LOCATION ABAJO UTEstablished Series
TAXONOMIC CLASS: Fine, smectitic, mesic Udic Paleustolls
TYPICAL PEDON: Abajo loam, rangeland. (Colors are for air dry soil unless otherwise noted.)
A1--0 to 2 inches; brown (7.5YR 5/3) loam, dark reddish brown (5YR 3/3) moist; weak medium blocky structure that parts to weak fine granular; hard, friable, slightly sticky, slightly plastic; many fine roots; few fine pores; neutral (pH 7.2); abrupt wavy boundary. (8 to 14 inches thick)
A2--2 to 10 inches; reddish brown (5YR 4/3) sandy clay loam, dark reddish brown (5YR 3/3) moist; weak medium blocky structure that parts to weak fine granular; hard, friable, slightly sticky, slightly plastic; many fine roots; few fine pores; neutral (pH 7.1); abrupt wavy boundary. (1 to 2 inches thick)
Bt1--10 to 20 inches; reddish brown (5YR 5/4) clay, reddish brown (5YR 4/4) moist; moderate fine prismatic structure that parts to moderate fine subangular blocky; extremely hard, very firm, sticky, very plastic; few fine roots; few fine pores; moderately thick continuous clay films; neutral (pH 7.1); clear wavy boundary. (6 to 10 inches thick)
Bt2--20 to 40 inches; brown (7.5YR 5/4) cobbly clay loam, brown (7.5YR 4/4) moist; moderate medium prismatic structure that parts to moderate fine and very fine subangular blocky; extremely hard, very firm, very sticky, plastic; few fine roots; moderately thick continuous clay films; slightly calcareous; about 25 percent cobbles, some are highly weathered; moderately alkaline (pH 7.9); clear wavy boundary. (20 to 28 inches thick)
C--40 to 50 inches; brown (7.5YR 5/4) cobbly clay loam, brown (7.5YR 4/4) moist; massive; very hard, very firm, very sticky, plastic; about 35 percent cobbles, highly weathered; slightly calcareous; moderately alkaline (pH 8.2).
TYPE LOCATION: San Juan County, Utah; 3 miles south of courthouse in Monticello; west bank cut of Highway U47; E 1/4 corner of section 13, T.34S., R.23E.
RANGE IN CHARACTERISTICS:
Mollic epipedon thickness: 10 to 16 inches
Depth to bedrock: 40 to more than 60 inches
Mean annual soil temperature: 47 degrees to 50 degrees F.
Soil moisture: Intermittently moist in the soil moisture control section in some part during July-September and December-March. Driest during May and June. Soil moisture regime is udic ustic.
A horizon
Hue: 5YR or 7.5YR
Value 4 or 5 dry, 2 or 3 moist
Chroma: 2 or 3 moist and 3 or 4 dry.
Rock fragments: The surface is cobbly in places. In some pedons the A horizon consists largely of eolian deposits
B2t horizon
Hue: 5YR or 7.5YR
Value: 5 or 6 dry, 4 or 5 moist
Chroma: 4 through 6
Texture: clay, heavy clay loam or cobbly heavy clay loam. Generally the upper part of the B2t horizon is not cobbly
Calcium carbonate equivalent: 1 to 5 percent.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: These soils are on old stream terraces and fans at elevations of 6,800 feet to 7,500 feet. Slopes are 0 to 25 percent. These soils formed in alluvium mainly from intrusive igneous rocks, such as diorite, andesite, dacite and trachyte porphyries, but in some areas from sandstone. The climate is dry subhumid. The average annual precipitation is 15 to 17 inches. The mean annual air temperature is 46 degrees to 48 degrees F. and the frost-free period is about 130 to 140 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Ackmen, Monticello, Northdale, Scorup and Vega soils. All of these soils are fine-silty in the control section and have less than 35 percent clay. Also, Ackmen and Vega soils do not have argillic horizons.
DRAINAGE AND PERMEABILITY: Well-drained; medium to slow runoff; slow permeability in the B horizon.
USE AND VEGETATION: Used mainly for range and nonirrigated winter wheat. Some are used for irrigated crops of alfalfa, small grains and improved pasture. The natural vegetation is mainly oakbrush, bitterbrush, big sagebrush, junegrass, western wheatgrass, and a few yellow pine trees.
DISTRIBUTION AND EXTENT: Southeastern Utah, possibly adjacent parts of Colorado. These soils are moderately extensive. MLRA is 39 and 48A.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Phoenix, Arizona
SERIES ESTABLISHED: San Juan Area. Utah, 1952
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - The zone from the surface of the soil to a depth of about 10 inches. (A horizons)
Argillic horizon - The zone from 10 inches to a depth of 40 inches. (Bt horizons)