LOCATION FLATCREEK MTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, calcareous, frigid Vertic Ustifluvents
TYPICAL PEDON: Flatcreek silty clay, in rangeland (colors are for dry soil unless otherwise noted).
A--0 to 3 inches; grayish brown (10YR 5/2) silty clay, dark gray (10YR 4/1) moist; strong fine angular blocky structure; very hard, firm, very sticky and very plastic; many fine and very fine roots and few medium roots; mildly alkaline (pH 7.6); clear smooth boundary. (2 to 4 inches thick)
By--3 to 11 inches; grayish brown (10YR 5/2) silty clay, dark gray (10YR 4/1) moist; weak medium prismatic structure parting to strong medium and coarse subangular blocky; extremely hard, firm, very sticky and very plastic; common fine and very fine roots; few fine and very fine tubular pores; few fine masses of gypsum; slightly effervescent; strongly alkaline (pH 8.6); clear wavy boundary. (6 to 10 inches thick)
Byz--11 to 20 inches; grayish brown (10YR 5/2) silty clay, dark gray (10YR 4/1) moist; weak medium prismatic structure parting to strong medium subangular blocky; extremely hard, firm, very sticky and very plastic; common fine and very fine roots; few very fine tubular pores; few pressure faces; few fine masses of gypsum and other salts; slightly effervescent; moderately alkaline (pH 8.4); clear wavy boundary. (8 to 12 inches thick)
BCyz1--20 to 43 inches; grayish brown (2.5Y 5/2) stratified clay and silty clay, dark grayish brown (2.5Y 4/2) moist; massive; extremely hard, firm, very sticky and very plastic; few fine and very fine roots; common very fine tubular pores; common fine masses of gypsum and other salts; slightly effervescent; moderately alkaline (pH 8.4); clear wavy boundary. (16 to 30 inches thick)
BCyz2--43 to 60 inches; light brownish gray (2.5Y 6/2) stratified clay and silty clay, grayish brown (2.5Y 5/2) moist; few fine faint light yellowish brown (2.5Y 6/4) mottles; massive; extremely hard, firm, very sticky and very plastic; few very fine tubular pores; few fine masses of gypsum and other salts; slightly effervescent; moderately alkaline (pH 8.4).
TYPE LOCATION: Chouteau County, Montana; 2,300 feet south and 200 feet west of the NE corner of sec. 9, T. 21 N., R. 12 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 43 to 46 degrees F.
Moisture control section - between 4 and 12 inches.
Control section - 45 to 60 percent clay, cracks 1 cm wide at 20 inches and COLE of more than 0.07.
Depth to Byz horizon - 8 to 14 inches.
Depth to seasonal high water table - 42 to 60 inches during the period from November to June.
Soil phases - occasionally flooded.
A horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 moist
Chroma: 1 or 2
Clay content: 40 to 60 percent
EC: 0 to 4
Reaction: pH 7.4 to 8.4
SAR: 0 to 4
By horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 1 or 2
Texture: silty clay or clay
Clay content: 40 to 60 percent
Gypsum: 0.5 to 1 percent
EC: 2 to 8
SAR: 4 to 13
Reaction: pH 7.9 to 9.0
Calcium carbonate equivalent: 1 to 3 percent
Byz horizon - Hue: 10YR or 2.5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 1 or 2
Texture: silty clay or clay
Clay content: 40 to 60 percent
Gypsum: 0.5 to 1 percent
EC: 8 to 16
SAR: 4 to 13
Reaction: pH 7.9 to 9.0
Calcium carbonate equivalent: 2 to 5 percent
BCyz horizons - Hue: 10YR or 2.5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2, 3, or 4
Mottles: few or common in lower part
Texture: stratified clay and silty clay
Clay content: 40 to 60 percent
Gypsum: 0.5 to 2 percent
EC: 8 to 16
SAR: 4 to 13
Reaction: pH 7.9 to 9.0
Calcium carbonate equivalent: 2 to 5 percent
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - flood plains.
Elevations - 2,800 to 3,400 feet.
Slopes- 0 to 2 percent.
Parent material - alluvium derived mainly from semiconsolidated sedimentary beds.
Climate - long, cold winters; moist springs; and warm, dry summers.
Mean annual precipitation - 14 to 17 inches.
Mean annual air temperature - 42 to 45 degrees F.
Frost-free period - 100 to 120 days.
DRAINAGE AND PERMEABILITY: Somewhat poorly drained; slow runoff; very slow permeability.
USE AND VEGETATION: Flatcreek soils are used mainly for range. Potential native vegetation is mainly western wheatgrass, alkali sacaton, inland saltgrass, greasewood, and Nuttall saltbush.
DISTRIBUTION AND EXTENT: Flatcreek soils are of small extent in north-central Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Chouteau County, Montana, 1992. Series name is from a stream in south-central Chouteau County.
REMARKS: Soil interpretation record: MT1346. Diagnostic horizons and features recognized in this pedon are: an ochric epipedon form 0 to 3 inches (A horizon); a horizon of gypsum accumulation (By horizon); horizons of accumulations of gypsum and other salts (BCyz1 and BCyz2 horizons); and a particle size control section from 10 to 40 inches. Flatcreek soils have a frigid temperature regime and an ustic moisture regime bordering on aquic.