LOCATION ILEX COEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Calcic Haplustalfs
TYPICAL PEDON: Ilex loam on a 3 percent southwest slope at 7,560 feet in rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 2 inches; reddish brown (5YR 5/3) loam, dark reddish brown (5YR 3/3) moist; moderate medium platy structure parting to weak medium granular; soft, very friable, nonsticky and nonplastic; neutral (pH 7.0); abrupt smooth boundary.
BA--2 to 6 inches; reddish brown (5YR 4/3) clay loam, dark reddish brown (5YR 3/3) moist; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; neutral (pH 7.0); clear wavy boundary.
Bt1--6 to 12 inches; reddish brown (5YR 4/4) clay loam, dark reddish brown (5YR 3/4) moist; moderate medium subangular blocky structure; hard, firm, very sticky and very plastic; few faint discontinuous clay films on the faces of peds; neutral (pH 7.0); clear wavy boundary.
Bt2--12 to 22 inches; yellowish red (5YR 4/6) clay loam, yellowish red (5YR 4/6) moist; strong coarse prismatic structure parting to strong medium angular blocky; extremely hard, very firm, very sticky and very plastic; many prominent continuous clay films on the faces of peds; slightly alkaline (pH 7.5); abrupt wavy boundary.
2Btk--22 to 37 inches; light yellowish brown (10YR 6/4) clay, yellowish brown (10YR 5/4) moist; strong medium prismatic structure parting to strong medium angular blocky; extremely hard, very firm, very sticky and very plastic; many prominent continuous clay films on the faces of peds; common large soft seams of calcium carbonate; violently effervescent; moderately alkaline (pH 8.0); clear wavy boundary.
2Bk1--37 to 44 inches; very pale brown (10YR 7/4) clay, light yellowish brown (10YR 6/4) moist; strong medium prismatic structure parting to moderate medium subangular blocky; very hard, very firm, very sticky and very plastic; common large soft seams and soft masses of calcium carbonate; violently effervescent; moderately alkaline (pH 8.2); clear wavy boundary.
2Bk2--44 to 60 inches; brownish yellow (10YR 6/6) clay, brownish yellow (10YR 6/6) moist; massive; very hard, very firm, very sticky and very plastic; common large soft seams and soft masses of calcium carbonate; violently effervescent; moderately alkaline (pH 8.2).
TYPE LOCATION: Montezuma County, Colorado; located west of McPhee Reservoir, about 400 feet west and 1,850 feet south of the northeast corner of sec. 4, T. 38 N., R. 16 W.; Tremble Point, Colorado USGS quad; lat. 37 degrees 35 minutes 00 seconds N. and long. 108 degrees 36 minutes 45 seconds W., NAD 27.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 42 to 46 degrees F
Mean annual summer soil temperature: 60 to 65 degrees F
Surface rock fragments: 0 to 10 percent gravel
Particle-size control section: 35 to 50 percent clay
Depth to calcic horizon: 25 to 40 inches
Depth to secondary calcium carbonate: 14 to 30 inches
Depth to lithologic discontinuity: 20 to 60 inches to clayey residuum
A horizon:
Hue: 5YR or 7.5YR
Value: 4 or 5 dry, 3 or 4 moist
Chroma: 2 to 4 dry and moist
Rock fragments: 0 to 5 percent sandstone gravel
Reaction: neutral to moderately alkaline
Bt horizon:
Hue: 5YR to 10YR
Value: 3 to 7 dry, 3 to 7 moist
Chroma: 2 to 6 dry or moist
Texture: clay loam or clay,
Rock fragments: 0 to 10 percent sandstone gravel
Reaction: neutral to moderately alkaline
Bk horizon:
Hue: 7.5YR to 2.5Y
Value: 6 to 8 dry, 5 to 8 moist
Chroma: 2 to 6 dry or moist
Texture: loam, clay loam, or clay
Rock fragments: 0 to 5 percent sandstone gravel
Calcium carbonate equivalent: 5 to 40 percent
Reaction: moderately or strongly alkaline
COMPETING SERIES: The only current competitor is the
Iles series.
Iles soils do not have a lithologic discontinuity and have a soil moisture control section that is affected by precipitation that falls evenly throughout the year.
GEOGRAPHIC SETTING:
Parent material: eolian deposits derived from sandstone over clayey residuum weathered from Mancos shale
Landform: hills
Slopes: 2 to 25 percent
Elevation: 7,100 to 8,500 feet
Mean annual air temperature: 43 to 47 degrees F
Mean annual precipitation: 15 to 20 inches
Precipitation is fairly evenly distributed throughout the year with July and August being slightly wetter and June being slightly dryer.
Frost-free period: 75 to 100 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Granath, Ormiston and Pramiss soils. Granath has a mollic epipedon. Ormiston is skeletal and Pramiss is moderately deep to a paralithic contact. All are on similar landscapes.
DRAINAGE AND PERMEABILITY: well drained, high or very high runoff, slow permeability
USE AND VEGETATION: Used for grazing, and some nonirrigated cropland. Native vegetation is mainly Gambel's oak, western wheatgrass, needleandthread, Arizona fescue, and junegrass
DISTRIBUTION AND EXTENT: Southwest Colorado. LRR E, MLRA 48A. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Cortez Area, Colorado, Parts of Dolores and Montezuma Counties, 1997.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Argillic horizon: The zone from 6 to 37 inches. (Bt1 and Bt2, 2Btk)
Calcic horizon: The zone from 37 to 44 inches. (2Bk1)
Lithologic discontinuity: The discontinuity with clayey residuum at 22 inches. (2Btk, 2Bk1, and 2Bk2)
Particle-size control section: The zone from 6 to 26 inches. (Bt1, Bt2, and 2Btk)
Soil Taxonomy Second Edition, 1999
These soils are borderline mesic-frigid. Future temperature studies are needed to resolve this issue.
Given the right conditions the Mancos shale weathers easily and completely. In this pedon no, or very little, evidence of the original rock structure is seen below 22 inches. However, because the landform is stable and there is no evidence the lower part of this pedon has moved, the parent material is considered to be residuum.