LOCATION BOLACK                  MT

Established Series
Rev. BDD-GLS-KLS
01/2023

BOLACK SERIES

The Bolack series consists of very deep, poorly drained soils that formed in clayey alluvium. These soils are on flood plains. Slopes are 0 to 2 percent. Mean annual precipitation is about 410 mm, and the mean annual air temperature is about 6 degrees C.

TAXONOMIC CLASS: Fine, mixed, superactive, frigid Typic Endoaquolls

TYPICAL PEDON: Bolack silt loam, native grass (colors are for moist soil unless otherwise noted).

Oi--0 to 8 cm; peat (0 to 10 cm thick)

A--8 to 33 cm; black (10YR 2/1) silt loam, dark gray (10YR 4/1) dry; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; many very fine roots; many fine irregular pores; neutral (pH 7.0); clear smooth boundary. (18 to 38 cm thick)

Bg1--33 to 43 cm; dark gray (10YR 4/1) silty clay loam, light gray (10YR 7/1) dry; many fine distinct dark yellowish brown (10YR 4/6) redox concentrations; weak medium subangular blocky structure; hard, firm, sticky and plastic; many fine and very fine roots; many fine and medium tubular pores; neutral (pH 7.0); clear smooth boundary.

Bg2--43 to 71 cm; grayish brown (10YR 5/2) clay; light gray (10YR 7/2) dry; many medium distinct dark yellowish brown (10YR 4/4) moist redox concentrations; moderate medium and coarse subangular blocky structure; very hard, extremely firm, very sticky and very plastic; common fine and medium roots; common fine tubular pores; slightly alkaline (pH 7.4); gradual smooth boundary.

Bg3--71 to 119 cm; light brownish gray (10YR 6/2) clay; light gray (10YR 7/2) dry; many large distinct dark yellowish brown (10YR 4/4) moist redox concentrations; moderate medium subangular blocky structure; very hard, extremely firm, very sticky and very plastic; few fine and medium roots; few fine tubular pores; slightly alkaline (pH 7.6); gradual smooth boundary. (Combined thickness of the Bg horizons is 23 to 127 cm.)

Cg--119 to 160 cm; gray (10YR 6/1) gravelly clay, white (10YR 8/1); many large distinct dark yellowish brown (10YR 4/4) moist redox concentrations; massive; very hard, extremely firm, very sticky and very plastic; 20 percent pebbles; slightly effervescent; moderately alkaline (pH 8.0).

TYPE LOCATION: Lake County, Montana; about 550 meters east and 575 meters south of the NW corner of sec. 1, T. 18 N., R. 20 W.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature--6 to 8 degrees C
Soil moisture control section--10 and 30 cm
Mollic epipedon thickness--18 to 50 cm
Depth to seasonal water table--30 to 60 cm

Particle-size control section:
Clay content--35 to 60 percent
Some pedons have a thin, 3 to 10 cm, surface layer of peat.

A horizon
Value--3 through 5 dry; 2 or 3 moist
Clay content--18 to 27 percent
Reaction--pH 6.6 to 7.3

Bg1 horizon
Value--5 through 7 dry; 3 or 4 moist
Chroma--1 or 2
Redoximorphic features--few to many 10YR 4/4, 10YR 4/6 redox concentrations
Texture--silty clay or silty clay loam
Clay content--27 to 45 percent
Reaction--pH 6.6 to 7.3

Bg2 and Bg3 horizons
Hue--5Y, 2.5Y, or 10YR
Value-5 through 7 dry; 4 through 6 moist
Chroma--0, 1 or 2
Redoximorphic features--few to many 10YR 4/4, 10YR 4/6 redox concentrations; none to common 10YR 6/1 redox depletions
Texture--clay or silty clay
Clay content--40 to 60 percent
Reaction--pH 7.4 to 7.8

Cg horizon
Hue--5Y, N, 2.5Y, or 10YR
Value--6 through 8 dry; 4 through 6 moist
Chroma--0, 1, or 2
Redoximorphic features--few to many 10YR 4/4, 10YR 4/6 redox concentrations; none to common 10YR 6/1 redox depletions
Texture--clay or silty clay
Clay content--40 to 60 percent
Rock fragment content--0 to 25 percent gravel
Reaction--pH 7.4 to 8.4

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING:
Landform--flood plains
Elevation--775 to 1000 meters
Slope--0 to 2 percent
Parent material--alluvium
Climate--long, cold winters; moist springs; warm summers
Mean annual precipitation--310 to 460 mm
Mean annual air temperature--5 to 7 degrees C
Frost-free period--100 to 120 days

GEOGRAPHICALLY ASSOCIATED SOILS: None listed

DRAINAGE AND PERMEABILITY: Poorly drained; slow permeability

USE AND VEGETATION: Bolack soils are used mainly for rangeland, pastureland, hayland, and wildlife habitat. The potential native vegetation is mainly tufted hairgrass, mannagrasses, northern reedgrass, tall sedges, and tall brushes.

DISTRIBUTION AND EXTENT: Bolack soils are of small extent in the mountain valleys of western Montana; MLRA 44A.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Lake County, Montana, 1991; proposed in Lake County, Montana, 1986; Bolack is a coined name.

REMARKS: Soil Interpretation Record: MT1015
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon--8 to 33 cm (A horizon)
Horizons with redoximorphic features--33 to 160 cm (Bg1, Bg2, Bg3 and Cg horizons)
Particle-size control section--25 to 100 cm (part of the A horizon, all of the Bg1 and Bg2 horizons and part of the Bg3 horizon)

Bolack soils have a frigid soil temperature regime and an aquic soil moisture regime.

Converted to metric and O horizons were updated to start at zero. Competing series section was not updated. 01/2023

---

National Cooperative Soil Survey
U.S.A.