LOCATION PINACOL COEstablished Series
TAXONOMIC CLASS: Clayey-skeletal, smectitic, frigid Typic Haplustalfs
TYPICAL PEDON: Pinacol loam, on a southwest facing, simple, 20 percent slope in ponderosa pine at an elevation of 7,300 feet. (Colors are for dry soil unless otherwise noted.)
Oi--0 to 1 inch; organic layer of partly decomposed needles, leaves, and twigs. (0 to 3 inches thick)
A--1 to 4 inches; grayish brown (10YR 5/2) loam, very dark grayish brown (10YR 3/2) moist; moderate fine granular structure; soft, very friable; nonsticky and nonplastic; many fine and very fine roots; 2 percent pebbles, 2 percent cobble, 1 percent stones; slightly acid (pH 6.2); clear smooth boundary. (3 to 7 inches thick)
E--4 to 13 inches; light brown (7.5YR 6/3) loam, brown (7.5YR 4/3) moist; weak fine granular structure; soft, friable, nonsticky and slightly plastic; many fine and very fine roots; 5 percent pebbles, 5 percent cobble, 3 percent stones; slightly acid (pH 6.2); clear smooth boundary. (0 to 11 inches thick)
Bt1--13 to 20 inches; brown (7.5YR 5/4) stony clay loam, brown (7.5YR 4/4) moist; moderate medium angular blocky structure parting to moderate medium subangular blocky; hard, firm, sticky and plastic; few distinct clay films on faces of peds; 5 percent pebbles, 10 percent cobble, 10 percent stones; slightly acid (pH 6.1); gradual smooth boundary.
Bt2--20 to 33 inches; reddish brown (5YR 5/4) very stony clay loam, reddish brown (5YR 4/4) moist; moderate medium angular blocky structure; hard, firm, sticky and plastic; many distinct clay films on faces of peds; few fine and medium roots; 15 percent pebbles, 20 percent cobble, 15 percent stones; slightly acid (pH 6.1); gradual smooth boundary.
Bt3--33 to 49 inches; reddish brown (5YR 5/4) very stony clay loam, reddish brown (5YR 4/4) moist; strong medium angular blocky structure; hard, firm, sticky and plastic; many distinct clay films on faces of peds; 15 percent pebbles, 20 percent cobble, 15 percent stones; slightly acid (pH 6.2); gradual wavy boundary. (combined thickness of the Bt horizons is 20 to 44 inches)
C--49 to 61 inches; reddish brown (5YR 5/4) very stony clay loam, reddish brown (5YR 4/4) moist; massive; hard, firm, sticky and plastic; 15 percent gravel, 20 percent pebbles, 20 percent stones; slightly acid (pH 6.2).
TYPE LOCATION: La Plata County, Colorado; about 5 miles northwest of Durango; located about 500 feet N. and 1,100 feet E. of the southwest corner of sec. 25, T. 36 N., R. 10 W.; Durango West USGS quad; lat. 37 degrees 20 minutes 37 seconds N. and long. 107 degrees 54 minutes 56 seconds W., NAD 27
RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 42 to 47 degrees F.
Mean summer soil temperature: 59 to 64 degrees F. without an O horizon.
Particle-size control section (weighted average):
Clay content: 35 to 50 percent
A horizon:
Hue: 7.5YR or 10YR
Value: 3 to 5 dry, 2 to 4 moist
Chroma: 2 to 4, dry or moist
Reaction: slightly acid to slightly alkaline
E horizon ( a BE horizon in some pedons):
Hue: 7.5YR or 10YR
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 2 to 4, dry or moist
Texture: Loam, Clay loam
Reaction: slightly acid to slightly alkaline
Bt horizon:
Hue: 5YR or 7.5YR
Value: 5 or 6 dry, 4 to 6 moist
Chroma: 3 to 6 dry or moist
Texture: Clay loam, Clay, Sandy clay
Rock fragments: averages 35 to 80 percent gravel, cobble and stones of granitic and sandstone origin
Reaction: slightly acid to slightly alkaline
COMPETING SERIES: These are the Fishers and Ring series. Fishers soils have rock fragments of basalt. Ring soils are presumed to be moist in the moisture control section in early summer and dry in late summer.
GEOGRAPHIC SETTING:
Parent material: slope alluvium over outwash derived from mixed sources, and has eolian influence in some pedons.
Landform: hillslopes, mesas, and structural benches.
Slopes: 1 to 40 percent
Elevation: 7,000 to 8,500 feet
Mean annual air temperature: 40 to 45 degrees F.
Mean annual precipitation: 18 to 25 inches.
Wettest months: July and August receive slightly more precipitation than other months.
Driest months: May and June receive the least precipitation, however the soils are still moist from snowmelt.
Frost-free period: 80 to 115 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Fortwingate, Goldbug, and Nordicol series.
Fortwingate soils are moderately deep to sandstone bedrock and are on mountain slopes.
Goldbug soils have less than 35 percent rock fragments in the particle-size control section and are on mountain slopes.
Nordicol soils have a mollic epipedon, are loamy-skeletal and are on mountain slopes.
DRAINAGE AND PERMEABILITY: Well drained, low to very high runoff, slow permeability.
USE AND VEGETATION: These soils are used for timber production, livestock grazing, and wildlife habitat. The native vegetation consists of ponderosa pine, Gambel's oak, snowberry, Arizona fescue, and needlegrasses.
DISTRIBUTION AND EXTENT: Southwestern Colorado. LRR E, MLRA 48A. This series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Cortez Soil Survey Area, Colorado, 1997.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: The zone from 1 to 13 inches. (A and E horizons)
Argillic horizon: The zone from 13 to 49 inches. (Bt horizons)
Particle-size control section: The zone from 13 to 33 inches. (Bt1 and Bt2 horizons)
Keys to Soil Taxonomy: Series classified according to Eighth Edition, 1998.