LOCATION BIGMON COTentative Series
TAXONOMIC CLASS: Loamy, mixed, superactive, calcareous, mesic Lithic Ustic Torriorthents
TYPICAL PEDON: Bigmon sandy loam, 10 percent slope at an elevation of 6300 feet. (Colors are for dry soil unless otherwise noted.)
A--0 to 3 inches (0 to 8 cm); light brown (7.5YR 6/4) sandy loam, brown (7.5YR 4/4) moist; weak fine granular structure; soft, friable, slightly sticky and non plastic; slightly effervescent; 8 percent channers, 2 percent flagstones; slightly alkaline (pH 7.6); clear smooth boundary. (2 to 4 inches [5 to 10 cm] thick)
C--3 to 7 inches (8 to 17 cm); light brown (7.5YR 6/4) sandy loam, brown (7.5YR 5/4) moist; weak fine granular structure; soft, friable, slightly sticky and slightly plastic; slightly effervescent; 8 percent channers; slightly alkaline (pH 7.8); clear wavy boundary. (3 to 7 inches [8 to 18 cm] thick)
Cr--7 to 10 inches (17 to 25 cm); weathered sandstone. (0 to 4 [0 to 11 cm] inches thick)
R--10to 15 inches (25 to 38 cm); hard Dakota sandstone.
TYPE LOCATION: Montrose County, Colorado; located about 100 feet south and 1200 feet east of the northwest corner of sec. 15, T. 49 N., R. 11 W.; Hoovers Corner USGS quad; lat. 38 degrees 31 minutes 5 seconds N. and long. 108 degrees 5 minutes 28 seconds W.
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is affected by precipitation that is evenly distributed throughout the year, with the exception of a slight increase in the spring and a significant increase in late summer. Aridic moisture regime bordering on ustic.
Mean annual soil temperature: 48 to 50 49 to 51 degrees F
Depth to lithic contact: 8 to 16 inches (20 to 40 cm) to hard Dakota sandstone
Depth to paralithic contact (where present): 5 to 8 inches (13 to 20 cm) to weathered sandstone
Particle-size control section (weighted average):
Clay content: 15 to 18 percent
Rock fragments: 8 to 23 percent sandstone
Channers: 8 to 20 percent
Flagstones: 0 to 3 percent
A horizon:
Hue: 7.5YR
Value: 3 to 6 dry or moist
Chroma: 3 or 4 dry or moist
Texture: sandy loam
Clay content: 15 to 18 percent
Rock fragments: 8 to 23 percent sandstone
Channers: 8 to 20 percent
Flagstones: 0 to 3 percent
Calcium carbonate equivalent: 0 to 10 percent
Electrical conductivity (mmhos/cm): 0 to 1
Reaction: slightly alkaline (7.4 to 7.8)
C horizon:
Hue: 7.5YR
Value: 4 to 6 dry or moist
Chroma: 4 dry or moist
Texture: fine sandy loam, sandy loam, loam, channery fine sandy loam, channery sandy loam, channery loam Clay content: 15 to 18 percent
Rock fragments: 8 to 22 percent sandstone
Channers: 8 to 20 percent
Flagstones: 0 to 2 percent
Calcium carbonate equivalent: 0 to 10 percent
Electrical conductivity (mmhos/cm): 0 to 1
Reaction: slightly alkaline to moderately alkaline (7.6 to 8.2)
COMPETING SERIES: These are the
Hideout,
Lazear,
Rizno,
Simel,
Skyvillage,
Tesihim, and
Travessilla soil series. Hideout soils are derived from eolian sediments and are found on hillslopes and structural benches. Lazear soils have clay content greater than 18 percent. Rizno soils have hues redder than 7.5YR. Simel soils are derived from
Carmel formation mudstones and siltstones. Skyvillage soils have soil moisture control section is dry mid-February through June and moist periodically November to mid-February. Tesihim soils are derived from volcanic tuff. Travessilla soils have temperatures greater than 53 degrees F.
GEOGRAPHIC SETTING:
Parent material: slope alluvium and residuum derived from sandstone
Landform: backslopes of mesas, backslopes of cuestas
Slopes: 2 to 12 percent
Elevation: 5500 to 7300 feet
Mean annual air temperature: 47 to 49 degrees F
Mean annual precipitation: 10 to 12 inches
Precipitation pattern: Precipitation is evenly distributed throughout the year, with the exception of a slight increase in the spring and a significant increase in late summer.
Frost-free period: 125 to 145 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Blancot and Mags series. The Blancot soils are very deep and are on valley sides and ridges. The Mags soils are very deep, have an argillic horizon and are on structural benches.
DRAINAGE AND PERMEABILITY: well drained, moderate runoff, moderate to moderately rapid permeability
USE AND VEGETATION: Used mainly for rangeland. Vegetation consists of galleta, crested wheatgrass, Wyoming big sagebrush, scattered pinyon pine and Utah juniper.
DISTRIBUTION AND EXTENT: Uncompahgre Plateau, western Colorado; LRR D, MLRA 34; minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: Montrose County, Colorado, Ridgway soil survey area. The name is coined from a large mesa in the area called Monitor Mesa .
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Series control section: The zone from 0 to 11 inches.
Particle-size control section: The zone from 0 to 7 inches. (A, C horizons)
Ochric epipedon: The zone from 0 to 3 inches. (A horizon)
Lithic contact: The contact with unweathered sandstone at 11 inches. (R horizon)
Paralithic contact: The contact with weathered sandstone at 7 inches. (Cr horizon)
The assignment of the cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.
Taxonomic Version: Second edition, 1999.