LOCATION ORACLE AZEstablished Series
TAXONOMIC CLASS: Loamy, mixed, superactive, thermic, shallow Ustic Haplargids
TYPICAL PEDON: Oracle gravelly coarse sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.) Surface cover of about 40 percent fine and medium gravel, 10 percent cobble and 5 percent stone.
A--0 to 4 inches (0 to 10 cm); brown (7.5YR 4/4) gravelly coarse sandy loam, dark brown (7.5YR 3/4), moist; weak thin platy parting to weak fine granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine roots; common very fine interstitial pores; 12 percent fine and 12 percent medium gravel; noneffervescent; neutral (pH 6.6); abrupt smooth boundary.
Bt1--4 to 11 inches (10 to 28 cm); reddish brown (5YR 4/4) sandy clay loam, reddish brown (5YR 4/4), moist; strong medium and coarse subangular blocky structure; hard, firm, very sticky and very plastic; common very fine and few coarse roots; common very fine tubular pores; common continuous distinct clay films on faces of peds and rock fragments; 5 percent fine and 5 percent medium gravel; noneffervescent; neutral (pH 6.6); clear smooth boundary.
Bt2--11 to 19 inches (28 to 48 cm); reddish brown (5YR 4/3) sandy clay loam, yellowish red (5YR 4/6), moist; moderate fine and medium prismatic parting to strong fine and medium angular blocky structure; very hard, very firm, very sticky and very plastic; common very fine roots between peds; common very fine tubular pores; common continuous distinct clay films on faces of peds and rock fragments; 2 percent fine and 3 percent medium gravel; noneffervescent; neutral (pH 6.6); abrupt wavy boundary.
Crt--19 to 60 inches (48 to 152 cm) weathered granite (grus) with many distinct continuous clay films on rock fragments
TYPE LOCATION: Pinal County, Arizona, located at latitude 32 degrees, 36 minutes 24.00seconds north, longitude 110 degrees, 48 minutes 10.00seconds west NAD83; and about 2,000 feet north and 1,600 feet west of the southwest corner of Section 34, Township 9 S, Range 15 E; USGS Quadrangle - Oracle
RANGE IN CHARACTERISTICS:
Soil moisture - Intermittently moist in some part of the soil moisture control section during July-September and December-March. Driest during May and June. The epipedon is moist in some part less than 90 days (cumulative) when the soil temperature is above 41 degrees F. in 7 out of 10 years. Ustic aridic soil moisture regime.
Soil temperature: 59 to 69 degrees F.
Rock fragments: averages 1 to 35 percent fine granitic gravel in the control section; 5 to 65 percent on the surface
Depth to bedrock: 5 to 20 inches. Usually weathered to a depth of 60 inches or more
Reaction: slightly acid to moderately alkaline
A horizon
Hue: 5YR, 7.5YR, 10YR
Value: 3 to 5 dry, 2, 3, or 4 moist
Chroma: 2 to 4, dry or moist
B horizon
Hue: 5YR, 7.5YR
Value: 3 to 5 dry, 2 to 4 moist
Chroma: 2 to 4 dry, 2 to 6 moist
Texture: clay loam, loam, sandy clay loam (18 to 35 percent clay)
Cr horizon
Extremely weakly cemented to moderately cemented granite (grus)
COMPETING SERIES: This is the Brunkcow (AZ) series. Brunkcow soils have a lithic contact below the paralithic contact.
GEOGRAPHIC SETTING: Oracle soils are on hills and pediments. They formed in residuum and slope alluvium material weathered from coarse grained granite or granodiorite. Elevations range from 3,000 to 5,400 feet. Slope is 1 to 50 percent. The mean annual precipitation is 12 to 16 inches with summer thunderstorms and gentle winter rain. The mean annual air temperature is 57 to 67 degrees F. The frost-free period is about 180 to 255 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Andrada, Deloro, Lampshire and Romero series. Andrada soils have a calcic horizon. Deloro soils are clayey-skeletal. Lampshire and Romero soils do not have argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderately slow permeability.
USE AND VEGETATION: These soils are used for livestock grazing, wildlife habitat, mining and homesites. Vegetation is mainly beargrass, calliandra, shrubby buckwheat, sideoats grama, hairy grama, cane beardgrass, plains lovegrass and threeawn, with a scattered overstory of manzanita, juniper and Emory oak.
DISTRIBUTION AND EXTENT: Southern Arizona. The Oracle series is moderately extensive. MLRAs are 38 and 41.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Page-Trowbridge Experiment Range, Arizona; 1952.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from 0 to 4 inches (A horizon)
Argillic horizon - the zone from 4 to 19 inches (Bt1, Bt2 horizons)
Paralithic contact - the boundary at 19 inches (Crt horizon)
The type location was moved in June 2005. The new type location is in an area consistent with an ustic aridic soil moisture regime.
Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Tenth Edition, 2006.
Revised for the correlation of AZ661, 2/2009, WWJ
Revised for the correlation of AZ675, 5/2009, WWJ