LOCATION IRONCO UTEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, frigid Aridic Argiustolls
TYPICAL PEDON: Ironco extremely cobbly loam, on a 40 percent east facing slope -- rangeland. (Colors are for air dry soil unless otherwise noted.)
A1--0 to 4 inches; brown (10YR 5/3) extremely cobbly loam, dark brown (7.5YR 3/2) moist; weak fine granular structure; soft, friable, slightly sticky and slightly plastic; few coarse and medium, common fine and many very fine roots; few medium, common fine and many very fine tubular pores; 35 percent cobbles and 25 percent gravel; neutral (pH 7.2); clear smooth boundary. (3 to 4 inches thick)
A2--4 to 11 inches; brown (10YR 5/3) very cobbly loam, very dark brown (7.5YR 3/2) moist; moderate very fine granular structure; soft, friable, moderately sticky and slightly plastic; few medium and fine and common very fine roots; few medium and common fine and very fine tubular pores; 15 percent cobbles and 25 percent gravel; slightly alkaline (pH 7.4); clear wavy boundary. (2 to 9 inches thick)
Bt1--11 to 15 inches; brown (7.5YR 5/4) very gravelly clay loam, dark brown (7.5YR 3/4) moist; moderate medium subangular blocky structure parting to moderate very fine subangular blocky; hard, firm, moderately sticky and moderately plastic; few medium and fine, and common very fine roots; few medium, common fine and many very fine pores; few faint clay films on faces of peds and on rock fragments; 10 percent cobbles and 25 percent gravel; slightly alkaline (pH 7.6); clear irregular boundary. (4 to 10 inches thick)
Bt2--15 to 25 inches; brown (7.5YR 5/4) very cobbly clay loam, dark brown (7.5YR 3/4) moist; moderate medium subangular blocky structure; hard, firm, moderately sticky and moderately plastic; few medium, fine and very fine roots; few medium, common fine and many very fine tubular pores; common distinct clay films on faces of peds and on rock fragments; 15 percent cobbles and 25 percent gravel; slightly alkaline (pH 7.6); gradual smooth boundary. (10 to 21 inches thick)
Bt3--25 to 46 inches; brown (7.5YR 5/4) very gravelly clay loam, dark brown (7.5YR 4/4) moist; moderate medium subangular blocky structure parting to strong very fine subangular blocky; hard, firm, moderately sticky and moderately plastic; few fine and very fine roots; few medium and common fine and very fine tubular pores; common distinct clay films on faces of peds and on rock fragments; thin carbonate coating on underside of some rock fragments; 10 percent cobbles and 30 percent gravel; slightly alkaline (pH 7.6); gradual wavy boundary. (0 to 21 inches thick)
Bt4--46 to 60 inches; yellowish red (5YR 5/6) very gravelly clay loam, yellowish red (5YR 4/6) moist; moderate medium subangular blocky structure parting to strong very fine subangular blocky; very hard, firm, moderately sticky and moderately plastic; few fine and very fine roots; few fine and common very fine tubular pores; many distinct clay films on faces of peds and on rock fragments; 5 percent cobbles and 40 percent gravel; slightly alkaline (pH 7.6).
TYPE LOCATION: Iron County, Utah; about 2.2 miles north-northeast of Silver Peak; 1,850 feet west of the SE corner of section 32, T.35S., R.14W; lat. 37 degrees 42 minutes 25 seconds N. and long. 113 degrees 26 minutes 20 seconds W., NAD27
RANGE IN CHARACTERISTICS:
Soil moisture: The soil moisture control section is moist in some part 35 to 50 days during the summer and dry for 60 to 90 days during the 120 days following the winter solstice. The soil moisture control section is affected by precipitation that is evenly distributed through the year with the exception of a significant increase in the early spring with May and June being the driest months. The soil moisture regime is ustic bordering on aridic.
Mean annual soil temperature: 42 to 47 degrees F.
Mean annual summer soil temperature: 65 to 70 degrees F.
Thickness of the mollic epipedon: 10 to 15 inches
Depth to the base of the argillic horizon: 54 or more inches
Particle-size control section (weighted average): 27 to 35 percent clay and 35 to 50 percent rock fragments.
A horizon:
Hue: 5YR through 10YR
Value: 4 or 5 dry, 2 or 3 moist
Chroma: 1 to 3 dry or moist
Texture: very cobbly loam, extremely cobbly loam, very gravelly loam, or very bouldery loam
Reaction: neutral or slightly alkaline
Bt horizon:
Hue: 2.5YR through 7.5YR
Value: 4 to 6 dry, 3 to 5 moist
Chroma: 3 to 6 dry or moist
Texture: very stony sandy clay loam, very stony clay loam, very gravelly clay loam, very cobbly clay loam
Rock fragments: 35 to 50 percent
Reaction: neutral to moderately alkaline, but may range to slightly acid below 40 inches.
COMPETING SERIES: These are the Badito, Hauz, San Isabel, Simmont, and Zillman series.
Badito,
Hauz and Simmont: have a lithic contact between 20 and 40 inches deep
San Isabel: have a lithologic discontinuity with sandy-skeletal materials at 10 to 20 inches deep
Zillman: have argillic horizons whose base does not extend below 30 inches and have soil moisture control sections that are more moist during the months of
May and June.
GEOGRAPHIC SETTING:
Parent material: slope alluvium and colluvium derived from intermediate igneous rocks
Landform: mountain slopes
Slopes: 6 to 60 percent
Elevation: 6,400 to 8,000 feet
Mean annual temperature: 40 to 45 degrees F.
Mean annual precipitation: 12 to 16 inches with early spring being the wettest months and May and June being the driest months
Freeze-free period: 80 to 120 days
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Quilt and Ocambee soils. Quilt soils have more than 35 percent clay in the control section. Ocambee soils have bedrock at depths of 20 to 40 inches and have greater than 35 percent clay in the control section. These soils are intermixed on the landscape with the Ironco soils.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately slow permeability.
USE AND VEGETATION: These soils are used as rangeland and wildlife habitat. Native vegetation is pinyon, Utah juniper, woody phlox, Gambel oak, big sagebrush, birchleaf mountainmahogany, prickley gilia, lupine, tall native bluegrass, mountain junegrass, bottlebrush, squirreltail and Sandberg bluegrass.
DISTRIBUTION AND EXTENT: Southwestern Utah. The Ironco series is not extensive. LRR E, MLRA 47.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Moffat County, (Moffat County Area), Colorado, 1992.
REMARKS: This soil was reclassified from a Typic Argiborolls to an Aridic Argiborolls in October 1994 based on 12 to 16 inch precipitation and upland range sites. Classification was changed to superactive, frigid Aridic Argiustolls 12/98. The pedon used to establish the series in the Moffat County Area, Colorado soil survey is typic ustic and is excluded from the current Ironco concept. Any previous pedons correlated to the Ironco series in northeastern Utah or northwestern Colorado no longer fit the current Ironco concept.
The diagnostic features and horizons recognized in this pedon are:
Particle-size control section - the zone from 11 to 31 inches (Bt1, Bt2, and Bt3 horizons).
Mollic epipedon - the zone from the soil surface to a depth of 11 inches (A and BA horizons).
Argillic horizon - the zone from 11 to 60 inches (Bt horizons).
Taxonomic version: Eighth Edition, 1998.