LOCATION POWDERHORN COEstablished Series
TAXONOMIC CLASS: Fine, smectitic Alfic Argicryolls
TYPICAL PEDON: Powderhorn loam, grassland. (Colors are for dry soil unless otherwise noted.)
Oi--0 to 2 inches; undecomposed organic material, chiefly needles, leaves, twigs, and bark.
Oe--2 to 4 inches; partially decomposed organic material like that of the horizon above.
A--4 to 16 inches; dark gray (10YR 4/1) loam, black (10YR 2/1) moist; strong fine crumb and granular structure; soft, very friable, slightly sticky and slightly plastic; neutral; clear smooth boundary. (6 to 12 inches thick)
E--16 to 21 inches; pinkish white (7.5YR 8/2) gravelly loam, pinkish gray (7.5YR 6/2) moist; moderate thin platy structure parting to very fine subangular blocks and granules; very hard, friable, slightly sticky and slightly plastic; peds are extremely hard, 15 percent fine angular granite pebbles and much medium and coarse angular granite sand; slightly acid; gradual wavy boundary. (4 to 8 inches thick)
E/B--21 to 28 inches; pinkish white (7.5YR 8/2) and reddish brown (5YR 5/3) gravelly clay loam (composite texture), pinkish gray (7.5YR 6/2) and reddish brown (5YR 4/3) moist; moderate very fine subangular blocky structure; peds are very hard, friable, slightly sticky and slightly plastic; this horizon consists of clayey material like that of the underlying horizon imbedded in a matrix like that of the overlying horizon. 25 percent fine angular granite pebbles; a large proportion of sand fraction is medium and coarse angular granite sand; slightly acid; gradual irregular boundary. (4 to 10 inches thick)
Bt1--28 to 44 inches; reddish brown (5YR 5/4) gravelly clay, reddish brown (5YR 4/3) moist; moderate medium angular blocky structure; very hard, friable, moderately sticky and moderately plastic; peds are extremely hard, firm; many distinct clay films on peds and in root channels and pores; 20 percent granite pebbles; a high percentage of the sand fraction is medium and coarse granite sand; moderately acid; gradual wavy boundary. (6 to 20 inches thick)
Bt2--44 to 50 inches; reddish brown (5YR 5/3) gravelly light clay, reddish brown (5YR 4/3) moist; weak medium subangular blocky structure; very hard, friable, moderately sticky and moderately plastic; peds are extremely hard, firm; common distinct clay films on peds and in root channels and pores; 20 percent granite pebbles; a high proportion of the sand fraction is medium and coarse angular granite sand; moderately acid; gradual wavy boundary. (4 to 8 inches thick)
C--50 to 60 inches; reddish brown (5YR 5/4) gravelly clay loam, reddish brown (5YR 4/4) moist; massive; extremely hard, friable, slightly sticky and slightly plastic; few manganese concretions; 20 percent fine angular granite pebbles; a high percentage of the sand fraction is medium and coarse angular granite sand; slightly acid.
TYPE LOCATION: Gunnison County, Colorado; SE1/4 sec. 5, T. 46 N., R. 1 W.
RANGE IN CHARACTERISTICS: (depths given are measured from the mineral soil surface)
Soil moisture regime: udic
Mean annual soil temperature: 37 to 44 degrees F.
Mean summer soil temperature: 45 to 47 degrees F. with an 0 horizon as much as 4 inches thick.
Depth to calcareous material: more than 40 inches.
Depth to the top of the argillic horizon: less than 24 inches.
Depth to the base of the argillic horizon: 15 to 50 inches. Within the sand fraction a high percentage is medium and coarser angular sand having a large proportion of flat bearing surfaces between sand grains.
Particle-size control section:
Clay content: 35 to 50 percent
Rock fragment content: 15 to 35 percent
A horizon:
Hue: 5YR to 10YR
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 1 to 3, dry and moist
Texture, fine earth fraction:
Rock fragment content: 5 to 35 percent, mainly gravel
Reaction: moderately acid to slightly alkaline
E horizon:
Hue: 5YR to 10YR
Value: 5 to 8 dry, 4 to 7 moist
Chroma: 1 to 3, dry and moist
Texture, fine earth fraction:
Rock fragment content: 5 to 35 percent, mainly gravel
Reaction: moderately acid to slightly alkaline
Bt horizon:
Hue: 10R to 5YR
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 1 to 6, dry and moist
Texture, fine earth fraction: CL, SC, C
Clay content: 35 to 50 percent, and 5 to 40 percent silt, and 15 to 55 percent sand, with more than 15 percent being fine or coarser sand.
Base saturation: 60 to 100 percent
Rock fragment content: 5 to 35 percent, being mostly gravel.
Reaction: moderately acid to slightly alkaline
C horizon:
Hue: 10R to 5YR
Texture, fine earth fraction: CL, C and averages more than 35 percent clay to depths of at least 50 inches.
Rock fragment content: 15 to 35 percent
Reaction: moderately acid to slightly alkaline
COMPETING SERIES: These are the
Cebone,
Donald, and
Hayrack series.
Other soils that may be competitors when their classification is updated are the:
Gaylord and
Mord series.
Cebone: have a paralithic contact at depths of 20 to 40 inches.
Donald and Gaylord: are calcareous in the lower part of the solum or in the C horizon and have subhorizons of secondary calcium carbonate accumulation.
Hayrack and
Mord: have hue of 7.5YR or yellower. In addition Mord soils are more than 50 inches deep to the base of the argillic horizon.
GEOGRAPHIC SETTING:
Parent material: moderately fine to fine textured material strongly influenced by coarse grained granite.
Landform: terraces, till plains, valley sideslopes, and alluvial fans.
Slope: 2 to 50 percent.
Elevation: 8,500 to 10,000 feet.
Mean annual air temperature: 34 to 41 degrees F.
Mean annual precipitation: 18 to 22 inches.
Wettest months: spring and summer.
Driest months:
Frost-free period: 30 to 70 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Vulcan and Cebolia soils. Vulcan soils have argillic horizons with more than 35 percent rock fragments. Cebolia soils have an abrupt textural boundary between the A and Bt horizons.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; slow permeability.
USE AND VEGETATION: These soils are used primarily for native pastureland. Native vegetation is mainly big sagebrush, Thurber's fescue, mountain bluegrass, and scattered spruce and fir.
DISTRIBUTION AND EXTENT: Mountain areas of central Colorado. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Gunnison County, Colorado, 1974.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon: the zone from 4 to 16 inches. (A horizon)
Albic horizon: the zone from 16 to 21 inches. (E horizon)
Argillic horizon: the zone from 28 to 50 inches.(Bt horizon)
Keys to Soil Taxonomy: Classified according to the Eighth Edition, 1998