LOCATION MONAHAN COEstablished Series
TAXONOMIC CLASS: Fine, smectitic Ustollic Haplocryalfs
TYPICAL PEDON: Monahan gravelly loam, on a 6 percent slope in grassland at an elevation of 9,350 feet. (Colors are for dry soil unless otherwise noted.) Described on July 23, 1981.
A1--0 to 4 inches; brown (10YR 4/3) gravelly loam, very dark grayish brown (10YR 3/2) moist; weak thick platy structure parting to moderate fine granular structure; slightly hard, very friable, slightly sticky and nonplastic; 16 percent gravel; neutral (pH 6.6); abrupt smooth boundary.
A2--4 to 8 inches; brown (10YR 4/3) gravelly loam, dark brown (10YR 3/3) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky and nonplastic; 16 percent gravel; neutral (pH 6.8); abrupt smooth boundary. (Combined thickness of the A horizons is 6 to 8 inches)
BA--8 to 13 inches; yellowish brown (10YR 5/4) gravelly sandy clay loam, dark yellowish brown (10YR 3/4) moist; weak fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; 16 percent gravel; neutral (pH 6.8); abrupt smooth boundary. (0 to 7 inches thick)
Bt1--13 to 19 inches; yellowish brown (10YR 5/4) gravelly sandy clay loam, dark yellowish brown (10YR 3/4) moist; moderate medium subangular blocky structure; hard, friable, moderately sticky and moderately plastic; common distinct clay films on faces of peds; 34 percent gravel; neutral (pH 6.8); clear smooth boundary.
Bt2--19 to 33 inches; very pale brown (10YR 7/4) clay, dark yellowish brown (10YR 4/6) moist; strong medium prismatic structure; very hard, friable, very sticky and very plastic; common distinct clay films on faces of peds; 5 percent gravel; slightly alkaline (pH 7.4); clear smooth boundary. (Combined thickness of the Bt horizons is 18 to 24 inches)
Bk--33 to 60 inches; very pale brown (10YR 7/3) sandy clay loam, light yellowish brown (10YR 6/4) moist; massive; very hard, friable; slightly sticky and slightly plastic; common fine carbonate masses in the matrix; 4 percent gravel; slightly effervescent; slightly alkaline (pH 7.8). (18 to 30 inches thick)
TYPE LOCATION: Park County, Colorado; about 15 miles south of Hartsel; located about 900 feet north and 1,200 feet west of the southeast corner of sec. 24, T. 14 S., R. 76 W.; Agate USGS quad; lat. 38 degrees 48 minutes 43 seconds N. and long. 105 degrees 50 minutes 18 seconds W., NAD 1983.
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.
Depth to argillic horizon: 8 to 16 inches
Depth to secondary calcium carbonate: 30 to 34 inches
Thickness of the ochric epipedon: 6 to 8 inches
Linear extensibility: 3.0 to 5.9 percent
Base saturation, by NH4OAc: 85 to 100 percent (estimated)
Particle-size control section (weighted average):
Clay content: 37 to 45 percent
Rock fragments: 10 to 25 percent
A horizons
Hue: 10YR, 7.5YR
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 2 or 3 dry; 2 or 3 moist
Clay content: 18 to 26 percent
Gravel content: 15 to 25 percent, indurated
Organic matter content: 2.0 to 4.0 percent
BA horizon (not in all pedons)
Hue: 10YR, 7.5YR
Value: 4 to 6 dry; 3 to 5 moist
Chroma: 3 or 4 dry; 4 moist
Texture: gravelly sandy clay loam, gravelly clay loam, gravelly loam
Clay content: 20 to 30 percent
Gravel content: 15 to 25 percent, indurated
Organic matter content: 0.0 to 1.0 percent
Bt horizons
Hue: 10YR, 7.5YR
Value: 5 to 7 dry; 3 to 6 moist
Chroma: 3 to 6 dry; 3 to 6 moist
Texture: gravelly sandy clay loam, gravelly clay loam, gravelly clay, clay, sandy clay loam, clay loam
Clay content: 25 to 40 percent in the upper part, 30 to 45 percent in the lower part
Gravel content: 2 to 35 percent, indurated
Reaction: neutral or slightly alkaline (pH 6.6 to 7.8)
Organic matter content: 0.0 to 0.5 percent
Bk horizon
Hue: 10YR, 7.5YR
Value: 5 to 7 dry; 4 to 6 moist
Chroma: 3 to 6 dry; 3 to 6 moist
Texture: sandy clay loam, clay, clay loam
Clay content: 24 to 45 percent
Carbonate clay content: 0 to 2 percent
Gravel content: 2 to 15 percent, indurated
Calcium carbonate equivalent: 2 to 5 percent
Electronic conductivity: 0 to 2
COMPETING SERIES: These are the
Brinkert and
Chedsey series.
The Brinkert soils do not have accumulations of secondary carbonates.
The Chedsey soils have bedrock between 20 and 40 inches.
GEOGRAPHIC SETTING:
Parent material: slope alluvium derived from shale
Landform: pediments
Slopes: 3 to 25 percent
Elevation: 9,000 to 10,000 feet
Mean annual temperature: 35 to 39 degrees F.
Mean annual precipitation: 12 to 16 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 Gebson and Temdille series. The Gebson soils are fine-loamy. The Temdille soils are sandy-skeletal.
DRAINAGE AND PERMEABILITY: Well drained, slow permeability
USE AND VEGETATION: These soils are used for livestock grazing and wildlife habitat. Native vegetation consists mainly of Arizona fescue, western wheatgrass, prairie Junegrass, blue grama, bottlebrush squirreltail, needleandthread, rabbitbrush, and slimstem muhly.
DISTRIBUTION AND EXTENT: Central Colorado; LRR E, MLRA 48B; moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Park County, Colorado, Teller-Park soil survey area, Colorado, 2010. The name was taken from nearby Monahan Gulch.
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 13 to 23 inches. (Bt1, Bt2 horizons)
Ochric epipedon: from 0 to 8 inches. (A1, A2 horizons)
Argillic horizon: from 13 to 33 inches. (Bt1, Bt2 horizons)
Secondary carbonates: from 33 to 60 inches. (Bk horizon)
The mineralogy class is unconfirmed. Where this soil is mapped over Pierre shale in Park County it is possibly mixed rather than smectitic.
Taxonomic Version: Classified according to Keys to Soil Taxonomy, 11th Edition, 2010.