LOCATION ROMOUND COEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, active, mesic Ustic Haplogypsids
TYPICAL PEDON: Romound silt loam - grassland. (Colors are for dry soil unless otherwise noted.)
A--0 to 4 inches (0 to 10 cm); pale brown (10YR 6/3) silt loam, brown (10YR 4/3) moist; weak fine granular and weak medium subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine and fine roots; 14.0 percent calcium carbonate equivalent; violently effervescent; moderately alkaline; clear smooth boundary. (3 to 5 inches thick.)
Bw--4 to 14 inches (10 to 35 cm); brown (10YR 5/3) loam, brown (10YR 4/3) moist; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common very fine roots; 14.0 percent calcium carbonate equivalent; 3.0 gypsum equivalent; few medium soft masses of carbonate throughout; violently effervescent; 2 percent gravel; moderately alkaline; abrupt smooth boundary. (6 to 12 inches thick.)
Cy1--14 to 24 inches (35 to 61 cm); pink (7.5YR 8/3) loam, light brown (7.5YR 6/3) moist; massive; slightly hard, friable, slightly sticky and slightly plastic; few very fine roots; 10.0 percent calcium carbonate equivalent; 36.0 gypsum equivalent; many medium gypsum crystals throughout; violently effervescent; 3 percent gravel; slightly alkaline; clear wavy boundary.
Cy2--24 to 30 inches (61 to 76 cm); pink (7.5YR 7/3) loam, light brown (7.5YR 6/3) moist; massive; slightly hard, very friable, slightly sticky and slightly plastic; 8.0 percent calcium carbonate equivalent; 39.0 gypsum equivalent; many medium gypsum crystals; violently effervescent; 5 percent gravel; slightly alkaline; abrupt irregular boundary. (Combined thickness of the Cy1 and Cy2 horizons is 11 to 23 inches.)
Cr--30 inches (76 cm); soft interbedded shale and gypsum; 24.0 gypsum equivalent.
TYPE LOCATION: Las Animas County, Colorado; approximately 1,800 feet west and 1,950 feet south of the northeast corner of section 2, T. 28 S., R. 53 W.; Latitude 37 degrees 38 minutes 20 seconds N., and Longitude 103 degrees 19 minutes 15 seconds W.; Rock Canyon USGS quad; NAD 83.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature: 47 to 58 degrees F.
Mean summer soil temperature: 59 to 79 degrees F.
Moisture control section: moist in some or all parts in April and May, and intermittently moist June to August. Aridic moisture regime bordering on ustic.
Depth to the paralithic contact: 20 to 40 inches.
Depth to uniformly calcareous material: 0 to 4 inches
Particle size control section:
Clay content: 18 to 30 percent
Silt content: 20 to 60 percent
Sand content: 25 to 60 percent
Rock fragments: 0 to 20 percent and typically averages less than 5 percent.
A horizon:
Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 or 3
Texture: loam or silt loam, and less commonly fine sandy loam. Reaction: moderately alkaline or strongly alkaline
Calcium carbonate equivalent: 5 to 15 percent.
Bw horizon:
Hue: 7.5YR to 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2 or 3
Texture: loam or silt loam
Reaction: moderately alkaline or strongly alkaline
Calcium carbonate equivalent: 5 to 15 percent
Cy horizons:
Hue: 7.5YR to 2.5Y
Value: 6 to 8 dry, 5 or 6 moist
Chroma: 2 to 4
Gypsum content: 15 to 45 percent
Calcium carbonate equivalent: 1 to 10 percent
Reaction: slightly alkaline or moderately alkaline
COMPETING SERIES: There are presently no competing series in the fine-loamy, mixed family of Ustic Haplogypsids.
GEOGRAPHIC SETTING:
Landform: plains, pediments and structural benches adjacent to steep canyons
Parent material: slope alluvium and eolian deposits over residuum from soft interbedded shale and gypsum
Average annual precipitation: 11 to 14 inches, approximately 2/3 of which falls during the months of April through August
Average annual temperature: 50 to 54 degrees F.
Frost-free season: 125 to 165 days
Elevation ranges from 4,200 to 5,000 feet.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Ovmesa and Rizozo soils. Ovmesa soils are less than 20 inches deep to paralithic contact. Rizozo soils are less than 20 inches deep to lithic contact.
DRAINAGE AND PERMEABILITY: Well drained. Medium to rapid runoff. Moderate permeability.
USE AND VEGETATION: These soils are used for rangeland. Native vegetation is principally short grassed and shrubs such as bigelow sagebrush, blue grama, sideoats grams, sand dropseed, and black grama which are adapted to the high gypsum content.
DISTRIBUTION AND EXTENT: Southeastern Colorado. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Las Animas County, Colorado 2007.
REMARKS: Diagnostic horizons and features in this pedon are:
Ochric epipedon: 0 to 4 inches
Cambic horizon: 4 to 14 inches
Gypsic horizon: 14 to 30 inches
Paralithic contact: 30 to 60 inches
Ustic-aridic moisture regime
MLRA 69
Remarks: The name is coined from Round Mound, a butte in the area.
This soil was originally classified as a Cambic Gypsiorthids and is reclassified with the changes to the Aridisols. Laboratory sample S99CO071001.
Taxonomic Version: Keys to Soil Taxonomy, Tenth Edition, 2006