LOCATION TONRA MTEstablished Series
TAXONOMIC CLASS: Fine-loamy over sandy or sandy-skeletal, mixed, superactive, mesic Ustic Haplocalcids
TYPICAL PEDON: Tonra silty clay loam - cultivated. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 3 inches; light brownish gray (10YR 6/2) silty clay loam, dark grayish brown (10YR 4/2) moist; weak fine granular structure; soft, friable, moderately sticky, moderately plastic; many very fine roots; slightly calcareous; moderately alkaline (pH 8.4); clear boundary. (3 to 6 inches thick)
Bw1--3 to 11 inches; grayish brown (10YR 5/2) clay loam, dark grayish brown (10YR 4/2) moist; moderate medium and fine blocky structure; soft, friable, moderately sticky, moderately plastic; many very fine roots; few very fine pores; few pebbles; strongly calcareous; strongly alkaline (pH 8.6); gradual boundary. (7 to 9 inches thick)
Bw2--11 to 23 inches; light brownish gray (10YR 6/2) clay loam, grayish brown (10YR 5/2) moist; moderate medium and fine blocky structure; slightly hard, friable, moderately sticky, moderately plastic; common very fine roots; many very fine pores; few pebbles; strongly calcareous with few lime segregations in the lower part; strongly alkaline (pH 8.6); gradual boundary. (11 to 13 inches thick)
Ck--23 to 29 inches; very pale brown (10YR 8/2) coarse sandy clay loam, light gray (10YR 7/2) moist; massive; soft, friable, moderately sticky, moderately plastic; few very fine roots; many very fine pores; common pebbles; strongly calcareous with lime segregations and lime-coated pebbles; strongly alkaline (pH 9.0). (6 to 10 inches thick)
2C--29 to 52 inches; coarse sand, gravel and cobbles. The coarse fragments are larger than 3 inches and 60 percent passes a No. 10 sieve; all are coated with lime.
TYPE LOCATION: Carbon County, Montana; 1,320 feet east and 1,100 feet north of SW corner of SW corner of sec. 5, T.7S., R.23E.
RANGE IN CHARACTERISTICS: Depth to sand and gravel substrata ranges from 20 to 40 inches. Gravel and cobbles in the A, Bw, and Ck horizons range from 2 to 10 percent. The hue is 10YR or 2.5Y. Mean annual temperature ranges from 48 to 50 degrees F. and average summer temperature ranges from 60 to 65 degrees F.
The A horizon has value of 5 or 6 dry.
The Bw horizon is slightly to strongly calcareous.
The Ck horizon has 20 to 30 percent CaC03 equivalent excluding coarse fragments. Cobbles and pebbles in the 2C horizon are thinly to thickly coated with lime.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Tonra soils are on valley floors and flood plains. They formed in alluvium containing granite, limestone and quartzite gravel. Mean annual temperature ranges from 47 to 49 degrees F., mean annual precipitation is 9 to 12 inches, mean summer temperature is greater than 59 degrees F., and mean winter temperature is 25 to 30 degrees F. The frost-free season is 120 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Colby, Haverson, Heldt, and Treasure soils. Colby soils have a fine-silty control section. Haverson soils have no B horizon and usually have a stratified C horizon. Heldt soils have a fine control section. Treasure soils have an argillic horizon.
DRAINAGE AND PERMEABILITY: Well-drained, slow runoff, moderate permeability.
USE AND VEGETATION: Used for pasture of tame grasses and for cultivation of row crops.
DISTRIBUTION AND EXTENT: The Tonra series occurs in south-central areas of Montana and possibly adjacent areas of Wyoming. It is of limited extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Carbon County (Bridger Area), Montana, 1971.