LOCATION BRUNOPEAK AZEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, mixed, superactive, thermic Aridic Paleustolls
TYPICAL PEDON: Brunopeak very gravelly sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.) 60 to 90 percent of the surface is covered with gravel and cobbles
A--0 to 3 inches; dark brown (7.5YR 3/2) very gravelly sandy loam, very dark brown (7.5YR 2.5/2) moist; weak thick platy parting to weak fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; common very fine and fine roots; common fine irregular and tubular pores; 45 percent gravel; noneffervescent; moderately acid (pH 6.0); abrupt smooth boundary. (1 to 4 inches thick)
Bt1--3 to 16 inches; dark reddish brown (5YR 3/2) extremely gravelly clay loam, dark reddish brown (5YR 3/2) moist; moderate very fine and fine subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common very fine and fine roots; common fine irregular and tubular pores; many distinct clay films on rock fragments and common distinct clay films on faces of peds; 50 percent gravel, 20 percent cobble; noneffervescent; slightly acid (pH 6.2); clear smooth boundary.
Bt2--16 to 42 inches; dark reddish brown (2.5YR 3/4) extremely cobbly sandy clay, dark reddish brown (2.5YR 3/4) moist; moderate very fine, fine and medium subangular blocky structure; moderately hard, firm, moderately sticky and moderately plastic; common very fine and fine and few coarse roots; common fine irregular and tubular pores; many distinct clay films on rock fragments and common distinct clay films on faces of peds; common distinct organic coatings on faces of peds; 35 percent gravel and 30 percent cobble; noneffervescent; slightly acid (pH 6.4); abrupt wavy boundary.
Bt3--42 to 60 inches; dark reddish brown (2.5YR 3/4) extremely cobbly sandy clay loam, dark reddish brown (2.5YR 3/4) moist; moderate very fine and fine subangular blocky structure; moderately hard, firm, moderately sticky and moderately plastic, common very fine, fine and medium roots; common fine irregular and tubular pores; many distinct clay films on rock fragments; common distinct clay films on faces of peds; common distinct organic coatings on faces of peds; 30 percent gravel and 40 percent cobble; noneffervescent; neutral (pH 6.6). (Combined thickness of the Bt horizons is 55 to 60 inches)
TYPE LOCATION: Cochise County, Arizona; located about 2,200 feet north and 300 feet west of the southeast corner of section 15, Township 19 S., Range 28 E.; Stanford Canyon topography map; latitude 31 degrees, 46 minutes, 40 seconds North and longitude 109 degrees, 27 minutes, 25 seconds West.
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. Aridic Ustic soil moisture regime.
Soil Temperature: 59 to 64 degrees F.
Rock fragments: greater than 35 percent gravel and cobbles
Clay content: greater than 35 percent in the control section
Organic matter: 1 to 3 percent
A horizon
Hue: 7.5YR, 5YR
Value: 3 or 4 dry, 2.5 or 3 moist
Chroma: 2 or 3, dry or moist
Texture: fine sandy loam, sandy loam
Reaction: moderately acid to slightly acid
Bt horizon
Hue: 2.5YR, 5YR
Value: 3 or 4 dry, 2.5 through 4 moist
Chroma: 2 through 4 dry or moist
Texture: clay loam, sandy clay, clay
Reaction: slightly acid to neutral
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: The Brunopeak soils are in the Chihuahuan desert on fan terraces at elevations of 4,600 to 6,200 feet. Slope ranges from 15 to 40 percent. These soils formed from mixed fan alluvium. The mean annual precipitation is 16 to 20 inches and occurs as thunderstorms during July to September and as gentle rains during December and January. The mean annual air temperature is 57 to 62 degrees F. The frost-free period is 160 to 210 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Terrarossa and Blacktail soils. These soils are also fine textured and average less than 35 percent rock fragments.
DRAINAGE AND PERMEABILITY: Well drained; high to very high runoff; slow permeability.
USE AND VEGETATION: Used for livestock grazing and wildlife habitat. Vegetation includes plains lovegrass, sideoats grama, Texas bluestem, wooly bunchgrass, cane beardgrass, blue grama, hairy grama, and purple grama.
DISTRIBUTION AND EXTENT: Southeastern Arizona portion of the Chihuahuan desert. MLRA is 41. Brunopeak soils are of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Cochise County, Arizona; Soil Survey of Cochise County, Arizona, Douglas -Tombstone Part; 2000.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from 0 to 16 inches (A and Bt1 horizons)
Pale feature - Abrupt textural change between A and Bt1
Argillic horizon - The zone from 3 to 60 inches (Bt1, Bt2 and Bt3 horizons)
Soil Taxonomy Second Edition, 1999