LOCATION VASSETT WYEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, superactive, frigid Aridic Argiustolls
TYPICAL PEDON: Vassett silt loam--on a northeast-facing slope of 2 percent, utilized as rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 9 inches; dark brown (7.5YR 4/2) silt loam (7.5YR 3/2) moist; weak medium subangular blocky structure parting to moderate fine granular; slightly hard, friable, mildly alkaline (pH 7.6); clear smooth boundary (4 to 9 inches thick).
Bt--9 to 24 inches; brown (7.5YR 5/3) silty clay loam, dark brown (7.5YR 4/3) moist; moderate coarse prismatic structure parting to strong fine angular blocky; hard, firm; many moderately thick clay films on faces of peds; moderately alkaline (pH 8.0); clear smooth boundary (12 to 16 inches thick).
Bk1--24 to 36 inches; brown (7.5YR 5/3) silt loam, dark brown (7.5YR 4/4) moist; moderate coarse subangular blocky structure; slightly hard, friable; violently effervescent, lime segregated as common fine masses, threads, and seams; strongly alkaline (pH 8.6) clear smooth boundary. (8 to 12 inches thick).
Bk2--36 to 60 inches; light reddish brown (5YR 6/4) silt loam, yellowish red (5YR 4/6) moist; massive; slightly hard, very friable; violently effervescent, lime segregated as common fine masses, threads and seams; strongly alkaline (pH 8.6).
TYPE LOCATION: Weston County, Wyoming; 7 miles west of Four Corners, 850 feet south and 400 feet west of the center of sec. 11, T. 47 N., R. 62 W.
RANGE IN CHARACTERISTICS: Depth to calcareous material ranges from 16 to 25 inches. The mollic epipedon is 7 to 15 inches thick and typically extends into the upper argillic horizon. The mean annual soil temperature is 40 to 47 degrees F., and the mean annual summer temperature is 59 to 65 degrees F. EC is 0 to 2 mmhos throughout the profile.
The A horizon has hue of 2.5YR through 7.5YR, value of 3 through 5 dry, 2 or 3 moist, and chroma of 2 or 3. Texture is silt loam or loam with 15 to 27 percent clay. Reaction ranges from neutral to mildly alkaline.
The Bt horizon has hue of 2.5YR through 7.5YR, value of 4 through 6 dry, 3 through 5 moist, and chroma of 2 through 4. Texture is silty clay loam or clay loam with 18 to 35 percent clay and with less than 15 percent coarser than very fine sand. Structure is prismatic and blocky of moderate to strong grade. Reaction ranges from mildly to moderately alkaline.
The Bk1 horizon has hue of 5YR or 7.5YR, value of 4 through 6 dry, 4 or 5 moist, and chroma of 3 or 4. Texture is typically silt loam but may be silty clay loam. It has moderate or strong, coarse or medium subangular blocky structure. Calcium carbonate equivalent ranges from 5 to 10 percent. Reaction ranges from moderately to strongly alkaline.
The Bk2 horizon has hue of 5YR or 7.5YR, value of 5 or 6 dry, 4 or 5 moist, and chroma of 3 through 6. Texture is typically silt loam but may be silty clay loam with 15 to 30 percent clay. It contains few to common, fine or medium segregations of calcium carbonate. It is estimated to have 5 to 10 percent calcium carbonate equivalent. Reaction ranges from moderately to strongly alkaline.
COMPETING SERIES: These are the
Brussett,
Granath, and
Ralph
series in the same family. Brussett soils have hue of 10YR or yellower throughout. Granath soils are free of carbonates to 40 inches or more. Ralph soils have a paralithic contact at depths of 20 to 40 inches.
GEOGRAPHIC SETTING: Vassett soils are on nearly level to gently sloping relict fan aprons and upland terraces. Slopes are 0 to 10 percent. They formed in silty alluvium from mixed sources. Elevation is 4,600 to 6,000 feet. The average annual precipitation ranges from 15 to 19 inches, and the average annual temperature ranges from 40 to 45 degrees F. The frost-free season is 90 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Colnevee and Colhill soils. Colnevee soils lack the mollic epipedon and argillic horizon. The Colhill soils are loamy-skeletal.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderate permeability.
USE AND VEGETATION: These soils are used for rangeland, hayland, and cropland. Native vegetation consists of western wheatgrass, green needlegrass, needleandthread, and blue grama.
DISTRIBUTION AND EXTENT: Black Hills area of northeastern Wyoming. This is of minor extent.
MLRA OFFICE RESPONSIBLE: Bismarck, North Dakota
SERIES ESTABLISHED: Weston County, Wyoming; 1983.