LOCATION GRAYPOINT COEstablished Series
TAXONOMIC CLASS: Fine-loamy over sandy or sandy-skeletal, mixed, superactive, frigid Typic Haplargids
TYPICAL PEDON: Graypoint gravelly sandy loam in grassland at an elevation of 7,679 feet. (Colors are for dry soil unless otherwise noted.)
A--0 to 4 inches; light brownish gray (10YR 6/2) gravelly sandy loam, dark grayish brown (10YR 4/2) moist; moderate fine granular structure; very friable, soft; 20 percent gravel, mostly basalt; many dark magnetic mineral grains in the sand and silt fractions; neutral (pH 7.2); clear smooth boundary. (3 to 5 inches thick)
Bt--4 to 13 inches; brown (10YR 5/3) gravelly sandy clay loam, brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate fine subangular blocks; friable, slightly hard, slightly plastic; peds are hard; many thin glossy patches on faces of peds; wax-like coatings in root channels and pores; wax-like bridges between sand grains; 20 percent gravel, mostly basalt; many dark colored magnetic mineral grains in the sand and silt fractions; slightly alkaline (pH 7.6); clear wavy boundary. (5 to 11 inches thick)
BCk--13 to 16 inches; pale brown (10YR 6/3) gravelly loam, brown (10YR 4/3) moist; weak fine subangular blocky structure; very friable, slightly hard; few thin glossy patches on faces of peds and discontinuous glossy coatings in root channels; wax-like bridges between some sand grains; 30 percent gravel, mostly basalt; many dark magnetic mineral grains in the sand and silt fractions; visible secondary calcium carbonate occurring as concretions, thin seams, and streaks, and as coatings on the gravel fragments; calcareous; moderately alkaline (pH 8.2); clear wavy boundary. (2 to 4 inches thick)
2Bk--16 to 60 inches; variegated colors, sand, gravel, and cobbles, mostly basalt; about 40 percent gravel and 15 percent cobbles; calcium carbonate coatings on the rock fragments in the upper part of the horizon. The horizon has grayish appearance when exposed on road cuts.
TYPE LOCATION: Alamosa County, Colorado; 600 feet south and 450 feet east of the NW corner of Sec. 36, T. 39 N., R. 9 E.
RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges from 41 to 47 degrees F, and mean summer soil temperature ranges from 59 to 70 degrees F. The soils range from slightly acid to moderately alkaline. Depth to uniformly calcareous material ranges from 6 to 20 inches. Depth to the sandy-skeletal 2C horizon and depth to the base of the argillic horizon range from 10 to 20 inches. Depth to continuous subhorizons of visible secondary calcium carbonate and/or sulfate accumulation ranges from 8 to 20 inches. Rock fragments range from 0 to 75 percent in a major part of the solum. They dominantly range in size from 1 to 10 inches.
The A horizon has hue of 5Y through 7.5 YR, value of 5 or 6, 3 to 5 moist, and chroma of 2 or 3.
The Bt horizon has hue of 5Y through 7.5 YR, value of 5 or 6, 4 or 5 moist, and chroma of 2 through 4. Clay ranges from 18 to 35 percent. Sand coarser than very fine sand ranges from 35 to 70 percent.
COMPETING SERIES: This is the San Arcacio series. San Arcacio soils have sandy-skeletal substratums at a depth of more than 20 inches below the surface.
GEOGRAPHIC SETTING: Graypoint soils are on alluvial fans and alluvial flats. Slope gradients range from 0 to 10 percent. The soils formed in alluvial sediments derived from igneous and metamorphic rock. The average annual precipitation is 5 to 8 inches, approximately 4 inches of which falls during the months of April through August. Mean annual air temperature ranges from 41 to 46 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Mosca and San Luis soils. Both of these series have natric horizons.
DRAINAGE AND PERMEABILITY: Well-drained; medium to slow runoff; moderately permeability.
USE AND VEGETATION: These soils are used principally as native pastureland, but they may be irrigated successfully in places with proper management. Principal native plants are rabbitbrush and greasewood.
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:
The superactive cation exchange activity class was added in 03/2003 to the taxonomic classification by the National Soil Survey Center on request of the Lakewood MLRA office, without review of the soil series property data. The remainder of this document has not been updated. The parent material at the type location is mixed from igneous and metamorphic rock; volcanic rock only makes up 30 percent, JWB, 4/2009. The original concept for the parent material was basalt. In Costilla County, CO the parent material is derived from granite, gneiss, and mica schist.