LOCATION RUNLETT COEstablished Series
TAXONOMIC CLASS: Fine, smectitic Pachic Argicryolls
TYPICAL PEDON: Runlett loam, on a south facing, simple, 14 percent slope in rangeland at an elevation of 10,700 feet. (Colors are for dry soil unless otherwise noted.) When described on June 26, 1989 the soil was moist throughout.
A1--0 to 14 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist: moderate medium granular structure; soft, friable, slightly sticky and slightly plastic; 5 percent gravel; slightly acid (pH 6.2); clear smooth boundary. (10 to 20 inches thick)
A2--14 to 19 inches; brown (7.5YR 5/2) loam, dark brown (7.5YR 3/2) moist; moderate medium granular structure; soft, friable, slightly sticky and slightly plastic; 5 percent gravel; moderately acid (pH 6.0); clear smooth boundary. (4 to 12 inches thick)
Bt1--19 to 22 inches; brown (7.5YR 5/3) clay loam; brown (7.5YR 4/3) moist; moderate medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; many prominent clay films on faces of peds; 5 percent gravel; slightly acid (pH 6.4); clear smooth boundary. (3 to 24 inches thick)
Bt2--22 to 27 inches; brown (7.5YR 5/4) clay, brown (7.5YR 4/4) moist; strong medium angular blocky structure; hard, firm, very sticky and very plastic; many prominent clay films on faces of peds; 2 percent cobbles and 5 percent stones; neutral (pH 7.0); abrupt irregular boundary. (0 to 12 inches thick)
R--27 inches; limestone bedrock fractured and weathered in the upper part with soil material in cracks and between upper layers of limestone.
TYPE LOCATION: La Plata County, Colorado; about 5 miles northeast of Vallecito Reservoir; located about 1,200 feet N. and 3,100 feet E. of the northwest corner of sec. 11, T. 37 N., R. 6 W.; Vallecito USGS quad; lat. 37 degrees 29 minutes 10 seconds N. and long. 107 degrees 30 minutes 10 seconds W., NAD 27
RANGE IN CHARACTERISTICS:
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.
Depth to lithic contact: 20 to 40 inches to limestone or sandstone
Thickness of the mollic epipedon: 16 to 24 inches
Particle-size control section:
Clay content: 35 to 50 percent
Rock fragment content: 0 to 20 percent
A horizon:
Hue: 7.5YR or 10YR
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 1 to 3, dry and moist
Rock fragment content: 0 to 15 percent
Reaction: moderately acid or slightly 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 or C
Rock fragment content: 0 to 20 percent
Reaction: moderately acid to neutral
COMPETING SERIES: These are the Bischoff, Burnette, Cochetopa, Faim, Fulcher, Grouseville, Guero, Mancos, Perinos, Richens, Skutum, and Teedown.
In addition, these soils may be competitors when their classification is updated: Friana, Luna, Mayflower, Paulson, Slights, Sudpeak, and Toponce.
All except
Luna and
Mayflower do not have bedrock at depths shallower than 40 inches.
Luna: are formed in ash and tuff, have ash and tuff paralithic layers, and are in a climatic setting that receives 18 to 30 inches of annual precipitation.
Mayflower: have hue of 5YR or 2.5YR in the Bt horizons and are in a climatic setting that receives about 20 inches of precipitation annually.
GEOGRAPHIC SETTING:
Parent material: slope alluvium and residuum derived mostly from limestone, sandstone, and shale.
Landform: mesas, mountain slopes, structural benches.
Slopes: 5 to 45 percent
Elevation: 9,500 to 11,000 feet
Mean annual air temperature: 32 to 38 degrees F.
Mean annual precipitation: 35 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 60 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Sessions, Needleton, and Clayburn soils.
Clayburn soils are very deep. They are on mountain slopes, toeslopes, and footslopes.
Needleton soils are very deep and have more than 35 percent rock fragments in the particle size control section. They are on mountain slopes.
Sessions soils are very deep. They are on mountain slopes and structural benches.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; slow permeability.
USE AND VEGETATION: These soils are used for rangeland and wildlife habitat. Native vegetation consists of Thurber's fescue, Colombia needlegrass, mountain brome, wheatgrasses, American vetch, and aspen pea vine.
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: La Plata County, Animas-Dolores Area, Colorado. 1989. The name is taken from a park in the vicinity.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon (Pachic feature): The zone from 0 to 19 inches. (A1 and A2 horizons)
Argillic horizon: The zone from 19 to 27 inches. (Bt1 and Bt2 horizons)
Lithic contact: Limestone bedrock at 27 inches.
Particle size control section: The zone from 19 to 27 inches. (Bt1 and Bt2 horizons)
Keys to Soil Taxonomy: Classified according to the Eighth Edition, 1998