LOCATION GERBANA                 MT

Tentative Series
Rev. LCB-RJE-JAL
01/2023

GERBANA SERIES

The Gerbana series consists of moderately deep, well drained soils that formed in residuum from semiconsolidated shale and mudstone. These soils are on sedimentary plains. Slopes are 2 to 8 percent. Mean annual precipitation is about 16 inches and mean annual temperature is about 41 degrees F.

TAXONOMIC CLASS: Fine, smectitic, frigid Vertic Argiustolls

TYPICAL PEDON: Gerbana silty clay, 3 percent slope in nonirrigated cropland (colors are for dry soil unless noted otherwise).

Ap--0 to 6 inches; grayish brown (10YR 5/2) silty clay, very dark grayish brown (10YR 3/2) moist; moderate very fine granular structure; slightly hard, very friable, moderately sticky and moderately plastic; many very fine roots; slightly effervescent; moderately alkaline (pH 8.2); clear smooth boundary. (5 to 7 inches thick)

Bt--6 to 15 inches; grayish brown (10YR 5/2) silty clay, dark grayish brown (10YR 4/2) moist; strong medium prismatic structure parting to strong medium and fine subangular blocky; hard, firm, moderately sticky and moderately plastic; common very fine roots; many very fine tubular and interstitial pores; continuous distinct very dark grayish brown (10YR 3/2) moist clay films of faces of peds; common distinct pressure faces; slightly effervescent; moderately alkaline (pH 8.2); gradual smooth boundary. (5 to 15 inches thick)

Btk--15 to 30 inches; light brownish gray (10YR 6/2) silty clay, dark grayish brown (10YR 4/2) moist; moderate medium and fine subangular blocky structure; hard, firm, moderately sticky and moderately plastic; common very fine roots; many very fine tubular and interstitial pores; many distinct clay films on faces of peds; common distinct pressure faces; strongly effervescent; moderately alkaline (pH 8.4); gradual smooth boundary. (5 to 20 inches thick)

Bk--30 to 35 inches; light brownish gray (10YR 6/2) silty clay loam, dark grayish brown (10YR 4/2) moist; weak medium and coarse subangular blocky structure; hard, firm, moderately sticky and slightly plastic; common very fine roots; 10 percent small flat and angular shale chips; disseminated lime; common fine seams and masses of lime; strongly effervescent; moderately alkaline (pH 8.4); gradual smooth boundary. (5 to 10 inches thick)

Cr--35 to 60 inches; light olive gray (5Y 6/2) semiconsolidated shale and mudstone, olive gray (5Y 5/2) moist; common seams and masses of gypsum in upper part; strongly effervescent.

TYPE LOCATION: Meagher County, Montana; 1,500 feet south and 1,500 feet east of the NW corner of sec. 33, T. 7 N., R. 8 E.

RANGE IN CHARACTERISTICS:

Soil temperature - 40 to 45 degrees F.
Moisture control section - between 4 and 12 inches.
Mollic epipedon thickness - 7 to 10 inches.
Depth to Cr horizon - 20 to 40 inches.
When dry, the soil cracks are 1/2 to 1-1/2 inches wide at the surface and extend to a depth of 20 to 30 inches.

Ap horizon - Hue: 10YR or 2.5Y
Value: 4 or 5 dry
Chroma: 2 or 3
Texture: silty clay loam or silty clay
Clay content: 35 to 45 percent
Reaction: pH 7.9 to 8.4

Bt horizon - Hue: 10YR or 2.5Y
Value: 4, 5, or 6 dry; 3 or 4 moist
Chroma: 2 or 3
Clay content: 45 to 55 percent
Linear extensibility: greater than 6.0 cm
Reaction: pH 7.9 to 8.4

Btk horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3
Clay content: 40 to 50 percent
Linear extensibility: greater than 6.0 cm
Calcium carbonate equivalent: 1 to 5 percent
Reaction - pH 7.9 to 8.4

Bk horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry
Texture: silty clay loam or silty clay
Clay content: 35 to 45 percent
Calcium carbonate equivalent: 5 to 10 percent
Reaction: pH 7.9 to 8.4

COMPETING SERIES:

BEARPAW - is very deep.
BURNEL - is very deep, mollic more than 16 inches thick.
CEDARSPRINGS - is very deep, does not have horizons of carbonate accumulation.
CERRO - is very deep.
COBEN - is very deep.
DANVERS - is very deep, has a calcic horizon.
FERGUS - is very deep.
FRIANA - is very deep, has a lithologic discontinuity, does not have horizons of carbonate accumulation.
Gerber - is very deep, has a lithologic discontinuity of till.
GRAIL - is deep or very deep, mollic more than 16 inches thick.
MONDAMIN - is very deep.
PAGODA - is very deep, mollic more than 16 inches thick.
REGENT - does not have a Btk horizon.
REGET - has clay or clay loam Bt horizons.
Ridgeview - is very deep.
WYOLA - is very deep.
SUPOSO - is very deep, mollic more than 16 inches thick.
TOMASAKI - is very deep, has a lithologic discontinuity.
TSOODZIL - is very deep, does not have horizons of carbonate accumulation.
YANKEE - is very deep, mollic more than 16 inches thick.

GEOGRAPHIC SETTING:

Landform - sedimentary plains.
Elevation - 5,000 to 5,500 feet.
Parent material - residuum weathered from semiconsolidated shale and mudstone.
Climate - long, cold winters; moist springs; short, warm summers.
Mean annual precipitation - 15 to 19 inches, most of which falls during spring and early summer.
Mean annual air temperature - 38 to 43 degrees F.
Frost-free period - 70 to 90 days.

GEOGRAPHICALLY ASSOCIATED SOILS: None listed.

DRAINAGE AND PERMEABILITY: Well drained; slow permeability.

USE AND VEGETATION: Gerbana soils are used for rangeland and nonirrigated cropland. The potential native vegetation is mainly rough fescue, bluebunch wheatgrass, Idaho fescue, green needlegrass, western wheatgrass, sandberg bluegrass, prairie junegrass, forbs, and shrubs.

DISTRIBUTION AND EXTENT: Gerbana soils are of small extent. They are mainly in west-central Montana.

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

SERIES PROPOSED: Meagher County, Montana, 1990. Gerbana is a coined name.

REMARKS: Soil interpretation record: MT1463. Diagnostic horizons and features recognized in this pedon are: a mollic epipedon from the surface to 7 inches, mixed (Ap, Bt horizons); an argillic horizon from 6 to 30 inches (Bt, Btk horizons); a paralithic contact at a depth of 35 inches (Cr horizon). Gerbana soils have a frigid temperature regime and an ustic moisture regime.

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National Cooperative Soil Survey
U.S.A.