LOCATION BLACKMOUNT              CA

Established Series
Rev. YHH
04/2015

BLACKMOUNT SERIES

The Blackmount series consists of deep, well drained soils that formed from alluvium derived from granite, schist, gneiss, quartzite, limestone, dolomite and some volcanic rocks. Blackmount soils are on dissected old alluvial fans and have slopes of 1 to 8 percent. The mean annual precipitation is about 5 inches and the mean annual soil temperature is about 64 degrees F.

TAXONOMIC CLASS: Sandy-skeletal, mixed, thermic Typic Haplargids

TYPICAL PEDON: Blackmount very gravelly sandy loam - rangeland. (Colors are for dry soil unless otherwise noted.) 80 percent of surface covered with a pebble pavement. The pebbles have a well developed desert varnish on exposed surfaces.

A1--0 to 1 inch; pale brown (10YR 6/3) extremely gravelly sandy loam, brown (10YR 5/3) moist; weak coarse prismatic structure; slightly hard, friable, nonsticky and nonplastic; common very fine roots; many very fine, fine and medium vesicular pores; 60 percent pebbles; strongly effervescent; strongly alkaline (pH 8.6); abrupt smooth boundary. (1/2 to 3 inches thick)

B21tsa--1 to 5 inches; yellowish red (5YR 5/6) very gravelly sandy loam, yellowish red (5YR 4/6) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; common fine interstitial and tubular pores; few thin clay films in tubular and interstitial pores and colloid bridging between sand grains; 50 percent pebbles and few cobbles; common to many large white salt or gypsum crystals; strongly effervescent; moderately alkaline (pH 8.4); clear wavy boundary (0 to 6 inches thick)

B22tcasa--5 to 10 inches; yellowish red (5YR 5/6) very gravelly sandy loam, yellowish red (5YR 4/6) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; common fine interstitial and tubular pores; few thin clay films in pores and colloid bridging between sand grains; 40 percent pebbles and 10 percent cobbles; strongly effervescent; strongly alkaline (pH 8.6); clear wavy boundary. (4 to 8 inches thick)

Clcasa--10 to 42 inches; pale brown (10YR 6/3) stratified very gravelly loamy sand and very gravelly sand, brown (10YR 5/3) moist; massive and single grained; slightly hard and loose, very friable, and loose; few very fine roots; many fine interstitial pores; 50 percent pebbles and 15 percent cobble; common thin coatings of lime on pebbles; violently effervescent; strongly alkaline (pH 8.6); gradual wavy boundary. (20 to 60 inches thick)

C2--42 to 60 inches; pale brown (10YR 6/3) extremely cobbly sand, brown (10YR 5/3) moist; single grained loose; many fine interstitial pores; 40 percent cobbles and 30 percent pebbles; slightly effervescent; strongly alkaline (pH 8.6).

TYPE LOCATION: San Bernardino County, California; in the SW1/4 sec. 22, T. 20 N., R. 9 E.

RANGE IN CHARACTERISTICS: Solum thickness is 5 to 10 inches. The mean annual soil temperature is 60 degrees F to 72 degrees F. These soils are usually dry; they are moist for short periods during the winter and summer months, but are dry in the spring and fall. These soils are calcareous throughout, and are moderately alkaline or strongly alkaline.

The A1 horizon is covered by a gravel erosion pavement containing 50 to 80 percent 1/2 to 3 inch pebbles. Few cobbles may occur. It has hue of 10YR or 7.5YR, value of 6 or 7 dry, 4 or 5 moist, and chroma of 2 through 4.

The B2t horizon has hue of 5YR or 7.5YR, value 5 or 6 dry, 4 or 5 moist, and chroma of 4 through 6. It is gravelly or very gravelly sandy loam, loam, or sandy clay loam. Coarse fragments average about 35 to 55 percent, consisting mainly of pebbles but including up to 15 percent cobbles. Fine salt and gypsum segregations occur in some pedons but are not diagnostic of the series.

The C horizon has hue of 10YR or 7.5YR, value of 5 through 8 dry, 4 through 6 moist, and chroma of 2 through 4. Textures are normally stratified ranging from very or extremely gravelly, or very, or extremely cobbly sand or loamy sand. Thin strata, up to 4 inches thick, of very gravelly sandy loam occur in some pedons. Coarse fragments range from 50 to 80 percent. Lime coatings are on coarse fragments and sand grains in the upper part. The horizon may also contain salt and gypsum segregations.

COMPETING SERIES: These are the Bitter Spring, Bitter, Pinaleno, Chuckawalla, Cristobal, and Pinant series in other families. Bitter, Bitter Spring, and Pinaleno soils have a loamy-skeletal particle-size control section. In addition Bitter and Pinaleno soils have 10 to 30 inch thick sola, and Pinaleno soils are also noncalcareous in the A and upper Bt horizons and are slightly acid to mildly alkaline to a depth of 12 inches. Chuckawalla, Cristobal, and Pinant soils have temperatures warmer than 72 F.

GEOGRAPHIC SETTING: Blackmount soils are on old dissected alluvial fans, between more recent alluvial fans and the toe slopes of steep and very steep hills and mountains at elevations of 2,500 to 3,600 feet. Slopes are dominantly 1 to 5 percent, but range up to 8 percent. These soils formed in alluvium from a wide variety of igneous, sedimentary, and metamorphic rocks including schist, granite , quartzite, gneiss, andesite, rhyolite, limestone, and other related rocks. The climate is hot and arid with a mean annual temperature of 65 degrees to 70 degrees F., average January temperature of 45 degrees to 51 degrees F, and average July temperature of 82 degrees to 92 degrees F. The mean annual precipitation is 4 to 7 inches.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Arizo, Nickel, Cove, and Bluepoint soils, and the competing Bitter soils. Arizo, Nickel, Cave, and Bluepoint soils lack an argillic horizon. Arizo soils have a sandy-skeletal particle-size control section. Nickel soils have a calcic horizon, Cave soils have an indurated petrocalcic horizon. Bluepoint soils have a sandy particle-size control section.

DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderate permeability.

USE AND VEGETATION: These soils are used for limited livestock grazing and wildlife habitat. The native vegetation consists of a sparse stand of creosotebush, white bursage and cacti. Limited quantities of annuals grow following winter and summer rains.

DISTRIBUTION AND EXTENT: These soils are of moderate extent in southeastern California and souther Nevada.

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

SERIES ESTABLISHED: Kingston-Amargosa Area, Parts of Inyo and San Bernardino Counties, California, 1979.

OSED scanned by SSQA. Last revised by state on 7/79.

Responsibility for this series was transferred from Davis to Phoenix 4/2015. The last revision to the series was 7/1979. ET

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National Cooperative Soil Survey
U.S.A.