LOCATION TWIN CREEK MT+UT WY

Established Series
Rev. COC/SHB/EMM
04/2012

TWIN CREEK SERIES

The Twin Creek series consists of very deep, well drained soils that formed in alluvium from siltstone and sandstone and from scoria or porcelanite beds. These soils are on terraces, footslopes and fans in narrow valleys within sedimentary uplands and have slopes ranging from 0 to 25 percent. Mean annual precipitation is about 16 inches and the mean annual air temperature is about 43 degrees F.

TAXONOMIC CLASS: Fine-loamy, mixed, superactive, frigid Typic Haplustolls

TYPICAL PEDON: Twin Creek loam, cultivated. (Colors are for dry soil unless otherwise noted.)

Ap--O to 7 inches, brown (7.5YR 4/2) loam, very dark brown (7.5YR 2/2) moist; moderate fine granular structure; slightly hard, very friable, slightly sticky and s1ightly plastic; common fine and very fine roots; neutral; abrupt wavy boundary. (5 to 8 inches thick)

Bw1--7 to 13 inches, brown (7.5YR 4/2) loam, dark brown (7.5YR 3/2) moist; moderate medium and coarse prismatic structure parting to weak medium subangular blocky; hard, friable, slightly sticky and slightly plastic; common fine and very fine roots; many fine and very fine pores, few medium pores; neutral; clear wavy boundary. (2 to 6 inches thick)

Bw2--13 to 19 inches, brown (7.5YR 5/2) loam, brown (7.5YR 4/2) moist; moderate medium and coarse prismatic structure parting to weak medium subangular blocky; hard, friable, slightly sticky and slightly plastic; common fine and very fine roots; many fine and very fine pores, few medium pores; slightly effervescent; moderately alkaline; clear wavy boundary. (8 to 12 inches thick)

Bk1--19 to 25 inches, brown (7.5YR 5/2) loam, brown (7.5YR 4/2) moist; moderate coarse prismatic structure parting to weak medium subangular blocky; few fine and very fine roots; many fine and very fine pores, few medium pores; common fine soft masses of segregated lime; strongly effervescent; moderately alkaline; clear wavy boundary. (4 to 10 inches thick)

Bk2--25 to 45 inches, pinkish gray (7.5YR 6/2) loam, brown (7.5YR 4/2) moist; weak medium subangular blocky structure; hard, friable, slightly sticky and s1ightly plastic; few fine and very fine roots; common fine and very fine pores; many fine soft masses and threads of segregated lime; strongly effervescent; strongly alkaline; gradual wavy boundary.

C--45 to 60 inches, reddish brown (5YR 5/3) clay loam, dark reddish brown (5YR 3/3) moist; massive; hard, friable, moderately sticky and moderately plastic; strongly effervescent; moderately alkaline.

TYPE LOCATION: Cascade County, Montana; 1,320 feet north and 1,000 feet east of the south west corner of section 16, T. 18N ., R. 7E .

RANGE IN CHARACTERISTICS:
Solum thickness (including the Bk1 horizon) - 20 to 36 inches thick.
Mollic epipedon thickness - 7 to 14 inches thick.
Mean annual soil temperature - 40 to 47 degrees F.
Hue (in whole soil) - 7.5YR through l0R.
The 10- to 40-inch control section averages 20 to 30 percent clay, 40 to 60 percent silt plus very fine sand, and 15 to 30 percent fine and coarser sand.

A horizon
Value - 3 or 4 dry, 2 or 3 moist
Chroma - 2 or 3
Texture -loam, clay loam, or silty clay loam
Rock fragments - 0 to 10 percent gravel
Reaction - neutral to mildly alkaline

B horizon
Value - 4 or 5 dry, 2 to 4 moist
Chroma - 2 or 3
Texture - mainly loam or clay loam but some pedons have lenses of silt loam and sandy loam.
Rock fragments - 0 to 35 percent gravel
Reaction - neutral to strongly alkaline
Structure - moderate to strong prismatic structure

COMPETING SERIES:
Amor (ND) - Has a paralithic contact between 20 and 40 inches.
Azaar (MT) - Has a lithic contact between 20 and 40 inches.
Diagulch (UT) - Does not have a cambic horizon.
Hibar (MT) - Has a lithic contact between 20 and 40 inches.
Max (ND) - has hues of 2.5Y or 5Y in the C horizon.
Peerless (MT) - has more than 25 percent rock fragments in the subsoil.
Prospect (MT) - has a C horizon formed in stony till.
Quigley (MT) - has a lithologic discontinuity.
Shambo (ND) - Has hues of 5Y to 10YR throughout.
Tansem (ND) - Has hues of 2.5Y or 10YR throughout.
Tewfel (MT) - has a paralithic contact between 20 an 40 inches.

GEOGRAPHIC SETTING:

Landform - terraces and foot slopes and fans in narrow valleys within the sedimentary uplands.
Elevation - 2,500 to 4,100 feet.
Slope - from 0 to 25 percent.
Parent material - calcareous reddish loam or silt loam local alluvium derived from the red siltstones, sandstones, and the scoria or porcelanite beds.
Climate - cool, moist-semiarid with long, cold dry winters and warm summers.
Mean annual precipitation - 15 to 17 inches, more than 70 percent of which falls during spring and early summer.
Mean annual temperature is about 41 degrees F. to 44 degrees F.
Mean January temperature is 18 degrees F. to 25 degrees F.
Mean July temperature is 66 to 70 degrees F.
Frost free period - (32 degrees F) growing season is 105 to 135 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Big Timber, Litimber, Relan and Ringling soils. Big Timber soils have a paralithic contact within a depth of 20 inches. Litimber soils have a fine textured control section. Relan soils have a coarse-loamy control section. Ringling soils have a fragmental control section.

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

USE AND VEGETATION: These soils are used mainly for irrigated and non-irrigated cropland, but some areas are still in range. The principal native vegetation is Idaho fescue, bluebunch wheatgrass, western wheatgrass and prairie junegrass.

DISTRIBUTION AND EXTENT: Twin Creek soils are moderately extensive near the mountains in central and east-central Montana, and in northern Wyoming. This series is of moderate extent.

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

SERIES ESTABLISHED: Sheridan County, Wyoming, 1932.

REMARKS: The Twin Creek soils were formerly classified as Chestnut soils.

OSED scanned by NSSQA. Last revised by state on 1/75. Reclassified in 2001 from Fine-loamy, mixed, superactive, frigid Haploborolls to Fine-loamy, mixed, superactive, frigid Haplustolls. Revisions from scanned copy made in 2012. This series should be investigated as part of an update project, and ranges in characteristics checked.

National Cooperative Soil Survey
U.S.A.