LOCATION GORUS MTEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, superactive Lamellic Haplocryepts
TYPICAL PEDON: Gorus silt loam, forested (colors are for dry soil unless otherwise noted).
O--0 to 2 inches; undecomposed and partially decomposed forest litter.
A--2 to 3 inch; grayish brown (10YR 5/2) silt loam; dark grayish brown (10YR 3/2) moist; moderate fine granular structure; soft, very friable, slightly sticky and slightly plastic; many fine roots; slightly acid (pH 6.4); clear smooth boundary. (1 to 2 inches thick)
E--3 to 9 inches; white (10YR 8/1) silt loam, light gray (10YR 7/2) moist; weak medium platy structure; soft, very friable, slightly sticky and slightly plastic; many fine roots, few pores; slightly acid (pH6.4); clear smooth boundary. (4 to 8 inches thick)
E/B--9 to 14 inches; very pale brown (10YR 7/3) silt loam, pale brown (10YR 6/3) moist; weak angular blocky structures; slightly hard, friable, slightly sticky and plastic; common fine roots, few fine pores; few thin lamellae; slightly acid (pH 6.2); clear smooth boundary. (4 to 8 inches thick)
Bw--14 to 22 inches; light yellowish brown (10YR 6/4) silt loam, yellowish brown (10YR 5/6) moist; weak fine and medium subangular blocky structure; soft, friable, slightly sticky and slightly plastic; common fine roots, few fine pores; neutral (pH 7.0); clear smooth boundary. (7 to 10 inches thick)
C--22 to 40 inches; very pale brown (10YR 6/4) silt loam, brownish yellow (10YR 6/6) moist; massive; soft very friable, slightly sticky and slightly plastic; few roots, few fine pores; neutral (pH 7.2); clear smooth boundary. (14 to 20 inches thick)
2C2--40 to 60 inches; brown (7.5YR 5/4) gravelly clay loam, dark brown (7.5 YR 4/4) moist; massive; slightly hard, firm, sticky and plastic; 20 percent pebbles; neutral (pH 7.0)
TYPE LOCATION: Ravalli County, Montana; 800 feet west and 1,200, feet north of the SE corner of sec. 16 T. 3 N.,R. 21 W.
RANGE IN CHARACTERISTICS:
Soil temperature - 44 to 47 degrees F.
Moisture control section - Moist during June through August; 5 and 15 inches approximately (includes E, E/B, Bw horizons).
Control section - 10 to 25 percent clay.
Rock fragments - 15 to 35 percent below about 30 inches.
A horizon - Hue: 10YR or 7.5 YR
Value: 4 or 5 dry; 2 or 3 moist
Chroma: 2 or 3
Texture, less than 2 mm: silt loam
Clay content: 5 to 12 percent
Reaction: pH 5.6 to 6.5
E horizon - Hue: 10YR, 2.5Y, or 7.5 YR
Value: 7 or 8 dry; 6 or 7 moist
Chroma: 1, 2, or 3
Texture, less than 2 mm: silt loam
Clay content: 5 to 12 percent
Reaction: pH 5.6 to 6.5
E/B horizon - Hue: 2.5Y, 7.5 YR, or 10YR
Value: 5, 6, or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: silt loam
Clay content: 15 to 25 percent
Reaction: pH 6.1 to 6.5
Bw horizon - Hue: 2.5Y, 7.5 YR, or 10YR
Value: 5, 6, or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: silt loam
Clay content: 10 to 20 percent
Reaction: pH 6.1 to 6.5
C1 horizon - Hue: 2.5Y, 7.5 YR, or 10YR
Value: 5, 6, or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: silt loam
Clay content: 10 to 20 percent
Reaction: pH 6.1 to 7.3
2C2 horizon - Hue: 10YR, 7.5YR, or 2.5Y
Value: 5, 6, or 7 dry; 4, 5, or 6 moist
Chroma: 2, 3, or 4
Texture, less than 2 mm: loam or clay loam
Clay content: 20 to 35 percent
Rock fragments: 5 to 35 percent pebbles
Reaction: pH 6.6 to 7.3
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: The Gorus soils are on fans and foothills. Elevations are 3,500 to 5,000 feet. Slopes are 0 to 25 percent. There soils are formed in loess-like material. The climate is characterized by long, cold winters; moist springs; and warm dry summers. The mean annual precipitation is 15 to 19 inches. Mean annual temperature is 42 to 45 degrees F. The frost-free period is 70 to 100 days.
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff, moderate permeability.
USE AND VEGETATION: Gorus soils are used mainly as woodland and pasture. Potential native vegetation is mainly Ponderosa pine, mallow ninebark, common snowberry, kinnikinnik, and pinegrass.
DISTRIBUTION AND EXTENT: Gorus soils are of small extent in western Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Bitteroot Valley area, Montana, 1947.
REMARKS: Soil Interpretation Record: MT0520. Diagnostic horizons and features recognized in this pedon are: an ochric epipedon from the soil surface to 7 inches (A and E horizons); lamellae in E/B horizon, 7 to 12 inches; and a cambic horizon from 7 to 20 inches (E/B and Bw horizons). Alfic Cryochrepts have an ochric epipedon, a cambic horizon, and a zone that would be an argillic except for thickness. Laboratory data: S55MT.
4/2008 This series was never entered into the OSD files. An old copy of the OSD was located during the re-classification of the cryepts and was entered to the OSD files as reference. Classification was originally Fine-loamy, mixed Alfic Cryochrepts.