LOCATION TANNA              MT+SD
Established Series
Rev. DRS-GFB-CJH
10/1999

TANNA SERIES


The Tanna series consists of moderately deep, well drained soils that formed in residuum weathered from semiconsolidated shale, mudstone, or siltstone, or in glaciofluvial deposits or alluvium over the bedrock. These soils are on alluvial fans, strath terraces, escarpments, sedimentary plains, till plains, and hills. Slopes are 0 to 45 percent. Mean annual precipitation is about 12 inches, and mean annual air temperature is about 41 degrees F.

TAXONOMIC CLASS: Fine, smectitic, frigid Aridic Argiustolls

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

Ap--0 to 6 inches; grayish brown (10YR 5/2) clay loam, very dark grayish brown (10YR 3/2) moist; moderate fine granular structure; hard, very friable, sticky and plastic; many fine and very fine roots; neutral (pH 7.0); abrupt wavy boundary. (3 to 8 inches thick)

Bt--6 to 17 inches; brown (10YR 5/3) clay loam, dark brown (10YR 4/3) moist; moderate medium prismatic structure parting to strong fine and medium blocky; very hard, friable, sticky and plastic; many fine and very fine roots; many fine and very fine pores; many distinct clay films on faces of peds; 5 percent channers; slightly alkaline (pH 7.8); clear wavy boundary. (5 to 16 inches thick)

Bk1--17 to 27 inches; light brownish gray (2.5Y 6/2) clay loam, dark grayish brown (2.5Y 4/2) moist; moderate medium and coarse prismatic structure; very hard, friable, sticky and plastic; common fine and very fine roots; many fine and very fine pores; 5 percent channers; continuous distinct lime coating on channers; common fine masses of segregated lime; strongly effervescent; moderately alkaline (pH 8.4); gradual wavy boundary. (9 to 15 inches thick)

Bk2--27 to 31 inches; pale brown (10YR 6/3) very channery loam, brown (10YR 4/3) moist; massive; hard, very friable, slightly sticky and nonplastic; common fine and very fine roots; many fine and very fine pores; 55 percent channers; continuous distinct lime coating on channers; disseminated lime, few fine masses of lime; strongly effervescent; moderately alkaline (pH 8.2); gradual wavy boundary. (0 to 6 inches thick)

Cr--31 to 60 inches; semiconsolidated shale and mudstone interbedded with layers of hard sandstone.

TYPE LOCATION: Cascade County, Montana; 400 feet north and 150 feet east of the SW corner of sec. 34, T. 22 N., R. 3 E.

RANGE IN CHARACTERISTICS:

Soil temperature - 40 to 47 degrees F.

Moisture control section - between 4 and 12 inches; dry in some part six-tenths or more of the cumulative days per year when the soil temperature at a depth of 20 inches is 41 degrees F or higher.

Mollic epipedon thickness - 7 to 12 inches (includes part of the argillic horizon).

Depth to Bk horizon - 10 to 20 inches.

Depth to bedrock - 20 to 40 inches.

Ap horizon - Hue: 10YR or 2.5Y

Value: 2 or 3 moist

Chroma: 2 or 3

Texture: loam, silt loam, clay loam, or silty clay loam

Clay content: 20 to 35 percent

Rock fragments: 0 to 25 percent--0 to 15 percent cobbles, 0 to 10 percent channers or pebbles

Reaction: pH 6.6 to 7.8

Bt horizon - Hue: 10YR or 2.5Y

Value: 4, 5 or 6 dry; 3 or 4 moist

Chroma: 2 or 3

Texture: clay loam, silty clay loam, clay, or silty clay

Clay content: 35 to 50 percent

Rock fragments: 0 to 10 percent--0 to 5 percent cobbles, 0 to 5 percent channers

Electrical conductivity: less than 4 mmhos/cm

Reaction: pH 6.6 to 8.4

Bk1 horizon - Hue: 10YR or 2.5Y

Value: 5 or 6 dry, 4 or 5 moist

Chroma: 2 or 3

Texture: clay loam, silty clay loam, or clay

Clay content: 35 to 50 percent

Rock fragments: 0 to 10 percent--0 to 5 percent cobbles, 0 to 5 percent channers

Electrical conductivity: 2 to 4 mmhos/cm

Calcium carbonate equivalent: 5 to 15 percent

Reaction: pH 7.4 to 8.4

Bk2 horizon - Hue: 10YR or 2.5Y

Value: 5, 6 or 7 dry, 4, 5 or 6 moist

Chroma: 1, 2, 3, or 4

Texture: loam, clay loam, clay, or silty clay loam

Clay content: 15 to 45 percent

Rock fragments: 0 to 60 percent--0 to 5 percent cobbles, 10 to 55 percent channers

Electrical conductivity: 2 to 4 mmhos/cm

Calcium carbonate equivalent: 5 to 15 percent

Reaction: pH 7.4 to 9.0

Some pedons have a Bky horizon with few to common threads of gypsum.

Cr horizon - semiconsolidated shale and mudstone with thin layers of hard sandstone that are rippable

COMPETING SERIES:

Ethridge (MT) - does not have a paralithic contact above 40 inches.

Holderness (CO) - does not have a paralithic contact above 40 inches.

Morop (CO) - does not have a paralithic contact above 40 inches.

Nunnston (WY) - does not have a paralithic contact above 40 inches.

Quilt (UT) - does not have a paralithic contact above 40 inches.

Scobey (MT) - does not have a paralithic contact above 40 inches.

Syblon (MT) - does not have a Bk horizon.

Ulric (WY) - does not have a paralithic contact above 40 inches.

GEOGRAPHIC SETTING:

Landform - alluvial fans; stream terraces; escarpments; hills; till plains; sedimentary plains.

Elevation - 2,700 to 5,400 feet.

Slope- 0 to 45 percent.

Parent material - residuum derived from semiconsolidated shale, mudstone, or siltstone, or these materials interbedded with thin layers of hard sandstone or in glaciofluvial deposits or alluvium over this bedrock.

Climate - long, cold, dry winters; moist springs; warm summers.

Mean annual precipitation - 10 to 14 inches.

Mean annual air temperature - 39 to 45 degrees F.

Frost-free period - 90 to 135 days.

DRAINAGE AND PERMEABILITY: Well drained; slow permeability.

USE AND VEGETATION: Tanna soils are used mainly as rangeland and for dryland crops. Potential native vegetation is mainly western wheatgrass, bluebunch wheatgrass, green needlegrass, perennial forbs, and shrubs.

DISTRIBUTION AND EXTENT: Tanna soils are of moderate extent in central Montana and Colorado.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota

SERIES ESTABLISHED: Cascade County, Montana, 1969.

REMARKS: Soil interpretation records: MT0128.

Diagnostic horizons and features recognized in this pedon are: mollic epipedon - the zone from the surface of the soil to a depth of 7 inches (after mixing) (Ap and Bt horizons); argillic horizon - the zone from 6 to 17 inches (Bt horizon); lime accumulation - the zone from 17 inches to the paralithic contact (Bk1 and Bk2 horizons); particle-size control section - the zone from 7 to 17 inches (Bt horizon); paralithic contact - at a depth of 31 inches (Cr horizon). Tanna soils have a frigid temperature regime and an ustic moisture regime bordering on aridic.


National Cooperative Soil Survey
U.S.A.