LOCATION SELEVIN AZEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, mixed, superactive, thermic Calcic Paleargids
TYPICAL PEDON: Selevin extremely stony loam - rangeland. (Colors are for dry soil unless otherwise noted.)
Al--0 to 2 inches; reddish brown (5YR 4/4) extremely stony loam, dark reddish brown (5YR 3/4) moist; weak fine platy structure; slightly hard, very friable, slightly sticky; common very fine and fine roots; many very fine and fine vesicular and few very fine tubular pores; 35 percent stones, 30 percent cobble and l0 percent gravel; slightly acid (pH 6.5); abrupt smooth boundary. (l to 2 inches thick)
A2--2 to 5 inches; reddish brown (5YR 4/4) very stony sandy clay loam, dark reddish brown (5YR 3/4) moist; moderate medium subangular blocky structure; slightly hard, very friable, sticky and slightly plastic; common very fine, fine and few medium roots; common very fine and fine tubular pores; 30 percent stones and l0 percent gravel; neutral (pH 7.0); abrupt wavy boundary. (3 to 5 inches thick)
2Bt1--5 to l3 inches; dark reddish brown (2.5YR 3/4) very stony clay, dark reddish brown (2.5YR 3/4) moist; moderate medium prismatic structure parting to strong medium subangular blocky; hard, firm, very sticky and very plastic; many very fine, common fine and few medium roots; many very fine and fine tubular pores; many pressure faces; 30 percent stones and l0 percent gravel; slightly alkaline (pH 7.5); clear wavy boundary. (7 to l0 inches thick)
2Bt2--l3 to l9 inches; reddish brown (2.5YR 4/4) very stony clay, dark reddish brown (2.5YR 3/4) moist; strong medium prismatic structure parting to strong medium angular blocky; hard, firm, very sticky and very plastic; many very fine, common fine and few medium roots; common very fine and fine tubular pores; many pressure faces; 30 percent stones and l0 percent gravel; slightly alkaline (pH 7.5); clear wavy boundary. (5 to 8 inches thick)
2Btk--l9 to 23 inches; reddish brown (2.5YR 4/4) very stony clay, dark reddish brown (2.5YR 3/4) moist; strong medium angular blocky structure; hard, firm, very sticky and very plastic; common very fine and fine roots; common very fine tubular pores; many pressure faces; 35 percent stones and l0 percent gravel; common medium soft calcium carbonate masses and filaments; violently effervescent; moderately alkaline (pH 8.0); abrupt wavy boundary. (4 to 7 inches thick)
3Bk--23 to 60 inches; pinkish white (5YR 8/2) extremely stony sandy loam, pinkish gray (5YR 7/2) moist; massive; hard, firm, slightly sticky; few very fine interstitial pores; 65 percent stones with a thin coating of calcium carbonate; many soft masses of calcium carbonate; weakly cemented in places; violently effervescent; moderately alkaline (pH 8.2).
TYPE LOCATION: Graham County, Arizona; 200 feet west and l,500 feet south of the northeast corner of section 28, T.7 S., R.24 E.; about 8 miles southwest of the town of Pima.
RANGE IN CHARACTERISTICS:
Soil Moisture: Intermittently moist in some part of the soil moisture control section during July-September and December-February. Driest during May and June. Ustic aridic soil moisture regime.
Soil Temperature: 62 to 70 degrees F.
Rock fragments: 35 to 75 percent
Depth to calcium carbonate: 16 to 25 inches
Depth to calcic horizon: 20 to 32 inches
Organic matter: 1 to 2 percent in the surface
A horizon
Hue: 5YR, 7.5YR, 10YR
Value: 2 through 5, dry or moist
Chroma: 2 through 4, dry or moist
Reaction: slightly acid or neutral
Bt horizon
Hue: 2.5YR, 5YR
Value: 3 through 5 dry, 2 to 5 moist
Chroma: 3 through 6 dry, 2 to 6 moist
Texture: clay, sandy clay, sandy clay loam, clay loam
Calcium carbonate: segregated as filaments, seams and soft masses
Reaction: neutral to moderately alkaline
Bk horizon
Hue: 5YR, 7.5YR
Value: 6 through 8, dry or moist
Chroma: 2 through 4, dry or moist
Texture: sandy loam, loam, sandy clay loam, clay loam
Cementation: none to strong discontinuous
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Selevin soils are on fan mesas or fan terraces at elevations of 2,800 to 5,000 feet. Slopes range from 2 to l5 percent. These soils formed in cobbly and stony alluvium from granite and gneiss. The mean annual air temperature is 60 to 68 degrees F. and the mean annual precipitation is l2 to l6 inches. The frost-free period is l80 to 230 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Alsco, Comoro, Eloma, Maloy, and White House soils. Alsco and Maloy soils have loamy-skeletal control sections. Comoro soils do not have argillic horizons and have coarse-loamy control sections. Eloma soils do not have abrupt textural changes. White House soils have less than 35 percent coarse fragments in the control section.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; slow permeability.
USE AND VEGETATION: Used for livestock grazing. Vegetation is tobosa, curly mesquite, bush muhly, black grama, slim tridens, cane bluestem, fluffgrass, green sprangletop, hairy grama, sideoats grama, false mesquite, Mormon tea, range ratany, catclaw, mesquite, whitethorn, janusia, prickly pear and cholla.
DISTRIBUTION AND EXTENT: Southern Arizona. These soils are of small extent. MLRA 41.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Gila-Duncan Area, Arizona, Parts of Graham and Greenlee Counties; l979.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 5 inches (A1, A2 horizons)
Argillic horizon - the zone from 5 to 23 inches (2Bt1, 2Bt2, 2Btk horizons)
Calcic horizon - the zone from 23 to 60 inches (3Bk horizon)
Pale feature - abrupt textural change at 5 inches
Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Tenth Edition, 2006.
Revised for the correlation of AZ661, 2/2009, WWJ