LOCATION MANCOS COEstablished Series
TAXONOMIC CLASS: Fine, smectitic Pachic Argicryolls
TYPICAL PEDON: Mancos loam, on a west facing, simple, 3 percent slope in aspen woodland at an elevation of 9.300 feet. (Colors are for dry soil unless otherwise noted.)
A--0 to 8 inches; dark grayish brown (10YR 4/2) loam, very dark grayish brown (10YR 3/2) moist; moderate medium granular structure; slightly hard, friable, nonsticky and nonplastic; neutral (pH 6.6); clear smooth boundary. (7 to 20 inches thick)
AB--8 to 15 inches; dark grayish brown (10YR 4/2) clay loam, very dark grayish brown (10YR 3/2) moist; weak medium subangular blocky structure parting to moderate medium granular; slightly hard, friable, slightly sticky and slightly plastic; neutral (pH 6.8); clear smooth boundary. (0 to 12 inches thick)
Bt1--15 to 21 inches; dark grayish brown (10YR 4/2) clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium angular blocky structure; very hard, very firm, moderately sticky and moderately plastic; few distinct clay films on faces of peds; 7 percent gravel; slightly acid (pH 6.2); clear smooth boundary. (5 to 20 inches thick)
Bt2--21 to 26 inches; brown (10YR 5/3) clay loam, brown (10YR 4/3) moist; weak medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few distinct clay films on faces of peds; 7 percent gravel; slightly acid (pH 6.2); clear smooth boundary. (0 to 10 inches thick)
BC--26 to 34 inches; pale brown (10YR 6/3) gravelly sandy clay loam, brown (10YR 5/3) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; 25 percent gravel; slightly acid (pH 6.4); clear wavy boundary. (0 to 10 inches thick)
R--34 inches; hard shale bedrock.
TYPE LOCATION: Montezuma County, Colorado; about 10 miles northeast of Mancos; about 900 feet west, and 300 feet south of the northeast corner of sec. 21, T. 37 N., R. 12 W.; Rampart Hills USGS quad; lat. 37 degrees 27 minutes 00 seconds N. and long. 108 degrees 10 minutes 47 seconds W., NAD 27
RANGE IN CHARACTERISTICS:
Soil moisture regime: udic; dry in some part of the moisture control section for 45 to 90 cumulative days (ustic udic subclass)
Mean annual soil temperature: 38 to 43 degrees F.
Mean summer soil temperature: 52 to 58 degrees F.
Depth to lithic contact: 20 to 40 inches.
Thickness of the mollic epipedon: 16 to 30 inches and may include part or all of the Bt.
Particle-size control section:
Clay content: 35 to 55 percent
Rock fragment content: 0 to 15 percent
A horizon:
Hue: 7.5YR or 10YR
Value: 3 to 5 dry, 2 or 3 moist
Chroma: 1 to 3, dry and moist
Reaction: moderately acid to neutral
Bt horizon:
Hue: 7.5YR or 10YR
Value: 3 to 6 dry, 3 to 5 moist
Chroma: 2 to 6, dry and moist
Texture: C or CL
Rock fragment content: 0 to 15 percent
Reaction: moderately acid or slightly acid
BC or C horizon when present:
Hue: 7.5YR or 10YR
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 3 to 6, dry and moist
Texture, fine earth fraction: SCL
Rock fragment content: 15 to 35 percent
Reaction: moderately acid to neutral
COMPETING SERIES: These are the
Bischoff,
Burnette,
Cochetopa,
Faim,
Fulcher,
Grouseville,
Guero,
Perinos,
Richens,
Runlett,
Skutum, and
Teedown series.
In addition, soils that may be competing when their classification is updated are the:
Friana,
Luna,
Mayflower,
Paulson,
Slights,
Sudpeak, and
Toponce series.
All except Luna, Mayflower, and Runlett 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 has 85 to 120 day frost-free period.
Mayflower: have hue of 5YR or redder in the Bt horizons, are neutral to slightly alkaline through the Bt, and have carbonates in the lower part of the B horizon.
Runlett: are dry in some part of the moisture control section for fewer than 45 cumulative dayshave a udic soil moisture regime and are in a climatic setting that receives 30 to 45 inches of precipitation annually.
GEOGRAPHIC SETTING:
Parent material: slope alluvium derived dominantly from shale and sandstone.
Landform: structural benches and mesas.
Slopes: 1 to 15 percent
Elevation: 8,500 to 9,600 feet
Mean annual air temperature: 36 to 42 degrees F.
Mean annual precipitation: 25 to 30 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 80 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Skisams, Skutum, Helmet, and Behanco series. All are on the same landform as Mancos.
Skisams soils are shallow over bedrock.
Skutum and
Helmet soils do not have bedrock above 40 inches.
Behanco soils have more than 35 percent rock fragments in the particle size control section.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; slow or moderately slow permeability.
USE AND VEGETATION: These soils are used for livestock grazing, wildlife habitat and timber production. Native vegetation consists of quaking aspen, snowberry, Thurber's fescue, Parry's danthonia, Arizona fescue, elk sedge, bluegrass, and mountain brome.
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 ESTABLISHED: Montezuma County, Animas-Dolores Soil Survey Area, Colorado, 2003. The name is taken from the river of the same name.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon: The zone from 0 to 21 inches. (A, AB, and Bt1 horizons)
Argillic horizon: The zone from 15 to 26 inches. (Bt1 and Bt2 horizons)
Lithic contact: Hard shale bedrock at 34 inches.
Particle size control section: The zone from 15 to 26 inches. (Bt1 and Bt2 horizons)
Keys to Soil Taxonomy: Classified according to the Eighth Edition, 1998