LOCATION YAMPA CO+UTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Aridic Calciustepts
TYPICAL PEDON: Yampa very cobbly loam, on a northwest facing, convex, 10 percent slope in pinyon pine and Utah juniper at an elevation of 6,600 feet. (Colors are for dry soil unless otherwise noted.) When described on May 12, 1994 the soil was moist from 0 to 13 inches.
The surface is covered by 15 percent limestone or sandstone gravel, 10 percent cobbles, and 1 percent stones.
A--0 to 7 inches; brown (7.5YR 4/3) very cobbly loam, dark brown (7.5YR 3/4) moist; weak fine subangular blocky structure parting to moderate fine granular; soft, very friable, slightly sticky and slightly plastic; many very fine and fine, common medium roots; few very fine tubular pores; 25 percent gravel, 20 percent cobbles; common fine irregular soft masses of calcium carbonate throughout; strongly effervescent; 19 percent calcium carbonate equivalent; moderately alkaline (pH 8.1); clear smooth boundary. (3 to 15 inches thick)
Bk1--7 to 13 inches; pinkish gray (7.5YR 7/2) extremely gravelly loam, light brown (7.5YR 6/3) moist; weak fine subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine and fine, many medium and coarse roots; few very fine tubular pores; 50 percent gravel, 15 percent cobbles; many medium and coarse irregular soft masses of calcium carbonate throughout; violently effervescent; 33 percent calcium carbonate equivalent; strongly alkaline (pH 8.6); clear smooth boundary. (Combined thickness of the Bk horizon is 45 to 57 inches thick)
Bk2--13 to 31 inches; pinkish white (7.5YR 8/2) very cobbly loam, pink (7.5YR 7/3) moist; weak fine and medium subangular blocky structure; slightly hard, friable, sticky and plastic; few fine and medium roots; common very fine tubular pores; 25 percent gravel, 20 percent cobbles; many medium and coarse irregular soft masses of calcium carbonate throughout; violently effervescent; 39 percent calcium carbonate equivalent; strongly alkaline (pH 9.0) gradual smooth boundary.
Bk3--31 to 60 inches; light reddish brown (5YR 6/3) extremely cobbly sandy loam, reddish brown (5YR 5/4) moist; massive; slightly hard, friable, nonsticky and slightly plastic; few fine roots; few very fine tubular pores; 45 percent gravel, 30 percent cobbles, 5 percent stones; many fine and medium irregular soft masses of calcium carbonate throughout; violently effervescent; 24 percent calcium carbonate equivalent; strongly alkaline (pH 8.6).
TYPE LOCATION: Moffat County, Colorado; located about 1,300 feet west and 800 feet south of the northeast corner of sec. 30, T. 6 N., R. 100 W.; Haystack Rock USGS quad; lat. 40 degrees 26 minutes 48 seconds N. and long. 108 degrees 40 minutes 4 seconds W., NAD 1927
RANGE IN CHARACTERISTICS:
Soil moisture regime: Ustic moisture regime bordering on aridic.
Mean annual soil temperature: 42 to 46 degrees F.
Mean annual summer soil temperature: 63 to 68 degrees F.
Surface rock fragments: 0 to 25 percent sandstone or limestone gravel, 0 to 25 percent sandstone or limestone cobbles, and 0 to 15 percent sandstone or limestone stones.
Particle-size control section: 5 to 35 percent clay and 15 to 40 percent calcium carbonate equivalent
Depth to calcic horizon: 4 to 7 inches
Depth to secondary calcium carbonate: 0 to 10 inches
Thickness of the calcic: 45 to 57 inches
A horizon:
Hue: 5YR or 7.5YR
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 2 to 4 dry or moist
Texture: very cobbly loam or gravelly loam
Rock fragments: 15 to 50 percent limestone or sandstone gravel or cobbles
Calcium carbonate equivalent: 5 to 20 percent
Reaction: slightly alkaline or moderately alkaline
Bk horizon:
Hue: 5YR or 7.5YR
Value: 5 to 8 dry, 5 to 7 moist
Chroma: 2 to 6 dry or moist
Texture: loam or clay loam modified by 35 to 80 percent sandstone or limestone gravel and cobbles in the upper part and loamy sand or sandy loam modified by 35 to 80 percent sandstone or limestone gravel and cobbles in the lower part.
Rock fragments: 35 to 80 percent limestone or sandstone gravel or cobbles
Calcium carbonate equivalent: 10 to 45 percent
Reaction: moderately alkaline or strongly alkaline
COMPETING SERIES: These are the
Barkelew,
Bronec,
Tabyago, and
Wildmount series.
Barkelew and Wildmount: have cambic horizons with less than 15 percent calcium carbonate equivalent and the top of the calcic horizon starts below 10 inches deep
Bronec: has hue of 10YR or yellower
Tabyago: has a lithic contact with sandstone between 20 and 40 inches deep
GEOGRAPHIC SETTING:
Parent material: slope alluvium, alluvium, and colluvium derived from limestone and sandstone
Landform: mountains, structural benches, alluvial fans, and fan remnants
Slopes: 3 to 65 percent
Elevation: 6,000 to 8,000 feet
Mean annual air temperature: 42 to 45 degrees F.
Mean annual precipitation: 12 to 16 inches, distributed evenly throughout the year with a slight increase in the late summer and early fall
Frost-free period: 75 to 95 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Grapit,
Pensore,
Cragnot, and
Strell series.
Grapit, Pensore, and Cragnot soils have carbonatic families.
Strell soils have bedrock above 20 inches.
DRAINAGE AND PERMEABILITY: Well drained, low to high runoff, moderately slow permeability.
USE AND VEGETATION: These soils are used for livestock grazing and wildlife habitat. Native vegetation is bluebunch wheatgrass, Indian ricegrass, Utah juniper, pinyon pine, and western wheatgrass.
DISTRIBUTION AND EXTENT: Northwestern Colorado and northeastern Utah. LRR D, E, MLRA 34, 47. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Moffat county, (Dinosaur National Monument) Colorado. 1997. The name is taken from a geographic location in the Dinosaur National Monument.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: The zone from 0 to 7 inches. (A horizon)
Calcic horizon: The zone from 7 to 60 inches. (Bk horizons)
ADDITIONAL DATA: Percent calcium carbonate determined by calcimeter. Activity class is estimated.
The classification was changed from Haplocalcidic Ustochrepts to Aridic Calciustepts 12/98.
Keys to Soil Taxonomy: Eighth Edition, 1998