LOCATION GEBSON COEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive Calcic Argicryolls
TYPICAL PEDON: Gebson sandy loam, on a 3 percent slope in grassland at an elevation of 8,850 feet. (Colors are for dry soil unless otherwise stated.) Described on September 25, 1884.
A--0 to 6 inches; brown (10YR 5/3) loam, dark brown (10YR 3/3) moist; weak fine granular structure; soft, very friable, slightly sticky slightly plastic; 8 percent gravel; neutral (pH 6.6); abrupt smooth boundary. (3 to 7 inches thick)
Bt--6 to 11 inches; brown (10YR 5/3) clay loam, dark brown (10YR 3/3) moist; moderate medium granular structure parting to moderate subangular blocky; hard, firm, moderately sticky, and moderately plastic; common distinct clay films on faces of peds; 5 percent gravel; neutral (pH 6.8); abrupt smooth boundary. (4 to 32 inches thick)
Bk1--11 to 19 inches; light gray (10YR 7/2) loam, light yellowish brown (10YR 6/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; 5 percent gravel; violently effervescent; few fine carbonate masses on faces of peds; 17 percent calcium carbonate equivalent; moderately alkaline (pH 8.2); clear smooth boundary.
Bk2--19 to 29 inches; very pale brown (10YR 7/3) loam, very pale brown (10YR 7/4) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; 5 percent gravel; strongly effervescent; few fine carbonate masses on faces of peds; 15 percent calcium carbonate equivalent; moderately alkaline (pH 8.2); gradual smooth boundary.
Bk3--29 to 60 inches; light gray (2.5Y 7/2) loam, grayish brown (2.5Y 5/2) moist; massive; hard, friable, slightly sticky and slightly plastic; 5 percent gravel; strongly effervescent; few fine carbonate masses on faces of peds; 10 percent calcium carbonate equivalent; moderately alkaline (pH 8.2). (combined thickness of the Bk horizons is greater than 50 inches)
TYPE LOCATION: Park County, Colorado; located about 3 miles southeast of Hartsel, about 1500 feet south and 900 feet west of the northeast corner of sec. 22, T. 12 S., R. 75 W.; Antero Reservoir NE USGS quad; lat. 38 degrees 59 minutes 43 seconds N. and long. 105 degrees 45 minutes 50 seconds W., NAD 83.
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is usually dry in late spring and early summer, moist in some part in late July and August, and intermittently dry in fall; ustic regime bordering on aridic.
Mean annual soil temperature: 37 to 41 degrees F.
Mean summer soil temperature: 51 to 58 degrees F.
Thickness of mollic epipedon: 10 to 13 inches
Depth to argillic horizon: 2 to 13 inches
Depth to calcic horizon: 10 to 27 inches
A horizon:
Hue: 7.5YR, 10YR
Value: 3 to 5 dry; 2 or 3 moist
Chroma: 2 or 3 dry; 2 or 3 moist
Texture: very gravelly loam, loam, sandy loam
Clay content: 10 to 27 percent
Gravel content: 0 to 59 percent
Organic matter content: 2.0 to 4.0 percent
Bt horizon:
Hue: 7.5YR, 10YR
Value: 3 to 8 dry; 3 to 5 moist
Chroma: 2 to 4 dry; 2 to 6 moist
Texture: sandy clay loam, clay loam, loam, gravelly clay loam, gravelly loam, gravelly sandy clay loam
Clay content: 18 to 35 percent
Sand content: 40 percent or more, over 30 percent fine sand or coarser
Gravel content: 0 to 30 percent
Reaction: neutral or slightly alkaline (pH 6.6 to 7.8)
Bk horizons:
Hue: 10YR, 7.5YR, 2.5Y
Value: 5 to 8 dry; 3 to 7 moist
Chroma: 2 to 6 dry; 2 to 4 moist
Texture: sandy clay loam, sandy loam, loam, gravelly sandy clay loam, gravelly sandy loam, gravelly loam, loam
Clay content: 10 to 30 percent
Carbonate clay content: 1 to 3 percent
Sand content: 40 percent or more, over 35 percent fine sand or coarser
Gravel content: 0 to 30 percent
Calcium carbonate equivalent: 5 to 20 percent
Reaction: slightly alkaline or moderately alkaline (pH 7.4 to 8.4)
COMPETING SERIES: These are the
Accola,
Elispring,
Glentivar,
Madigan,
Michelson,
Monida,
Morset,
Northorn,
Oro Fino, and
Philipsburg series.
Accola soils have an O horizon, and have an ustic regime that does not border aridic.
Elispring, Glentivar, Madigan soils are moderately deep to a lithic contact.
Michelson soils have a lithologic discontinuity.
Monida soils have a xeric moisture regime.
Morset soils are not well separated; they are not moist in the soil moisture control section in summer and early fall (have a sagebrush plant community).
Oro Fino soils are sandy in the lower Bk horizon.
Philipsburg soils have an ustic regime that does not border aridic, and are not moist in summer and early fall.
Northorn soils have a udic moisture regime.
GEOGRAPHIC SETTING:
Parent material: alluvium and/or slope alluvium from mixed sources, slope alluvium derived from volcanic breccia
Landform: fan remnants, pediments
Slopes: 1 to 25 percent
Elevation: 8,800 to 10,100 feet
Mean annual temperature: 35 to 39 degrees F.
Mean annual precipitation: 10 to 17 inches
Precipitation pattern: Monthly precipitation is lowest in winter and greatest in July and August.
Frost-free period: 50 to 80 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Hodden, Glentivar, and Betemer series. The Hodden soils are loamy-skeletal. The Glentivar soils are moderately deep to limestone, sandstone, and shale. The Betemer soils are shallow to volcanic breccia.
DRAINAGE AND PERMEABILITY: Well drained; moderate or moderately slow permeability.
USE AND VEGETATION: These soils are used for livestock grazing and wildlife habitat. Native vegetation consists mainly of western wheatgrass, Arizona fescue, mountain muhly, blue grama, needleandthread, and prairie Junegrass.
DISTRIBUTION AND EXTENT: Central Colorado; LRR E, MLRA 48B; moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Moffat County (Moffat County Area), Colorado, 1992. The type location is in the Teller-Park Area soil survey, where this soil was proposed in 1984. The name is coined.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Series control section: The zone from 0 to 60 inches.
Particle-size control section: The zone from 6 to 11 inches. (Bt horizon)
Mollic epipedon: from 0 to 11 inches. (A, Bt horizons)
Argillic horizon: from 6 to 11 inches. (Bt horizon)
Calcic horizon: from 11 to 29 inches. (Bk1, Bk2 horizons)
Secondary carbonates: from 11 to 60 inches. (Bk1, Bk2, Bk3 horizons)
Cryic temperature regime.
The classification when established was fine-loamy, mixed Argic Cryoborolls. Years later it was discovered that the typical pedon did not have an epipedon thick enough for a mollic epipedon, and the classification was changed to Ustollic Haplocryalfs. During the correlation of the Teller-Park Area in 2010, the type location was moved to a pedon that better represented the original concept of this series, and the classification changed to Calcic Argicryolls.
The concept of this series is restricted to grassland plant communities that do not have a significant big sagebrush component. The Gebson series is in areas that do not receive large amounts of winter precipitation and are strongly affected by monsoon rains falling in late July and August; these areas typically do not support big sagebrush. The soil correlated to Gebson in northwest Colorado is no longer considered within the series concept.