LOCATION THESSVO MT
Established Series
Rev. GFB-JJU-RJS
06/2011
THESSVO SERIES
The Thessvo series consists of very deep, well drained soils that formed in alluvium. These soils are on alluvial fans, fan remnants and stream terraces. Slopes are 0 to 4 percent. Mean annual precipitation is about 12 inches, and mean annual air temperature is about 41 degrees F.
TAXONOMIC CLASS: Fine-loamy over sandy or sandy-skeletal, mixed, superactive, frigid Aridic Haplustepts
TYPICAL PEDON: Thessvo loam, cultivated (colors are for dry soil unless otherwise noted).
Ap--0 to 4 inches; grayish brown (10YR 5/2) loam, brown (10YR 4/3) moist; moderate fine and medium subangular blocky structure parting to weak fine granular; soft, very friable, moderately sticky and slightly plastic; many very fine and few fine roots; many very fine and common fine interstitial pores; 10 percent gravel; finely disseminated calcium carbonate; strongly effervescent; slightly alkaline (pH 7.7); clear smooth boundary. (3 to 6 inches thick)
Bk1--4 to 11 inches; brown (10YR 5/3) loam, brown (10YR 4/3) moist; moderate medium prismatic structure parting to moderate fine and medium subangular blocky; slightly hard, friable, moderately sticky and slightly plastic; many very fine and few fine roots; many very fine and few fine tubular and interstitial pores; 10 percent gravel; finely disseminated calcium carbonate and many fine masses of calcium carbonate; strongly effervescent; moderately alkaline (pH 7.9); clear smooth boundary. (7 to 14 inches thick)
Bk2--11 to 15 inches; very pale brown (10YR 7/3) gravelly loam, pale brown (10YR 6/3) moist; weak medium prismatic structure parting to moderate fine and medium subangular blocky; slightly hard, friable, slightly sticky and slightly plastic; common fine roots; many very fine tubular and interstitial pores; 20 percent gravel; finely disseminated calcium carbonate, many fine masses of calcium carbonate, and common prominent calcium carbonate casts on undersides of rock fragments; violently effervescent; moderately alkaline (pH 8.3); clear abrupt boundary. (0 to 5 inches thick)
2C--15 to 60 inches; pale brown (10YR 6/3) extremely gravelly sand, brown (10YR 5/3) moist; single grain; loose, nonsticky and nonplastic; common very fine roots; 50 percent gravel and 15 percent cobbles; strongly effervescent; moderately alkaline (pH 8.0).
TYPE LOCATION: Beaverhead County, Montana. 400 feet north and 350 feet east of the southwest corner of section 1, T. 8S, R. 9W; Dillon West topographic quadrangle; Lat. 45 degrees 9 minutes 40 seconds N. and Long. 112 degrees 39 minutes 40 seconds.
RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 40 to 47 degrees F.
Depth to secondary calcium carbonate accumulation - 3 to 6 inches
Depth to lithologic discontinuity - 11 to 20 inches
A horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 or 6 dry; 3 or 4 moist
Chroma: 2 or 3; dry or moist
Texture: loam, sandy loam or sandy clay loam
Clay content: 15 to 25 percent
Rock fragments: 0 to 30 percent--0 to 25 percent gravel, 0 to 5 percent cobbles
Calcium carbonate equivalent: 0 to 15 percent
Reaction: pH 6.6 to 8.2
Bk1 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3; dry or moist
Texture: loam, sandy loam or sandy clay loam
Clay content: 18 to 25 percent
Rock fragments: 0 to 35 percent gravel--0 to 35 percent gravel, 0 to 5 percent cobbles
Calcium carbonate equivalent: 5 to 15 percent
Reaction: pH 7.4 to 8.4
Bk2 horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 6 or 8 dry; 5 or 7 moist
Chroma: 2 or 3; dry or moist
Texture: loam, sandy loam or sandy clay loam
Clay content: 18 to 25 percent
Rock fragments: 0 to 35 percent gravel--0 to 35 percent gravel, 0 to 5 percent cobbles
Calcium carbonate equivalent: 15 to 30 percent
Reaction: pH 7.9 to 8.4
2C horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 to 4; dry or moist
Texture: sand, loamy sand, loamy coarse sand or coarse sand
Clay content: 0 to 10 percent
Rock fragments: 35 to 85 percent--35 to 65 percent gravel, 0 to 20 percent cobbles
Calcium carbonate equivalent: 0 to 15 percent
Reaction: 7.4 to 8.4
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING:
Landform - alluvial fans, fan remnants and stream terraces
Elevation - 4,800 to 6,500 feet
Slope - 0 to 4 percent
Parent material - alluvium
Climate - long, cold winters; moist springs; warm summers
Mean annual precipitation - 10 to 14 inches
Mean annual temperature - 37 to 45 degrees F.
Frost-free period - 70 to 105 days
GEOGRAPHICALLY ASSOCIATED SOILS: None listed.
DRAINAGE AND PERMEABILITY: Well drained; moderate permeability above the 2C horizon and very rapid permeability in the 2C horizon.
USE AND VEGETATION: Thessvo soils are used mainly as cropland.
DISTRIBUTION AND EXTENT: Thessvo soils are of small extent in southwest Montana. MLRA - 44B.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.
SERIES ESTABLISHED: Beaverhead County, Montana, 2001.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - from 0 to 4 inches (Ap horizon)
Secondary carbonate accumulation - from 4 to 15 inches (Bk1, Bk2 horizons)
Lithilogic discontinuity - at 15 inches (2C horizon)
Particle-size control section - from 10 to 40 inches (part of Bk1, Bk2, part of 2C horizons)
Thessvo soils have a frigid temperature regime and an ustic moisture regime bordering on aridic.
National Cooperative Soil Survey
U.S.A.