LOCATION BLACKMESA               NV

Established Series
Rev. DJM/LJL/TM
04/2015

BLACKMESA SERIES

The Blackmesa series consists of shallow to a duripan, well drained soils that formed in loess over residuum derived from basalt . Blackmesa soils are on mesas. Slope ranges from 4 to 15 percent. The mean annual precipitation is about 6 inches and the mean annual temperature is about 72 degrees F.

TAXONOMIC CLASS: Loamy, mixed, active, hyperthermic, shallow Typic Haplodurids

TYPICAL PEDON: Blackmesa gravelly fine sandy loam, wildlife habitat. (Colors are for dry soil unless otherwise noted.) The soil surface is covered by approximately 60 percent pebbles (15 percent basalt rocks and 45 percent duripan fragments) and 20 percent cobbles.

A--0 to 2 inches; yellowish brown (10YR 5/4) gravelly fine sandy loam, dark yellowish brown (10YR 4/4) moist; moderate medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; few very fine roots; common very fine and fine interstitial and few fine vesicular pores; 20 percent pebbles; violently effervescent (9 percent calcium carbonate equivalent in the fine-earth fraction); moderately alkaline (pH 8.4); clear smooth boundary. (1 to 4 inches thick)

Bkq1--2 to 8 inches; yellowish brown (10YR 5/4) gravelly fine sandy loam, dark yellowish brown (10YR 4/4) moist; massive; soft, very friable, nonsticky and nonplastic; common very fine and few fine roots; many very fine and fine interstitial and common fine tubular pores; 20 percent pebbles and 10 percent cobbles; common, fine, prominent, calcium carbonate masses; many, coarse, prominent, calcium carbonate and silica pendants on the undersides of rock fragments; violently effervescent (15 percent calcium carbonate equivalent in the fine-earth fraction); strongly alkaline (pH 8.6); clear wavy boundary. (5 to 8 inches thick)

Bkq2--8 to 13 inches; light brown (7.5YR 6/4) gravelly fine sandy loam, brown (7.5YR 5/4) moist; massive; soft, very friable, slightly sticky and slightly plastic; common very fine, fine and few medium roots; few fine interstitial pores; 20 percent pebbles and 5 percent cobbles; many, coarse, prominent, calcium carbonate masses; many, coarse, prominent, calcium carbonate and silica pendants on the undersides of rock fragments; violently effervescent; (30 percent calcium carbonate equivalent in the fine-earth fraction); strongly alkaline (pH 8.6); abrupt wavy boundary. (4 to 8 inches thick)

Bqkm--13 inches; very pale brown (10YR 8/4) duripan, yellowish brown (10YR 5/4) moist; strong medium platy structure in the upper part and massive below; very rigid; indurated in upper part by laminae of opaline silica in a 1 millimeter to 5 millimeters thick continuous laminar cap, very strongly cemented throughout the matrix in lower part of horizon by carbonate and silica; calcium carbonate as laminae and as coats on rock fragments and mineral grains. (36 to 60 inches thick)

TYPE LOCATION: Clark County, Nevada; in the Lake Mead National Recreation Area about 1 mile south of the junction of Northshore road and the Callville Bay road on the summit of Black Mesa; 545 feet north and 2,300 feet west of the southeast corner of section 31, T. 20 S., R. 65 E.; USGS Government Wash 7.5 minute topographic quadrangle; 36 degrees 9 minutes 38.9 seconds north latitude and 114 degrees 45 minutes 59 seconds west longitude; UTM 11s, 0700916e, 4004095n: NAD 83.

RANGE IN CHARACTERISTICS:

Soil moisture - Usually dry, moist in some part for short periods during winter and early spring and for brief periods between July and October following convection storms. The soils have a typic aridic moisture regime.

Mean annual soil temperature - 72 to 76 degrees F.

Depth to calcic horizon - 1 to 4 inches.

Depth to duripan - 10 to 14 inches.

Depth to bedrock - Greater than 40 inches to a lithic contact. Hard bedrock is estimated to be within 80 inches of the soil surface.

Control section - Percent clay: 5 to 15 percent
Rock fragments: 15 to 35 percent, mainly gravel. Lithology of fragments are 50 percent indurated to strongly cemented duripan fragments and 50 percent basalt.
Calcium carbonate equivalent in the less than 20 millimeter fraction: Averages 10 to 40percent.
Reaction - Moderately alkaline or strongly alkaline.

A horizon - Value: 5 or 6 dry.
Chroma: 3 or 4, dry or moist.
Calcium carbonate equivalent in the fine earth fraction: 5 to 10percent.

Bkq1 horizon - Hue: 7.5YR or 10YR.
Value: 5 or 6 dry, 4 or 5 moist.
Texture: Fine sandy loam or sandy loam.
Structure: Massive or subangular blocky.
Calcium carbonate equivalent in the fine earth fraction: 15 to 30percent.
Salinity (EC): 2 to 4 mmhos/cm.
Sodicity (SAR): 5 to 10.

Bkq2 horizon - Hue: 7.5YR or 10YR.
Value: 5 or 6 dry, 4 or 5 moist.
Texture: Loam or fine sandy loam.
Calcium carbonate equivalent in the fine earth fraction: 15 to 35percent.
Salinity (EC): 2 to 4 mmhos/cm.
Sodicity (SAR): 5 to 10.

Bqkm horizon - Cementation class: Indurated by secondary silica in continuous laminar cap, very strongly cemented or strongly cemented by secondary silica and carbonates below the laminar cap.

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING: Blackmesa soils are on mesas. These soils formed in loess over residuum derived from basalt. Slope ranges from 4 to 15 percent. Elevations are 1,700 to 2,200 feet. The climate is arid with cool, moist winters and hot, dry summers. The mean annual precipitation is 5 to 7 inches, mean annual temperature is 70 to 74 degrees F., and the frost-free period is 280 to 340 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Callville and Sunrock soils. Callville soils are loamy, shallow to paralithic contacts, and have gypsic horizons. Sunrock soils are loamy-skeletal, very shallow to lithic contacts, and do not have diagnostic subsurface horizons.

DRAINAGE AND PERMEABILITY: Well drained; very high runoff; moderately rapid permeability.

USE AND VEGETATION: These soils are used for rangeland and wildlife habitat. The present vegetation is mainly creosotebush and white bursage.

DISTRIBUTION AND EXTENT: Mojave Desert of south Nevada. MLRA 30. These soils are not extensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: PHOENIX, ARIZONA

SERIES ESTABLISHED: Clark County Area, Nevada, 2006. Proposed in Clark County, Nevada, 2000. The name is coined from Black Mesa where it is located.

REMARKS: The active cation exchange activity class is estimated. Laboratory data is needed to confirm this placement.
Diagnostic horizons and features recognized in this pedon are:

Ochric epipedon - 0 to 2 inches (A horizon).
Calcic horizon - 2 to 13 inches (Bkq1 and Bkq2 horizons).
Duripan - 13 to greater than 50 inches (Bqkm horizon).
Particle-size control section - 0 to 13 inches (A, Bkq1, and Bkq2 horizons).

---

National Cooperative Soil Survey
U.S.A.