LOCATION SIG COEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Lithic Dystrocryepts
TYPICAL PEDON: Sig gravelly loam, on a southwest facing, simple, 20 percent slope in spruce-fir woodland at an elevation of 10,000 feet. (Colors are for dry soil unless otherwise noted.) When described on October 1, 1987 the soil was moist from the surface to bedrock.
Oi--0 to 2 inches; organic layer of needles, leaves and roots. (0 to 3 inches thick)
A--2 to 9 inches; light reddish brown (5YR 6/3) gravelly loam, reddish brown (5YR 4/3) moist; moderate fine granular structure; soft, very friable, nonsticky and nonplastic; 25 percent gravel, 5 percent cobble, and 1 percent stones; moderately acid (pH 5.6); gradual wavy boundary. (2 to 8 inches thick)
Bw--9 to 16 inches; reddish brown (5YR 5/4) very gravelly loam, reddish brown (5YR 4/4) moist; weak medium subangular blocky structure parting to weak fine granular; soft, very friable, nonsticky and nonplastic; 30 percent gravel, 15 percent cobble and 2 percent stones; moderately acid (pH 5.6); abrupt wavy boundary. (6 to 14 inches thick)
R--16 inches; hard granite bedrock, fractured in upper few inches.
TYPE LOCATION: San Juan County, Colorado; about 33 miles north of Durango on Coal Bank Pass, located about 1,100 feet west and 2,700 feet north of the southeast corner of Sec. 6, T. 39 N., R. 8 W. Engineer Mountain USGS quad.; lat. 37 degrees, 40 minutes, 43 seconds N. long. 107 degrees, 47 minutes, 01 second 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: 34 to 38 degrees F.
Mean summer soil temperature: 40 to 46 degrees F. with an O horizon
Base saturation: 40 to 60 percent (estimated)
Lithology of rock fragments: granite
Depth to lithic contact: 8 to 20 inches
Particle-size control section:
Clay content: 18 to 27 percent
Rock fragment content: 35 to 65 percent, mostly gravel and cobbles
A horizon:
Hue: 5YR or 7.5YR
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 2 to 4, dry and moist
Rock fragment content: 15 to 35 percent, mostly gravel and cobble
Reaction: strongly acid or moderately acid
Bw 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: L, SL, SCL
Rock fragments: 35 to 65 percent, mostly gravel and cobble
Reaction: strongly acid or moderately acid
COMPETING SERIES: These are the Crawfish and Shermount series.
Crawfish: formed in material weathered from basalt or andesitic basalt and have 10 to 18 percent clay in the particle size control section.
Shermount: formed in residuum and colluvium from sedimentary rock with a component of volcanic ash in the upper part.
GEOGRAPHIC SETTING:
Parent material: slope alluvium and colluvium derived principally from granite.
Landform: mountain slopes and structural benches.
Slopes: 15 to 45 percent
Elevation: 8,500 to 11,500 feet
Mean annual air temperature: 32 to 38 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 snow covered in many places into June and the soils are moist from snowmelt.
Frost-free period: 40 to 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Haviland,
Needleton, and
Snowdon series. All are on mountain slopes and structural benches.
Haviland soils are fine-loamy and are very deep, and in addition are on mesas.
Needleton soils are very deep, and have argillic horizons.
Snowdon soils have argillic horizons, and in addition are on mesas.
DRAINAGE AND PERMEABILITY: Well drained, medium to high runoff, moderate permeability.
USE AND VEGETATION: These soils are used for Timber production, recreation, and wildlife habitat. Native vegetation consists of Engelmann's spruce, subalpine fir, Rocky Mountain Douglas fir, quaking aspen, snowberry, Myrtle whortleberry, kinnickinnick, aspen peavine, mountain brome, elk sedge, and needlegrass.
DISTRIBUTION AND EXTENT: Western Colorado. LRR E, MLRA 48A. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: San Juan County, Colorado, Animas-Dolores Soil Survey Area, 2002. Series proposed in 1988. The name is taken from a creek of the same name.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: The zone from 2 to 9 inches. (A horizon)
Cambic horizon: the zone from 9 to 16 inches. (Bw horizon)
Lithic contact: hard bedrock at 16 inches. (R layer)
Keys to Soil Taxonomy: Classified according to the Eighth Edition, 1998. Mineralogy is assumed mixed rather than isotic because reaction ranges as high as moderately acid (no lab data is available).
Activity class presumed from the general trend of other soils in the area.