LOCATION TERCIO COEstablished Series
TAXONOMIC CLASS: Fine, smectitic Ustic Glossocryalfs
TYPICAL PEDON: Tercio cobbly loam, on a north facing, convex, 28 percent slope in forest at an elevation of 8880 feet. (Colors are for dry soil unless otherwise noted.) When described on July 10, 1985 the soil was moist from 0 to 38 inches.
Oi--0 to 2 inches; partially decomposed moss, needles and twigs. (0 to 2 inches thick)
E--2 to 10 inches; very pale brown (10YR 7/3) cobbly loam, brown (10YR 4/3) moist; moderate fine granular structure; slightly hard, friable, slightly sticky and slightly plastic; 5 percent gravel, 10 percent cobbles; strongly acid (pH 5.3); clear smooth boundary. (6 to 10 inches thick)
E/B--10 to 16 inches; 60 percent very pale brown (10YR 7/3) very cobbly loam, brown (10YR 4/3) moist and 40 percent light yellowish brown (10YR 6/4) very cobbly clay loam, dark yellowish brown (10YR 4/4) moist; moderate fine and medium subangular blocky structure; hard, firm, sticky and plastic; 15 percent gravel, 30 percent cobbles; moderately acid (pH 6.0); clear smooth boundary. (4 to 8 inches thick)
Bt1--16 to 30 inches; light yellowish brown (10YR 6/4) gravelly clay, brown (10YR 4/3) moist; strong coarse blocky structure; extremely hard, very firm, very sticky and very plastic; many thin clay films on faces of peds; 15 percent gravel, 5 percent cobbles; moderately acid (pH 5.8); gradual smooth boundary.
Bt2--30 to 38 inches; yellowish brown (10YR 5/4) cobbly clay, brown (10YR 4/3) moist; common fine distinct yellowish brown (10YR 5/6) relict redox concentrations on ped faces; strong medium blocky structure; extremely hard, very firm, very sticky and very plastic; common thin patchy clay films on faces of peds; 10 percent gravel, 20 percent cobbles; moderately acid (pH 5.6); clear wavy boundary. (Combined Bt1 and Bt2 thickness is 20 to 40 inches)
BC--38 to 70 inches; yellowish brown (10YR 5/4) cobbly clay loam, brown (10YR 4/3) moist; many fine distinct yellowish brown (10YR 5/6) relict redox concentrations on ped faces; moderate fine subangular blocky structure; very hard, very firm, sticky and plastic; 20 percent cobbles, 15 percent shale parafragments; strongly acid (pH 5.2).
TYPE LOCATION: Las Animas County, Colorado; about 4.7 miles southwest of Tercio; located in an unsectionalized area about 1.5 miles north of the New Mexico state line and 800 feet north of Rincon Creek, T. 35 S., R. 68 W.; Torres USGS quad; lat. 37 degrees 00 minutes 43 seconds N. and long. 105 degrees 02 minutes 14 seconds W., NAD 1927
RANGE IN CHARACTERISTICS:(depths are from the mineral soil surface)
Soil moisture: The soil moisture control section is moist March through August and dry December through February; Udic moisture regime bordering on ustic.
Mean annual soil temperature: 38 to 40 degrees F
Mean annual summer soil temperature: 45 to 47 degrees F
Depth to albic horizon: 0 to 2 inches
Depth to argillic horizon: 10 to 18 inches
Depth to glossic horizon: 6 to 10 inches
Depth to redox concentrations: 26 to 40 inches
Thickness of the argillic horizon: 20 to 40 inches
Particle-size control section (weighted average):
Clay content: 40 to 50 percent
Sand content: 20 to 30 percent
Rock fragments: 20 to 30 percent
An A horizon is present in some pedons.
E horizon:
Hue: 7.5YR or 10YR
Value: 6 or 7 dry, 4 or 5 moist
Chroma: 2 or 3
Clay content: 18 to 27 percent
Rock fragments: 15 to 35 percent
Reaction: strongly acid or moderately acid
E/B horizon:
Hue: 7.5YR or 10YR
Value: 6 or 7 dry, 4 or 5 moist (E part)
Value: 5 or 6 dry, 4 or 5 moist (B part)
Chroma: 2 or 3 (E part), 4 to 6 (B part)
Texture (B): cobbly silty clay loam, very cobbly clay loam, cobbly clay loam
Texture (E): very cobbly loam
Clay content: 27 to 40 percent
Rock fragments: 25 to 50 percent, 5 to 15 percent gravel, 20 to 35 percent cobbles
Reaction: moderately acid or slightly acid
Bt horizons:
Hue: 7.5YR to 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 4 to 6
Texture: gravelly clay, cobbly clay
Clay content: 40 to 55 percent
Rock fragments: 15 to 35 percent
Base saturation: 50 to 80 percent
Reaction: moderately acid or slightly acid
BC horizon:
Hue: 7.5YR to 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 4 to 6
Texture: gravelly clay, cobbly clay, cobbly clay loam
Clay content: 35 to 55 percent
Rock fragments: 15 to 35 percent
Pararock fragments: 15 to 25 percent, dominantly shale
Base saturation: 50 to 80 percent
Reaction: strongly acid or moderately acid
COMPETING SERIES: These are the
Cowd (CO),
Dell (WY), and
Graneros (CO) series.
Cowd soils: average less than 15 percent rock fragments in the control section
Dell soils: have a lithic contact at depths of 40 to 60 inches
Graneros soils: are 20 to 40 inches to paralithic contact
GEOGRAPHIC SETTING:
Parent material: colluvium and residuum derived from shale and siltstone, commonly the Raton Formation.
Landform: mountain slopes
Slopes: 15 to 40 percent
Elevation: 8,000 to 10,000 feet
Mean annual temperature: 38 to 42 degrees F
Mean annual precipitation: 20 to 26 inches
Precipitation pattern: continental climate
wettest period: April through August
driest period: December through February
Frost-free period: 40 to 60 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cucharas and Graneros series. The Cucharas soils have a mollic epipedon and are on open backslopes.
DRAINAGE AND PERMEABILITY: moderately well drained, rapid runoff, very slow permeability.
USE AND VEGETATION: Woodland and wildlife habitat. Native plant community is Rocky Mountain Douglas fir, white fir, quaking aspen, common juniper, kinnikinnick, mountain brome, and sedges.
DISTRIBUTION AND EXTENT: Southern Rocky Mountains, Colorado; LRR E, MLRA 48A; small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Las Animas county, Colorado, 2007, Las Animas County Area and parts of Huerfano County soil survey area, Colorado. The name was taken from a townsite in the area.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Particle-size control section: The zone from 10 to 30 inches. (Bt1 and Bt2 horizons)
Albic horizon: The zone from 2 to 10 inches. (E horizon)
Glossic horizon: The zone from 10 to 16 inches. (E/B horizon)
Argillic horizon: The zone from 16 to 38 inches. (Bt1 and Bt2 horizons)
Redoximorphic concentrations are relict and do not reflect the current drainage class of this soil.
The assignment of the cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.
Taxonomic Version: Tenth Edition, 2006