LOCATION TRIVAR WYEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, frigid Typic Calciustolls
TYPICAL PEDON: Trivar silt loam-rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 2 inches; dark brown (7.5YR 4/2) silt loam, dark brown (7.5YR 3/2) moist; weak very fine granular structure; soft, very friable, nonsticky and nonplastic; slightly effervescent, calcium carbonate disseminated; moderately alkaline (pH 8.4); clear smooth boundary. (1 to 4 inches thick)
Bw--2 to 7 inches; dark brown (7.5YR 4/2) silt loam, dark brown (7.5YR 3/2) moist; moderate medium subangular blocky structure parting to moderate fine subangular blocky; slightly hard, very friable, slightly sticky and slightly plastic; few faint clay films on vertical faces of peds; strongly effervescent; calcium carbonate disseminated; moderately alkaline (pH 8.4); clear smooth boundary. (4 to 9 inches thick)
Bk1--7 to 20 inches; pinkish white (7.5YR 8/2) silt loam, light brown (7.5YR 6/4) moist; moderate medium and fine subangular blocky structure; hard, very friable, sticky and slightly plastic; violently effervescent; common prominent calcium carbonate coatings on underside of gravel; 10 percent gravel; strongly alkaline (pH 8.5); gradual smooth boundary. (9 to 19 inches thick)
2Bk2--20 to 41 inches; pink (5YR 7/4) gravelly sandy loam, light reddish brown (5YR 6/4) moist; massive; soft, friable, nonsticky and nonplastic; violently effervescent; many prominent calcium carbonate coatings on undersides of gravel and cobbles; 20 percent gravel, 5 percent cobbles; moderately alkaline (pH 8.2); diffuse wavy boundary. (14 to 34 inches thick)
2Bk3--41 to 63 inches; reddish yellow (5YR 7/6) very gravelly sandy loam, yellowish red (5YR 5/6) moist; massive; loose, friable, nonsticky and nonplastic; violently effervescent; common prominant calcium carbonate coatings on undersides of gravel and cobbles; 30 percent gravel, 5 percent cobbles; moderately alkaline (pH 8.2).
TYPE LOCATION: Sheridan County, Wyoming; SE1/4, SW1/4 of sec. 13, T. 56 N., R. 87 W.
RANGE IN CHARACTERISTICS: The mollic epipedon is 7 to 13 inches thick. These soils are typically calcareous to the surface. Where pedons are leached a few inches, they are always calcareous when mixed to 7 inches. The mean annual soil temperature is 39 to 45 degrees F., and the mean summer soil temperature is 59 to 63 degrees F. When averaged, clay content ranges from 10 to 18 percent in the partical size control section and coarse fragments range from 0 to 35 percent above 40 inches.
The A horizon has hue of 10YR through 5YR, value of 3 through 5 dry, 2 or 3 moist, and chroma of 2 or 3. Reaction is typically moderately alkaline and less typically mildly alkaline.
The Bw horizon, when present, has hue of 10YR through 5YR, value of 4 or 5 dry, 2 or 3 moist, and chroma of 2 or 3. Texture is loam or silt loam with 18 to 27 percent clay. Coarse fragments range from 0 to 15 percent. Reaction is moderately alkaline or strongly alkaline.
The Bk horizon has hue of 10YR through 5YR, value of 6 through 8 dry, 4 through 7 moist, and chroma of 2 through 4. Texture is silt loam or loam with 18 to 27 percent clay and 0 to 15 percent coarse fragments. Calcium carbonate equivalent ranges from 10 to 35 percent. Reaction is moderately alkaline or strongly alkaline.
The 2Bk horizon has hue of 10YR through 5YR, value of 7 or 8 dry, 5 through 7 moist, and chroma of 2 through 6. Texture is sandy loam or loam with 10 to 18 percent clay. Coarse fragments range from 25 to 35 percent in the upper part to up to 70 percent below 40 inches. Calcium carbonate equivalent ranges from 15 to 35 percent. Reaction is moderately alkaline or strongly alkaline.
COMPETING SERIES: This is the Manhattan series. The Manhattan soils lack the fine-loamy Bw and Bk horizons in the upper part of the control section.
GEOGRAPHIC SETTING: Trivar soils are on nearly level to steeply sloping fan pediments and toeslopes at the base of mountains. Slopes range from 0 to 25 percent. Elevations range from 4,000 to 6,000 feet. The mean annual precipitation is about 17 inches but ranges from 15 to 19 inches. The mean annual temperature is about 42 degrees F.
but ranges from 40 to 45 degrees F. The frost-free season is estimated to range from 80 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Trimad and Twin Creek soils. Trimad soils lack a B horizon and are in the loamy-skeletal family. Twin Creek soils have no coarse fragments in the substrata.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability; runoff is slow or medium.
USE AND VEGETATION: Rangeland and wildlife habitat. Native vegetation consists of Columbia needlegrass, Idaho fescue, Montana wheatgrass, prairie junegrass, and bluebunch wheatgrass.
DISTRIBUTION AND EXTENT: Northeastern Wyoming. The series is of minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado
SERIES ESTABLISHED: Sheridan County Area, Wyoming; 1987.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 7 inches (A, Bw)
Calcic horizon - 7 to 63 inches (Bk1, 2Bk2, 2Bk3)
Lithologic discontinuity - 20 inches (2Bk2,2Bk3)
SIR- WY0696