LOCATION TANNA MT+SDEstablished Series
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.