LOCATION GRAYSILL COEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive Eutric Haplocryalfs
TYPICAL PEDON: Graysill loam , on a west facing, simple, 55 percent slope in spruce-fir woodland at an elevation of 10,000 feet. (Colors are for dry soil unless otherwise noted.)
Oi--0 to 2 inches; organic mat of roots, needles, leaves and twigs. (0 to 3 inches thick)
E--2 to 14 inches; light reddish brown (5YR 6/3) loam, reddish brown (5YR 4/3) moist; moderate medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; 5 percent gravel; very strongly acid (pH 5.0); gradual wavy boundary. (6 to 14 inches thick.)
EB--14 to 22 inches; reddish brown (2.5YR 5/4) light clay loam, reddish brown (2.5YR 4/4) moist; weak medium subangular blocky structure parting to moderate medium granular; slightly hard, friable, moderately sticky and moderately plastic; 5 percent gravel; strongly acid (pH 5.2); gradual wavy boundary. (0 to 10 inches thick.)
Bt--22 to 37 inches; red (2.5YR 5/6) clay loam, reddish brown (2.5YR 4/4) moist; moderate medium subangular blocky structure parting to moderate medium granular; hard, firm, moderately sticky and moderately plastic; 5 percent cobble, 5 percent gravel; 1 percent stones; common distinct clay films on faces of peds; strongly acid (pH 5.2); abrupt wavy boundary. (14 to 25 inches thick.)
R--37 inches; hard red sandstone fractured in upper part.
TYPE LOCATION: San Juan County, Colorado, along Hotel Draw road about 35 miles north of Durango, Colorado; located about 200 feet north and 500 feet west of the southeast corner of Sec. 10, T. 39 N., R 10 W.; Hermosa Peak USGS quad; lat. 37 degrees 39 minutes 22 seconds N. and long. 107 degrees 56 minutes 50 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).
Mean annual soil temperature: 35 to 40 degrees F.
Mean summer soil temperature: 41 to 46 degrees F. with an O horizon
Lithology of rock fragments: sandstone, shale
Depth to lithic contact: 20 to 40 inches from mineral soil surface to sandstone
Particle-size control section:
Clay content: 18 to 35 percent
Silt content: 20 to 50 percent
Sand content: 20 to 60 percent
E horizon:
Hue: 2.5YR to 7.5YR
Value: 6 or 7 dry, 4 or 5 moist
Chroma: 2 or 3, dry and moist
Rock fragment content: 0 to 15 percent
Base saturation: 50 to 70 percent (by ammonium acetate, estimated)
Reaction: very strongly acid or strongly acid
Bt horizon:
Hue: 2.5YR or 5YR
Value: 4 to 6 dry, 3 or 4 moist
Chroma: 4 to 6, dry and moist
Texture, fine earth fraction: L or CL
Rock fragment content: 5 to 35 percent
Base saturation: 50 to 70 percent (by ammonium acetate, estimated)
Reaction: very strongly acid or strongly acid
COMPETING SERIES: These are the Haviland, Hierro, Jaegie, Sapphire, Tongue River, Trapper, and Weminuche series.
Other soils that may be competitors when the classification is updated are the: Ericson, Indart, Whitefish, and Woodrock series.
Castelleia,
Ericson,
Owlcreek,
Swifton, and Trapper: lack bedrock above 40 inches.
Limber: are slightly acid to slightly alkaline in the E and B horizons.
Indart: have a paralithic contact at 20 to 40 inches.
Whitefish: have continuous horizons of lime accumulation.
Woodrock: are in a climatic setting that receives about 24 inches of precipitation that is mostly in the spring and summer and the soils are formed residually from granite or locally transported material.
GEOGRAPHIC SETTING:
Parent material: residuum or slope alluvium derived from redbed sandstone and interbedded shale.
Landform: mountain slopes, ridges and mesas.
Slopes: 5 to 60 percent
Elevation: 9,000 to 11,500 feet
Mean annual air temperature: 30 to 38 degrees F.
Mean annual precipitation: 35 to 45 inches.
Wettest months: July and August receives 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: 50 to 70 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Needleton, Scotch and Haviland series. All are on mountain slopes.
Needleton soils are very deep and have more than 35 percent rock fragments in the argillic horizon.
Scotch soils are over bedrock at depths of 20 inches or less.
Haviland soils are very deep.
DRAINAGE AND PERMEABILITY: Well drained; medium to high runoff; moderate or moderately slow permeability.
USE AND VEGETATION: These soils are used for woodland, livestock grazing, and wildlife habitat. Principal native vegetation is subalpine fir, Rocky Mountain Douglas fir, Engelmann's spruce, quaking aspen, kinnickinnick, snowberry, sedge, mountain brome, and forbs.
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: San Juan, County, Colorado, Animas-Dolores Soil Survey Area, 2002. Series proposed in 1984. The name is taken from a nearby mountain peak.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon and albic horizon: The zone from 2 to 14 inches. (E horizon)
Argillic horizon: The zone from 22 to 37 inches. (Bt horizon)
Lithic contact: sandstone bedrock at 37 inches.
Keys to Soil Taxonomy: Classified according to the Eighth Edition, 1998
Activity class is presumed based on general trend of other soils in the area.