LOCATION BLACKSTON CO+NM UT

Established Series
Rev. AJC/SSP/JWB
04/2011

BLACKSTON SERIES

The Blackston series consists of very deep, well drained soils that formed in alluvium and slope alluvium that may be underlain by residuum derived from mixed sources. Blackston soils are on edges of old high terraces, on fan remnants and on structural benches. Slopes range from 0 to 40 percent. The mean annual precipitation is about 8 inches and the mean annual temperature is about 52 degrees F.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Typic Haplocalcids

TYPICAL PEDON: Blackston very gravelly sandy clay loam - grassland. (Colors are for dry soil unless otherwise noted.)

A--0 to 3 inches; very pale brown (10YR 7/3) very gravelly sandy clay loam, brown (10YR 4/3) moist; weak medium platy and moderate medium granular structure; soft, very friable, slightly sticky and slightly plastic; many very fine and fine roots; 40 percent gravel; strongly effervescent, disseminated carbonates, 12 percent calcium carbonate equivalent; moderately alkaline (pH 8.2); clear smooth boundary. (3 to 9 inches thick)

Bk1--3 to 7 inches; very pale brown (10YR 7/4) gravelly clay loam, yellowish brown (10YR 5/4) moist; weak medium subangular blocky structure; slightly hard, friable, moderately sticky and moderately plastic; common fine and coarse roots inside and between peds; few very fine and fine vesicular pores; 20 percent gravel; strongly effervescent, calcium carbonates segregated in common fine and medium irregular soft masses and few distinct carbonates coating gravel and disseminated carbonates, 24 percent calcium carbonate equivalent; moderately alkaline (pH 8.2); clear wavy boundary. (4 to 16 inches thick)

Bk2--7 to 15 inches; very pale brown (10YR 8/2) very gravelly sandy clay loam, very pale brown (10YR 7/3) moist; massive; hard, friable, slightly sticky and slightly plastic; few very fine and fine roots; 35 percent gravel, 10 percent cobbles; violently effervescent, calcium carbonates segregated in common fine and medium irregular soft masses and common distinct carbonates coating gravel and cobble and disseminated carbonates, 30 percent calcium carbonate equivalent; moderately alkaline (pH 8.2), clear wavy boundary. (0 to 16 inches thick)

2Bk3--15 to 35 inches; very pale brown (10YR 7/4) extremely gravelly sandy loam, light yellowish brown (10YR 6/4) moist; massive; soft, very friable, nonsticky and nonplastic; few very fine and fine roots; 45 percent gravel, 20 percent cobbles; strongly effervescent, calcium carbonates segregated in common fine and medium irregular soft masses and common distinct carbonates coating gravel and cobble and disseminated carbonates, 15 percent calcium carbonate equivalent; moderately alkaline (pH 8.2); clear wavy boundary. (0 to 25 inches thick)

2C--35 to 60 inches; very pale brown (10YR 7/4) extremely gravelly sand, yellowish brown (10YR 5/4) moist; single grain; loose, nonsticky and nonplastic; 50 percent gravel, 25 percent cobbles; strongly effervescent, common distinct carbonates coating gravel and cobbles and disseminated carbonates, 10 percent calcium carbonate equivalent; moderately alkaline (pH 8.2).

TYPE LOCATION: Mesa County, Colorado; 1,800 feet east and 1,000 feet north of the southwest corner of Sec. 28, T. 12 S., R. 99 W. Latitude 38 degrees, 58 minutes, 37 seconds north; longitude 108 degrees, 27 minutes, 52 seconds west.

RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is affected by peak periods of precipitation during the spring, late summer, and early fall. The soil is driest during the month of June. These soils are dry in all parts of the moisture control section more than 3/4 of the time the soil temperature is above 41 degrees F. Typic aridic soil moisture regime.
Mean annual soil temperature: 50 to 54 degrees F.
Mean summer soil temperature: 60 to 78 degrees F
Depth to calcic horizon: 3 to 20 inches
Depth to lithologic discontinuity: 8 to 40 inches to contrasting sand and gravel strata
Organic carbon of surface 15 inches: average .4 to .75 percent
Sand/clay ratio of surface 15 inches: less than 1 to 2.

