LOCATION THIOKOL UT+IDEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, active, mesic Sodic Calcixerepts
TYPICAL PEDON: Thiokol silt loam--nonirrigated cropland. (Colors are for dry soil unless otherwise noted.)
Ap--0 to 5 inches; light brownish gray (10YR 6/2) silt loam, dark grayish brown (10YR 4/2) moist; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and few medium roots; common fine pores; strongly effervescent; strongly alkaline (pH 8.8); abrupt smooth boundary. (3 to 8 inches thick)
A--5 to 9 inches; light brownish gray (10YR 6/2) silt loam, dark grayish brown (10YR 4/2) moist; weak medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; common fine and few medium roots; common fine pores; strongly effervescent; strongly alkaline (pH 8.7); clear smooth boundary. (2 to 5 inches thick)
Bw--9 to 20 inches; light brownish gray (10YR 6/2) silt loam, grayish brown (10YR 5/2) moist; moderate medium subangular blocky structure; slightly hard, friable, slightly sticky and slightly plastic; few fine roots; few fine and very fine pores; strongly effervescent; strongly alkaline (pH 8.8); gradual wavy boundary. (6 to 16 inches thick)
Bkn1--20 to 28 inches; very pale brown (10YR 8/2) silt loam, pale brown (10YR 6/3) moist; massive; very hard, friable, moderately sticky and slightly plastic; few very fine roots; few very fine pores; violently effervescent; very strongly alkaline (pH 9.4) gradual wavy boundary. (5 to 25 inches thick)
Bkn2--28 to 36 inches; pale yellow (2.5Y 8/2) silt loam, light brownish gray (2.5Y 6/2) moist; massive; very hard, friable, moderately sticky and slightly plastic; few fine and very fine pores; violently effervescent; very strongly alkaline (pH 9.5); gradual wavy boundary. (0 to 20 inches thick)
Cn--36 to 60 inches; pale yellow (2.5Y 8/2) silt loam, light brownish gray (2.5Y 6/2) moist; massive; very hard, friable, slightly plastic; few fine pores; violently effervescent; very strongly alkaline (pH 9.7).
TYPE LOCATION: Box Elder County, Utah; about 2.25 miles west and 1.25 miles north of the Valley exit from Interstate 84 in Blue Creek Valley; approximately 1,750 feet west and 1,500 feet north of the southeast corner of section 13, T. 13 N., R. 6 W.; USGS Howell 7.5 minute topographic quadrangle; 41 degrees 51 minutes 27 seconds north latitude and 112 degrees 28 minutes 56 seconds west longitude, NAD27; UTM zone 12N 376914E, 4635017N, NAD83.
RANGE IN CHARACTERISTICS:
Soil moisture - The soils are dry for less than 50 percent of the time in all parts of the moisture control section during the period when the soil temperature is above 41 degrees F., and are continually dry for 90 consecutive days in all parts of the moisture control section in most years during the summer months. They are moist for 60 consecutive days out of the 120 days following the winter solstice in 7 out of 10 years; Xeric moisture regime that borders on aridic.
Mean annual soil temperature - 47 to 51 degrees F.
Ochric epipedon thickness - 5 to 13 inches.
Depth to calcic horizon - 13 to 22 inches.
Particle-size control section - Clay content: 18 to 27 percent.
A horizon - Hue: 10YR or 2.5Y.
Value: 6 or 7 dry, 4 or 5 moist.
Chroma: 2 or 3, dry or moist.
Reaction: Slightly alkaline through strongly alkaline.
Effervescence: Slightly effervescent or strongly effervescent.
Bw horizon - Hue: 10YR or 2.5Y.
Value: 6 or 7 dry, 4 through 6 moist.
Chroma: 2 or 3, dry or moist.
Texture: Loam or silt loam.
Reaction: Slightly alkaline through strongly alkaline.
Effervescence: Slightly effervescent or strongly effervescent.
Bkn and Cn horizons - Hue: 10YR through 5Y.
Value: 5 through 8 dry, 4 through 7 moist.
Chroma: 2 through 4, dry or moist.
Texture: Silty clay loam or silt loam, with very fine sandy loam in the lower horizons in some pedons.
Reaction: Moderately alkaline to very strongly alkaline (up to pH 9.8).
Sodicity (SAR): 10 to 20.
Calcium carbonate equivalent: 15 to 45 percent.
Other features: Exchangeable sodium percentage (ESP) is more than 15 percent within 40 inches of the soil surface.
COMPETING SERIES: There are currently no other series in this family.
GEOGRAPHIC SETTING: Thiokol soils are on broad, intermediate and high-level lake terraces. These soils formed in lacustrine deposits derived from calcareous sedimentary rocks such as limestone and sandstone. Slopes are 0 to 10 percent. Elevations range from 4,300 to 5,125 feet. The mean annual precipitation is 12 to 14 inches, the mean annual temperature is 45 to 52 degrees F., and the frost-free period is 90 to 150 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Hansel, Kearns, Mellor, Pomat, and Timpanogos soils. Hansel soils have argillic horizons. Kearns soils have mollic epipedons. Mellor soils have natric horizons. Pomat soils do not have diagnostic subsurface horizons. Timpanogos soils have mollic epipedons and argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; low or medium surface runoff; moderate permeability.
USE AND VEGETATION: Thiokol soils are used for irrigated and nonirrigated cropland as well as rangeland. The native vegetation is dominantly Wyoming big sagebrush and grasses.
DISTRIBUTION AND EXTENT: Northern Utah and southern Idaho. These soils are moderately extensive. MLRA 28A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona.
SERIES ESTABLISHED: Box Elder County (Eastern Part), Utah, 1969.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil surface to 9 inches (Ap and A horizons).
Cambic horizon - The zone from 9 to 20 inches (Bw horizon).
Calcic horizon - The zone from 20 to 36 inches (Bk1 and Bk2 horizons).
Particle-size control section - The zone from 10 to 40 inches (Bk1 and Bk2 horizons and parts of the Bw and C horizons).
This revision of April 2005 updates the taxonomic class from Fine-silty, mixed, active, mesic Sodic Xeric Haplocalcids based on vegetative production and correlation to an Upland rangeland ecological site for most acres of Thiokol. More measurements of sodium levels are needed to determine whether the Sodic subgroup classification is warranted for most acreage of Thiokol. Low rainfall phases of Thiokol and phases of Thiokol in Idaho will be correlated to a series with an aridic moisture regime.
The active cation exchange activity class was added to the taxonomic classification in December 2002 based on soil property data.
In Utah some phases of this series are correlated with Semidesert range sites.
In future correlations, areas currently mapped Thiokol that are in nonirrigated cropland will be correlated as Sodic Calcixerepts.
In August 1994 the classification was changed from Xerollic Calciorthids to Sodic Xeric Haplocalcids. This incorporated the sodic feature and updated the series according to the Aridisol amendment.
ADDITIONAL DATA: The typical pedon at the series type location has partial characterization data by the Soils Laboratory from Utah State University (USU) Logan, UT and is published on pages 216-217, Table 9 of the Soil Survey of Box Elder County, Utah, Eastern Part.