LOCATION ROATCAP COTentative Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, mesic Typic Calcigypsids
TYPICAL PEDON: Roatcap channery fine sandy loam, 4 percent slope at an elevation of 5,640 feet in rangeland. (Colors are for dry soil unless otherwise noted.)
A1--0 to 2 inches (0 to 5 cm); pale brown (10YR 6/3) channery fine sandy loam, brown (10YR 4/3) moist; strong fine platy structure parting to weak very fine granular; slightly hard, very friable, nonsticky and slightly plastic; common very fine roots; 5 percent calcium carbonate equivalent, strongly effervescent; 25 percent channers; moderately alkaline (pH 8.0); abrupt smooth boundary.
A2--2 to 6 inches (5 to 15 cm); light brown (7.5YR 6/4) channery fine sandy loam, brown (7.5YR 4/4) moist; weak medium subangular blocky structure parting to weak fine granular; slightly hard, friable, slightly sticky and slightly plastic; common fine and very fine roots; 5 percent calcium carbonate equivalent, strongly effervescent; 15 percent channers; moderately alkaline (pH 8.2); clear wavy boundary. (The combined thickness of the A horizon is 2 to 10 inches thick.)
Bk--6 to 16 inches (15 to 41 cm); very pale brown (10YR 7/3) very channery fine sandy loam, brown (10YR 5/3) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; 10 percent calcium carbonate segregates as in seams and pendants on bottoms of rock fragments, 20 percent calcium carbonate equivalent, violently effervescent; 45 percent channers, 10 percent flagstones; strongly alkaline (pH 8.6); clear wavy boundary. (6 to 13 inches thick)
By--16 to 24 inches (41 to 61 cm); very pale brown (10YR 8/3) extremely channery gypsiferous fine sandy loam, brown (10YR 5/3) moist; single grained; loose, nonsticky and nonplastic; 5 percent calcium carbonate equivalent, slightly effervescent; 15 percent by volume gypsum crystals throughout, 35 percent gypsum by weight; 50 percent channers, 24 percent flagstones; slightly alkaline (pH 7.4), abrupt wavy boundary. (4 to 11 inches thick)
R--24 inches (61 cm); unweathered sandstone bedrock.
TYPE LOCATION: Montrose County, Colorado; about 1,400 feet south and 500 feet east of the northwest corner of Sec. 8, T. 50 N., R. 11 W. Latitude 38 degrees, 37 minutes, 02 seconds N.; Longitude 108 degrees, 07 minutes, 51 seconds W.
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is affected by precipitation that is evenly distributed throughout the year, with the exception of a slight increase in the spring and a significant increase in late summer. The soils is driest during May and June. Typic aridic moisture regime.
Mean annual soil temperature: 51 to 53 degrees F
Depth to lithic contact: 20 to 40 inches to sandstone
Depth to calcic horizon: 2 to 7 inches
Depth to gypsic horizon: 9 to 17 inches
Particle-size control section (weighted average):
Clay content: 10 to 18 percent
Rock fragments: 35 to 80 percent sandstone channers and flagstones
A horizon:
Hue: 7.5YR or 10YR
Value: 5 to 7 dry; 3 to 5 moist
Chroma: 3 to 6 dry or moist
Clay content: 12 to 18 percent
Rock fragments: 15 to 25 percent sandstone channers
Calcium carbonate equivalent: 0 to 10 percent
Gypsum: 0 to 4 percent
Reaction: moderately to strongly alkaline
Bk horizon:
Hue: 7.5YR to 2.5Y
Value: 6 to 8 dry; 4 to 7 moist
Chroma: 3 to 6 dry or moist
Texture: very channery fine sandy loam, very channery sandy clay loam
Clay content: 12 to 25 percent
Rock fragments: 30 to 60 percent sandstone channers; 0 to 10 percent sandstone flagstones
Calcium carbonate equivalent: 15 to 25 percent
Gypsum: 0 to 4 percent
Reaction: moderately to strongly alkaline
By horizon:
Hue: 2.5Y to 7.5YR
Value: 6 to 8 dry; 5 to 7 moist
Chroma: 2 to 6 dry or moist
Texture: very channery gypsiferous sandy clay loam, very channery gypsiferous sandy loam, extremely channery gypsiferous fine sandy loam
Clay content: 7 to 25 percent
Rock fragments: 15 to 55 percent sandstone channers; 0 to 25 percent sandstone flagstones
Calcium carbonate equivalent: 0 to 10 percent
Gypsum: 15 to 55 percent
Reaction: slightly to moderately alkaline
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Parent material: loamy slope alluvium derived from sandstone and shale over loamy residuum derived from interbedded sandstone and shale
Landform: dipslopes on cuestas and summits on mesas
Slopes: 0 to 15 percent
Elevation: 5,000 to 5,700 feet
Mean annual temperature: 49 to 51 degrees F
Mean annual precipitation: 10 to 12 inches
Relative effective annual precipitation: 8 to 10 inches
Precipitation pattern: The soil moisture control section is affected by precipitation that is evenly distributed throughout the year, with the exception of a slight increase in the spring and a significant increase in late summer.
Frost-free period: 140 to 160 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Hoovers soils on similar landform positions. Hoovers soils have a lithic contact above 20 inches and do not have gypsic horizons.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; medium to high runoff; moderately rapid permeability.
USE AND VEGETATION: These soils are used principally for livestock grazing. Native vegetation consists mainly of galleta, saline wildrye, Indian ricegrass, and shadscale.
DISTRIBUTION AND EXTENT: Eastern edge of the Uncompahgre Plateau in Western Colorado; LRR D, MLRA 36; minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: Ridgway Soil Survey Area, Montrose County, Colorado, 1986. The name is taken from a nearby reservoir.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Series control section: The zone from 0 to 24 inches (0 to 61 cm).
Particle-size control section: The zone from 10 to 24 inches (25 to 61 cm). (Bk and By horizons)
Ochric epipedon: The zone from 0 to 6 inches (0 to 15 cm). (A1 and A2 horizons)
Calcic horizon: The zone from 6 to 16 inches (15 to 41 cm). (Bk horizon)
Gypsic horizon: The zone from 16 to 24 inches. (By horizon)
Lithic contact: The contact with sandstone at 24 inches (61 cm). (R layer)
This soil occurs in a climatic 10 to 12 inch precipitation zone that is generally considered to be ustic aridic. However, the vegetation is more indicative of a typic aridic soil moisture regime.
The assignment of the cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.
Taxonomic Version: Soil Taxonomy 9th edition, 2003.