LOCATION GUERO COTentative Series
TAXONOMIC CLASS: Fine, smectitic Pachic Argicryolls
TYPICAL PEDON: Guero loam - rangeland. (Colors are for dry soil unless otherwise stated.)
A1--0 to 6 inches; brown (7.5YR 4/2) loam, dark brown (7.5YR 3/2) moist; moderate medium granular structure; soft, very friable, nonsticky and nonplastic; 5 percent pebbles; neutral (pH 6.8); gradual wavy boundary. (5 to 8 inches thick)
A2--6 to 18 inches; brown (7.5YR 4/2) loam, dark brown (7.5YR 3/2) moist; moderate medium granular structure; soft, very friable, nonsticky and nonplastic; 5 percent pebbles; neutral (pH 6.8); gradual wavy boundary. (11 to 15 inches thick)
Bt1--18 to 24 inches; brown (7.5YR 5/2) cobbly clay, dark brown (7.5YR 4/4) moist; strong medium subangular blocky structure; extremely hard, extremely firm, very sticky and very plastic; common distinct clay films on ped faces; 5 percent pebbles, 10 percent cobble; neutral (pH 6.8) gradual wavy boundary. (4 to 8 inches thick)
Bt2--24 to 39 inches; light brown (7.5YR 6/4) cobbly clay, dark brown (7.5YR 4/4) moist; strong medium subangular blocky structure; extremely hard, extremely firm, very sticky and very plastic; common distinct clay films on ped faces; 15 percent pebbles, 15 percent cobble, neutral (pH 6.8); gradual wavy boundary. (12 to 20 inches thick)
BCt--39 to 60 inches; light brown (7.5YR 6/4) cobbly clay, dark brown (7.5YR 4/4) moist: massive; extremely hard, extremely firm, very sticky and very plastic; few faint clay films on ped faces; 10 percent pebbles, 20 percent cobble; neutral (pH 6.8).
TYPE LOCATION: Gunnison County, Colorado; 1600 feet south and 1300 feet east of the northwest corner of Sec. 7, T. 49 N., R. 5 W. Latitude: 38 degrees, 31 minutes, 21 seconds north; Longitude: 107 degrees, 26 minutes, 59 seconds west.
RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges from 40 to 44 degrees F. The thickness of the mollic epipedon ranges from 16 to 20 inches. The mollic epipedon may include the upper parts of the Bt horizon. Rock fragment content is 0 to 35 percent and is mainly pebbles and cobble. Reaction ranges from neutral to slightly acid throughout. The moisture control section is dry in some part about half the time, when the soil temperature at 20 inches is greater than 41 degrees F.
The A horizon has hue of 10YR or 7.5YR, value of 3 through 5 dry, 2 or 3 moist and chroma of 2 or 3.
The Bt horizon has hue of 10YR through 5YR, value of 4 through 6 dry, 3 through 5 moist, and chroma of 2 through 4. Clay content is 35 to 50 percent.
The BCt horizon has hue of 10YR through 5YR, value of 4 through 6 dry, 3 through 5 moist, and chroma of 2 through 4. Clay content is 35 to 50 percent.
COMPETING SERIES: These are the Burnette (MT), Cochetopa (CO), Faim (UT), Friana (AZ), Fulcher (CO), Paulson (WY), Perinos (T)(UT), Richens (UT), Runlett (T)(CO), Skutum (UT), slights (T)(ID), Sudduth (CO), Sudpeak (ID), Teedown (T)(CO), and Toponce (ID) soils. The Burnette, Paulson, and Fulcher series have a consistent k horizon above 40 inches. In addition, the Fulcher soil has a moisture control section that is dry in most parts when the soil temperature at 20 inches is greater than 41 degrees F. Cochetopa soils have rock fragments that are dominantly stones. Faim soils have less than 35% clay in the BC or C horizons. Friana soils are deep with cindery clay above 40 inches, and are formed in mixed sediments from ash, cinders, and basalt. The Grouseville soil has a soil reaction of mildly or moderately alkaline in the Bt and the moisture control section is dry in most parts about half the time when the soil temperature at 20 inches is greater than 41 degrees F. The Luna soils are formed in ash and Tuff, and have a paralithic layer above 40 inches. The dMancos and Richens soils have a lithic contact at depths of 20 to 40 inches. The Mayflower and Skutum soils have a paralithic contact above 40 inches. The Perinos soils have hues of 5YR and redder in the Bt horizon. The slights and Toponce soils have a moderately acid soil reaction in the Bt horizon. The Sudduth soils have a lithologic discontinuity at 12 to 24 inches. Sudpeak soils are moderately well drained with a water table at depth. The Teedown soils have moisture control sections that are usually moist when the soil temperature at 20 inches is greater than 41 degrees F.
GEOGRAPHIC SETTING: Guero soils are on plateaus, mesa tops, hilltops, and sideslopes. Slopes range from 5 to 65 percent. The soils formed in residuum, till, and colluvium from tuff, breccia, andesite, and rhyolite. The mean annual air temperature ranges from about 38 to 42 degrees F. The mean annual precipitation is 24 to 28 inches. The mean summer precipitation is about 10 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Clayburn and Quander series. The Clayburn soil is fine-loamy and the Quander soil is loamy-skeletal.
DRAINAGE AND PERMEABILITY: Well drained; moderate to very rapid runoff; slow permeability.
USE AND VEGETATION: These soils are used for rangeland, recreation and wildlife habitat. Principal native vegetation is aspen, bearded wheatgrass, slender wheatgrass, and elk sedge.
DISTRIBUTION AND EXTENT: Black Mesa of the West Elk Mountains in southwest Colorado. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: Grand Mesa, West Elk Soil Survey Area, Gunnison County, Colorado, 1985.
REMARKS: Diagnostic features include an argillic horizon from 18 to 39 inches, and a mollic epipedon from 0 to 18 inches. The name is taken from a local mountain peak. Last updated by the state 4/93.