LOCATION COLSTRIP MTEstablished Series
TAXONOMIC CLASS: Loamy, mixed, superactive, calcareous, frigid Aridic Lithic Ustorthents
TYPICAL PEDON: Colstrip loam, in rangeland. (Colors are for dry soil unless otherwise noted)
A--0 to 4 inches; light brownish gray (2.5Y 6/2) loam, dark grayish brown (2.5Y 4/2) moist; weak very thin and thin platy structure parting to weak very fine and fine granular; slightly hard, very friable, slightly sticky and slightly plastic; many very fine roots; strongly effervescent; slightly alkaline (pH 7.8); clear smooth boundary. (2 to 4 inches thick)
Bw--4 to 7 inches; light olive brown (2.5Y 5/4) loam, olive brown (2.5Y 4/4) moist; weak medium prismatic structure parting to moderate fine and medium subangular blocky; hard, very friable, slightly sticky and slightly plastic; many very fine roots; many very fine pores; 10 percent channers; strongly effervescent; slightly alkaline (pH 7.8); clear smooth boundary. (0 to 5 inches thick)
C--7 to 16 inches; light yellowish brown (2.5Y 6/4) channery loam, olive brown (2.5Y 4/4) moist; massive; hard, very friable, slightly sticky and slightly plastic; common very fine roots; common very fine pores; 15 percent channers; strongly effervescent; moderately alkaline (pH 8.2); abrupt smooth boundary. (1 to 16 inches thick)
R--16+ inches; hard sandstone.
TYPE LOCATION: Rosebud County, Montana; 2,500 feet west and 2,000 feet north of the southeast corner of sec. 7, T. 6 S., R. 43 E. Birney, Montana topographic quadrangle; Latitude 45 degrees, 19 minutes, 10 seconds North, and Longitude 105 degrees, 30 minutes, 30 seconds West.
RANGE IN CHARACTERISTICS:
Soil temperature - 42 to 46 degrees F.
Moisture control section - between 8 inches and the lithic contact, dry in 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. Ustic soil moisture regime bordering on Aridic.
Depth to lithic contact - 10 to 20 inches.
A horizon:
Hue: 5YR, 7.5YR, 10YR or 2.5Y
Value: 4 to 6; 3 to 5 moist
Chroma: 2 to 4
Texture: loam
Clay content: 7 to 18 percent
Rock fragments: 0 to 35 percent
Reaction: 6.6 to 8.4
Bw horizon:
Hue: 5YR, 7.5YR, 10YR or 2.5Y
Value: 5 to 7; 4 to 6 moist
Chroma: 2 to 4
Texture: loam, sandy loam or fine sandy loam
Clay content: 7 to 18 percent
Rock fragments: 0 to 35 percent channers
Calcium carbonate equivalent: 5 to 10 percent
Reaction: 7.4 to 8.4
C horizon:
Hue: 5YR, 7.5YR, 10YR or 2.5Y
Value: 5 to 7; 4 to 6 moist
Chroma: 2 to 4
Texture: loam, sandy loam or fine sandy loam
Clay content: 7 to 18 percent
Rock fragments: 0 to 35 percent channers
Calcium carbonate equivalent: 5 to 10 percent
Reaction: 7.4 to 8.4
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - sedimentary plains.
Elevation - 3,100 to 3,800 feet.
Slope- 0 to 15 percent.
Parent material - residuum from sandstone.
Climate - long, cold winters; moist springs; warm summers.
Mean annual precipitation - 10 to 14 inches.
Mean annual air temperature - 42 to 46 degrees F.
Frost-free period - 110 to 120 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Yamacall, Delpoint and Cabbart soils. Yamacall soils are very deep and occur on footslopes. Delpoint soils are moderately deep and are on back slopes. Cabbart soils are on similar landscape positions as Colstrip and do not have a lithic contact.
DRAINAGE AND PERMEABILITY: Well drained; moderately rapid permeability; runoff is negligible to low depending on slope.
USE AND VEGETATION: Colstrip soils are used mainly for rangeland. Potential native vegetation is bluebunch wheatgrass, western wheatgrass and needleandthread.
DISTRIBUTION AND EXTENT: The Colstrip soil is of limited extent in south-central Montana.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Denver, Colorado.
SERIES PROPOSED: Garfield County, Montana. 11/2000. The name is from a town in Rosebud County, Montana.
REMARKS: Diagnostic horizons and features recognized in this pedon are: particle-size control section: 10 to 16 inches (C horizon); ochric epipedon: from the soil surface to a depth of 7 inches after mixing (A and Bw horizons); Lithic contact: the contact with sandstone at 16 inches (R layer).
The soil has previously correlated as the Travessilla series or as taxadjuncts to the Redcreek and Rentsac series.