LOCATION PAHROC                  NV

Established Series
Rev. DJM/BAL/JVC/JBF
06/2016

PAHROC SERIES

The Pahroc series consists of shallow to a duripan, well drained soils that formed in alluvium derived from mixed rocks. Pahroc soils are on fan remnants. Slopes are 2 to 15 percent. The mean annual precipitation is about 175 mm and the mean annual temperature is about 13 degrees C.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic, shallow Typic Haplodurids

TYPICAL PEDON: Pahroc gravelly loam--rangeland. (Colors are for dry soil unless otherwise noted.) The soil surface has a desert pavement of subangular to rounded gravel and cobbles mainly of dolomite and limestone; exposed parts of the fragments have a thin coat of desert varnish and the bottoms have pendants of calcium carbonate.

A--0 to 4 cm; light gray (10YR 7/2) gravelly loam, grayish brown (10YR 5/2) moist; weak thick platy structure; slightly hard, friable, slightly sticky and slightly plastic; many fine and medium vesicular pores; about 30 gravel; violently effervescent; strongly alkaline (pH 8.6); abrupt smooth boundary. (3 to 8 cm thick)

Bk1--4 to 15 cm; very pale brown (10YR 7/3) gravelly loam, brown (10YR 5/3) moist; massive; soft, very friable, nonsticky and nonplastic; common fine roots; many very fine and fine irregular pores; 30 percent gravel with pendants of secondary carbonate on bottoms; violently effervescent; strongly alkaline (pH 8.6); clear wavy boundary. (10 to 30 cm thick)

Bk2--15 to 30 cm; very pale brown (10YR 8/3) very gravelly loam, brown (10YR 5/3) moist; massive; hard, firm, slightly sticky and nonplastic; few fine roots; many very fine and fine irregular pores; about 50 percent gravel; violently effervescent; strongly alkaline (pH 8.5); abrupt slightly wavy boundary. (13 to 25 cm thick)

Bqkm--30 to 81 cm; white (10YR 8/1) cemented material, light gray (10YR 7/2) moist; massive; extremely hard, extremely firm; indurated by silica and secondary carbonates; very few very fine irregular pores; the upper part of the horizon has a very dense laminar surface that contains no visible pores and does not dissolve in concentrated hydrochloric acid; violently effervescent; strongly alkaline (pH 8.6); gradual wavy boundary. (46 to 90 cm thick)

2Bqk--81 to 152 cm; very pale brown (10YR 8/2) very gravelly coarse sandy loam, pale brown (10YR 6/3) moist; massive; slightly hard and hard, firm and friable, nonsticky and nonplastic; many very fine and fine, and few medium irregular pores; about 50 percent gravel; several discontinuous silica-cemented laminar horizons less than 5 cm thick that are extremely hard and extremely firm that do not dissolve in concentrated hydrochloric acid; violently effervescent; carbonate coats on nearly all rock fragments; moderately alkaline (pH 8.4)

TYPE LOCATION: Lincoln County, Nevada; northwest of Hiko along the county road to Coal Valley; about 0.4 mile west of Nevada State Highway 28 and 30 feet south of the county road; approximately 2,480 feet east and 1,920 feet south of the northwest corner of section 35, T. 3 S., R. 60 E.; USGS Fossil Peak 7.5 minute topographic quadrangle; latitude 37 degrees 38 minutes 41 seconds N and longitude 115 degrees 13 minutes 7 seconds W; WGS84 Decimal Degrees 37.6447222 latitude, -115.2186111 longitude.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually moist for short periods in winter and early spring and intermittently moist for 5 to 10 days cumulative due to convection storms in July through September; typic aridic moisture regime.
Mean annual soil temperature: 12 to 15 degrees C.
Depth to duripan: 25 to 50 cm.
Reaction: Moderately alkaline or strongly alkaline.

Particle-size control section - Clay content: 8 to 18 percent.
Rock fragments: 35 to 60 percent, mostly gravel, but up to 10 percent cobbles.

A horizon
Hue: 10YR or 7.5YR.
Value: 6 or 7 dry; 4 through 6 moist.
Chroma: 2 or 3, dry or moist.

Bk horizons
Hue: 10YR or 7.5YR.
Value: 7 or 8 dry, 6 or 7 moist.
Chroma: 1 through 3, dry or moist.
Texture: Loam or fine sandy loam.

2Bqk horizon
Hue: 10YR or 7.5YR.
Value: 6 through 8 dry, 4 through 7 moist.
Chroma: 1 through 3, dry or moist.
Texture: Coarse sandy loam or loamy coarse sand.
Rock fragments: 35 to 80 percent.
Other features: Horizon is weakly cemented with lenses of strongly silica and carbonate cemented material.

COMPETING SERIES: These are the Osobb, Osoll, Otomo, and Treadwell series.

Osobb and Osoll soils have a duripan over bedrock at 50 to 100 cm. Otomo soils are not moist 10 to 20 days during the summer months due to convection storms in July through September. Treadwell soils have duripans at depths of 10 to 25 cm.

GEOGRAPHIC SETTING: Pahroc soils are on fan remnants that have been dissected by intermittent drainage channels. These soils formed in mixed alluvium derived from ignimbrite, dolomite, limestone, quartzite, sandstone, and shale. Slopes are 2 to 8 percent. Elevations are 1,070 to 1,830 meters. The mean annual precipitation is 150 to 200 mm, the mean annual temperature is 12 to 15 degrees C., and the frost-free period is 160 to 180 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Alko, Bastian, Crystal Springs, Geer, and Leo soils. Bastian soils lack duripans but contain durinodes and are somewhat poorly drained. Geer soils lack duripans and coarse-loamy particle-size control sections. Leo soils are sandy-skeletal, very deep, and do not have diagnostic subsurface horizons.

DRAINAGE AND PERMEABILITY: Well drained; permeability is very slow; moderately high saturated hydraulic conductivity.

USE AND VEGETATION: Pahroc soils are used for rangeland and wildlife habitat. Commonly the vegetation is a nearly pure stand of blackbrush but it includes some Nevada ephedra, dahlia, bush muhly and galleta. At a typical site the plant density ranges from 5 to 10 percent.

DISTRIBUTION AND EXTENT: South-central Nevada. These soils are moderately extensive. MLRA 29.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California.

SERIES ESTABLISHED: Pahranagat Valley SCD, Lincoln County, Nevada, 1940.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 18 cm (A, Bk1 and part of Bk2 horizons).
Calcic horizon - The zone from 4 to 30 cm (Bk1 and Bk2 horizons).
Indurated duripan - The zone from 30 to 81 cm (Bqkm horizon).
Particle-size control section - The zone from the soil surface to 30 cm (A, Bk1, and Bk2 horizons).

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National Cooperative Soil Survey
U.S.A.