LOCATION PERFECTO COEstablished Series
TAXONOMIC CLASS: Sandy-skeletal, mixed Typic Cryorthents
TYPICAL PEDON: Perfecto very cobbly very fine sandy loam, on a northwest facing 45 percent mountain slope under lodgepole pine at an elevation of 10,020 feet. (colors are for dry soil unless otherwise noted)
Oi--0 to 1 inch; mat of slightly decomposed needles, twigs, and leaves (0 to 2 inches thick)
A--1 to 5 inches; grayish brown (10YR 5/2) very cobbly very fine sandy loam, very dark grayish brown (10YR 3/2) moist; moderate medium and coarse platy structure; soft, very friable, nonsticky and nonplastic; 25 percent gravel, 15 percent cobbles; neutral (pH 6.6); gradual wavy boundary. (0 to 5 inches thick)
E1--5 to 10 inches; light brownish gray (10YR 6/2) extremely cobbly sandy loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; 40 percent gravel, 25 percent cobbles; 1 mm silt caps on rock fragments; slightly acid (pH 6.4); gradual wavy boundary.
E2--10 to 17 inches; light brownish gray (10YR 6/2) extremely cobbly loamy sand, dark brown (10YR 3/3) moist; single grained; loose, nonsticky and nonplastic; 40 percent gravel, 30 percent cobbles, 5 percent stones; 3 mm silt caps on rock fragments; slightly acid (pH 6.4); gradual wavy boundary. (combined thickness of the E horizons is 10 to 20 inches)
Bw--17 to 66 inches; light yellowish brown (10YR 6/4) extremely cobbly sand, strong brown (7.5YR 4/6) moist; single grained; loose, nonsticky and nonplastic; 45 percent gravel, 35 percent cobbles, 10 percent stones; 3 mm silt caps on rock fragments; slightly acid (pH 6.2). (30 to 55 inches thick)
TYPE LOCATION: Gunnison County, Colorado; about 5 miles northwest of Sargents, Colorado; located about 350 feet north and 2,250 feet east of the southwest corner of Section 36, T. 49 N., R. 4 E.; USGS Sargents topographic quadrangle; latitude 38 degrees, 27 minutes, 30 seconds north and longitude 106 degrees, 28 minutes, 53 seconds west, NAD 1927.
RANGE IN CHARACTERISTICS: Depths in this section are measured from the top of the mineral soil surface.
Soil moisture: The soil moisture control section (smcs) is affected by precipitation that falls evenly throughout the year with the exception of a significant increase in July and August. The smcs is driest during the fall. The smcs is too dry for Udic and is considered to have an Ustic soil moisture regime.
Mean annual soil temperature: 35 to 45 degrees F.
Particle-size control section: 4 to 10 percent clay, 50 to 90 percent rock fragments.
A horizon:
Hue: 7.5YR or 10YR
Value: 3 to 5 dry, 2 or 3 moist
Chroma: 2 or 3 dry or moist
Reaction: slightly acid (pH 6.1) to neutral (pH 7.3)
Rock fragments: granite, granodiorite, granodiorite gneiss, or quartz monzonite. 35 to 50 percent total rock fragments; 15 to 30 percent gravel, 15 to 35 percent cobbles, 0 to 10 percent stones.
E horizon (upper part):
Hue: 7.5YR or 10YR
Value: 6 or 7 dry, 3 to 5 moist
Chroma: 2 or 3 dry or moist
Texture: extremely cobbly sandy loam, very cobbly sandy loam
Reaction: moderately acid (pH 5.6) to slightly acid (pH 6.5)
Rock fragments: granite, granodiorite, granodiorite gneiss, or quartz monzonite; 50 to 90 percent total rock fragments; 30 to 50 percent gravel, 20 to 50 percent cobbles, 0 to 10 percent stones.
E horizon (lower part):
Hue: 7.5YR or 10YR
Value: 5 to 7 dry, 3 to 5 moist
Chroma: 2 to 4 dry or moist
Texture: extremely cobbly loamy sand, very cobbly loamy sand, extremely cobbly sand
Reaction: moderately acid (pH 5.6) to slightly acid (pH 6.5)
Rock fragments: granite, granodiorite, granodiorite gneiss, or quartz monzonite; 50 to 90 percent total rock fragments; 30 to 50 percent gravel, 20 to 50 percent cobbles, 0 to 10 percent stones.
Bw horizon:
Hue: 7.5YR or 10YR
Value: 5 to 7 dry, 3 to 5 moist
Chroma: 4 to 6 dry or moist
Texture: extremely cobbly sand, extremely cobbly loamy sand, very cobbly sand, very cobbly loamy sand
Reaction: moderately acid (pH 5.6) to slightly acid (pH 6.5)
Rock fragments: granite, granodiorite, granodiorite gneiss, OR quartz monzonite; 50 to 90 percent total rock fragments; 30 to 55 percent gravel, 20 to 50 percent cobbles, 0 to 15 percent stones.
COMPETING SERIES: These are the Alflack, Canlodore, Castlepeak, Chena, Cryomont, Graylock, Nataga, Nizina, Obscurity, Pirapeak, Ragamuffin, Stecum, and Studebaker soils.
Alflack: lithic contact between 20 and 40 inches
Canlodore: lack silt caps and rock fragments are sandstone and/or quartzite
Castlepeak: lacks an albic horizon
Cryomont, Nataga: lack silt caps and have typic udic soil moisture regimes
Graylock: lithic contact at 40 to 60 inches
Chena, Nizina: lack silt caps and occur in a subarctic climate
Obscurity: formed in mud flow materials produced by the Mt.
St. Helens eruption of 1980
Pirapeak: lack silt caps and have a xeric soil moisture pattern
Ragamuffin, Stecum: paralithic contact at 20 to 40 inches
Studebaker: formed in avalanche debris flows produced by the Mt. St. Helens eruption of 1980
GEOGRAPHIC SETTING:
Parent material: slope alluvium and colluvium derived from granite, granodiorite, granodiorite gneiss, or quartz monzonite
Landform: mountain slopes and ridges
Slopes: 15 to 65 percent
Elevation: 9,000 to 11,600 feet
Mean annual temperature: 30 to 40 degrees F.
Mean annual precipitation: 18 to 28 inches
Frost-free period: 40 to 65 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Goosepeak, Legault, and Ohman soils. Goosepeak soils are on backslopes and toeslopes and have more than 20 percent clay in the particle-size control section. Legault soils are on backslopes and shoulders and have a paralithic contact at less than 20 inches. Ohman soils are on backslopes and summits and have a paralithic contact at less than 40 inches.
DRAINAGE AND PERMEABILITY: somewhat excessively drained; very high runoff; moderately rapid permeability.
USE AND VEGETATION: This soil is used for wood products. Potential native vegetation is lodgepole pine with an understory of common juniper, elk sedge, kinnikinnick, and russet buffaloberry. It is in the Lodgepole Pine Woodland Site, Forest Cover Type 218.
DISTRIBUTION AND EXTENT: Western Colorado in LRR E and MLRA 48A. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Cochetopa Soil Survey Area, Gunnison National Forest, Gunnison County, Colorado, 1999. The name comes from Perfecto Creek within the area.
REMARKS: Diagnostic horizons and features recognized in this pedon.
Particle-size control section: the zone from 10 to 40 inches. (E2 and Bw horizons)
Albic horizon: the zone from 5 to 17 inches. (E1, E2 horizons)
The presence of silt caps is considered to be diagnostic for this pedon.
Supporting lab data is not available for this soil. In any future investigations the possibility of spodic horizon should be determined.
Taxonomic version: Eighth Edition, 1998.