LOCATION OSCURA NMEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, calcareous, thermic Ustic Torrifluvents
TYPICAL PEDON: Oscura silty clay -- rangeland. (Colors are for dry soils unless otherwise noted.)
A--0 to 10 inches; light brown (7.5YR 6/4) silty clay, dark brown (7.5YR 3/4) moist; weak thin platy in the upper 2 inches; otherwise weak fine subangular blocky structure; very hard, friable, sticky, plastic; many fine roots; many pores; strongly effervescent with calcium carbonate disseminated; slightly alkaline; abrupt smooth boundary. (6 to 16 inches thick)
C1--10 to 13 inches; light brown (7.5YR 6/4) very fine sandy loam, dark brown (7.5YR 3/4) moist; massive; slightly hard, very friable, common fine roots; common fine and few fine tubular pores; strongly effervescent calcareous with calcium carbonate disseminated; slightly alkaline; abrupt smooth boundary. (0 to 5 inches thick)
C2--13 to 18 inches; pinkish gray (7.5YR 6/2) clay, brown (7.5YR 4/2) moist; massive; very hard, firm, sticky, plastic; common fine roots; few fine and very fine soft salt crystals; common and few fine tubular pores; strongly effervescent with calcium carbonate disseminated; slightly alkaline; abrupt smooth boundary. (3 to 10 inches thick)
C3--18 to 22 inches; pinkish gray (7.5YR 6/2) very fine sandy loam, brown (7.5YR 4/2) moist; massive; slightly hard, very friable; common fine roots; common fine pores; strongly effervescent with calcium carbonate disseminated; slightly alkaline; abrupt smooth boundary. (0 to 5 inches thick)
C4--22 to 39 inches; light brown (7.5YR 6/4) clay, dark brown (7.5YR 3/4) moist; massive; very hard, firm, sticky, plastic; few fine roots; few tubular pores; strongly effervescent with calcium carbonate disseminated; slightly alkaline; clear smooth boundary. (15 to 30 inches thick)
C5--39 to 60 inches; brown (10YR 5/3) heavy silty clay loam, very dark brown (10YR 2/2) moist; massive; hard, friable, sticky; common fine pores; strongly effervescent with calcium carbonate disseminated; slightly alkaline.
TYPE LOCATION: Otero County, New Mexico; in the northeast corner of the White Sands Missile Range; 0.9 mile east from basalt lava flow on Road 12, then 200 yards north and immediately west of fence.
RANGE IN CHARACTERISTICS:
Soil moisture - Intermittently moist in the soil moisture control section during July-August. The soil is moist for less than 90 cumulative days during the growing season in the control section. The soil does not receive significant amounts of moisture in the moisture control section during winter months.
Ustic aridic soil moisture regime.
The particle-size control section averages between 35 to 50 percent clay.
Reaction: slightly to moderately alkaline
Salinity: slight to moderate
Calcium carbonate: 5 to 15 percent
Annual soil temperature: 59 to 65 degrees F.
A horizon
Hue: 5YR, 7.5YR or 10YR
Value: 4 through 6 dry, and 3 through 5 moist
Chroma: 2 through 4
C horizon
Hue: 5YR, 7.5YR or 10YR
Value: 4 through 7 dry, and 3 through 5 moist
Chroma: 2 through 4
In some pedons a buried horizon may occur below a depth of 40 inches.
COMPETING SERIES: There are no competitors.
GEOGRAPHIC SETTING: The Oscura soils are in floodplains at elevations of 4,300 to 5,700 feet. The landscapes are nearly level with slope gradients ranging from 0 to 3 percent. The soils formed in fine textured sediments. Annual precipitation is about 8 to 11 inches with a summer maximum. The annual temperature is about 57 to 62 degrees F. Frost-free period is 180 to 210 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Barana, Mimbres and Marcial soils. Barana soils have argillic horizons. Mimbres soils have cambic horizons and fine-silty control sections. Marcial soils have illitic mineralogy.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; slow permeability.
USE AND VEGETATION: Used primarily for military research and for grazing. Native vegetation is principally vine mesquite, sacaton, alkali sacaton, tobosa, burro grass, chamiza and mesquite.
DISTRIBUTION AND EXTENT: South-central New Mexico. This soil occurs in LRR-D, MLRA 42. The series is inextensive (about 5,000 acres)
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Otero County (White Sands Missile Range Area), New Mexico, 1970.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface to a depth of about 25 cm. (A horizon)
Entisol feature - The absence of diagnostic subsurface horizons
Particle-size control section - the zone from 10 to 40 in. (C1, C2, C3, C4, C5 horizons)
Fluvial feature - Irregular decrease in organic carbon in the zone from 10 to 60 inches (C1, C2, C3, C4, C5 horizons)
Classified according to Soil Taxonomy Second Edition, 1999.