Particle-size control section (weighted average):
Clay content: less than 18 percent
Particle-size control section (weighted average), above lithologic discontinuity:
Clay content: 18 to 35 percent
Silt content: 25 to 55 percent
Sand content: 20 to 50 percent; less than 45 percent fine sand or coarser
Rock fragments: 25 to 65 percent
Texture: very gravelly loam, sandy clay loam, or clay loam
Particle-size control section (weighted average), below lithologic discontinuity:
Rock fragments: 35 to 80 percent

A horizon:
Hue: 5YR to 10YR
Value: 5 to 7 dry, 3 to 6 moist
Chroma: 2 to 4 dry or moist
Texture (fine earth): sandy clay loam, sandy loam, fine sandy loam or loam
Rock fragments: 5 to 60 percent gravel
Reaction: moderately or strongly alkaline

Bk horizon:
Hue: 5YR through 10YR
Value: 6 to 8 dry, 5 to 7 moist
Chroma: 2 to 4 dry, 3 or 4 moist
Texture (fine earth): fine sandy loam, sandy loam, loam, sandy clay loam, or clay loam
Rock fragments: 0 to 60 percent gravel, cobbles and stones
Calcium carbonate equivalent: 15 to 40 percent
Reaction: moderately or strongly alkaline

Some pedons have Bw horizons above the calcic horizon with less than 15 percent calcium carbonate equivalent.

2Bk and 2C horizons:
Hue: 7.5YR or 10YR
Value: 6 to 8 dry, 4 to 7 moist
Chroma: 2 to 4 dry or moist
Texture (fine earth): loam, sandy loam, fine sandy loam, loamy sand, sand
Rock fragments: 15 to 80 percent gravel, cobbles and stones
Reaction: moderately alkaline or strongly alkaline

COMPETING SERIES: These are the Clifsand, Seeg, Stent and Utaline soils.

Clifsand, Seeg and Stent soils have less than 18 percent clay in the upper part of the particle-size control section.

Utaline soils have 18 to 35 percent clay throughout the particle-size control section.

GEOGRAPHIC SETTING:
Parent material: alluvium and slope alluvium derived from mixed sources; some pedons have underlying residuum and a lithic contact between a depth of 60 to 197 inches
Landform: high terraces, fan remnants and structural benches
Slope: 0 to 40 percent
Elevation: 4,900 to 6,300 feet
Mean annual precipitation: 5 to 9 inches
Mean annual temperature: 48 to 52 degrees F.
Mean summer temperature: 70 to 74 degrees F.
Frost-free period: 125 to 160 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Avalon, Farb, and Persayo soils and the competing Utaline soils. Farb soils have a lithic contact above 20 inches. Avalon soils have less than 35 percent rock fragments in the particle-size control section. Persayo soils have a paralithic contact above 20 inches.

DRAINAGE AND PERMEABILITY: Well drained; negligible to high runoff; moderate permeability.

USE AND VEGETATION: These soils are used principally as native pastureland. Native vegetation is mainly scattered snakeweed, cactus, and galleta grass. In Utah this soil has been correlated to the Desert Loam and Desert Stony Loam (Shadscale-Bud Sagebrush) range sites.

DISTRIBUTION AND EXTENT: The western slope of Colorado and adjoining parts of eastern and central Utah. The series is of moderate extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Mesa County (Lower Colorado Area), Colorado, 1970.

REMARKS: Diagnostic horizons and features recognized in this pedon are:

Particle-size control section: The zone from 10 to 40 inches. (Bk2, 2Bk3, and 2C horizons)
Ochric epipedon: The zone from 0 to 3 inches. (A horizon)
Calcic horizon: The zone from 3 to 35 inches. (Bk and 2Bk horizons)
Lithologic discontinuity: The contact with sandy-skeletal materials at 15 inches.
In the future Blackston will limited to areas with 5 to 9 MAP, 48 to 52 MAAT, and 125 to 160 FFP.

The type location was changed within Mesa County in 1991. Last updated by the state 5/99.

Taxonomic version: Eleventh Edition, 2010.

National Cooperative Soil Survey
U.S.A.