LOCATION WILLOW CREEK WY

Established Series
Rev. AJC, RJE, JAL
11/2022

WILLOW CREEK SERIES

The Willow Creek series consists of very deep, well drained soils formed in calcareous, silty materials derived from siltstone and limestone. They are on gently to moderately sloping alluvial fans and valley sideslopes. Slopes range from 2 to about 20 percent. At the type location the average annual precipitation is 24 inches with peak periods of precipitation in the spring and early summer. Mean annual temperature is about 38 degrees F., mean summer temperature is about 54 degrees F.

TAXONOMIC CLASS: Fine-silty, mixed, superactive Ustic Argicryolls

TYPICAL PEDON: Willow Creek silt loam - grassland (Colors are for dry soil unless otherwise noted.)

A--0 to 5 inches; dark grayish brown (10YR 4/2) silt loam, very dark brown (10YR 2/2) moist; strong fine crumb structure; soft, very friable; neutral (pH 6.6); clear smooth boundary. (4 to 8 inches thick)

AB--5 to 9 inches; dark grayish brown (10YR 4/2) heavy silt loam, very dark brown (10YR 2/2) moist moderate fine subangular blocky structure that parts to strong fine granules; hard, very friable; few thin glossy patches on faces of some peds; neutral (pH 6.6); gradual smooth boundary. (3 to 6 inches thick)

Bt1--9 to 12 inches; grayish brown (10YR 5/2) light silty clay loam, very dark grayish brown (10YR 3/2) moist; moderate medium prismatic structure that parts to moderate medium subangular blocks; very hard, friable; faint nearly continuous clay films on faces of peds and in root channels and pores; neutral (pH 7.0); clear smooth boundary. (O to 6 inches thick)

Bt2--12 to 30 inches; light yellowish brown (10YR 6/4) light silty clay loam, dark yellowish brown (10YR 4/4) moist; moderate medium prismatic structure that parts to moderate medium subangular blocks; very hard, friable; faint nearly continuous clay films on faces of peds and in root channels; neutral (pH 7.0); clear smooth boundary. (8 to 40 inches thick)

BC--30 to 36 inches; light olive brown (2.5Y 5/4) light silty clay loam, olive brown (2.5Y 4/4) moist; moderate medium subangular blocky structure; very hard, firm; few thin glossy patches on faces of peds; slightly alkaline (pH 7.6); clear smooth boundary. (3 to 5 inches thick)

Ck--36 to 60 inches; light olive brown (2.5Y 5/4) silt loam, olive brown (2.5Y 4/4) moist; massive; very hard, firm; visible secondary carbonate occurring as concretions and in thin seams and streaks; calcareous; moderately alkaline (pH 8.0).

TYPE LOCATION: Sheridan County, Wyoming; approximately 1/4 mile south of the N1/4 corner of sec. 9, T 55N., R.89W.

RANGE IN CHARACTERISTICS: The mollic epipedon ranges from 7 to 15 inches thick, depth to calcareous material ranges from 12 to 46 inches, and the solum ranges from 20 to 50 inches thick. Organic carbon in the mollic epipedon ranges from .8 to 3 percent and decreases uniformly with increasing depth. The soils are 80 to 100 percent base saturated. Rock fragments range from 0 to 10 percent but are typically less than 3 percent and consist mainly of shale chips. The mean annual soil temperature ranges from 32 degrees to 48 degrees F. Mean summer soil temperature ranges from 40 degrees to 58 degrees F.

The A horizon has hue of 5Y through 7.5YR, value of 3 through 5 dry, 2 or 3 moist, and chroma of 1 through 3. It usually has crumb or granular structure but has subangular blocky structure in some pedons. This horizon is soft or slightly hard and is slightly acid to slightly alkaline.

The Bt horizon has hue of 5Y through 7.5YR, value of 5 or 6 dry, 3 through 5 moist, and chroma of 2 through 6. It usually has prismatic structure but has subangular blocky structure in some pedons. This horizon is typically silt loam or silty clay loam but clay ranges from 18 to 35 percent, silt from 40 to 70 percent, and sand from 5 to 35 percent with less than 15 percent fine or coarser sand. It has oriented clay films in some part. It is slightly acid to slightly alkaline.

The C horizon has hue of 5Y through 7.5YR. It has 4 to 14 percent calcium carbonate equivalent and is moderately or strongly alkaline.

COMPETING SERIES: This is the Westelk series. Westelk soils have a para-lithic contact at depths of 20 to 40 inches, and are noncalcareous throughout.

GEOGRAPHIC SETTING: The Willow Creek soils are on gently to moderately sloping alluvial fans and valley sideslopes. Slopes usually range from 2 to about 20 percent. These soils formed in thick, calcareous, silty materials derived from siltstone and limestone. At the type location the average annual precipitation is 24 inches with peak periods of precipitation in the spring and early summer. Mean annual temperature is 38 degrees F., mean summer temperature is 54 degrees F.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bozeman and Turnerville soils. Bozeman soils have mollic epipedons more than 16 inches thick. Turnerville soils have an ochric epipedon and an albic horizon.

DRAINAGE AND PERMEABILITY: Well-drained; medium runoff; moderate permeability.

USE AND VEGETATION: Used for cropland or for native pastureland. Native vegetation is bluegrass, fescues, and sage.

DISTRIBUTION AND EXTENT: Wyoming. The series is of moderate extent.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana

SERIES Established: Sheridan County, Wyoming, 1932.

National Cooperative Soil Survey
U.S.A.