LOCATION MILVAR WYEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Calcic Paleargids
TYPICAL PEDON: Milvar stony loam-rangeland. (Colors are for dry soil unless otherwise stated.) About 40 percent of the surface is covered with pebbles, cobbles and stones. Class 4 stoniness.
A--0 to 2 inches; brown (10YR 5/3) stony loam, very dark grayish brown (10YR 3/2) moist; moderate medium and fine granular structure; soft, very friable, nonsticky and nonplastic; many very fine, fine, and few medium roots; 10 percent pebbles, 5 percent cobbles, 5 percent stones; moderately alkaline (pH 8.0); abrupt wavy boundary. (1 to 4 inches thick)
AB--2 to 3 inches; brown (10YR 5/3) loam, dark brown (10YR 3/3) moist; weak medium prismatic structure parting to moderate medium subangular blocky; slightly hard, very friable, slightly sticky and slightly plastic; many very fine, fine, and few medium roots; 10 percent pebbles; mildly alkaline (pH 7.8); abrupt wavy boundary. (0 to 3 inches thick)
Bt--3 to 13 inches; brown (7.5YR 5/4) gravelly heavy clay loam, brown (7.5YR 4/4) moist; strong medium prismatic structure parting to strong medium and fine subangular blocky; very hard, firm, very sticky and very plastic; common very fine, fine, and few medium roots; continuous moderately thick and few thick clay films on faces of peds; 15 percent pebbles; mildly alkaline (pH 7.8); clear wavy boundary. (8 to 20 inches thick)
Btk--13 to 16 inches; brown (7.5YR 5/4) gravelly clay loam, brown (7.5YR 5/4) moist; weak medium prismatic structure parting to weak medium subangular blocky; common very fine, fine, and few medium roots; few moderately thick clay films on faces of peds; strongly effervescent, carbonates disseminated and as common medium seams and pendants on bottom of coarse fragments; 15 percent pebbles, 5 percent cobbles; mildly alkaline (pH 8.2); clear wavy boundary. (2 to 6 inches thick)
Bk1--16 to 26 inches; very pale brown (10YR 8/3) very gravelly loam, pale brown (10YR 6/3) moist; massive; slightly hard, friable, slightly sticky and nonplastic; few very fine, fine, and medium roots; violently effervescent, carbonates disseminated and as many large seams; 30 percent pebbles, 5 percent cobbles; moderately alkaline (pH 8.4); gradual wavy boundary. (6 to 12 inches thick)
2Bk2--26 to 60 inches; pale brown (10YR 6/3) very gravelly loamy sand, yellowish brown (10YR 5/4) moist; single grain; loose, loose, nonsticky and nonplastic; slightly effervescent, carbonates disseminated and as few large seams and soft masses; 40 percent pebbles, 15 percent cobbles, 5 percent stones; moderately alkaline (pH 8.2).
TYPE LOCATION: Fremont County, Wyoming; approximately 200 feet north and 2,350 feet west of the SE corner of sec. 22, T. 28 N., R. 90 W.
RANGE IN CHARACTERISTICS: Depth to the nonlimiting very gravelly loamy sand substrata ranges from 20 to 40 inches. The mean annual soil temperature ranges from 41 to 45 degrees F., and the mean summer temperature ranges from 59 to 63 degrees F. Bedrock occurs at depths greater than 60 inches. EC is less than 2 mmhos throughout the soil.
The A horizon has hue of 10YR or 7.5YR, value of 4 or 5 dry, 3 or 4 moist, and chroma of 2 or 3. Coarse fragments are variable but range from 10 to 40 percent pebbles, 5 to 20 percent cobbles, and 1 to 5 percent stones. Reaction is mildly or moderately alkaline.
An AB or BA horizon is present in some pedons and has similar properties of both the A or Bt horizon.
The Bt horizon has hue of 7.5YR or 10YR, value of 4 through 6 dry, 4 or 5 moist, and chroma of 2 through 4. Matrix texture is heavy clay loam, sandy clay, or clay with 35 to 60 percent clay and from 10 to 35 percent coarse fragments, mainly pebbles with a few cobbles. Reaction is mildly or moderately alkaline.
The Btk horizon has similar properties to the Bt horizon except for the pedogenetic lime accumulation occurring as common seams and pendants on rock fragments.
The Bk horizon has hue of 10YR or 7.5YR, value of 7 or 8 dry, 6 or 7 moist, and chroma of 1 through 4. Texture is typically very gravelly loam but is very gravelly sandy loam in some pedons. Clay ranges from 18 to 27 percent. Coarse fragments range from 35 to 60 percent and include mainly pebbles with 0 to 15 percent cobbles and 0 to 5 percent stones. Calcium carbonate equivalent ranges form 15 to 30 percent and occurs as many large masses, seams, and as moderately thick pendants on rock fragments. Reaction is moderately or strongly alkaline.
The 2Bk horizon has hue of 10YR or 7.5YR, value of 5 through 7 dry, 4 through 6 moist, and chroma of 1 through 4. Texture is typically very gravelly loamy sand and less commonly very gravelly loamy fine sand. Clay ranges from 3 to 10 percent. Coarse fragments range from 35 to 60 percent, which are mainly pebbles and include 0 to 15 percent cobbles and 0 to 5 percent stones. Calcium carbonates range from 5 to 10 percent and are mainly disseminated with a few soft masses or seams. Reaction is moderately alkaline or strongly alkaline.
COMPETING SERIES: These are the Coalmont, Milren, and Phillips series. Coalmont soils have a paralithic contact at 20 to 40 inches. Milren and Phillips soils have clay loam or sandy clay loam substrata to depths greater than 40 inches. Phillips soils also have high bulk density till at less than 40 inches.
GEOGRAPHIC SETTING: Milvar soils are on relict terraces, outwash plains, and mountain toeslopes. These soils formed in old alluvium derived dominantly from mixed sources. Slopes are 0 to 6 percent. Elevations are 6,700 to 7,800 feet. The mean annual precipitation is about 12 inches and ranges from 10 to 14 inches. About half falls as snow and less commonly rain in April, May, and early June. The mean annual temperature is about 41 degrees and ranges from 38 to 44 degrees F. The estimated frost-free season ranges from 90 to 120 days depending upon elevation, aspect, and local air drainage.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Coalmont and Milren soils.
DRAINAGE AND PERMEABILITY: Well drained; moderately rapid or medium runoff; very slowly permeable in subsoil and moderately rapidly permeable in the substrata.
USE AND VEGETATION: Rangeland and wildlife habitat. Native vegetation consists of western wheatgrass, needleandthread, mutton bluegrass, low rabbitbrush, and big sagebrush.
DISTRIBUTION AND EXTENT: Cold plateaus and mountain basins in central Wyoming. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Fremont County, Wyoming, East Part; 1985.