LOCATION CRAGNOT COEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, carbonatic, frigid Aridic Calciustepts
TYPICAL PEDON: Cragnot very channery loam, on a north-facing, convex, 33 percent slope in pinyon pine and juniper at an elevation of 7,000 feet. (Colors are for dry soil unless otherwise noted.) When described on November 10, 1994 the soil was moist from 0 to 4 inches.
The surface is covered by 15 percent cobbles and 3 percent stones.
A--0 to 3 inches; dark brown (7.5YR 3/3) very channery loam, dark brown (7.5YR 3/3) moist; weak medium granular structure; slightly hard, friable, slightly sticky and slightly plastic; common fine roots; very few fine vesicular and tubular pores; 10 percent gravel, 30 percent channers, 10 percent flagstones; calcium carbonate disseminated; slightly effervescent; slightly alkaline (pH 7.8); clear smooth boundary. ( 3 to 8 inches thick)
Bk1--3 to 12 inches; light brown (7.5YR 6/4) very channery silt loam, brown (7.5YR 5/4) moist; weak fine subangular blocky structure; hard, friable, sticky and plastic; common fine and few medium roots; common fine vesicular and tubular pores; 10 percent gravel, 35 percent channers, 10 percent flagstones; many distinct calcium carbonate coats; violently effervescent; 32 percent calcium carbonate equivalent; strongly alkaline (pH 8.6); clear wavy boundary. (Combined thickness of the Bk horizon is 33 to 52 inches thick)
Bk2--12 to 30 inches; light brown (7.5YR 6/4) extremely channery silt loam, brown (7.5YR 5/4) moist; moderate fine subangular blocky structure; hard, firm, sticky and plastic; few fine and medium roots; common fine vesicular and tubular pores; 15 percent gravel, 40 percent channers, 15 percent flagstones; many distinct calcium carbonate coats; violently effervescent; 40 percent calcium carbonate equivalent; strongly alkaline (pH 8.6); clear wavy boundary.
Bk3--30 to 38 inches; brown (7.5YR 5/4) extremely channery silt loam, brown (7.5YR 5/4) moist; weak fine subangular blocky structure; hard, friable, slightly sticky and slightly plastic; few fine and medium roots; common fine vesicular and tubular pores; 15 percent gravel, 40 percent channers, 15 percent flagstones; many distinct calcium carbonate coats; violently effervescent; 44 percent calcium carbonate equivalent; strongly alkaline (pH 8.6); clear wavy boundary.
BCk--38 to 60 inches; strong brown (7.5YR 5/6) very channery silt loam, brown (7.5YR 4/4) moist; massive; hard, firm, sticky and plastic; very few fine roots; few fine vesicular and tubular pores; 10 percent gravel, 20 percent channers, 7 percent flagstones; few faint calcium carbonate coats; violently effervescent; 40 percent calcium carbonate equivalent; strongly alkaline (pH 8.8). (0 to 24 inches thick)
TYPE LOCATION: Moffat County, Colorado; located about 50 feet east and 1,250 feet north of the southwest corner, section 28, T. 6 N., R. 100 W. USGS Haystack Rock quadrangle; lat. 40 degrees 26 minutes 20 seconds N. and long. 108 degrees 38 minutes 39 seconds W., NAD 27
RANGE IN CHARACTERISTICS:
Soil moisture regime: Ustic moisture regime bordering on Aridic.
Soil temperature regime: frigid
Mean annual soil temperature: 42 to 46 degrees F.
Mean annual summer soil temperature: 63 to 68 degrees F.
Surface rock fragments: 0 to 20 percent sandstone and/or limestone gravels. 1 to 20 percent sandstone and/or limestone cobbles and/or channers. 0.1 to 3 percent sandstone and/or limestone stones and/or flagstones.
Particle-size control section: 12 to 30 percent clay and 35 to 70 percent rock fragments.
Depth to calcic horizon: 3 to 60 inches
Depth to secondary calcium carbonate: 0 to 5 inches
A horizon:
Value: 3 to 5 dry, 3 or 4 moist
Chroma: 2 to 4, dry or moist
Reaction: slightly or moderately alkaline
Bk horizon:
Value: 5 to 8 dry, 4 to 7 moist
Chroma: 2 to 6, dry or moist
Texture: loam, silt loam, sandy clay loam, or clay loam modified by 35 to 70 percent sandstone or limestone gravels, cobbles, or channers.
Calcium carbonate equivalent: 40 to 60 percent
Reaction: moderately or strongly alkaline
BCk horizon (if present):
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 3 to 6, dry or moist
Texture: sandy loam, loam, silt loam, sandy clay loam, or clay loam modified by 35 to 80 percent sandstone or limestone gravels, cobbles, or channers.
Reaction: moderately or strongly alkaline
COMPETING SERIES: These are the
Crago and
Roto series.
Crago soils have 2C horizons.
Roto soils are moderately deep over hard bedrock.
GEOGRAPHIC SETTING: Cragnot soils .
Parent material: residuum, colluvium, and alluvium derived from limestone.
Landform: hills and valleys.
Slopes: 6 to 75 percent
Elevation: 6,300 to 8,500 feet
Mean annual air temperature: 43 to 45 degrees F.
Mean annual precipitation: 12 to 14 inches.
Wettest months: Precipitation is relatively evenly distributed throughout the year.
Frost-free period: 75 to 95 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Lakebench,
Lodore,
Pensore, and
Yampa series.
Lakebench, Lodore, and Yampa: have less than 40 percent calcium carbonate equivalent in the control section.
Pensore: 10 to 20 inches to bedrock.
DRAINAGE AND PERMEABILITY: well drained, medium to high runoff, moderate or moderately slow permeability.
USE AND VEGETATION: Livestock grazing and wildlife habitat. Native vegetation is pinyon pine and Utah juniper with an understory of bluebunch wheatgrass, Indian ricegrass, and needleandthread.
DISTRIBUTION AND EXTENT: Northwestern Colorado. LRR D and E, MLRA 34, 47. This series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
ESTABLISHED: Moffat county (Dinosaur National Monument), Colorado, 1997. The name Cragnot is coined.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Calcic horizon: The zone from 3 to 60 inches. (Bk and BCk horizons)
ADDITIONAL DATA: Percent calcium carbonate determined by calcimeter. Activity class is estimated.
Keys to Soil Taxonomy: Seventh Edition, 1996
Classification needs to be updated when 1998 Keys are released (Aridic Calciustepts).