LOCATION BLACKBURN          MT
Established Series
Rev. JAL-EMM
03/2008

BLACKBURN SERIES


The Blackburn series consists of very deep, well drained soils formed in volcanic ash over colluvium from argillite. These soils are on mountains. Slopes are 35 to 65 percent. Mean annual precipitation is about 25 inches and mean annual temperature is about 45 degrees F.

TAXONOMIC CLASS: Coarse-loamy, mixed, superactive Andic Haplocryepts

TYPICAL PEDON: Blackburn silt loam - forest cover. (Colors are for dry soil unless otherwise noted.)

0i--0 to 1/2 inches; litter of needles and twigs over a dark colored layer of matted organic material.

E--1/2 to 1 inch; white (10YR 8/1) loam, light brownish gray (10YR 6/2) moist; weak thin platy structure; soft, friable; slightly acid; abrupt broken boundary. (0 to 2 inches thick)

Bw1--1 to 4 inches; very pale brown (10YR 7/3) silt loam, reddish brown (5YR 4/4) with some gray spots, moist; weak medium subangular blocky structure; soft, very friable; many medium and coarse roots; porous; slightly acid; clear wavy boundary.

Bw2--4 to 11 inches; very pale brown (10YR 7/4) silt loam, strong brown (7.5YR 4/6) moist; weak medium subangular blocky structure; soft, very friable; many medium and coarse roots; porous; slightly acid; clear wavy boundary. (Combined thickness of Bw horizons is 7 to 15 inches)

2A&Bb--11 to 17 inches; light gray (10YR 7/2) and yellowish brown (10YR 5/4) gravelly loam, brown (7.5YR 5/4) and reddish brown (5YR 4/4) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many medium and few coarse roots; many medium pores; 30 percent gravel; slightly acid; gradual smooth boundary. (2 to 8 inches thick)

2B&Ab1--17 to 36 inches; yellowish brown (10YR 5/4) and very pale brown (10YR 7/3) gravelly loam, brown (7.5YR 4/4) moist; moderate medium and coarse subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; faint patchy clay films in cavities; common fine roots; few medium and common fine tubular pores; 30 percent gravel; slightly acid; gradual wavy boundary. (8 to 15 inches thick)

2B&Ab2--36 to 42 inches; strong brown (7.5YR 5/6) and light yellowish brown (10YR 6/4) gravelly loam, brown (7.5YR 5/4) and brown (7.5YR 4/4) with mottles of reddish yellow (7.5YR 6/8) moist; moderate coarse subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; few medium roots; common fine tubular pores; 35 percent gravel; slightly acid; clear wavy boundary. (8 to 10 inches thick)

2Ckb--42 to 70 inches; alternating layers of soft weathered shale and gray loam; violently effervescent.

TYPE LOCATION: Mineral County, Montana; 0.3 miles from old U.S. Highway 10 on Boyd Mountain Road (unsurveyed). Photo EDS-5-156 on line 42.

RANGE IN CHARACTERISTICS:

Average annual soil temperature - 41 to 45 degrees F.
Average summer soil temperature - 45 to 47 degrees F. under forest cover.

Bw horizons - Hue: 10YR or 7.5YR
Value: 6 or 7 dry, 4 or 5 moist
Chroma: 3 to 6
Clay content: 7 to 15 percent
Rock fragments: 0 to 5 percent gravel
Reaction: pH 6.1 to 6.5

2A&B and 2B&A horizons - Hue: 10YR or 7.5YR
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 2 to 6
Clay content: 7 to 15 percent
Rock fragments: 15 to 35 percent--0 to 5 percent cobbles, 15 to 35 percent gravel
Reaction: pH 6.1 to 6.5

2Ck horizon - Hue: 10YR or 7.5YR
Value: 5 to 7 dry, 4 to 6 moist
Chroma: 2 to 6
Clay content: 7 to 15 percent
Rock fragments: 15 to 35 percent--0 to 5 percent cobbles, 15 to 35 percent gravel
Reaction: pH 6.1 to 7.8

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING:

Landform- mountains
Elevation - 2,500 to 4,500 feet
Slope - 35 to 65 percent
Parent material - volcanic ash over colluvium from argillite
Climate - cool subhumid
Mean annual temperature - 44 to 46 degrees F.
Mean annual precipitation - 22 to 30 inches
Frost-free period - 30 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: None listed.

DRAINAGE AND PERMEABILITY: Well-drained; moderate permeability

USE AND VEGETATION: Used for timber production. Vegetation is Douglas-fir, grand fir, western larch, white pine and lodgepole pine in the overstory with ground cover of rose, spiraea, pinegrass, Oregongrape and serviceberry.

DISTRIBUTION AND EXTENT: Northwestern Montana. The series is not extensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Mineral County (St. Regis-Nine Mile Area), Montana, 1970.

The 3/2008 description reflects a change in classification from Coarse-loamy, mixed, superactive Andic Eutrocryepts to Coarse-loamy, mixed, superactive Andic Haplocryepts due to revision of the cryepts great groups and subgroups. The competing series section was not updated and should be reviewed after all the cryepts have been re-classified.


National Cooperative Soil Survey
U.S.A.