LOCATION SIXMILE CO+WY
Established Series
Rev. AJC-SSP-KLS
05/2023
SIXMILE SERIES
The Sixmile series consists of moderately deep, well drained soils that formed in slope alluvium or colluvium over residuum derived from shale. Sixmile soils are on hills, pediments and homoclinal ridges of bedrock controlled landscapes. Slopes range from 10 to 50 percent. The mean annual precipitation is about 405 mm and the mean annual air temperature is about 9 degrees C.
TAXONOMIC CLASS: Fine-loamy, mixed, superactive, mesic Aridic Haplustepts
TYPICAL PEDON:Sixmile clay loam - grassland. (Colors are for dry soil unless otherwise noted.)
A--0 to 10 cm; reddish gray (5YR 5/2) clay loam, dark reddish gray (5YR 4/2) moist; moderate fine granular structure; soft, very friable; moderately sticky and moderately plastic; slightly effervescent; moderately alkaline (pH 8.2); gradual wavy boundary. (8 to 15 cm thick)
BCk1--10 to 51 cm; gray (5YR 6/1) clay loam, dark gray (5YR 4/1) moist; massive; hard, very friable, moderately sticky and moderately plastic; few calcium carbonate concretions occurring discontinuously and erratically throughout the horizon; slightly effervescent; moderately alkaline (pH 8.2); gradual wavy boundary.
BCk2--51 to 76 cm; reddish gray (10R 5/1) clay loam, dark reddish gray (10R 4/1) moist; massive; hard, very friable, moderately sticky and moderately plastic; few calcium carbonate concretions occurring discontinuously and erratically; slightly effervescent; moderately alkaline (pH 8.2); gradual wavy boundary. (Combined thickness of BCk horizons - 45 to 95 cm thick)
Cr--76 cm; reddish gray (10R 5/1) calcareous Morrison shale.
TYPE LOCATION: Boulder County, Colorado; approximately 198 meters west and 305 meters north of the SE corner of sec. 8, T.3N., R.70W.; Hygiene USGS quad; lat. 40 degrees, 14 minutes, 9 seconds N. and long. 105 degrees, 14 minutes, 45 seconds W., NAD83
RANGE IN CHARACTERISTICS:
Soil moisture - soil is moist during the months of April, May and June and driest in December, January and February
Mean annual soil temperature - 8 to 11 degrees C
Mean summer soil temperature - 15 to 26 degrees C
Depth to the paralithic contact - 50 to 100 cm to moderately cemented shale bedrock
Depth to cambic horizon - 8 to 20 cm
Particle-size control section:
Clay content - 18 to 35 percent
Sand content - 20 to 50 percent, with 15 to 35 percent being fine or coarser sand
Rock fragment content - 0 to 15 percent
A horizon
Hue: 10R through 5YR
Value: 4 through 7 dry, 3 through 6 moist
Chroma: 1 through 4 dry or moist
Reaction: pH 7.4 to 8.4
Note: When the value is as dark as 5 dry and 3 moist the horizon is too thin or contains too little organic matter to be a mollic epipedon.
BCk horizon
Hue: 10R through 5YR
Texture: loam or clay loam
Calcium carbonate equivalent: 2 to 10 percent
Reaction: pH 7.9 to 9.0
COMPETING SERIES:
Atchison (KS) - are very deep; have hue more yellow than 5YR
Berthoud (OK) - are very deep; have hue more yellow than 5YR
Kachina (NM) - are very deep; are driest in
May and June
McRae (MT) - are very deep; have hue more yellow than 5YR
Teromote (NM) - are very deep; are driest in
May and June
Ziggy (WY) - are very deep; have hue more yellow than 5YR
GEOGRAPHIC SETTING:
Landform - hills, pediments and homoclinal ridges of bedrock controlled landscapes
Elevation - 1,575 to 2,300 meters
Slopes - 10 to 50 percent
Parent material - alluvium or colluvium over residuum derived from shale
Mean annual air temperature - 7 to 10 degrees C
Mean annual precipitation - 355 to 455 mm
Precipitation pattern - peak periods of precipitation occur in the spring and summer months
Frost-free period - 110 to 140 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well-drained; medium or rapid runoff; moderate permeability.
USE AND VEGETATION: Used as native pastureland or irrigate cropland. Principal native vegetation is blue grama, western wheatgrass, and cactus.
DISTRIBUTION AND EXTENT: Sixmile soils are of small extent in the foothills along the eastern front of the Rocky Mountains in central Colorado and in southeast Wyoming; MLRA 49 and 58B.
SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Boulder Area, Colorado, 1971.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Cambic horizon - 10 to 76 cm (BCk1, BCk2 horizons)
Secondary calcium carbonate accumulation - 10 to 76 cm (BCk1, BCk2 horizons)
Paralithic contact - 76 cm to moderately hard shale bedrock (Cr horizon)
Particle-size control section - 25 to 76 cm (BCk1, BCk2 horizons)
Sixmile soils have a mesic soil temperature regime and an ustic soil moisture regime bordering on aridic.
Converted to metric, formatting updated to current standards, and competing series section updated. 01/2021
National Cooperative Soil Survey
U.S.A.