LOCATION POMPEII AZEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, hyperthermic, shallow Typic Petrocalcids
TYPICAL PEDON: Pompeii extremely cobbly sandy loam, rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 2 inches; yellowish brown (10YR 5/4) extremely cobbly sandy loam, dark brown (10YR 3/3) moist; weak fine platy structure; soft, very friable, few very fine roots; few very fine vesicular pores; noneffervescent; moderately alkaline (pH 8.2); clear smooth boundary. (0 to 2 inches thick)
Bw--2 to 9 inches; light brown (7.5YR 6/4) very gravelly sandy loam, brown (7.5YR 4/4) moist; weak fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; common very fine roots matted around stones; few very fine discontinuous tubular pores; noneffervescent; slightly alkaline (pH 7.8); clear wavy boundary. (3 to 8 inches thick)
Bk--9 to 13 inches; brown (7.5YR 5/4) very gravelly sandy loam, brown (7.5YR 4/4) moist; weak fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; few very fine roots; few very fine discontinuous tubular pores; violently effervescent; moderately alkaline (pH 8.2); abrupt wavy boundary. (3 to 8 inches thick)
2Bkm-- 13 inches; pinkish white (7.5YR 8/2) indurated lime-cemented hardpan.
TYPE LOCATION: Pinal County, Arizona, on the Gila River Indian Reservation in the Santan Mountains about 2.5 miles northwest of Olberg; about 1500 feet west and 150 feet south of the northeast corner of sec. 35, T.3S., R.6E.
RANGE IN CHARACTERISTICS:
Soil moisture - Intermittently moist in some part of the soil moisture control section during July to September and December to February. Typic aridic soil moisture regime.
Depth to petrocalcic horizon - 6 to 20 inches
Mean annual soil temperature - About 71 to 76 degrees F.
Control section - Rock fragments: Averages 35 to 85 percent
Rock fragments on the surface: 85 percent gravel, cobble, and stones
A horizon
Hue: 7.5YR or 10YR
Value: 5 to 7 dry, 3 to 5 moist
Chroma: 3 or 4, dry or moist
Organic matter: less than 1 percent
Bk horizon
Hue: 7.5YR or 10YR
Value: 6 to 8 dry, 4 to 6 moist
Chroma: 3 to 6, dry or moist
Texture: sandy loam, coarse sandy loam
Petrocalcic horizon - Occurs as 5 to 10 inch thick layers alternating with layers of Bk soil material
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Pompeii soils are on fan terraces and hills. These soils formed in very gravelly moderately coarse and coarse textured mixed alluvium and colluvium from basalt. Slopes are 3 to 50 percent. Elevations are 800 to 2,500 feet. The climate is hot and arid with a mean annual precipitation of 5 to 10 inches; mean annual air temperature of 69 to 74degrees F. and a frost-free period of about 240 to 320 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ajo, Gunsight, and Lomitas soils. Ajo soils are moderately deep to a petrocalcic horizon and have argillic horizons. Gunsight soils are very deep and have calcic horizons. Lomitas soils have a lithic contact.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; medium or slow runoff; rapid permeability.
USE AND VEGETATION: Livestock grazing and recreation. The vegetation is principally white brittlebush, creosotebush, triangle bursage, littleleaf paloverde and cacti.
DISTRIBUTION AND EXTENT: Southwestern Arizona. These soils are not extensive. MLRA 40.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Maricopa County (Gila Bend-Ajo Area), Arizona, 1985.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Petrocalcic horizon - indurated lime-cemented hardpan at 13 inches. (Bkm horizon)
Particle size control section - The zone from the soil surface to 13 inches. (The A and B horizons)
Classified according to Keys to Soil Taxonomy Ninth Edition, 2003
In May 2005 the responsibility of the Pompeii series was transferred from MO2 (Davis California) to MO8 (Phoenix Arizona), since the series was no longer being correlated in Clark County Area, Nevada. The type location was relocated to the Gila River Indian Reservation in March 2006.