LOCATION GUNBARREL               CO+WY

Established Series
Rev: GB/SJJ
09/2016

GUNBARREL SERIES

The Gunbarrel series consists of very deep, somewhat poorly to poorly drained soils formed in wind reworked alluvium from volcanic rocks containing dominant amounts of dark gray and red volcanic mixed grains. Gunbarrel soils are on flood plains, terraces, and low alluvial fans. Slopes are 0 to 3 percent. The mean annual precipitation is about 7 inches and the mean annual temperature is about 42 degrees F.

TAXONOMIC CLASS: Mixed, frigid Typic Psammaquents

TYPICAL PEDON: Gunbarrel loamy sand - grassland. (Colors are for dry soil unless otherwise noted.)

A--0 to 5 inches; grayish brown (10YR 5/2) loamy sand, dark grayish brown (10YR 4/2) moist; single grained; loose; many dark gray and red magnetic mineral grains; moderately alkaline (pH 8.0); clear smooth boundary. (4 to 6 inches thick)

AC--5 to 10 inches; brown (10YR 5/3) loamy coarse sand, grayish brown (10YR 5/2) moist; weak coarse subangular blocky structure; loose; many dark gray and red magnetic mineral grains; moderately alkaline (pH 8.0); clear smooth boundary. (6 to 10 inches thick)

BCkg--10 to 60 inches; gray (2.5Y 6/1) loamy coarse sand, grayish brown (2.5Y 5/2) moist; single grained; loose; common medium distinct mottles, dark yellowish brown (10YR 4/6) moist; many dark gray and red magnetic sand grains; visible secondary calcium carbonate occurring as concretions and as coatings on the sand grains; calcareous; strongly alkaline (pH 9.0).

TYPE LOCATION: Alamosa County, Colorado; approximately 0.1 mile east and 40 feet south of the north quarter corner of Sec. 35, T. 40 N., R. 9 E.

RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges from 43 to 47 degrees F, and mean summer soil temperature ranges from 60 to 64 degrees F. Depth to calcareous material ranges from 0 to 20 inches. The soils range from moderately to very strongly alkaline. Exchangeable sodium ranges from 15 to 60 percent with subhorizons totaling more than 4 inches thick and containing more than 15 percent exchangeable sodium occurring above a depth of 24 inches. Conductivity ranges from 0 to 14 millimhos above a depth of 24 inches. Depth to a continuous horizon of visible secondary calcium carbonate and/or sulfate ranges from 10 to 40 inches. Rock fragments range 0 to 15 percent in a major part of the control section and are dominantly 1/2 to 10 inches in diameter. A water table ranges from 1.5 to 2.5 feet during most of the year.


The A horizon has hue of 5Y through 7.5YR, value of 5 or 6 dry, and 3 through 5 moist, with chroma of 2 or 3.

The AC horizon, when present, is intermediate in color to both the A and C horizons.

The BC or C horizon has hue of 5Y through 7.5YR, value of 5 or 6 dry, and 3 through 5 moist, with chroma of 1 through 4. Mottles are distinct to prominent. Calcium carbonate is less than 5 percent by weight.

COMPETING SERIES: These are the Deford and Minnewaukan series. Deford soils have moderately acid to mildly alkaline reactions in the upper 25 inches of the soil. Minnewaukan soils have less than 15 percent exchangeable sodium in the particle size control section. Both soils have higher mean annual precipitation.

GEOGRAPHIC SETTING: Gunbarrel soils are on low terraces, flood plains, and low alluvial fans. Slopes are 0 to 3 percent. The soils formed in wind reworked alluvium from volcanic rocks containing a high percentage of dark gray and red volcanic mineral grains. The average annual precipitation ranges from 6 to 9 inches, with peak periods of moisture in the middle and late summer months. Mean annual temperature is 41 to 45 degrees F. Elevation ranges from 6,500 to 7,800 feet. The frost-free period ranges from 85 to 100 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Corlett and McGinty soils. Corlett soils are well drained. McGinty soils are moderately coarse textured and have calcic horizons.

DRAINAGE AND PERMEABILITY: Somewhat poorly to poorly drained; slow runoff; rapid permeability. These soils have a fluctuating water table which stands within 30 inches of the surface during most seasons of the year and approaches 18 inches during seasonal highs of precipitation or runoff.

USE AND VEGETATION: These soils are used as native pastureland and for irrigated cropland, principally potatoes. Principal native plants are tall rabbitbrush, greasewood, alkali sacaton, and saltgrass.

DISTRIBUTION AND EXTENT: San Luis Valley Area of south-central Colorado. The series is of moderate extent.

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

SERIES ESTABLISHED: Rio Grande County, Colorado, 1972.

REMARKS: Diagnostic horizons and features recognized in this profile are:
Ochric Epipedon: The zone between 0 to 10 inches: (A and AC)
Secondary Carbonates: The zone between 10 to 60 inches (BCkg)
Redox Features: The zone between 10 to 60 inches (BCkg)

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National Cooperative Soil Survey
U.S.A.