LOCATION PALOS VERDES AZ+NVEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, thermic Durinodic Haplargids
TYPICAL PEDON: Palos Verdes gravelly sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 1 inch; brown (7.5YR 5/4) gravelly sandy loam, brown (7.5YR 4/4) moist; weak medium platy structure; slightly hard, very friable, nonsticky and nonplastic; few fine roots; many fine interstitial pores; 30 percent fine gravel; noneffervescent; slightly alkaline (pH 7.8); abrupt smooth boundary. (1 to 3 inches thick)
Bt1--1 to 3 inches; brown (7.5YR 5/4) gravelly sandy loam, brown (7.5YR 4/4) moist; weak thick platy parting to weak medium and fine subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common fine and very fine roots; common fine interstitial pores; 20 percent fine gravel; common faint clay films as bridges and lining pores; noneffervescent; neutral (pH 6.8); abrupt wavy boundary. (0 to 3 inches thick)
Bt2--3 to 8 inches; reddish brown (5YR 4/4) gravelly sandy clay loam, dark reddish brown (5YR 3/4) moist; weak medium subangular blocky structure; hard, friable, sticky and plastic; many very fine and fine and few medium roots; common fine and medium tubular and many fine interstitial pores; 30 percent fine gravel; common faint clay films on faces of peds and lining pores; noneffervescent; slightly alkaline (pH 7.5); clear wavy boundary. (3 to 6 inches thick)
Bt3--8 to 15 inches; reddish brown (5YR 4/4) gravelly sandy clay loam, dark reddish brown (5YR 3/4) moist; moderate medium subangular blocky structure; hard, friable, sticky and plastic; many very fine and few medium and fine roots; few fine and medium tubular and common fine interstitial pores; 30 percent fine gravel; many faint clay films on faces of peds and few distinct clay films in pores; noneffervescent; slightly alkaline (pH 7.5); clear wavy boundary. (4 to 8 inches thick)
Btk--15 to 19 inches; yellowish red (5YR 5/6) and reddish brown (5YR 4/4) gravelly sandy loam, yellowish red (5YR 4/6) and reddish brown (5YR 4/3) moist; moderate thick platy structure; very hard, firm, slightly sticky and slightly plastic; many very fine roots between plates and few very fine and fine roots in peds; many very fine tubular and common fine interstitial pores; 30 percent gravel; common faint clay films coating gravel; many medium distinct pinkish white calcium carbonate masses; violently effervescent; 28 percent calcium carbonate equivalent; moderately alkaline (pH 8.2); abrupt wavy boundary. (2 to 10 inches thick)
2Cd1--19 to 38 inches; pinkish white (7.5YR 8/2) and pink (7.5YR 8/4) sandy loam, light brown (7.5YR 6/4) moist; massive; very hard, very firm and brittle, nonsticky and nonplastic; many very fine roots in fractures; common very fine and few fine medium and coarse tubular pores; violently effervescent; 29 percent calcium carbonate equivalent; moderately alkaline (pH 8.2); clear wavy boundary. (2 to 30 inches thick)
2Cd2--38 to 64 inches; pinkish white (7.5YR 8/2) and pink (7.5YR 8/4) gravelly loamy coarse sand, light brown (7.5YR 6/4) moist; massive; very hard,, very firm and brittle, nonsticky and nonplastic; few very fine and fine roots in fractures; common fine and very fine interstitial and tubular pores and few coarse tubular pores; 20 percent gravel; violently effervescent; 10 percent calcium carbonate equivalent; moderately alkaline (pH 8.2).
TYPE LOCATION: Pima County, Arizona; corner of La Canada Draw and Magee Road; 500 feet west and 400 feet south of the northeast corner of section 34, T. 12 S., R. 13 E.
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. Typic aridic soil moisture regime.
Soil temperature - 66 to 72 degrees F.
Rock fragments - Averages 5 to 35 percent fine and medium gravel. Surface layer averages 5 to 65 percent gravel.
Depth to compacted unconsolidated sediments - 8 to 20 inches
Reaction - Ranges from neutral in the upper part to strongly alkaline in the lower compacted layers
A horizon
Hue: 7.5YR, 5YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2, 3, or 4, dry or moist
Bt horizon
Hue: 5YR, 7.5YR
Value: 4, 5, or 6 dry, 3, 4, or 5 moist
Chroma: 3, 4, or 6, dry or moist
Texture: sandy clay loam, clay loam, sandy loam (averages 18 to 35 percent clay)
Cd horizon
Hue: 5YR, 7.5YR
Value: 7 or 8 dry, 6 or 7 moist
Chroma: 2 through 4, dry or moist
Texture: When crushed, includes coarse sandy loam, loamy coarse sand, sandy loam, loamy fine sand, fine sand, loamy sand
Consistence: Brittle and firm or very firm when moist. Typically breaks down after prolonged soaking and shaking in water. Roots can enter the matrix when moist but is root restrictive when dry.
Genesis: Thought to be Pleistocene age sediments that were naturally compacted by a combination of paleo lake water loading and impregnation by calcium carbonate and low levels of silica.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Palos Verdes soils are on relict fan terraces. Slopes range from 2 to 15 percent. They formed in fan alluvium from granite, gneiss, schist, rhyolite, latite and volcanic ash. Elevations range from 2200 to 3600 feet. Mean annual precipitation is 10 to 12 inches, falling as thundershowers and as gentle rains in winter. Mean annual air temperature is 64 to 70 degrees F. The frost-free period is 230 to 280 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Anthony, Continental, Stagecoach and Pinaleno series. These soils do not have compacted layers.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderately slow permeability.
USE AND VEGETATION: Used for livestock grazing, wildlife habitat and low density urban construction. Vegetation is mainly desert shrubs and cacti, including paloverde, saguaro, bursage, whitethorn, creosotebush, barrel and prickly pear cacti, and bush muhly.
DISTRIBUTION AND EXTENT: Southern Arizona. The Palos Verdes soils are moderately extensive. MLRA 40.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Tucson Area, Pima County, Arizona; 1931.
REMARKS: Classification changed to better reflect the nature of the compacted layers. These layers are not duripans but are intergrades between rock (paralithic) material and unconsolidated alluvium. They are root restrictive when dry but not restrictive when moist.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 1 inch (A horizon)
Argillic horizon - The zone from 3 to 19 inches (Bt1, Bt2, Bt3, Btk horizons)
Compacted layers - The zone from 19 to 64 inches (2Cdk1, 2Cdk2 horizons)