LOCATION IRVINE             MT
Established Series
Rev. BDD-GLS-JAL
4/97

IRVINE SERIES


The Irvine series consists of very deep, well drained soils that formed in varved clayey lacustrine deposits. These soils are on dissected lake plains and stream terraces. Slopes are 4 to 65 percent. Mean annual precipitation is about 14 inches, and mean annual temperature is about 41 degrees F.

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.


National Cooperative Soil Survey
U.S.A.