LOCATION MARVAN MT+UTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, frigid Sodic Haplusterts
TYPICAL PEDON: Marvan clay, cultivated (colors are for dry soil unless otherwise noted).
Ap--0 to 4 inches; light brownish gray (2.5Y 6/2) clay, dark grayish brown (2.5Y 4/2) moist; moderate very fine granular structure that becomes cloddy where cultivated; very hard, friable, very sticky and very plastic; many fine and very fine roots; slightly effervescent; moderately alkaline (pH 7.9); abrupt wavy boundary. (3 to 7 inches thick)
Bss--4 to 11 inches; light brownish gray (2.5Y 6/2) clay, dark grayish brown (2.5Y 4/2) moist; moderate fine and very fine subangular blocky structure; extremely hard, firm, very sticky and very plastic; many fine and very fine roots; many fine and very fine pores and few medium pores; few faint slickensides; slightly effervescent; moderately alkaline (pH 7.9); clear wavy boundary. (7 to 18 inches thick)
Bssy--11 to 35 inches; light brownish gray (2.5Y 6/2) clay, dark grayish brown (2.5Y 4/2) moist; moderate fine and medium subangular blocky structure; extremely hard, friable, very sticky and very plastic; common fine and very fine roots; many fine and very fine pores; few distinct slickensides; many fine and medium masses of gypsum; slightly effervescent; moderately alkaline (pH 7.9); diffuse boundary. (15 to 30 inches thick)
Byz--35 to 60 inches; grayish brown (2.5Y 5/2) 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 fine and very fine pores; very thin stratifications of silty clay loam or silt loam; many fine masses of gypsum and other salts; slightly effervescent; moderately alkaline (pH 7.9).
TYPE LOCATION: Cascade County, Montana; 2,640 feet south and 150 feet west of the NE corner of sec. 8, T. 21 N., R. 2 E.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 47 degrees F.
Moisture control section - between of 4 and 12 inches; dry all parts between four-tenths and five-tenths of the cumulative days per year when the soil temperature at a depth of 20 inches is 41 degrees F or higher.
Soil Moisture Regime - Ustic moisture regime that borders on Aridic (Aridic-Ustic).
Summer temperature - 60 to 68 degrees F.
Depth to Bssy horizon - 10 to 24 inches.
EC- greater than 8 mmhos/cm below a depth of 35 inches.
When dry, the soil has 1/4- to 1-inch cracks that extend to a depth of about 20 inches. Slickensides range from few to common in all horizons except surface. Some pedons have a shale substratum. A saline phase with EC of 2 to 8 in the surface layer is recognized.
A Bw horizon is allowed.
Soil phases - wet, shaley substratum, saline.
Ap horizon - Hue: 2.5Y or 5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2, 3, or 4
Texture: clay, silty clay, or silty clay loam
Clay content: 40 to 60 percent
EC: 0 to 8 mmhos/cm; saline phase is 2 to 8 mmhos/cm
SAR: 0 to 4
Calcium carbonate equivalent: 1 to 5 percent
Reaction: pH 7.4 to 9.0
Bss horizon - Hue: 2.5Y or 5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2, 3, or 4
Texture: clay or silty clay
Clay content: 45 to 60 percent
EC: 2 to 8 mmhos/cm
SAR: 4 to 13; saline phase is 4 to 8 (Where the SAR is below 8, the sodium plus magnesium is greater than calcium plus exchange acidity.)
Calcium carbonate equivalent: 1 to 10 percent
Reaction: pH 7.9 to 9.0
Bssy or Bnssy horizon - Hue: 2.5Y or 5Y
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2, 3, or 4
Texture: clay or silty clay
Clay content: 45 to 60 percent
Gypsum: 1 to 5 percent
EC: 4 to 16 mmhos/cm; ECs are less then 8 above a depth of 35 inches.
SAR: 13 to 38
Calcium carbonate equivalent: 1 to 10 percent
Reaction: pH 7.9 to 9.0
Byz, Bnyz, or Bnssyz horizon - Hue: 2.5 or 5Y
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 2, 3, or 4
Texture: clay or silty clay that includes thin layers of silty clay loam and silt loam material
Clay content: 45 to 60 percent
Gypsum: 1 to 5 percent
EC: 8 to 16 mmhos/cm
SAR: 13 to 38
Calcium carbonate equivalent: 1 to 10 percent
Reaction: pH 7.9 to 9.0
COMPETING SERIES:
Bickerdyke (T)(MT) - noncalcareous throughout the profile.
GEOGRAPHIC SETTING:
Landform - alluvial fans; sedimentary plains; hills; drainageways; stream terraces.
Elevation - 1,900 to 4,000 feet.
Slope- 0 to 15 percent.
Parent material - alluvium, lacustrine deposits, or in material derived from semiconsolidated shale.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 10 to 14 inches.
Mean annual air temperature - 40 to 45 degrees F.
Frost-free period - 100 to 135 days.
DRAINAGE AND PERMEABILITY: Well drained; very slow permeability.
USE AND VEGETATION: Marvan soils are used mainly as rangeland, but some areas are used as dryland and irrigated cropland. The native vegetation is mainly green needlegrass, western wheatgrass, bluebunch wheatgrass, big sagebrush, Nuttall saltbush, forbs, and shrubs.
DISTRIBUTION AND EXTENT: These soils are of moderate extent in the eastern plains of Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: St. Paul, Minnesota
SERIES ESTABLISHED: Cascade County, Montana, 1975.
REMARKS: Soil interpretations records: MT0114, MT0222, MT0785. Diagnostic horizons and features recognized in this pedon are: ochric epipedon - from 0 to 7 inches (Ap, Bss horizons); slickensides between a depth of 4 and 35 inches (Bss, Bssy horizons); cracks to a depth of 20 inches (Ap, Bss, Bssy horizons); a particle-size control section from 10 to 40 inches (Bss, Bssy, Byz horizons). Marvan soils have a frigid temperature regime and an ustic moisture regime that borders on aridic.
ADDITIONAL DATA: Laboratory data S71MT-13-3.