LOCATION ATENCIO COEstablished Series
TAXONOMIC CLASS: Fine-loamy over sandy or sandy-skeletal, mixed, superactive, mesic Aridic Argiustolls
TYPICAL PEDON: Atencio sandy loam, uncultivated. (Colors are for dry soil unless otherwise noted.)
A1--0 to 5 inches; dark reddish gray (5YR 4/2) sandy loam, dark reddish brown (5YR 3/2) moist; moderate medium granular structure; soft, loose; many fine and medium roots; 5 percent gravel; mildly alkaline; clear smooth boundary. (4 to 7 inches thick)
B1--5 to 11 inches; reddish brown (5YR 4/3) sandy loam, dark reddish brown (5YR 3/3) moist; weak medium subangular blocky structure; slightly hard, very friable; many fine and medium roots; 5 percent gravel; mildly alkaline; clear smooth boundary. (5 to 8 inches thick)
B2t--11 to 23 inches; reddish brown (5YR 4/4) gravelly sandy clay loam, reddish brown (5YR 4/3) moist; moderate medium prismatic structure parting to weak medium subangular blocky; hard, friable, slightly sticky and plastic; many fine and medium roots; 15 percent gravel; slightly effervescent; mildly alkaline; clear smooth boundary. (10 to 14 inches thick)
B3ca--23 to 28 inches; brown (7.5YR 5/4) gravelly sandy loam, dark brown (7.5YR 4/4) moist; weak medium subangular blocky structure; slightly hard, friable; many fine and medium roots; 20 percent gravel; strongly effervescent; mildly alkaline; clear smooth boundary. (4 to 9 inches thick)
IICca--28 to 54 inches; sand, pebbles and cobbles; some visible calcium carbonate as coatings on coarse fragments; 30 percent sand, 40 percent pebbles, 30 percent cobbles; violently effervescent.
TYPE LOCATION: Garfield County, Colorado; about 5 miles southeast of Glenwood Springs; 600 feet southwest of Roaring Fork River; 320 feet north and 150 feet west of the SE corner of Sec. 35, T. 6 S., R. 89 W.
RANGE IN CHARACTERISTICS: The mollic epipedon ranges from 9 to 15 inches thick. Depth to the underlying sand, pebbles, and cobbles ranges from 23 to 38 inches. These soils are usually leached to a depth of 10 to 17 inches.
The A horizon has hue of 2.5YR through 7.5YR, value of 4 or 5 dry, 2 or 3 moist, and chroma of 3 through 5. This horizon is commonly sandy loam, but ranges to loam or gravelly loam.
The B2t horizon has hue of 10R through 5YR, value of 4 through 6 dry, 3 through 5 moist, and chroma of 3 through 5. It is usually sandy clay loam in the fine earth fraction and has 18 to 35 percent clay and 5 to 35 percent pebbles.
The IICca horizon has 20 to 40 percent cobbles and 35 to 50 percent pebbles. Sand ranges from medium to coarse and from 25 to 40 percent by volume.
COMPETING SERIES: These are the Altvan, Archerson, Eckley, Newlin, Redridge, Tuthill, and Wheatridge series. Eckley, Newlin, and carbonate accumulation, and are noncalcareous throughout the solum. Archerson, Altvan, and Tuthill soils have hue of 7.5YR or yellower. Redridge soils lack calcium carbonate accumulation and are noncalcareous.
GEOGRAPHIC SETTING: Atencio soils are on sloping alluvial fans and terraces. Slopes are 0 to 12 percent. Elevations range from 5,000 to 6,500 feet. The soils formed in alluvium from red shale and sandstone. The average annual precipitation is about 16 inches and is evenly distributed throughout the year. Mean annual temperature is 48 to 51 degrees F. The frost-free season is about 115 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Azeltine and Begay soils. Azeltine soils lack an argillic horizon. Begay soils have a cambic horizon and contain less than 35 percent coarse fragments in the control section.
USE AND VEGETATION: These soils are used principally for livestock grazing, irrigated hayland, or occasionally for irrigated cropland. Native vegetation is mainly bluegrass, big sagebrush, rabbitbrush, and western wheatgrass.
DISTRIBUTION AND EXTENT: Lower foothill valley areas of western Colorado. The series is inextensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Rifle Area, Colorado, 1977.
REMARKS: Last updated by the state 1/77.
The superactive cation exchange activity class was added in 03/2003 to the taxonomic classification by the National Soil Survey Center on request of the Lakewood MLRA office, without review of the soil series property data. The remainder of this document has not been updated.