LOCATION PROMONTORY              AZ

Established Series
Rev. WJ/PH/PDC/WWJ/RKS/HCD
08/2019

PROMONTORY SERIES

The Promontory series consists of very shallow and shallow to a hardpan, well drained soils formed in alluvium from rhyolite. Promontory soils are on mesas and plateaus. Slopes range from 3 to 12 percent. The mean annual precipitation is about 12 inches. The mean annual air temperature is about 53 degrees F.
TAXONOMIC CLASS: Loamy, mixed, superactive, mesic, shallow Ustic Petrocalcids
TYPICAL PEDON: Promontory gravelly sandy loam - woodland. (Colors are for dry soil unless otherwise noted.)
A--0 to 2 inches; brown (7.5YR 5/4) gravelly sandy loam, brown (7.5YR 4/4) moist; weak thin platy parting to weak fine granular structure; soft, very friable, nonsticky and nonplastic; few very fine roots; few very fine irregular pores; 30 percent gravel; strongly effervescent, 4 percent calcium carbonate equivalent; slightly alkaline (pH 7.8); abrupt smooth boundary. (1 to 3 inches thick)
Bw1--2 to 12 inches; strong brown (7.5YR 4/6) gravelly sandy clay loam, brown (7.5YR 4/4) moist; weak fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; common fine and medium roots; common fine irregular pores; 20 percent gravel and 5 percent cobble; violently effervescent, 8 percent calcium carbonate equivalent; moderately alkaline (pH 8.0); abrupt smooth boundary. (1 to 14 inches thick)
Bw2--12 to 17 inches; brown (7.5YR 5/4) gravelly sandy clay loam, brown (7.5YR 4/4) moist; weak fine subangular blocky structure; soft, very friable, slightly sticky and slightly plastic; common fine and medium roots; common fine irregular pores; 20 percent gravel and 5 percent cobble; violently effervescent, 8 percent calcium carbonate equivalent; moderately alkaline (pH 8.0); abrupt smooth boundary. (2 to 14 inches thick)
2Bkm--17 to 19 inches; calcium carbonate cemented petrocalcic with discontinuous laminar cap; abrupt smooth boundary. (2 to 14 inches thick)
3R--19 inches; rhyolite bedrock.
TYPE LOCATION: Mohave County, Arizona; 35 degrees, 28 minutes, 20 seconds north latitude, and 113 degrees, 39 minutes, 52 seconds west longitude. About 330 feet south of the northeast corner of section 16, T.24 N., R.13 W.
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. Ustic aridic soil moisture regime.
Soil Temperature: 54 to 57 degrees F.
Reaction: slightly or moderately alkaline
Rock fragments: 5 to 35 percent rhyolite gravel
Organic matter content: 1 to 2 percent in the surface
Clay content: 20 to 35 percent in the control section
Depth to hardpan: 4 to 19 inches
Depth to bedrock: 6 to 20 inches
A horizon
Hue: 7.5YR, 10YR
Value: 4 or 5, dry or moist
Chroma: 3 or 4, dry or moist
B horizons
Value: 3 through 5, dry or moist
Chroma: 4 through 6, dry or moist
Calcium Carbonate Equivalent: 5 to 15 percent
COMPETING SERIES: These are the Pastern (UT), Pastura (NM), Rolie (AZ), and Tassi (AZ) series. Pastern, Pastura, and Rolie soils do not have bedrock below the hardpan. Tassi soils have limestone bedrock below the hardpan.
GEOGRAPHIC SETTING: Promontory soils are on mesas and plateaus and have slopes of 3 to 12 percent. They formed in alluvium from rhyolite. Elevations range from 4300 to 5100 feet. The mean annual precipitation is 10 to 14 inches. The mean annual air temperature is 52 to 55 degrees F. The frost-free period is 150 to 165 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Kingtut, Prieta, Valena, and Carri soils. Kingtut soils are fine textured. Prieta soils are clayey-skeletal and do not have petrocalcic horizons. Valena soils do not have petrocalcic horizons. Carri soils are fine-loamy and moderately deep to granite.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderately slow permeability.
USE AND VEGETATION: This soil is used for livestock grazing, recreation and wildlife habitat. Vegetation is Stansbury cliffrose, sideoats grama, black grama, banana yucca, prickly pear and an overstory of Utah Juniper.
DISTRIBUTION AND EXTENT: Northwestern Arizona. This series is of minor extent. MLRA is 38.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: Mohave County, Arizona; Soil Survey of Mohave County, Arizona, Central Part; 2005. The name is taken from a topographical feature within the survey area.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from 0 to 2 inches (A horizon)
Cambic horizon - The zone from 2 to 17 inches (Bw1, Bw2 horizons)
Petrocalcic horizon - The zone from 17 to 19 inches (2Bkm horizon)
Lithic contact - The boundary at 19 inches (3R horizon)
Classified according to Keys to Soil Taxonomy Ninth Edition, 2003
Removed Esplin from competing series section because it changed to the Ustalfic Petrocalcids subgroup, tdc 08/2019.

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National Cooperative Soil Survey
U.S.A.