LOCATION HELMET COEstablished Series
TAXONOMIC CLASS: Fine, smectitic Vertic Argicryolls
TYPICAL PEDON: Helmet clay loam, on a north facing, 14 percent slope in spruce-fir woodland at an elevation of 9,760 feet. (Colors are for dry soil unless otherwise noted.) Described on July 20, 1989.
Oi--0 to 2 inches; organic mat of decomposing leaves, roots, and needles. (1 to 3 inches thick)
A--2 to 4 inches; dark brown (10YR 3/3) clay loam, very dark gray (10YR 3/1) moist; moderate medium and fine granular structure; slightly hard, very friable, slightly sticky and slightly plastic; 5 percent gravel; strongly acid (pH 5.2); clear wavy boundary. (2 to 10 inches thick)
BA--4 to 13 inches; grayish brown (10YR 5/2) clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine and medium subangular blocky structure parting to strong medium granular; slightly hard, firm, slightly sticky and moderately plastic; few faint clay films on faces of peds; 5 percent gravel; moderately acid (pH 5.6); clear wavy boundary. (0 to 12 inches thick)
Bt1--13 to 21 inches; light brownish gray (10YR 6/2) clay, dark grayish brown (10YR 4/2) moist; moderate coarse prismatic structure parting to strong medium angular blocky; extremely hard, very firm, moderately sticky and moderately plastic; many distinct clay films on faces of peds and in pores; 5 percent gravel; moderately acid (pH 5.6); gradual wavy boundary. (7 to 30 inches thick)
Bt2--21 to 28 inches; grayish brown (10YR 5/2) and yellowish brown (10YR 5/4) clay, dark brown (10YR 3/3) moist; strong medium angular and subangular blocky structure; extremely hard, very firm, moderately sticky and moderately plastic; common distinct clay films on faces of peds and in pores; 5 percent gravel; moderately acid (pH 5.8); gradual wavy boundary. (0 to 20 inches thick)
BC--28 to 46 inches; grayish brown (10YR 5/2) and yellowish brown (10YR 5/4) silty clay, very dark grayish brown (10YR 3/2) and dark yellowish brown (10YR 4/4) moist; moderate coarse subangular blocky structure; very hard, very firm, moderately sticky and moderately plastic; few faint clay films in pores; 10 percent gravel and shale chips; slightly acid (pH 6.2); gradual wavy boundary. (0 to 25 inches thick)
C--46 to 62 inches; grayish brown (10YR 5/2) silty clay loam, brown (10YR 4/3) moist; massive; hard, firm, slightly sticky and moderately plastic; 5 percent gravel and shale chips, 5 percent cobble; slightly acid (pH 6.2).
TYPE LOCATION: Montezuma County, Colorado; about 10 miles northeast of Mancos along Forest Service road 566; about 2500 feet south and 50 feet west of the northeast corner of Sec. 27, T. 37 N., R. 12 W.; Rampart Hills USGS quad.; lat. 37 degrees, 26 minutes, 15 seconds N. and long. 108 degrees, 9 minutes, 35 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: 36 to 42 degrees F.
Mean annual summer soil temperature: 42 to 46 degrees F. with an O horizon and 50 to 56 degrees F. without an O horizon.
Depth to the base of the argillic horizon: 26 to 60 inches
Thickness of the mollic epipedon: 10 to 16 inches
Lithology of rock fragments: diorite, rhyolite, and shale
Particle-size control section:
Clay content: 35 to 55 percent
Rock fragment content: 2 to 15 percent
A horizon:
Hue: 7.5YR or 10YR
Value: 3 or 4 dry, 2 or 3 moist
Chroma: 1 to 3, dry and moist
Texture: L or CL
Rock fragment content: 0 to 10 percent
Reaction: strongly acid to slightly acid
Bt horizon:
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 3 or 4 moist
Chroma: 2 to 4, dry and moist
Texture: CL or C
Rock fragment content: 2 to 15 percent
Reaction: moderately acid or slightly acid
BC horizon, when present:
Hue: 7.5YR or 10YR
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 2 to 4, dry and moist
Texture: SIC, SICL, or C
Rock fragment content: 0 to 15 percent
Reaction: moderately acid or slightly acid
C horizon:
Hue: 7.5YR or 10YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 to 4, dry or moist
Texture: SIC, SICL, or C
Rock fragment content: 0 to 15 percent
Reaction: moderately acid or slightly acid
COMPETING SERIES: These are the Beaverdam, Buckskin, Cimarron, Cucharas, Gourley, Heathcoat, Savar, Slights, Sudduth, Sudpeak, Toponce, Wetopa, and Youman series.
Beaverdam soils are more than 60 inches to the base of the argillic horizon.
Buckskin,
Heathcoat,
Slights, and
Sudpeak soils have a xeric moisture regime.
Cimarron,
Savar, and
Youman soils have an ustic moisture regime.
Cucharas soils have a paralithic contact.
Gourley soils are more alkaline than slightly acid.
Sudduth soils do not have a udic moisture regime (are currently in ustic and xeric areas)
Toponce soils are in areas bordering xeric moisture regimes, and also have a mollic epipedon thicker than 16 inches.
Wetopa soils have a mollic epipedon thicker than 16 inches.
GEOGRAPHIC SETTING:
Parent material: slope alluvium derived from diorite, rhyolite, and shale.
Landform: mountain slopes
Slopes: 1 to 60 percent
Elevation: 9,000 to 10,500 feet
Mean annual air temperature: 34 to 40 degrees F.
Mean annual precipitation: 30 to 40 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: 60 to 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Teedown, Nordicol, Needleton, Clayburn, Frisco, and Snowdon soils.
Teedown and
Clayburn soils have Pachic surface horizons.
Nordicol,
Needleton, and
Frisco soils are loamy-skeletal.
Snowdon soils have bedrock above 20 inches.
DRAINAGE AND PERMEABILITY: Well drained; medium to high runoff; slow permeability.
USE AND VEGETATION: These soils are used for woodland, livestock grazing, and wildlife habitat. Native vegetation consists of quaking aspen, white fir, Engelmann's spruce, subalpine fir, Rocky Mountain Douglas fir, snowberry, elderberry, mountain brome, bluegrass, meadowrue, aspen peavine, wild celery, and other grasses and forbs.
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: Montezuma County, Animas-Dolores Soil Survey Area, Colorado, 1990.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon: The zone from 2 to 13 inches. (A and BA horizons)
Argillic horizon: The zone from 13 to 28 inches. (Bt1 and Bt2 horizons)
Particle size control section: The zone from 13 to 28 inches. (Bt1 and Bt2 horizons)
Keys to Soil Taxonomy: Classified according to the Eighth Edition, 1998
ADDITIONAL DATA: Hydrometer analysis done by CSU Soil Testing Lab., Fort Collins, Colo. 9/89.; Lab. numbers 2016 through 2020.