LOCATION ALAMADITAS COEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, smectitic, frigid Typic Argiustolls
TYPICAL PEDON: Alamaditas very cobbly loam - on a 25 percent, concave southeast facing slope under native pinyon and juniper woodland at an elevation of 8,600 feet. (Colors are for dry soil unless otherwise noted.)
A--0 to 2 inches; dark grayish brown (10YR 4/2) very cobbly loam, very dark grayish brown (10YR 3/2) moist; weak fine granular structure; soft, very friable, slightly sticky, slightly plastic; 20 percent pebbles, 20 percent cobble; slightly alkaline; abrupt smooth boundary. (2 to 4 inches thick)
AB--2 to 7 inches; dark grayish brown (10YR 4/2) very cobbly clay loam, very dark brown (10YR 2/2) moist; weak medium subangular blocky structure; very hard, friable, sticky, plastic; 20 percent pebbles, 20 percent cobble; 5 percent stones; slightly alkaline; clear smooth boundary. (4 to 7 inches thick)
Bt1--7 to 12 inches; very dark brown (7.5YR 3/2) very cobbly clay loam, dark brown (10YR 3/3) moist; moderate fine subangular blocky structure; very hard, firm, very sticky, plastic; few distinct clay films on faces of peds; 20 percent pebbles, 20 percent cobble, 5 percent stones; slightly alkaline; clear smooth boundary. (3 to 6 inches thick)
Bt2--12 to 17 inches; reddish brown (5YR 5/4) very cobbly clay loam, reddish brown (5YR 4/4) moist; moderate medium subangular blocky structure; very hard, firm, very sticky, plastic; common prominent clay films on faces of peds; 15 percent pebbles, 20 percent cobble, 5 percent stones; slightly alkaline; clear smooth boundary. (5 to 10 inches thick)
Bt3--17 to 23 inches; pale brown (10YR 6/3) very cobbly clay loam, dark grayish brown (10YR 4/2) moist; weak medium subangular blocky structure; hard, friable, sticky, plastic; few prominent clay films on faces of peds; 15 percent pebbles, 15 percent cobble, 10 percent stones; slightly alkaline; clear wavy boundary. (5 to 9 inches thick)
Bk--23 to 34 inches; light brownish gray (10YR 6/2) very cobbly loam, dark grayish brown (10YR 4/2) moist; weak coarse subangular blocky structure; slightly hard, very friable, slightly sticky, slightly plastic; strongly effervescent; 20 percent pebbles, 20 percent cobble, slightly alkaline; clear wavy boundary. (5 to 16 inches thick)
Cr--34 to 39 inches; weathered breccia.
R--39 inches; hard breccia bedrock.
TYPE LOCATION: Conejos County, Colorado; about 12 miles west and 3 miles south of Antonito; 1,250 feet north and 2,500 feet west of the SE corner of Sec. 9, T. 32N., R. 7 E. U.S.G.S. Fox Creek quad.; Lat. 37 degrees, 01 minutes, 30 seconds N., and Long. 106 degrees, 12 minutes, 32 seconds W.
RANGE IN CHARACTERISTICS: Mean annual soil temperatures range from 42 to 45 degrees F., and mean summer soil temperatures range from 59 to 63 degrees F. The thickness of the solum ranges from 25 to 38 inches. Depth to hard bedrock ranges from 20 to 40 inches. The mollic epipedon is 10 to 15 inches thick and often includes the upper part of the argillic horizon. The texture control section has 35 to 45 percent clay.
The A horizon has a hue of 7.5YR or 10YR, value of 3 to 5 dry, 2 or 3 moist, and chroma of 2 or 3. It commonly has cobbly or very cobbly modifiers. It is neutral to slightly alkaline.
The Bt horizon has a hue of 5YR through 10YR, value of 3 through 6 dry, 3 or 4 moist, and chroma of 2 through 4. It commonly is very cobbly clay loam but the fine earth fraction may include clay or sandy clay textures. It is neutral to slightly alkaline.
The Bk horizon has a hue of 7.5YR or 10YR, value of 6 through 8 dry, 4 or 5 moist, and chroma of 2 or 3. It is very gravelly or very cobbly sandy clay loam, loam, or clay loam. It is slightly alkaline or moderately alkaline.
COMPETING SERIES: These are the Kolob (UT), Showalter (UT), and the Sirref (UT) series. All lack bedrock within a depth of 40 inches.
GEOGRAPHIC SETTING: Alamaditas soils are on mountain backslopes and toe slopes at elevations of 8,600 to 9,500 feet. Slopes range from 15 to 45 percent. The soil formed in colluvium and residuum from breccia or tuff. The mean annual precipitation ranges from 14 to 20 inches. Mean annual temperature is 39 to 43 degrees F. Frost-free season is 90 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Comodore,
Posant, and
Tolman soils. Comodore soils occur on ridgetops and lack an argillic horizon. Posant soil is less than 20 inches to bedrock and occurs on ridges or steeper slopes than Alamaditas soil. Tolman soils are shallow to bedrock and have a loamy-skeletal argillic horion.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; slow permeability.
USE AND VEGETATION: Alamaditas soils are used for rangeland and recreation. Limited fuelwood and fencepost gathering also occurs. Tree canopy is pinyon pine, Rocky Mountain juniper, and scattered ponderosa pine. Understory vegetation is predominantly Arizona fescue, blue grama, mountain muhly, fringed sage, rabbitbrush, and wax currant.
DISTRIBUTION AND EXTENT: This soil is moderately extensive in southwestern Colorado.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Rio Grande National Forest - West Part, Conejos County, Colorado, 1987.
REMARKS: The series name is taken from a nearby mesa. Diagnostic horizons and features recognized are: a mollic epipedon from 0 to 12 inches; an argillic horizon from 7 to 23 inches; more than 35 percent rock fragments in the texture control section; a lithic contact at 39 inches; an ustic moisture regime; and a frigid temperature regime. Last updated by the state 6/95.