LOCATION OVMESA COEstablished Series
TAXONOMIC CLASS: Loamy, gypsic, mesic, shallow Ustic Haplogypsids
TYPICAL PEDON: Ovmesa loam, on a west facing, 8 percent slope in grass and shrubs at an elevation of 4,800 feet. (Colors are for dry soil unless otherwise noted.) When described on November 2, 1983 the soil was dry.
A--0 to 2 inches; light brown (7.5YR 6/4) loam, brown (7.5YR 4/4) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; 28 percent gypsum; strongly effervescent (12 percent calcium carbonate); moderately alkaline (pH 7.9); abrupt smooth boundary. (1 to 6 inches thick)
Bky--2 to 9 inches; pink (7.5YR 7/4) fine sandy loam, light brown (7.5YR 6/4) moist; massive; slightly hard, friable, nonsticky and nonplastic; many medium gypsum crystals and carbonate masses; 34 percent gypsum; strongly effervescent (9 percent calcium carbonate); slightly alkaline (pH 7.6); abrupt irregular boundary. (7 to 14 inches thick)
Cr1--9 to 14 inches; weakly cemented and moderately cemented gypsum with strongly cemented cobble size gypsum fragments; 46 percent gypsum (8 percent calcium carbonate); clear irregular boundary.
Cr2--14 to 40 inches; reddish brown (5YR 5/3) weakly cemented gypsum and shale; 16 percent gypsum.
TYPE LOCATION: Las Animas County, Colorado; about 22 miles east of Thatcher and 6 miles east of the Purgatoire river; located about 2,500 feet west and 1,100 feet north of the southeast corner of sec. 20, T. 28 S., R. 56 W.; OV Mesa USGS topographic quadrangle; latitude 37 degrees 35 minutes 20 seconds North and longitude 103 degrees 42 minutes 29 seconds West, datum NAD 27.
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is moist intermittently May through August; aridic moisture regime bordering on ustic.
Mean annual soil temperature: 50 to 56 degrees F
Mean summer soil temperature: 70 to 76 degrees F
Depth to paralithic contact: 8 to 20 inches to gypsum and shale
Depth to secondary calcium carbonate: 0 to 2 inches
Thickness of the gypsic horizon: 7 to 14 inches
Depth to gypsiferous material: typically at the surface
Depth to secondary carbonates: 0 to 2 inches
Percent gypsum plus calcium: 40 to 60 percent
Particle-size control section (weighted average):
Clay content: 10 to 18 percent
Sand content: 30 to 65 percent
Rock fragments: 0 to 15 percent gravel
A horizon:
Hue: 7.5YR or 10YR
Value: 5 to 7 dry, 4 or 5 moist
Chroma: 3 or 4
Clay content: 10 to 20 percent
Rock fragments: 0 to 15 percent gravel
Calcium carbonate equivalent: 5 to 15 percent
EC (mmhos/cm): 8 to 16
Gypsum: 25 to 40 percent
SAR: 1 to 10
Reaction: slightly alkaline or moderately alkaline. Reaction is buffered by percent gypsum.
Bky horizon:
Hue: 7.5YR or 10YR
Value: 6 to 8 dry, 5 to 7 moist
Chroma: 3 to 6
Texture: fine sandy loam, loam
Clay content: 10 to 18 percent
Rock fragments: 0 to 15 percent gravel
Pararock fragments: 0 to 15 percent soft gypsum
Calcium carbonate equivalent: 1 to 10 percent
EC (mmhos/cm): 8 to 16
Gypsum: 35 to 55 percent
SAR: 1 to 10
Reaction: slightly alkaline or moderately alkaline. Reaction is buffered by percent gypsum.
COMPETING SERIES: These are the
Rekop (WY), Retsabul (UT), and
Tanbark (NM) series.
Rekop soils: average 18 to 35 percent clay in the control section
Retsabul soils: have greater than 70 percent raw gypsum in the control section
Tanbark soils: have a moisture control section that is dry in
May and June.
GEOGRAPHIC SETTING:
Parent material: Slope alluvium and residuum derived from gypsum and shale
Landform: Plains, hill, pediment, structural bench
Slopes: 2 to 30 percent
Elevation: 4,400 to 5,000 feet
Mean annual temperature: 50 to 53 degrees F
Mean annual precipitation: 12 to 14 inches
Precipitation pattern: wettest period from May through August, driest December through February
Frost-free period: 125 to 155 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Romound and Rizozo series. The Romound soils have a paralithic contact at depths of 20 to 40 inches and are on backslopes and footslopes of pediments. The Rizozo soils have a lithic contact and are on scarps.
DRAINAGE AND SATURATED HYDRAULIC CONDUCTIVITY: Well drained, low to rapid runoff, moderately high saturated hydraulic conductivity.
USE AND VEGETATION: Rangeland and wildlife habitat. This soil has extremely poor vegetative cover. Native vegetation is mainly Bigalow sagebrush, black grama, blue grama, sideoats grama, sand dropseed, and oneseed juniper.
DISTRIBUTION AND EXTENT: Southeast Colorado; LRR G, MLRA 69; small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES PROPOSED: Las Animas County, Colorado, Las Animas County Area soil survey area, Colorado. The name is from a mesa.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Series control section: The zone from 0 to 9 inches.
Particle-size control section: The zone from 0 to 9 inches. (A and Bky horizons)
An ochric epipedon: The zone from 0 to 2 inches. (A horizons)
Gypsic horizon: the zone from 2 to 9 inches (Bky horizons)
Paralithic contact: The contact with gypsum at 9 inches. (Cr1 horizon)
Other features: Gypsic mineralogy, with gypsum plus calcium ranging from 40 to 60 percent.
Ustic aridic moisture regime
Remarks: The Ovmesa soil was originally included in the Rekop series in Las Animas County. Changes to the soil moisture control section in the Rekop series excludes the southeastern Colorado area.
11/2006 WAW After review of the series by the NSSC staff it was sugested this soil is a Gypsid. It borders to a Calcigypsid, however, the calcium content decreases with depth and is considered as non-pedogenic accumulations.
Taxonomic Version: Keys to Soil Taxonomy 10th Ed. 2006