LOCATION ROCKYROAD AZEstablished Series
TAXONOMIC CLASS: Clayey, smectitic, mesic Lithic Haplusterts
TYPICAL PEDON: Rockyroad very cobbly silty clay loam - woodland. (Colors are for dry soil unless otherwise noted.) Surface is partially covered by 25 percent basalt gravel, 20 percent cobble, 10 percent stone and 5 percent boulders. Several surface cracks and polyhedrons are present.
A--0 to 2 inches; variegated strong brown (7.5YR 4/6) and dark brown (7.5YR 3/3) very cobbly silty clay loam; dark brown (7.5YR 3/4) and very dark brown (7.5YR 2.5/2) moist; strong fine granular structure; soft, very friable, moderately sticky and moderately plastic; many very fine irregular pores; few vertical cracks filled with fine earth; noneffervescent; 15 percent gravel, 10 percent cobble, 5 percent stone and 5 percent boulder; neutral (pH 7.2), abrupt wavy boundary. (1 to 2 inches thick.)
Bt--2 to 4 inches; dark brown (7.5YR 3/3) clay; very dark brown (7.5YR 2.5/3) moist; strong medium subangular blocky structure parting to strong very fine angular blocky; hard, friable, very sticky and very plastic; common very fine and fine roots; many very fine irregular and few fine tubular pores; many distinct clay films on faces of peds and lining pores; few vertical cracks filled with fine earth; noneffervescent; less than 5 percent boulders and stones; neutral (pH 7.0); abrupt wavy boundary. (2 to 4 inches thick.)
Btss1--4 to 9 inches; reddish brown (5YR 4/4) clay; dark reddish brown (5YR 3/3) moist; strong medium prismatic structure parting to strong medium angular blocky; hard, firm, very sticky and very plastic; common fine and few medium roots; few fine tubular pores; many intersecting slickensides and pressure faces; few distinct clay films on faces of peds and lining pores; 3 to 7 millimeter wide vertical cracks which are about 4 inches apart; noneffervescent; neutral (pH 6.8); abrupt wavy boundary.
Btss2--9 to 17 inches; brown (7.5YR 4/4) clay; dark brown (7.5YR 3/4) moist; strong medium prismatic structure parting to strong medium angular blocky; hard, firm, very sticky and very plastic; common fine and medium roots; few fine tubular pores; many intersecting slickensides and pressure faces; very few faint clay films on faces of peds and lining pores; 5 to 7 millimeter wide vertical cracks which are about 4 inches apart; noneffervescent; 10 percent gravel concentrated in the lower part of the horizon; neutral (pH 6.8); abrupt wavy boundary. (Combined thickness of Btss horizons is 10 to 14 inches.)
Cr--17 to 19 inches; discontinuous weathered basalt. (0 to 2 inches thick.)
R--19 inches; basalt bedrock.
TYPE LOCATION: Mohave County, Arizona; on Lake Mead National Recreation Area, 1400 feet south and 1600 feet east of the northeast corner of sec. 10, T 32 N, R 11 W; 36 degrees, 6 minutes, 14 seconds north latitude and 113 degrees, 27 minutes, 4 seconds west longitude, NAD 83.
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: 50 to 56 degrees F.
Rock fragments: averages less than 15 percent in the particle-size control section. Surface layer rock fragments ranges up to 70 percent.
Depth to bedrock: 14 to 20 inches
A horizon
Hue: 5YR, 7.5YR
Value: 3 or 4 dry, 2.5 or 3 moist
Chroma: 2 to 6, dry or moist
Bt horizon
Hue: 5YR, 7.5YR
Value: 3 or 4 dry, 2.5 or 3 moist
Chroma: 3 or 4, dry or moist
Clay content: 40 to 55 percent clay
Btss horizons
Hue: 5YR, 7.5YR
Value: 3 or 4, dry or moist
Chroma: 2 to 4, dry or moist
Clay content: 50 to 60 percent clay
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Rockyroad soils are on plateaus and mesas at elevations of 5800 to 6600 feet. They formed in residuum from basalt. Slopes range from 2 to 10 percent. The mean annual precipitation is 13 to 18 inches. The mean annual air temperature is about 48 to 56 degrees F. The frost-free period is 135 to 150 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Luzena and
Kellypoint series.
Luzena soils do not have Btss horizons.
Kellypoint soils are moderately deep.
DRAINAGE AND PERMEABILITY: Well drained; medium to high runoff; very slow permeability.
USE AND VEGETATION: Rockyroad soils are used for recreation and grazeable woodland. Present vegetation is pinyon pine, Utah juniper, penstemon, eriognonum and prickly pear.
DISTRIBUTION AND EXTENT: North central Arizona; MLRA is 35. Rockyroad series are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Mohave County, Arizona, soil survey of Lake Mead National Recreation Area, and Grand Canyon soil survey area 2001
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the 0 to 2 inches (A horizon)
Argillic horizon - The zone from 2 to 17 inches (Bt, Btss1 and Btss2 horizons)
Lithic contact - The boundary at 19 inches (R horizon)