LOCATION PINWHEEL AZTentative Series
TAXONOMIC CLASS: Clayey-skeletal, mixed, superactive, thermic Ustic Haplargids
TYPICAL PEDON: Pinwheel very gravelly sandy loam, Juniper-pinon. (Colors are for dry soil unless otherwise noted.) Approximately 50 to 60 percent cover of sandstone gravel.
A--0 to 2 inches; yellowish red (5YR 4/6) very gravelly sandy loam, dark reddish brown (5YR 3/4) moist; weak fine and medium platy structure; soft, very friable; very few fine roots; 25 percent gravel; slightly effervescent; slightly alkaline (pH 7.6); clear, smooth boundary. (2 to 3 inches thick)
Bt1--2 to 8 inches; yellowish red (5YR 5/6) very gravelly clay, reddish brown (5YR 4/4) moist; moderate fine subangular blocky structure; slightly hard, friable, sticky and plastic; common fine and medium and coarse roots on boundary; few fine interstitial and tubular pores; few thin clay films on faces of peds; 70 percent layered gravel; strongly effervescent; moderately alkaline (ph 8.2); gradual, wavy boundary. (6 to 10 inches thick)
Bt2--8 to 24 inches; red (2.5YR 5/6) very cobbly sandy clay, dark red (2.5YR 3/6) moist; moderate fine subangular blocky structure; slightly hard, friable, sticky and plastic; many fine and medium and few coarse roots; few fine interstitial and tubular pores; few thin clay films on faces of peds; 80 percent layered cobble; strongly effervescent; moderately alkaline (ph 8.2); abrubt, irregular boundary. (12 to 20 inches thick)
R--24 inches; sandstone bedrock with soil material between fractures and in cracks. Few fine roots in fractures, which are occasionally coated with lime.
TYPE LOCATION: Yavapai County, Arizona. NW1/4 of the SW1/4 of Section 14, T. 17 N., R. 5 E. In the Sedona Ranger District, Coconino National Forest.
RANGE IN CHARACTERISTICS:
Depth to bedrock and thickness of the solum: 20 to 40 inches
Rock fragments: 35 to 80 percent coarse fragments by volume
Mean annual soil temperature: 61 to 63 degrees F.
Soil moisture: usually dry and never moist in some part for as long as 90 consecutive days during the growing season. Ustic aridic moisture regime.
Reaction: slightly to moderately alkaline.
A horizon
Hue: 5YR, 2.5YR
Value: 3 or 4
Color: 4 or 6
Organic matter: less than 1 percent
Texture: typically very gravelly sandy loam but includes very gravelly sandy clay loam.
B2t horizons
Hue: 5YR, 2.5YR
Value: 3 to 5
Chroma: 4 or 6
Effervescence: increases with depth
Texture: very gravelly clay, very cobbly sandy clay, gravelly clay and very gravelly clay loam
R horizon
Hard sandstone bedrock with soil material between fractures and in cracks.
COMPETING SERIES: This is the Eloma series. Eloma soils are very deep.
GEOGRAPHIC SETTING: Pinwheel soils are on uplands at elevations of 4,000 to 4,800 feet. Slopes range from 0 to 40 percent. Pinwheel soils formed in residuum weathered from sandstone. The climate is warm semiarid continental. Average annual precipitation is about 14 to 17 inches and the mean annual temperature is about 60 degrees F. The mean January temperature is about 42 degrees F. The mean January temperature is about 42 degrees F., and the mean July temperature is about 80 degrees F. Frost-free season is about 250 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Courthouse and Grindstone soils and Tobler soils. Tobler soils are deep and have less than 35 percent coarse fragments.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; slow permeability.
USE AND VEGETATION: These soils are used for winter range for livestock and wildlife, and for homesites. Native vegetation is mainly juniper (Juniperus osteosperma), pinon pine (Pinus edulis), turbinella oak (Quercus turbinella), manzanita (Arctostaphylos Pringlei), crucifixion thorn (Holacantha Emoryi), desert ceanothus (Ceanothus Greggi), mountain mahogany (Cercocarpus mountanus), yucca (Yucca spp.), silktassle (Garrya spp.), sideoats grama (Boutela curtipendula), algerita (Berberis trifoliata), threeawn (Aristada spp.), tobosa (Hilaria mutica), and mimosa.
DISTRIBUTION AND EXTENT: North Central Arizona. This series is of moderate extent. MLRA 38.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES PROPOSED: Yavapai County (Black Hills-Sedona Area), Arizona, 1975. The name is coined.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: The zone from the surface of the soil to a depth of 2 inches. (A horizon)
Argillic horizon: The zone from about 2 inches to 24 inches. (Bt horizons)
Classified according to Keys to Soil Taxonomy Tenth Edition, 2006