LOCATION MAGS COTentative Series
TAXONOMIC CLASS: Fine, mixed, superactive, mesic Ustic Haplargids
TYPICAL PEDON: Mags fine sandy loam, 4 percent slope at an elevation of 6520 feet in rangeland. (Colors are for dry soil unless otherwise noted.)
A--0 to 2 inches (0 to 6 cm); light brown (7.5YR 6/3) fine sandy loam, brown (7.5YR 4/3) moist; weak fine granular structure; soft, friable, slightly sticky and slightly plastic; common fine and medium roots; noneffervescent; slightly alkaline (pH 7.4); abrupt wavy boundary. (2 to 4 inches thick)
BE--2 to 5 inches (6 to 13 cm); pinkish gray (7.5YR 7/2) fine sandy loam, brown (7.5YR 5/3) moist; weak fine and medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and medium roots; noneffervescent; slightly alkaline (pH 7.6); clear wavy boundary. (0 to 3 inches thick)
Bt1--5 to 11 inches (13 to 29 cm); brown (7.5YR 5/3) clay loam, brown (7.5YR 4/3) moist; weak medium prismatic structure parting to moderate medium subangular blocky; hard, firm, moderately sticky and moderately plastic; common fine roots; 75 percent distinct clay films in pores and on faces of peds; slightly effervescent; moderately alkaline (pH 8.2); clear wavy boundary.
Bt2---11 to 24 inches (29 to 61 cm); brown (7.5YR 5/3) clay, brown (7.5YR 4/2) moist; weak medium prismatic structure parting to moderate medium subangular blocky; hard, firm, moderately sticky and very plastic; few fine roots; 75 percent distinct clay films in pores and faces of peds; slightly effervescent; moderately alkaline (pH 8.2); clear wavy boundary. (Total thickness of the Bt horizon is 5 to 20 inches.)
Btk1--24 to 32 inches (61 to 81 cm); light brown (7.5YR 6/3) clay, brown (7.5YR 5/2) moist; moderate medium subangular blocky structure; hard, very firm, moderately sticky and very plastic; few fine roots; 30 percent distinct clay films in pores and on faces of peds; 15 percent fine masses and threads of calcium carbonate, 10 percent calcium carbonate equivalent, strongly effervescent; moderately alkaline (pH 8.2); gradual wavy boundary.
Btk2--32 to 39 inches (81 to 100 cm); light brown (7.5YR 6/3) sandy clay loam, light brownish gray (10YR 6/2) moist; moderate medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; 5 percent faint clay films on faces of peds; 10 percent fine masses of calcium carbonate, 8 percent calcium carbonate equivalent, violently effervescent; moderately alkaline (pH 8.2); gradual wavy boundary. (Total thickness of the Btk horizon is 4 to 40 inches.)
BCk--39 to 80 inches (100 to 203 cm); light yellowish brown (10YR 6/4) sandy clay loam, pale brown (10YR 6/3) moist; weak fine subangular blocky structure; hard, firm, moderately sticky and moderately plastic; 2 percent very fine masses of calcium carbonate, 5 percent calcium carbonate equivalent, strongly effervescent; moderately alkaline (pH 8.2). (0 to 42 inches thick)
TYPE LOCATION: Montrose County, Colorado; located about 1950 feet west and 1300 feet south of the northeast corner of sec. 34, T. 49 N., R. 11 W.; Dry Creek Basin USGS quad; lat. 38 degrees 28 minutes 17 seconds N. and long. 108 degrees 5 minutes 1 second W., NAD 83.
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. Aridic moisture regime bordering on ustic.
Mean annual soil temperature: 49 to 51 degrees F
Depth to argillic horizon: 2 to 7 inches
Depth to secondary calcium carbonate: 19 to 24 inches
Particle-size control section (weighted average):
Clay content: 35 to 42 percent
Rock fragments: 0 to 10 percent shale and sandstone parachanners
A horizon:
Hue: 7.5YR
Value: 4 to 6 dry or moist
Chroma: 2 or 3 dry or moist
Texture: fine sandy loam
Clay content: 15 to 18 percent
Rock fragments: 0 to 12 percent channers, 0 to 1 percent flagstones
Calcium carbonate equivalent: 0 to 5 percent
Reaction: slightly alkaline
BA or BE horizon (where present):
Hue: 7.5YR
Value: 4 or 7 dry or moist
Chroma: 2 or 3 dry or moist
Texture: fine sandy loam, sandy loam
Clay content: 18 to 20 percent
Rock fragments: 0 to 10 percent channers
Calcium carbonate equivalent: 0 to 5 percent
Reaction: slightly alkaline
Bt or Btk horizon:
Hue: 7.5YR or 10YR
Value: 4 to 7 dry, 4 to 6 moist
Chroma: 2 or 3 dry or moist
Texture: sandy clay loam, clay loam, clay
Clay content: 32 to 42 percent
Pararock fragments: 0 to 10 percent sandstone or shale parachanners
Calcium carbonate equivalent:<p> 0 to 5 percent in Bt; 5 to 14 percent in Btk Reaction: moderately alkaline)
C horizon (where present):
Hue: 10YR
Value: 5 or 6 dry or moist
Chroma: 2 to 4 dry or moist
Texture: sandy clay loam, clay loam
Clay content: 30 to 33 percent
Pararock fragments: 0 to 10 percent sandstone or shale parachanners
Reaction: moderately alkaline
COMPETING SERIES: These are the Chafin, Hawaikuh, Lonti, Padilla, Servilleta, Silver, and Tobish soils.
Chafin: do not have secondary carbonates
Hawaikuh, Padilla: have hues 5YR or redder
Lonti: have up to 35 percent rock fragments in the particle size control section and are moister
Servilleta, Tobish: have lithic contacts between 20 and 40 inches deep
Silver: have calcic horizons below 40 inches and have basalt fragments
GEOGRAPHIC SETTING:
Parent material: slope alluvium derived from sandstone and shale
Landform: structural benches and summits of mesas
Slopes: 3 to 15 percent
Elevation: 5500 to 7300 feet
Mean annual temperature: 47 to 49 degrees F
Mean annual precipitation: 10 to 12 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: 125 to 145 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Lazear and Blancot soil series. The Lazear soils are very shallow or shallow to bedrock and do not have an argillic horizon. Blancot soils have a fine-loamy particle size control section.
DRAINAGE AND PERMEABILITY: well drained, moderate to high runoff, moderate permeability.
USE AND VEGETATION: Used mainly for livestock grazing. Present vegetation includes galleta, western wheatgrass, needleandthread, Wyoming big sagebrush, shadscale, some Utah juniper and scattered pinyon pine.
DISTRIBUTION AND EXTENT: Uncompahgre Plateau, western Colorado; LRR D, MLRA 36; minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES PROPOSED: Montrose County, Colorado, Ridgway soil survey area. The name is coined.
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Particle-size control section: The zone from 5 to 25 inches. (Bt1, Bt2, Btk1 horizons)
Ochric epipedon: The zone from 0 to 5 inches. (A, BE horizons)
Argillic horizon: The zone from 5 to 39 inches. (Bt1, Bt2, Btk1, Btk2 horizons)
Secondary carbonates: The zone from 24 to 60 inches. (Btk and BCk horizons)
The assignment of the cation-exchange activity class is inferred from lab data from similar soils in the surrounding area.
Taxonomic Version: Second Edition, 1999.