La Plata County, Colorado; about 19 miles north of Bayfield, Colorado, above Vallecito Reservoir; located about 900 feet north and 900 feet west of the southeast corner of Sec. 2, T. 37 N., R. 6 W.; Granite Peak USGS quad.; Lat. 37 degrees, 29 minutes, 53 seconds N., and Long. 107 degrees, 29 minutes, 53 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 days (cumulative). Typic udic.
Mean annual soil temperature: 35 to 42 degrees F.
Mean annual summer soil temperature: 42 to 46 degrees F. with an 0 horizon.
Depth to the top of the argillic horizon: 24 to 36 inches from the mineral surface.
Particle-size control section:
Clay content: 18 to 35 percent
Sand content: 20 to 50 percent
Silt content: 15 to 50 percent
Rock fragment content: 35 to 75 percent total rock fragments; 5 to 25 percent gravel, 10 to 50 percent cobbles, and 20 to 60 percent stones.
A horizon:
Hue: 7.5YR to 2.5Y
Value: 4 to 6 dry, 2 or 3 moist
Chroma: 1 to 3, dry and moist
Texture, fine earth fraction: FSL, L
Rock fragment content: 5 to 75 percent
Reaction: strongly acid to neutral
E horizon:
Hue: 7.5YR or 2.5Y
Value: 5 to 8 dry, 4 to 6 moist
Chroma: 2 to 4, dry and moist
Rock fragment content: 5 to 75 percent
Reaction: strongly acid to neutral
E/B or B/E horizon:
E part:
Hue: 7.5YR to 2.5Y
Value: 5 to 8 dry, 4 to 6 moist
Chroma: 2 to 4 dry and moist
Texture: FSL
B part:
Hue: 7.5YR to 2.5Y
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 3 to 6 dry and moist
Texture, fine earth fraction: SCL, CL
Rock fragment content: 10 to 75 percent
Reaction: strongly acid to neutral
Bt horizon:
Hue: 7.5YR to 2.5Y
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 3 to 6, dry and moist
Texture, fine earth fraction: CL, L, SCL
Rock fragment content: 35 to 85 percent
Reaction: strongly acid to slightly acid
BC horizon:
Hue: 7.5YR to 2.5Y
Texture, fine earth fraction: CL, SCL
Rock fragment content: 35 to 85 percent
Reaction: moderately acid to neutral
COMPETING SERIES: This is the Stemple series. In addition, the Coldcreek series may be competing when the classification is updated.
Coldcreek: have rock fragments that are mainly gravel and cobbles, lack Bt horizons and have an lithic contact at 42 inches.
Stemple: have a glossic horizon, and have E/Bt and Bt horizons that have rock fragments that are dominantly channers and flagstones.
GEOGRAPHIC SETTING:
Parent material: colluvium and slope alluvium derived from sandstone, shale, volcanic, and igneous rocks.
Landform: mountain slopes, cuestas, and hogbacks.
Slopes: 10 to 75 percent
Elevation: 8,000 to 11,500 feet
Mean annual air temperature: 30 to 40 degrees F.
Mean annual precipitation: 28 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 still moist from snowmelt.
Frost-free period: 40 to 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are
Tuckerville,
Nordicol, and
Weminuche series.
Tuckerville soils have the top of the argillic horizon less than 24 inches from the mineral soil surface.
Nordicol soils have a dark A horizon over 10 inches thick.
Weminuche soils have a loamy control section and have hue of 5YR or redder.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderate permeability in the upper part and moderately slow in the lower part.
USE AND VEGETATION: These soils are used for timber production, livestock grazing and wildlife habitat. Native vegetation consists of Engelmann's spruce, subalpine fir, aspen, Rocky Mountain Douglas fir, white fir, whortleberry, mountain snowberry, Thurber fescue, Arizona fescue, and mountain brome.
DISTRIBUTION AND EXTENT: Southwestern Colorado. LRR E, MLRA 48A. This series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: La Plata County Area, Colorado, 1982.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: The zone from 2 to 24 inches. (A, E1, and E2 horizons)
Argillic horizon: The zone from 32 to 49 inches. (Bt horizon)
Pale feature: The top of the argillic horizon is 24 inches or more below the mineral surface.
Particle size control section: the zone from 32 to 49 inches. (the argillic horizon)
Keys to Soil Taxonomy: Classified according to the Eighth Edition, 1998
Type location is moved from La Plata Soil Survey Area to Animas-Dolores Soil Survey Area in 1996.
The 4/2002 revision narrows the series concept to include only a typic-udic moisture regime. Outwash and till were also deleted from the parent materials. Vegetation was revised to reflect only the vegetation representative of typic-udic. It is recognized that more narrowing of the concept is needed, particularly to exclude soil properties that correspond to the precip zones and parent materials that are no longer part of the series.