LOCATION ARCHULETA          CO
Established Series
JPP/DKR/TWH
08/2000

ARCHULETA SERIES


The Archuleta series consists of shallow, well drained soils that formed in residuum or loamy slope alluvium over residuum, derived from interbedded sandstone and shale. Archuleta soils are on hills, ridges, canyons, and mountain slopes. Slopes range from 6 to 80 percent. Mean annual precipitation is about 20 inches, and the mean annual temperature is about 42 degrees F.

TAXONOMIC CLASS: Loamy, mixed, superactive, frigid, shallow Typic Haplustepts

TYPICAL PEDON: Archuleta loam, on a south facing, simple, 15 percent slope in ponderosa pine woodland at an elevation of 7,600 feet. (Colors are for dry soil unless otherwise noted.)

Oi--0 to 1 inch; organic mat of slightly decomposed pine needles and oak leaves. (0 to 2 inches thick)

A--1 to 5 inches; light brownish gray (10YR 6/2) loam, dark grayish brown (10YR 4/2) moist; moderate, medium granular structure; soft, very friable, nonsticky and nonplastic; 5 percent gravel; neutral (pH 6.6) clear wavy boundary. (3 to 8 inches thick)

Bw--5 to 13 inches; pale brown (10YR 6/3) clay loam, yellowish brown (10YR 5/4) moist; weak medium subangular blocky structure; hard, friable, moderately sticky and moderately plastic; 5 percent stones and gravel; neutral (pH 6.8); clear wavy boundary. (6 to 12 inches thick)

Cr--13 to 17 inches; weathered sandstone and shale.

TYPE LOCATION: La Plata County, Colorado; about 6 miles northwest of Bayfield, Colorado, along Wallace Gulch Road; located about 1,500 feet north and 200 feet west of the southeast corner of Section 19, T. 35 N., R. 7 W. Rules Hill USGS quad.; Lat. 37 degrees, 17 minutes, 04 seconds N., and Long. 107 degrees, 40 minutes, 04 seconds W.; NAD 27

RANGE IN CHARACTERISTICS:
(Depths given are measured from the mineral soil surface)
Soil moisture regime: Ustic moisture regime. The moisture control section is dry for 15 consecutive days from June 1 to July 30, when the soil temperature at 20 inches is greater than 41 degrees F. It is not dry in all parts of the moisture control section for at least 45 consecutive days following the summer solstice to October 20, and for at least 90 cumulative days during that period.

Mean annual soil temperature: 42 to 47 degrees F.
Mean annual summer soil temperature: 53 to 57 degrees F.
Depth to paralithic contact: 10 to 20 inches to weathered sandstone and shale.
Thickness of the ochric epipedon: 3 to 8 inches

Particle-size control section:
Clay content: 18 to 35 percent
Rock fragment content: total range of rock fragments is 0 to 35 percent, with gravel ranging from 0 to 20 percent, cobbles from 0 to 10 percent, and stones from 0 to 20 percent. All are sandstone derived.

A horizon:
Hue: 7.5YR to 5Y
Value: 5 to 7 dry, 3 to 6 moist
Chroma: 1 to 4 dry or moist
Texture: Loam, Clay loam, Sandy loam
Rock fragments: 0 to 50 percent sandstone fragments, 0 to 20 percent gravel, 0 to 20 percent cobble, and 0 to 15 percent stones
Reaction: slightly acid to slightly alkaline

Bw horizon:
Hue: 7.5YR to 5Y
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 1 to 4 dry or moist
Texture: Loam, Clay loam, Sandy clay loam, Sandy loam
Reaction: slightly acid to slightly alkaline

COMPETING SERIES: This is the Ridge series.

Ridge: have a horizon of secondary calcium carbonate accumulation and are calcareous throughout the profile.

GEOGRAPHIC SETTING: Archuleta soils.
Parent material: residuum or loamy slope alluvium over residuum derived from interbedded sandstone and shale.
Landform: hills, ridges, canyons, and mountain slopes.
Slopes: 6 to 80 percent
Elevation: 7,000 to 8,500 feet
Mean annual air temperature: 40 to 47 degrees F.
Mean annual precipitation: 15 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: 75 to 110 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Fortwingate, Goldbug, Herm, Horsethief, Sanchez, and Valto series.

Fortwingate soils are moderately deep.
Goldbug and Herm soils are very deep.
Horsethief soils are very deep and have more than 35 percent rock fragments in the particle size control section.
Sanchez and Valto soils have more than 35 percent rock fragments and are shallow over hard bedrock.

DRAINAGE AND PERMEABILITY: Well drained, high and very high runoff, moderate or moderately slow permeability.

USE AND VEGETATION: Archuleta soils are used for wildlife habitat, woodland, and livestock grazing. Native vegetation consists of ponderosa pine, Gambel's oak, mountain mahogany, antelope bitterbrush, fringe sagebrush, serviceberry, snowberry, Arizona fescue, mountain brome, bluegrass, elk sedge, junegrass, needlegrass, mountain muhly, and a few pinyon pine and Rocky Mountain juniper.

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: La Plata County, Colorado, 1982.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: The zone from 1 to 5 inches. (A horizon)
Cambic horizon: The zone from 5 to 13 inches. (Bw horizon)
Paralithic contact: The contact with weathered sandstone and shale at 13 inches. (Cr horizon)

Keys to Soil Taxonomy: Series classified according to Eighth Edition, 1998.

The superactive CEC activity class is presumed for this series based on the general trend indicated by lab data throughout this region.


National Cooperative Soil Survey
U.S.A.