LOCATION BLACKHAWK               NV

Established Series
Rev. DD/RB/JBF
05/2016

BLACKHAWK SERIES

The Blackhawk series consists of shallow over duripan, well drained soils that formed in a loess mantle over alluvium derived from mixed rocks. The Blackhawk soils are on fan piedmont remnants, fan remnant, fan aprons, and partial ballenas. Slopes are 0 to 50 percent. The mean annual precipitation is about 180 mm and the mean annual temperature is about 8 degrees C.

TAXONOMIC CLASS: Loamy, mixed, superactive, mesic, shallow Cambidic Haplodurids

TYPICAL PEDON: Blackhawk silt loam--rangeland. (Colors are for dry soils unless otherwise noted.)

A--0 to 8 cm; light brownish gray (10YR 6/2) silt loam, dark grayish brown (10YR 4/2) moist; weak thick platy structure; slightly hard, friable, slightly sticky and slightly plastic; few roots; many fine and medium vesicular pores; surface has polygonal cracks 3 to 4 cm deep and 8 to 15 cm across; strongly alkaline (pH 8.6); abrupt smooth boundary. (5 to 20 cm thick)

Bw--8 to 36 cm; light gray (10YR 7/2) silt loam, dark grayish brown (10YR 4/2) moist; weak medium and fine subangular blocky structure; slightly hard, friable, nonsticky and nonplastic; common fine roots; many very fine and fine interstitial pores; moderately alkaline (pH 8.3); abrupt smooth boundary. (15 to 38 cm thick)

Bqm--36 to 41 cm; light brownish gray (10YR 6/2) strongly silica-cemented duripan, dark grayish brown (10YR 4/2) moist; strong thin platy structure; very hard, very firm, few fine roots; many very fine interstitial pores; common thin silica films coating pores, bridging sand grains, and as discontinuous laminae; strongly alkaline (pH 8.8); abrupt smooth boundary. (5 to 13 cm thick)

Bqk--41 to 53 cm; pale brown (10YR 6/3) loam, dark grayish brown (10YR 4/2) moist; weak thick platy structure parting to weak fine angular blocky; slightly hard, friable, nonsticky and nonplastic; common very fine roots; many very fine tubular pores; 30 percent very hard, firm, brittle durinodes that contain common thin silica films in pores and bridges between sand grains; matrix is noneffervescent, strongly effervescent on few fine lime filaments and coatings on durinodes; strongly alkaline (pH 9.0); abrupt smooth boundary. (0 to 53 cm thick)

Bqkm--53 to 76 cm; pale brown (10YR 6/3) strongly silica- cemented duripan, dark grayish brown (10YR 4/2) moist; weak and moderate thick platy structure; extremely hard, extremely firm; few very fine and fine roots only in seams and between plates; few fine interstitial pores; many fine silica films in pores and bridging sand grains and common moderately thick discontinuous silica laminae; violently effervescent; very strongly alkaline (pH 9.2); abrupt wavy boundary. (0 to 25 cm thick)

2Bqk--76 to 122 cm; very pale brown (10YR 7/3) coarse sand, brown (10YR 5/3) moist; massive; slightly hard, very friable, nonsticky and nonplastic; few very fine roots; few fine and many very fine interstitial pores; 30 percent hard, firm, brittle durinodes; violently effervescent; strongly alkaline (pH 9.0); abrupt wavy boundary. (0 to 56 cm thick)

3C--122 to 152 cm; brown (10YR 5/3) very gravelly coarse sand, dark grayish brown (10YR 4/2) moist; massive; slightly hard, very friable, nonsticky and nonplastic; few very fine roots; many very fine and fine interstitial pores; 40 percent gravel; strongly alkaline (pH 8.6).

TYPE LOCATION: Pershing County, Nevada; approximately 21 miles south of Winnemucca; about 600 feet east and 1,300 feet south of the north 1/4 corner of section 3, T. 32 N., R. 38 E.; latitude 40 degrees 40 minutes 47 seconds N and longitude 117 degrees 41 minutes 22 seconds W; WGS84 Decimal Degrees 40.6800000 latitude, -117.688611 longitude.

