LOCATION OHMAN COEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, micaceous Lamellic Dystrocryepts
TYPICAL PEDON: Ohman very stony sandy loam, woodland. (Colors are for dry soil unless otherwise noted.)
Oi--0 inches to 2; slightly decomposed needles, twigs, bark, and leaves.
A--2 to 5 inches; very pale brown (10YR 7/3) very stony sandy loam, dark grayish brown (10YR 4/2) moist; moderate fine granular structure; soft, very friable, nonsticky and nonplastic; very strongly acid (pH 5.2); common mica particles as fine and medium sized sand; 18 percent gravel, 10 percent angular cobble, and 19 percent stone; strongly acid (pH 5.2); abrupt wavy boundary. (2 to 4 inches thick)
E--5 to 13 inches; pink (7.5YR 7/4) very gravelly sandy loam, brown (7.5YR 4/2) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; very strongly acid (pH 5.2); common mica particles as fine and medium sized sand; 40 percent angular and rounded gravel, 10 percent angular cobble; strongly acid (pH 5.2); clear wavy boundary. (4 to 9 inches thick)
E&Bt1--13 to 21 inches; reddish yellow (7.5YR 7/6) very gravelly sandy loam, yellowish red (5YR 5/6) moist; weak fine subangular blocky structure; loose, nonsticky and nonplastic; fine (less than 1.5 cm. in size) brittle spots; common manganese-iron nodes or concretions less than 0.5 centimeters in size; 1 - discontinuous lamellae 1 to 1.5 centimeter thick, reddish brown (5YR 4/4) sandy loam; common mica particles as fine and medium sized sand; 50 percent subangular gravel, 2 percent angular cobble; strongly acid (pH 5.1); gradual wavy boundary. (4 to 9 inches thick)
E&Bt2--21 to 35 inches; reddish yellow (7.5YR 6/6) extremely gravelly sandy loam, yellowish red (5YR 4/6) moist; moderate medium and fine platy structure; loose, nonsticky and nonplastic; 65 percent discontinuous brittle lenses; few manganese-iron concretions; 4 - lamellae 0.5 to 1 centimeter thick reddish brown (5YR 4/4) sandy loam; common mica particles as fine and medium sized sand; 55 percent angular gravel, 10 percent angular cobble, 1 percent stone; strongly acid (pH 5.2); clear smooth boundary. (10 to 16 inches thick)
Cr--35 inches; weathered granite.
TYPE LOCATION: Clear Creek County, Colorado; 100 feet south and 675 feet west of the NE corner of Sec. 30, T.4 S., R. 72 W. (Latitude: 39 degrees, 40 minutes, 48 seconds north; longitude: 105 degrees, 28 minutes, 58 seconds west)
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is ustic moisture regime bordering on udic.
Mean annual soil temperature: 38 to 42 degrees F
Mean summer soil temperature: 36 to 40 degrees F
Depth to paralithic contact: 20 to 40 inches
Particle-size control section (weighted average):
Clay content: 10 to 27 percent
Sand content: 45 to 66 percent
Rock fragments: 35 to 75 percent consisting of granitic and metamorphic rocks
Base saturation: 25 to 60 percent
A horizon:
Hue: 10YR or 7.5YR
Value: 5 through 7 dry, 3 through 6 moist
Chroma: 1 through 3
Reaction: strongly acid to slightly acid
E horizon:
Hue: 7.5YR or 5YR
Value: 5 through 7 dry, 3 through 5 moist
Chroma: 1 through 4
Texture: loamy sand, sandy loam, coarse sandy loam modified by rock fragments
Reaction: very strongly acid to slightly acid
E&Bt horizon(s):
Hue: 7.5YR or 5YR
Value: 4 through 7 dry, 3 through 5 moist
Chroma: 3 through 6
Texture: sandy loam modified by rock fragments
Silicate clays and cutans exist in the lamellae occurring both continuous and discontinuous. These lamellae do not total 15 cm. (6 inches) or more to be designated as an argillic subsoil.
Reaction: very strongly acid to slightly acid
C horizon (when present):
Hue: 7.5YR or 5YR
Texture: loamy sand, coarse sandy loam, sandy loam modified by rock fragments
Reaction: very strongly acid through moderately acid
COMPETING SERIES: This is the Mammoth series. Mammoth is very deep.
GEOGRAPHIC SETTING: Ohman soils are on mountain slopes and ridges. Slopes are 15 to 60 percent. The soils formed in colluvium and slope alluvium from mixed igneous and metamorphic rocks. Elevation is 7,400 to 10,500 feet. Mean annual precipitation is 18 to 24 inches. Mean annual temperature is 36 to 43 degrees. The mean annual summer temperature is 54 to 57 degrees. The average frost-free season is 35 to 75 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bendemeere, Mammoth, Legault, Hiwan, and Ivywild soils. Bendemeere and Mammoth soils do not have paralithic contact within 40 inches. Legault soils have a paralithic contact above 20 inches and lack lamellae in the profile. Hiwan soils have a lithic contact above 20 inches. Ivywild soils lack continuous lamellae in the cambic.
DRAINAGE AND PERMEABILITY: Well to somewhat excessively drained; moderate to rapid runoff; rapid permeability.
USE AND VEGETATION: These soils are used for recreation, woodland, wildlife habitat, and scattered homesite development. Native vegetation is lodgepole pine, Engelmann's spruce, subalpine fir, few scattered quaking aspen, Rocky Mountain Douglas-fir, and dwarf grouse whortleberry.
DISTRIBUTION AND EXTENT: Occurs in the central mountains of Colorado. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Clear Creek County, Georgetown Soil Survey Area, Colorado, 2000.
REMARKS: Diagnostic features include:
ochric epipedon from 2 to 13 inches
lamella at depths of 13 to 35 inches
paralithic contact at 35 inches.
Series name is from a high alpine lake near the Continental Divide in Clear Creek County, Colorado.
Taxonomic version: Eighth Edition, 1998
The mineralogy class was changed from paramicaceous to micaceous in 07/2010 by the National Soil Survey Center on request of the responsible MLRA regional office. The change was necessary based on the eleventh edition of the Keys to Soil Taxonomy, 2010.