LOCATION THERMOPOLIS             WY

Established Series
Rev. PSD/DEW/JCK
01/2016

THERMOPOLIS SERIES

The Thermopolis series consists of shallow, well drained soils that formed in slope alluvium or colluvium over residuum from reddish siltstone. These soils are on eroded fan remnants, dissected dip slopes, hills, and ridges. Slopes are 2 to 60 percent. Mean annual precipitation is about 356 mm, and mean annual air temperature is about 6.6 degrees C.

TAXONOMIC CLASS: Loamy, mixed, superactive, calcareous, frigid, shallow Ustic Torriorthents

TYPICAL PEDON: Thermopolis loam in rangeland at an elevation of 1,697 meters (colors are for dry soil unless otherwise noted).

A--0 to 10 cm; reddish brown (2.5YR 5/4) loam, reddish brown (2.5YR 4/4) moist; moderate fine granular structure; soft, very friable, slightly sticky and slightly plastic; common very fine and fine roots throughout; many very fine and common fine vesicular pores; finely disseminated carbonates; strongly effervescent; moderately alkaline (pH 8.2); clear smooth boundary. (5 to 13 cm thick)

C--10 to 38 cm; reddish brown (2.5YR 5/4) loam, reddish brown (2.5YR 4/4) moist; massive; hard, very friable, slightly sticky and slightly plastic; common very fine and fine roots throughout; common very fine and fine tubular pores; finely disseminated carbonates; 10 percent pararock fragments; strongly effervescent; moderately alkaline (pH 8.4); gradual wavy boundary. (13 to 43 cm thick)

Cr--38 cm; reddish brown, calcareous siltstone.

TYPE LOCATION: Fremont County, Wyoming; 806 meters south and 291 meters west of the northeast corner of section 5, T. 31 N., R. 98 W.; Weiser Pass USGS quadrangle; latitude 42 degrees 41 minutes 25.98 seconds N. and longitude 108 degrees 33 minutes 58.17 seconds W., NAD 83.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature - 4.4 to 8.3 degrees C
Depth to paralithic contact - 10 to 50 cm
Particle-size control section - averages 18 to 35 percent clay

Rock fragments are dominantly less than 150 mm

A horizon:
Hue: 10R to 7.5YR
Value: 3, 4, 5 or 6 dry; 3 or 4 moist
Chroma: 3, 4 or 6
Texture: loam or silt loam
Clay content: 18 to 27 percent
Rock fragments: 0 to 35 percent gravel, cobbles, or channers
Calcium carbonate equivalent: 0 to 15 percent
Gypsum: 0 to 4 percent
Exchangeable sodium: 0 to 15 percent
Electrical conductivity: 0 to 2 mmhos/cm
Reaction: pH 7.4 to 8.4

C horizon:
Hue: 10R to 5YR
Value: 3, 4 or 5 dry; 3, 4 or 5 moist
Chroma: 3, 4, 5 or 6
Texture: loam, silt loam, or silty clay loam
Clay content: 18 to 35 percent
Rock fragments: 0 to 35 percent gravel, cobbles, or channers
Calcium carbonate equivalent: 5 to 15 percent
Gypsum: 0 to 4 percent
Exchangeable sodium: 0 to 15 percent
Electrical conductivity: 0 to 2 mmhos/cm
Reaction: pH 8.0 to 9.0

COMPETING SERIES:
Blackhall (WY) - have less than 18 percent clay in the particle-size control section; have hue yellower than 7.5YR
Blazon (WY) - have hue yellower than 7.5YR
Byrnie (WY) - have less than 18 percent clay in the particle-size control section
Seaverson (WY) - have exchangeable sodium greater than 15 percent; have electrical conductivity greater than 2 mmhos/cm

GEOGRAPHIC SETTING:
Landform - eroded fan remnants, dissected dip slopes, hills, and ridges
Elevation - 1,372 - 2,377 meters
Slope - 2 to 60 percent slopes
Parent material - slope alluvium or colluvium over residuum
Mean annual precipitation - 254 to 356 mm
Mean annual air temperature - 3.9 to 7.8 degrees C
Frost-free period - 60 to 110 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Almy and Sinkson soils. Almy soils occur on more stable parts of the landscape and have a Bt horizon. Sinkson soils occur intermixed with Thermopolis soils and are deep.

DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.

USE AND VEGETATION: Thermopolis soils are used mainly for rangeland. Native vegetation is Wyoming big sagebrush, western wheatgrass, bluebunch wheatgrass, and prairie junegrass. Threadleaf sedge increases with extended grazing pressure. Rocky Mountain juniper occurs in areas near rock outcrop and increases with a reduction of wildfire.

DISTRIBUTION AND EXTENT: Thermopolis soils are of moderate extent in central and southern Wyoming. MLRAs - 34A, 43B, 46.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Fremont County, Wyoming, Lander Area; 1975.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - from 0 to 10 cm (A horizon)
Paralithic contact - at 38 cm (Cr horizon)
Particle-size control section - from 25 to 38 cm (part of the C horizon)

Thermopolis soils have a frigid temperature regime and an aridic moisture regime bordering on ustic.

Note: The need for documentation in support of an aridic soil moisture regime is recognized and should be investigated at the type location and across the extent of the series.

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National Cooperative Soil Survey
U.S.A.