LOCATION THUMBROCK UT+AZ CO
Established Series
Rev. KS/RLB
11/2022
THUMBROCK SERIES
The Thumbrock series consists of moderately deep, well drained, moderately rapidly permeable soils that formed in alluvium, colluvium and reworked eolian material weathered from sandstone or limestone. Thumbrock soils are on dissected pediments and hills. Slopes are 2 to 25 percent. The average annual precipitation is about 12 inches, and the mean annual air temperature is about 48 degrees F.
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, mesic Ustic Haplocalcids
TYPICAL PEDON: Thumbrock stony very fine sandy loam-rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 4 inches; yellowish red (5YR 5/6) stony very fine sandy loam, yellowish red (5YR 4/6) moist; weak thick platy crust 1 inch thick; weak fine granular structure below; soft, very friable; few medium and fine roots; 15 percent fine gravel; about 15 percent of the surface covered by stones; slightly calcareous; carbonates are disseminated; moderately alkaline (pH 8.0); clear smooth boundary. (2 to 7 inches thick)
Bw--4 to 10 inches; red (2.5YR 5/6) very fine sandy loam, red (2.5YR 4/6) moist; moderate medium subangular blocky structure; slightly hard, firm, slightly sticky and slightly plastic; few medium and fine roots; common fine and many very fine pores; 14 percent fine gravel; slightly calcareous; carbonates are disseminated; moderately alkaline (pH 8.2); abrupt wavy boundary. (3 to 14 inches thick)
Bk1--10 to 17 inches; pink (5YR 7/4) fine sandy loam, light reddish brown (5YR 6/4) moist; moderate medium platy structure; hard, slightly sticky and slightly plastic; few fine and very fine roots; few fine pores; very strongly calcareous; carbonates are weakly cemented; strongly alkaline (pH 8.6); clear smooth boundary. (5 to 12 inches thick)
Bk2--17 to 24 inches; pink (5YR 7/4) gravelly fine sandy loam, light reddish brown (5YR 6/4) moist; massive; slightly hard, firm; few very fine roots; common very fine pores; 25 percent gravel; very strongly calcareous; carbonates are weakly cemented; strongly alkaline (pH 8.6); abrupt wavy boundary. (5 to 13 inches thick)
R--24 inches; sandstone.
TYPE LOCATION: San Juan County, Utah; 1 mile northeast of Navajo Mountain School; SE 1/4 sec. 22, T. 43 S., R. 10 E.
RANGE IN CHARACTERISTICS:
Soil moisture - moist in 7 out of 10 years the soils are dry in all parts of the moisture control section for 50 to 75 percent of the time (cumulative) that the soil temperature at depth of 20 inches is above 41 degrees F. They are moist in some part of the moisture control section for 30 to 40 days during the summer and are dry in some parts of the moisture control section for 60 to 90 consecutive days during winter and early spring. Ustic aridic soil moisture regime.
Mean summer soil temperature at depth of 20 inches: 61 to 65 degrees F.
Mean annual soil temperature: 47 to 58 degrees F.
Depth to calcic horizon: 5 to 21 inches
Depth to bedrock: 20 to 40 inches deep over limestone and sandstone
A horizon
Hue: 7.5YR, 5YR, 2.5YR
Value: 5 or 6 dry, 3 to 5 moist
Chroma: 2 to 6, dry or moist
Rock fragment: 0 to 20 percent rock fragment and up to 15 percent stones cover surface
Reaction: slightly alkaline or moderately alkaline and is noneffervescent to slightly effervescent
Bw horizon
Hue: 7.5YR, 5YR, 2.5YR
Value: 4 to 7 dry, 3 to 6 moist
Chroma: 3 to 8, dry or moist
Texture: very fine sandy loam to fine sandy loam, sandy loam, loam, gravelly loam or gravelly loamy fine sand and has 5 to 20 percent gravel
Reaction: slightly alkaline to strongly alkaline, and slightly effervescent to moderately effervescent
Bk horizon
Hue: 7.5YR, 5YR, 2.5YR
Value: 5 to 8 dry, 4 to 7 moist
Chroma: 2 to 6 dry or moist
Texture: fine sandy loam, very fine sandy loam, loam, sandy loam
Rock fragments: 15 to 35 percent rock fragments
Reaction: moderately alkaline to strongly alkaline
Calcium carbonate equivalent: 15 to 40 percent
COMPETING SERIES: These are the
Abracon (UT),
Chroder (CO),
Chugcity (WY),
Chupadera (NM),
Cobbra (UT),
Harvey (NM),
Milok (UT),
Mivida (UT),
Nala (NM)
Sazi (UT), and
Yattle (CO) series. Abracon, Chroder, Cobbra, Harvey, Milok, Mivida, Nala and Yattle soils are deeper than 40 inches to bedrock. Chugcity soils have paralithic contact between 20 and 40 inches. Chupadera soils have hues yellower than 7.5YR and lack cambic horizons. Sazi soils contain less than 15 percent rock fragments in the particle-size control section. Chugcity, Chupadera, Harvey, Nala, and Yattle soils are in the Western Great
Plains (LRR-G) and are more moist in
May and June.
GEOGRAPHIC SETTING: Thumbrock soils are on dissected pediments, cuestas and hills at elevations of 5,400 to 7,000 feet. Slope gradients are 2 to 25 percent. These soils formed in alluvium, colluvium, and residuum and reworked eolian material weathered from sandstone or limestone. The climate is semiarid and the average annual precipitation ranges from 8 to 14 inches. The mean annual temperature is 45 to 56 degrees F. The mean summer temperature is 59 to 63 degrees F. and the freeze-free period ranges from 90 to 170 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
Begay,
Milok,
Mivida,
Palma,
Shedado and
Windwhistle soils. Begay, Mivida, and Milok soils lack a lithic contact within depth of 40 inches. Palma and Windwhistle soils have argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained; moderate to rapid runoff; moderate or moderately rapid permeability.
USE AND VEGETATION: These soils are used for livestock grazing. Potential vegetation is pinyon, juniper, blackbrush, Mormon tea and Indian ricegrass.
DISTRIBUTION AND EXTENT: Eastern Utah, South-Central Utah, Northern Arizona, and Southwestern Colorado. MLRA 35. Thumbrock soils are extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: San Juan County, Utah, 1976
REMARKS:
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface of the soil to 4 inches (A horizon)
Cambic horizon - the zone from 4 to 10 inches (Bw horizon)
Calcic horizon - the zone from 10 to 24 inches (Bk1 and Bk2 horizons)
Lithic contact - the boundary at 24 inches (R horizon)
The carbonates described as "weakly cemented" are assumed to slake in water
Ustic intergrade - soil moisture regime borders on an ustic regime
Classified according to Soil Taxonomy, Second Edition, 1999; Keys to Soil Taxonomy, Tenth Edition, 2003.
Update and revisions for the correlation of Glen Canyon National Recreation Area, January 2010, CEM
National Cooperative Soil Survey
U.S.A.