LOCATION COMOBABI AZEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, hyperthermic, shallow Typic Argidurids
TYPICAL PEDON: Comobabi extremely cobbly fine sandy loam, rangeland. (Colors are for dry soil unless otherwise noted.) About 80 percent of the surface is covered with gravel and cobbles.
A--0 to 1 inch; light brown (7.5YR 6/4) extremely cobbly fine sandy loam, brown (7.5YR 5/4) moist; weak fine granular structure; slightly hard, very friable; common fine roots; many very fine vesicular pores; slightly effervescent; about 30 percent gravel and 40 percent cobbles; ; moderately alkaline (pH 8.4); gradual wavy boundary. (1 to 4 inches thick)
Bt--1 to 10 inches; yellowish red (5YR 5/6) extremely cobbly sandy loam, yellowish red (5YR 4/6) moist; weak fine subangular blocky structure; slightly hard, very friable, slightly plastic; many very fine roots; common very fine irregular pores; few thin clay films on faces of peds and in pores; slightly effervescent; about 35 percent gravel and 40 percent cobbles; slightly alkaline (pH 7.8); gradual wavy boundary. (1 to 10 inches thick)
Btk--10 to 19 inches; yellowish red (5YR 5/8) extremely cobbly sandy clay loam, yellowish red (5YR 5/6) moist; moderate fine subangular blocky structure; hard, friable, slightly sticky and plastic; many very fine roots; few very fine tubular pores; clay films occurring as colloid stains and a s bridges between sand grains; common fine masses and filaments of lime; violently effervescent; about 35 percent gravel and 40 percent cobbles; moderately alkaline (pH 8.2); abrupt wavy boundary. (2 to 15 inches thick)
2Bkqm--19 to 27 inches; indurated silica lime-cemented duripan with a laminar horizon; extremely hard; violently effervescent. (Several feet thick)
TYPE LOCATION: Maricopa County, Arizona; about 7 miles north and 12 miles east of Gila Bend; 850 feet north and 2000 feet west of the southeast corner of sec. 25, T. 4 S., R. 3 W.
RANGE IN CHARACTERISTICS:
Soil Moisture - Intermittently moist in some parts of the soil moisture control section during July - September and December - February. Typic aridic moisture regime.
Organic Matter Content - Less than one percent.
Soil temperature - Greater than 72 degrees F.
Depth to Duripan - 7 to 20 inches.
Rock Fragments - Usually more than 50 percent with more cobbles and stones than pebbles.
A horizon
Hue: 7.5YR or 10YR
Value: 4 to 6
Chroma: 4 to 6
Texture: Fine sandy loam, loam, sandy loam (8 to 18 percent clay).
B horizon
Hue: 5YR or 7.5YR
Value: 4 to 6
Chroma: 5 to 8
Texture: Loam, sandy clay loam, sandy loam (13 to 25 percent clay).
COMPETING SERIES: This is the Sal series. Sal soils are saline and have rock fragments that are dominantly cobbles.
GEOGRAPHIC SETTING: Comobabi soils are on fan terraces. Slopes range from 5 to 15 percent. Elevation ranges from 1,200 to 2,100 feet. The soils have formed in fan alluvium from mixed sources and eolian deposits. The climate is hot, arid and continental. Average annual precipitation is from 5 to 10 inches occurring as summer thunderstorms and winter rains. The average annual temperature is about 72 degrees F. The frost-free period is 260 to 320 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cipriano, Laposa, Momoli, Pinamt, and Vaiva series. Laposa soils are 20 to 40 inches deep to bedrock. Vaiva soils have a lithic contact. Momoli and Pinamt are more than 40 inches deep. Cipriano soils lack an argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; permeability is moderate.
USE AND VEGETATION: Used primarily for rangeland and wildlife habitat. Native vegetation is creosotebush, triangleleaf bursage, ocotillo, buckhorn cholla, saguaro, paloverde, and annual grasses.
DISTRIBUTION AND EXTENT: Southern Arizona. The series is moderately 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:
1. Ochric epipedon - The zone from the surface to about 1 inch.
2. Argillic horizon - The zone from 10 to about 17 inches.
3. Petrocalcic horizon - The zone from about 19 inches to about 27 inches. This horizon is lime and silica-cemented and does not dissolve in acid when soaked overnight. Most areas have a thin laminar cap.
ADDITIONAL DATA: NSSL sample number S80AZ-013-002. Sampled as Piedra.