LOCATION NEEDLETON COEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive Eutric Haplocryalfs
TYPICAL PEDON: Needleton loam, on a south facing, simple, 55 percent slope in spruce-fir woodland at an elevation of 10,400 feet. (Colors are for dry soil unless otherwise noted.)
Oi--0 to 2 inches; partially decomposed organic material. (1 to 3 inches thick)
E--2 to 16 inches; light reddish brown (5YR 6/3) loam, reddish brown (5YR 4/3) moist; moderate very fine granular structure; soft, very friable, nonsticky and nonplastic, 7 percent gravel, 5 percent cobbles, 1 percent stones; strongly acid (pH 5.4) clear smooth boundary. (6 to 16 inches thick)
B/E--16 to 26 inches; (60 percent Bt) reddish brown (2.5YR 5/4) very cobbly sandy clay loam, dark reddish brown (2.5YR 3/4) moist, and (40 percent E) light reddish brown (2.5YR 6/4) very cobbly loam, reddish brown (2.5YR 5/4) moist; weak medium subangular blocky structure that parts to moderate fine granular; slightly hard, very friable, slightly sticky and slightly plastic; few faint clay films on ped faces of the B part; 20 percent gravel, 20 percent cobbles, 10 percent stones; slightly acid (pH 6.2); gradual wavy boundary. (8 to 14 inches thick)
Bt1--26 to 48 inches; reddish brown (2.5YR 5/4) very stony sandy clay loam, reddish brown (2.5YR 4/4) moist; moderate medium subangular blocky structure parting to strong medium granular; very hard, friable, moderately sticky and moderately plastic; few distinct clay films on faces of peds; 15 percent gravel, 20 percent cobbles, 20 percent stones; slightly acid (pH 6.2); clear wavy boundary. (14 to 26 inches thick)
Bt2--48 to 62 inches; reddish brown (2.5YR 5/4) very cobbly clay loam reddish brown (2.5YR 4/4) moist; moderate medium subangular blocky structure; very hard, firm, moderately sticky and moderately plastic; many prominent clay films on faces of peds; 15 percent gravel, 15 percent cobbles, 10 percent stones; moderately acid (pH 6.0).
TYPE LOCATION: San Juan County, Colorado; about 2 miles north of Purgatory Ski Area; located about 1,250 feet N. and 1000 feet W. of the southeast corner of sec. 16, T. 39 N., R. 9 W.; Engineer Mountain USGS quad; lat. 37 degrees 38 minutes 40 seconds N. and long. 107 degrees 51 minutes 22 seconds W., NAD 27.
RANGE IN CHARACTERISTICS: (depths given are measured from the mineral soil surface)
Soil moisture regime: udic; dry in some part of the moisture control section for less than 45 cumulative days (typic udic subclass); Are not dry in any part of the soil moisture control section when the soil temperature is above 41 degrees F.
Mean annual soil temperature: 34 to 38 degrees F.
Mean summer soil temperature: 41 to 46 degrees F. with an O horizon.
Depth to argillic horizon: 10 to 24 inches
Lithology of rock fragments: rhyolite, sandstone, limestone, shale
Particle-size control section (weighted averages):
Clay content: 26 to 32 percent
Rock fragment content: 35 to 75 percent
E horizon:
Hue: 2.5YR to 7.5YR
Value: 5 to 7 dry, 3 to 5 moist, when the upper 7 inches is mixed, moist value is 4 or 5.
Chroma: 2 to 4, dry and moist (may or may not be an albic horizon)
Texture, fine earth fraction: L, SL
Rock fragment content: 10 to 60 percent
Base saturation: 50 to 65 percent
Reaction: strongly acid or moderately acid
B/E horizon:
Bt part:
Hue: 2.5YR or 5YR
Value: 5 or 6 dry, 3 to 5 moist
Chroma: 3 to 6, dry and moist
Texture, fine earth fraction: SCL, CL, L
E part:
Hue: 2.5YR to 7.5YR
Value: 6 or 7 dry, 4 or 5 moist
Chroma: 3 or 4, dry and moist
Texture, fine earth fraction: L, SL
Rock fragment content: 35 to 75 percent
Base saturation: 50 to 65 percent
Reaction: very strongly acid to slightly acid
Bt horizon:
Hue: 2.5YR or 5YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 to 6, dry and moist
Texture, fine earth fraction: SCL, CL, or L
Rock fragment content: 35 to 75 percent
Base saturation: 60 to 90 percent
Reaction: very strongly acid to slightly acid
COMPETING SERIES: These are the Frisco, Helmville, Redondo, Tamarron, Tigeron, and Worock series.
In addition, the following soils may be competitors when their classification is updated: Cadotte, Hardzem, Hyattville, Lake Creek, Macfarlane, Tenrag series.
Cadotte: have sandy-skeletal material above 40 inches.
Frisco, Macfarlane, Redondo, Tigeron, and Worock: have hues of 7.5YR or yellower in the Bt horizon.
Hardzem and Tamarron: have a paralithic contact at 20 to 40 inches.
Helmville: have consistent horizons of calcium carbonate accumulation above depths of 40 inches.
Hyattville and Lake Creek: have a lithic contact at less than 40 inches.
Tenrag: have a lithic contact at depths of 40 to 60 inches.
GEOGRAPHIC SETTING:
Parent material: slope alluvium and colluvium derived from rhyolite, sandstone, limestone, and shale
Landform: mountain slopes
Slopes: 5 to 90 percent
Elevation: 8,200 to 11,500 feet
Mean annual air temperature: 32 to 38 degrees F.
Mean annual precipitation: 30 to 45 inches.
Wettest months: July, August, and September receive slightly more precipitation than other months.
Driest months: May and June receive the least precipitation, however the soils are still wet from snowmelt and the soils are usually covered with snow through mid June.
Frost-free period: 40 to 75 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Graysill, Haviland, Scotch, and Snowdon series.
Graysill soils are on mountain slopes, ridges and mesas, are moderately deep and are fine-loamy.
Haviland soils are on mountain slopes and mesas and are fine-loamy.
Scotch soils are on mountain slopes and ridges and are shallow over bedrock.
Snowdon soils are on mountain slopes, structural benches and ridges and are shallow over bedrock.
DRAINAGE AND PERMEABILITY: Well drained, low to high runoff, moderately slow permeability.
USE AND VEGETATION: These soils are used for timber production, livestock grazing, and wildlife habitat. Native vegetation is mainly subalpine fir, Engelmann's spruce, Rocky Mountain whortleberry, mountain brome, heartleaf arnica, Richardson's geranium, sedge, smallflowered woodrush, spike trisetum, and snowberry.
DISTRIBUTION AND EXTENT: Southwestern Colorado. LRR E, MLRA 48A. This series is of large extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: San Juan county, Colorado. Animas-Dolores Soil Survey Area. 1984. The name is taken from a railroad siding in the area.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon and albic horizon: The zone from 2 to 16 inches. (E horizon)
Argillic horizon: The zone from 16 to 62 inches. (B/E and Bt horizons)
Particle size control section: The zone from 16 to 36 inches (B/E and part of the Bt1 horizons)
Keys to Soil Taxonomy: Classified according to Eighth Edition, 1998
Activity class is presumed from the general trend of other soils in the area. Placement in the Eutric subgroup is based on a limited amount of lab data; pedons that are very strongly acid may have base saturation less than 50 percent in some part, hence in the Typic subgroup. This aspect of the series needs further study.