RANGE IN CHARACTERISTICS:
Soil moisture: Usually dry, moist in winter and early spring, dry late May through November; typic aridic soil moisture regime.
Mean annual soil temperature: 8 to 12 degrees C.
Depth to duripan: 36 to 50 cm.

Particle-size control section - Clay content: Averages 5 to 10 percent.
Rock fragments: Up to 30 percent, mainly gravel.
Silt plus very fine sand: 65 to 80 percent.

A horizon
Hue: 10YR or 2.5Y.
Value: 6 or 7 dry, 4 or 5 moist.
Chroma: 2 or 3.
Reaction: Slightly alkaline through strongly alkaline.

Bw horizons
Hue: 10YR or 2.5Y.
Value: 6 or 7 dry, 4 or 5 moist.
Chroma: 2 or 3.
Texture: Silt loam, loam, very fine sandy loam.
Clay content: Averages 5 to 10 percent.
Consistence: Nonsticky or sticky and nonplastic or plastic wet.
Rock fragments: 0 to 30 percent, mainly gravel.
Structure: Weak or moderate, thin to thick, platy, subangular blocky, or horizon is massive.
Reaction: slightly alkaline through strongly alkaline.

Bqm, Bqkm Bk and C horizons (When present above the duripan)
Hue: 10YR or 2.5Y.
Value: 5 through 7 dry, 4 through 6 moist.
Chroma: 2 or 3.
Structure: Weak to strong, thin or thick, platy, or horizon is massive.
Duripan - Consistence: Very hard or extremely hard.
Reaction: Moderately alkaline through very strongly alkaline.
Effervescence: Noneffervescent through violently effervescent.
Silica cementation: The duripan usually consists of two or more strongly cemented layers interbedded with weakly silica-cemented material or strata with friable matrix containing durinodes.

Bk and Bqk horizons
Textures: Immediately below the upper duripan of most pedons, textures are stratified loam to gravelly coarse sand.
Consistence: Soft or slightly hard, dry; very friable or friable, moist; nonsticky or sticky and nonplastic or plastic wet.

2Bqk, and 3C horizons
Texture: Unconformable strata of very gravelly or extremely gravelly sand, coarse sand, loamy coarse sand, and sandy loam are common below a depth of 75 cm.
Other features: Strata of clay are found below 75 cm in some pedons.

COMPETING SERIES: These are the Adelaide, Belcher, Timper and Truhoy series.

Adelaide soils have buried argillic horizons below the strongly cemented duripan. Belcher soils are calcareous in the series control section. Timper soils have calcareous soil profiles and a sandy loam particle-size control section. Truhoy soils have a Bqk horizon above the Bqm horizon and the depth to the duripan is 15 to 36 cm.

GEOGRAPHIC SETTING: Blackhawk soils are on fan piedmont remnants, fan remnant,fan aprons, and partial ballenas. These soils formed in a loess mantle superimposed over alluvium derived from mixed rocks. Slopes are dominantly 0 to 8 percent, but are as high as 50 percent on partial ballenas side slopes. Elevations are 1,220 to 1,890 meters. The climate is cool, arid with cool, moist winters and warm, dry summers. The mean annual precipitation is 150 to 200 mm; mean annual temperature is 7 to 10 degrees C, and the frost-free season is 100 to 110 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Duffer soils and the competing Adelaide soils. Duffer soils are somewhat poorly drained and have over 40 percent calcium carbonate equivalent in the series control section.

DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained; medium or slow runoff; moderately high saturated hydraulic conductivity.

USE AND VEGETATION: Rangeland and wildlife habitat. The present vegetation is mainly shadscale, bud sagebrush, bottlebrush squirreltail.

DISTRIBUTION AND EXTENT: North-central Nevada. These soils are not extensive. MLRA 24, 27.

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

SERIES ESTABLISHED: Pershing County, Nevada, 1972.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the surface to 18 cm (A and part of the Bw horizon).
Strongly cemented duripan - The zone from about 36 to 41 cm (Bqm horizon).
Particle-size control section - The zone from about 25 to 36 cm (part of the Bw horizon).

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National Cooperative Soil Survey
U.S.A.