LOCATION BILBURC AZEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Torrertic Paleustolls
TYPICAL PEDON: Bilburc very gravelly loam - woodland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 1 inch; brown (7.5YR 4/3) very gravelly loam, dark brown (10YR 3/3) moist; weak fine granular structure; soft, very friable, moderately sticky and moderately plastic; common fine roots; many very fine tubular pores; noneffervescent; 40 percent gravel; neutral (pH 7.0); abrupt smooth boundary. (1 to 8 inches thick)
A2--1 to 4 inches; dark brown (7.5YR 3/3) loam, dark brown (7.5YR 3/2) moist; moderate medium subangular blocky structure; soft, very friable, moderately sticky and moderately plastic; many very fine and fine roots; many very fine and fine and few medium tubular pores; noneffervescent; 5 percent gravel; neutral (pH 7.0); clear wavy boundary. (0 to 5 inches thick)
Bt--4 to 11 inches; dark brown (7.5YR 3/3) clay, dark brown (7.5YR 3/2) moist; strong fine angular blocky structure; hard, firm, very sticky and very plastic; common very fine through coarse roots; many very fine through coarse tubular pores; common faint clay films on faces of peds; slightly effervescent; 5 percent gravel; slightly alkaline (pH 7.4); clear wavy boundary. (6 to 15 inches thick)
Btkss1--11 to 17 inches; reddish brown (5YR 4/4) clay, dark reddish brown (5YR 3/4) moist; strong medium prismatic structure parting to strong medium angular blocky; very hard, very firm, very sticky and very plastic; few medium and coarse roots; few medium and coarse tubular pores; many slickensides; many distinct clay films on faces of peds; strongly effervescent; 5 percent gravel; moderately alkaline (pH 8.2); clear wavy boundary. (0 to 7 inches thick)
Btkss2--17 to 26 inches; reddish brown (2.5YR 4/4) clay, dark reddish brown (2.5YR 3/4) moist; strong coarse prismatic structure parting to strong medium angular blocky; very hard, very firm, very sticky and very plastic; few medium and coarse roots; few fine and medium tubular pores; many slickensides; many distinct clay films on faces of peds; few cracks between peds; common fine soft masses of calcium carbonate; strongly effervescent; moderately alkaline (pH 8.4); clear wavy boundary. (6 to 10 inches thick)
Btk--26 to 36 inches; reddish brown (5YR 5/4) clay loam, reddish brown (5YR 5/4) moist; massive; hard, friable, very sticky and very plastic; few coarse roots; few coarse tubular pores; common faint clay films on faces of peds; many coarse soft masses of calcium carbonate; 10 percent calcium carbonate coated gravel; violently effervescent; moderately alkaline (pH 8.4); abrupt smooth boundary. (0 to 10 inches thick)
R--36 inches; limestone bedrock.
TYPE LOCATION: Mohave County, Arizona; on the Lake Mead National Recreation Area; 800 feet east and 1200 feet north of the southeast corner of section 13, T. 31 N., R. 13 W.; 36 degrees, 4 minutes, 59 seconds north latitude; 113 degrees, 37 minutes, 48 seconds west longitude.
RANGE IN CHARACTERISTICS:
Soil moisture: usually dry in some part for 90 or more days cumulative and is moist in some part for 45 consecutive days during June through October and more than half the time that the soil temperature is above 41 degrees F. The soil is driest during May and June. Aridic ustic soil moisture regime.
Soil Temperature: 49 to 56 degrees F.
Rock fragments: averages less than 15 percent in the particle-size control section. Ranges to 70 percent in the surface layer.
Clay content: averages 35 to 55 percent in the particle-size control section.
Depth to bedrock: 20 to 40 inches.
Depth to calcic horizon: 14 to 30 inches.
Calcium carbonate equivalent: Averages 15 to 40 percent in the calcic horizon.
Slickensides: few to many and may occur in either the Bt or Btk horizons.
Cracking: cracks 5mm or more are present within 125cm of the surface in most years.
A horizons
Hue: 7.5YR, 10YR.
Value: 3 to 5 dry, 2 to 4 moist.
Chroma: 2 or 3, dry or moist.
Reaction: slightly acid to neutral
Mollic epipedon: may include the upper part of the argillic horizon in some pedons.
Bt horizon
Hue: 5YR, 7.5YR.
Value: 3 to 5 dry, 2 to 4 moist.
Chroma: 2 to 4, dry or moist.
Texture: clay loam, clay.
Reaction: slightly acid to slightly alkaline
Btkss horizon.
Hue: 2.5YR, 5YR, 7.5YR.
Value: 2.5 to 6 dry, or moist.
Chroma: 2 to 6, dry or moist.
Texture: clay, clay loam.
Btk or Bk horizons.
Hue: 2.5YR, 5YR, 7.5YR.
Value: 4 to 6 dry, or moist.
Chroma: 2 to 6, dry or moist.
Calcium carbonates equivalent: average 15 to 40 percent
COMPETING SERIES: This is the Binsin (AZ) series. Binsin soils are more than 60 inches deep to bedrock.
GEOGRAPHIC SETTING: Bilburc soils are on plateaus and mesas at elevations of 5800 to 6800 feet. They formed in residuum from the Kaibab Limestone. Slopes range from 1 to 15 percent. The mean annual precipitation is 13 to 18 inches. The mean annual air temperature is about 47 to 54 degrees F. The frost-free period is 120 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: In addition to the competing Binsin soils, they are the Disterheff, Natank and Yumtheska soils. Disterheff and Natank soils do not have a mollic epipedon. Yumtheska soils have a lithic contact within a depth of 20 inches.
DRAINAGE AND PERMEABILITY: Well drained; high or very high runoff; very slow permeability.
USE AND VEGETATION: Bilburc soils are used for recreation and wildlife habitat. Present vegetation is Utah juniper, pinyon pine, Wyoming big sagebrush, bottlebrush squirreltail, blue grama and Stansbury cliffrose.
DISTRIBUTION AND EXTENT: Northwestern Arizona. MLRA is 35. Clay loam upland; This series is of limited extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Mohave County, Arizona; Soil survey of Lake Mead National Recreation Areas; and Grand Canyon soil survey area 2001.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the 0 to 11 inches (A1, A2 and Bt horizons).
Argillic horizon - The zone from 4 to 36 inches (Bt, Btkss1, Btkss2 and Btk horizons).
Calcic horizon - The zone from 17 to 36 inches (Btkss2 and Btk horizons).
Lithic contact - The boundary at 36 inches (R horizon).
Pale feature - Clay increase of 20 percent or more (absolute) at the upper boundary of the argillic horizon (A2 and Bt horizons).
Vertic feature - Cracks within 125 cm of the surface (Btkss2 horizon).
Classification changed to Torrertic subgroup in 2006. This change was made to be consistent with the Vertic features described and the moisture regime.
Classified according to Keys to Soil Taxonomy Tenth Edition, 2006.
ADDITIONAL DATA: This soil was the subject of a soil nutrient study and was intensively sampled.