LOCATION IRVINE MTEstablished Series
TAXONOMIC CLASS: Fine, illitic, calcareous, frigid Typic Xerorthents
TYPICAL PEDON: Irvine silty clay, in rangeland (colors are for dry soil unless otherwise noted).
A--0 to 2 inches; light gray (10YR 7/1) silty clay, brown (10YR 5/3) moist; strong medium platy structure; slightly hard, friable, sticky and slightly plastic; many fine roots; many fine pores; slightly effervescent; slightly alkaline (pH 7.8) abrupt smooth boundary. (1 to 7 inches thick)
C1--2 to 8 inches; very pale brown (10YR 7/3) silty clay, brown (10YR 5/3) moist; weak coarse subangular blocky structure; slightly hard, friable, sticky and plastic; many fine roots; many fine pores; strongly effervescent; moderately alkaline (pH 8.0); gradual smooth boundary. (4 to 15 inches thick)
C2--8 to 14 inches; white (10YR 8/2) silty clay, pale brown (10YR 6/3) moist; massive; faint 1/4-inch to 3/4-inch-thick varves; hard, firm, sticky and slightly plastic; common fine roots; common pores; strongly effervescent; moderately alkaline (pH 8.4); gradual smooth boundary. (5 to 15 inches thick)
C3--14 to 60 inches; white (10YR 8/2) silty clay, pale brown (10YR 6/3) moist; massive; distinct 1/2-inch to 1-inch thick varves; hard, firm, sticky and slightly plastic; few fine roots; few fine pores; strongly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Lake County, Montana; 900 feet north and 700 feet east of the SW corner of sec. 17, T. 21 N., R. 21 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Moisture control section - between 4 and 12 inches.
Control section - 35 to 50 percent clay (dominantly illite) and less than 20 percent fine or coarser sand.
Rock fragments - 0 to 15 percent.
Depth to varves - weathered 5 to 20; unweathered 10 to 30.
A horizon - Hue: 10YR or 2.5Y
Value: 5, 6, or 7 dry; 4 or 5 moist
Chroma: 1, 2, or 3
Texture: silty clay or silty clay loam
Clay content: 35 to 50 percent
Rock fragments: 0 to 15 percent--0 to 10 percent cobbles, 0 to 5 percent pebbles
Reaction: pH 7.4 to 8.4
C1 horizon - Hue: 10YR or 2.5Y
Value: 7 or 8 dry; 5, 6, or 7 moist
Chroma: 2 or 3
Texture: silty clay or silty clay loam
Clay content: 35 to 50 percent
Rock fragments: 0 to 15 percent--0 to 10 percent cobbles, 0 to 5 percent pebbles
SAR: 8 to 13
EC: 0 to 4 mmhos/cm
Reaction: pH 7.4 to 8.4
C2 horizon - Hue: 10YR or 2.5Y
Value: 7 or 8 dry; 5, 6, or 7 moist
Chroma: 2 or 3
Texture: silty clay or silty clay loam
Clay content: 35 to 50 percent
Rock fragments: 0 to 15 percent--0 to 10 percent cobbles, 0 to 5 percent pebbles
SAR: 8 to 13
EC: 0 to 8 mmhos/cm
Reaction: pH 7.9 to 8.4
C3 horizon - Hue: 10YR or 2.5Y
Value: 7 or 8 dry; 5, 6, or 7 moist
Chroma: 2 or 3
Texture: silty clay or silty clay loam
Clay content: 35 to 50 percent
Rock fragments: 0 to 15 percent--0 to 10 percent cobbles, 0 to 5 percent pebbles
SAR: 8 to 13
EC: 0 to 8 mmhos/cm
Reaction: pH 7.9 to 9.0
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - dissected lake plains and stream terraces.
Elevation - 2,400 to 3,500 feet.
Slope- 4 to 65 percent.
Parent material - varved clayey lacustrine deposits.
Climate - cool, with long, cold winters; moist falls and springs; warm, dry summers.
Mean annual precipitation - 12 to 16 inches.
Mean annual temperature - 39 to 45 degrees F.
Frost-free period - 100 to 125 days.
DRAINAGE AND PERMEABILITY: Well drained; slow or very slow permeability.
USE AND VEGETATION: These soils are used mainly as pastureland and rangeland. The potential native vegetation is bluebunch wheatgrass, rough fescue, Sandberg bluegrass, and sagebrush.
DISTRIBUTION AND EXTENT: The Irvine soils are moderately extensive in the mountain valleys of northwestern Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Lake County, Montana, 1991; proposed in Lake County, Montana, 1974.
REMARKS: Soil interpretation records: MT0042. Diagnostic horizons and features recognized in this pedon are: an epipedon from the soil surface to 2 inches (A horizon); unweathered varves at a depth of 14 inches (C3 horizon); a particle-size control section from 10 to 40 inches (C2 and C3 horizons). Irvine soils have a frigid temperature regime and a xeric moisture regime bordering on ustic.