LOCATION BIGSAG MTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, calcareous, frigid Typic Halaquepts
TYPICAL PEDON: Bigsag silty clay, native grass (colors are for moist soil unless otherwise noted).
Anyz--0 to 4 inches; olive gray (5Y 4/2) silty clay, gray (5Y 5/1) dry; moderate fine subangular blocky structure; very hard, firm, very sticky and very plastic; common fine and very fine roots; few very fine tubular pores; few fine masses of gypsum and other salts; slightly effervescent; moderately alkaline (pH 8.4); clear smooth boundary. (2 to 4 inches thick)
Bnyzg1--4 to 15 inches; olive gray (5Y 4/2) silty clay, gray (5Y 5/1) dry; few fine distinct light olive brown (2.5Y 5/4) dry redox concentrations; weak medium subangular blocky structure; very hard, firm, very sticky and very plastic; few very fine roots; common very fine tubular pores; common fine seams and masses of gypsum and other salts; strongly effervescent; strongly alkaline (pH 8.8); clear wavy boundary. (6 to 15 inches thick)
Bnyzg2--15 to 30 inches; dark gray (5Y 4/1) silty clay, gray (5Y 5/1) dry; common fine distinct grayish brown (2.5Y 5/2) dry redox depletions; weak medium subangular blocky structure; very hard, firm, very sticky and very plastic; few very fine roots; common very fine tubular pores; common fine seams and masses of gypsum and other salts; strongly effervescent; strongly alkaline (pH 8.8); clear wavy boundary. (0 to 24 inches thick)
BCnyzg1--30 to 48 inches; olive gray (5Y 4/2) silty clay, olive gray (5Y 5/2) dry; many fine faint olive (5Y 5/3) dry redox concentrations; massive; extremely hard, very firm, very sticky and very plastic; common very fine tubular pores; common fine seams and masses of gypsum and other salts; strongly effervescent; strongly alkaline (pH 8.6); clear wavy boundary. (0 to 30 inches thick)
BCnyzg2--48 to 60 inches; dark gray (5Y 4/1) silty clay loam, gray (5Y 6/1) dry; many fine faint olive (5Y 5/3) dry redox concentrations; massive; very hard, firm, very sticky and very plastic; common very fine tubular pores; common fine seams and masses of gypsum and other salts; strongly effervescent; strongly alkaline (pH 8.6).
TYPE LOCATION: Chouteau County, Montana; 800 feet south and 600 feet east of the NW corner of sec. 23, T. 21 N., R. 10 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 44 to 47 degrees F.
Moisture control section - between 4 and 12 inches.
Depth to seasonal high water table - 12 to 24 inches during the period from December to June.
Depth to redoximorphic features - 3 to 20 inches.
Bknyzg and BCknyzg horizons are allowed.
Anyz horizon - Hue: 10YR, 2.5Y, 5Y
Value: 5 or 6 dry, 3 or 4 moist
Chroma: 1, 2
Texture: silty clay loam, silty clay, clay
Clay content: 35 to 60 percent
EC: greater than 16 mmhos/cm
SAR: 13 to 20
Reaction: pH 7.9 to 9.0
Bnyzg1 horizon - Hue: 2.5Y, 5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 1, 2
Redox features: none to common
Chroma: 3, 4
Texture: silty clay loam, clay loam, silty clay, clay
Clay content: 35 to 60 percent
EC: greater than 16 mmhos/cm
SAR: 13 to 40
Reaction: pH 8.5 to 9.0
Bnyzg2 and BCnyzg horizons - Hue: 2.5Y, 5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 1, 2
Redox concentrations: few to many--Hue: 2.5Y or 5Y--Value: 5 or 6 dry, 4 moist--Chroma: 3 or 4
Texture: silty clay loam, clay loam, silty clay, clay
Clay content: 35 to 60 percent
EC: greater than 16 mmhos/cm
SAR: 13 to 30, decreasing with depth
Reaction: pH 8.5 to 9.6
COMPETING SERIES:
Lolak (NV) - has redox features that have hue of 10YR, chroma of 2 or less above 40 inches, not strongly saline below 18 inches.
GEOGRAPHIC SETTING:
Landform - flood plains or lake plains typically adjacent to shallow saline lakes in old glacial channels.
Elevations - 2,600 to 3,400 feet.
Slopes- 0 to 2 percent.
Parent material - alluvium or glaciolacustrine deposits.
Climate - long, cold winters; moist springs; hot, dry summers.
Mean annual precipitation - 10 to 19 inches.
Mean annual temperature - 40 to 45 degrees F.
Frost-free period - 100 to 130 days.
DRAINAGE AND PERMEABILITY: Poorly drained; very slow permeability.
USE AND VEGETATION: Bigsag soils are used mainly for range. Potential native vegetation is mainly western wheatgrass, alkali sacaton, inland salt-grass, alkali bluegrass, greasewood, and Nuttall saltbush.
DISTRIBUTION AND EXTENT: Bigsag soils are of small extent in north-central Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Toole County, Montana, 1991. Series proposed Chouteau County, Montana, 1987. Series name is from a glacial channel of the Missouri River locally known as the Big Sag.
REMARKS: Soil interpretation record: MT1077. Diagnostic horizons and features recognized in this pedon are: an ochric epipedon when mixed to 7 inches (Anyz, Bnyzg1 horizons); a particle-size control section from 10 to 40 inches (Bnyzg1, Bnyzg2, and BCnyzg1 horizons); horizons with redoximorphic features below a depth of 4 inches. Bigsag soils have a frigid temperature regime and an aquic moisture regime.