LOCATION ARENA COEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Aquic Haplodurids
TYPICAL PEDON: Arena clay loam - grassland. (Colors are for dry soil unless otherwise noted.)
A1ca--0 to 8 inches; pinkish gray (7.5YR 6/2) light clay loam, dark brown (7.5YR 4/2) moist; moderate fine granular structure; weak platy in the upper one-half inch; soft, very friable, slightly plastic; few very fine and common fine roots; the horizon contains some secondary calcium carbonate and other salt accumulation; very strongly alkaline (pH 10.0); clear smooth boundary. (6 to 10 inches thick)
C1cag--8 to 24 inches; brownish gray (10YR 6/2) light clay loam, dark brown (10YR 4/2) moist; many large prominent yellowish brown (10YR 5/6) and dark gray (10YR 4/1) mottles; weak medium subangular blocky structure; hard, very friable, slightly plastic; few very fine and common fine roots; visible secondary calcium carbonate and other salts occurring as concretions, crystals, and in finely divided forms; horizon is brittle even when moist; very strongly alkaline (pH 9.8); clear smooth boundary. (10 to 30 inches thick)
C2si--24 to 60 inches; pale brown (10YR 6/3) and brown (10YR 5/3) moist; continuous, brittle, firm, porous duripan strongly cemented to indurated layers up to 6 inches thick above 40 inches; can be penetrated with a spade when moist, and with difficulty when dry; impervious to roots; contains 30 to 70 percent durinodes from a few centimeters to several inches in diameter that do not slake in water or acid but will often after alternate treatment with strong base and acid. (Several feet thick)
TYPE LOCATION: Alamosa County, Colorado; approximately 1,250 feet east and 950 feet north of the SW corner of Sec. 30, T. 38 N., R. 9 E.
RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges 43 to 47 degrees F, and mean summer soil temperature ranges from 59 to 64 degrees F. Depth to calcareous material ranges from 0 to about 6 inches. Depth to continuous subhorizons of secondary calcium carbonate and/or sulfate ranges from 6 to 40 inches but occurs above the duripan. Depth to the duripan ranges from 20 to 40 inches. Rock fragments range from 0 to 35 percent in the particle-size control section and dominantly are 1/2 to 10 inches in diameter. Hue ranges from 5Y through 7.5YR except that in some pedons a few subhorizons have hue of 5YR or redder occur discontinuously and occupy less than half the thickness of the control section. A seasonally high water table ranges from 1 to 2 feet below the surface.
The A horizon has value of 5 through 7, 4 or 5 moist, and chroma of 2 or 3. Reaction ranges from moderate to very strongly alkaline.
The Cca horizon above the duripan has value of 5 through 7, 4 or 5 moist, and chroma of 2 through 4. Mottles present are distinct to prominent.
The Csi horizon is at depths of 20 to 40 inches and ranges from 24 inches to several feet thick.
COMPETING SERIES: There are no known competing series in the same family and subgroup.
GEOGRAPHIC SETTING: Arena soils formed on flood plains or alluvial fans. Slope gradients range from 0 to 4 percent. The soils formed in mixed alluvium. At the type location the average annual precipitation is 7 inches, with peak periods of precipitation in the spring and early summer months. Mean annual temperature ranges 41 to 45 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Hooper and San Luis soils. Both of these soils lack duripan.
DRAINAGE AND PERMEABILITY: Poorly drained; slow runoff; slow permeability.
USE AND VEGETATION: These soils are used principally as native pastureland. Native vegetation is limited principally to greasewood and scattered saltgrass.
DISTRIBUTION AND EXTENT: San Luis Valley Area of south-central Colorado. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Rio Grande County, Colorado, 1972.
REMARKS: Last updated by the state 5/81.