LOCATION IRION TXEstablished Series
TAXONOMIC CLASS: Fine, smectitic, thermic Typic Haplusterts
TYPICAL PEDON: Irion clay--rangeland. (Colors are for dry soil unless otherwise stated).
A1--0 to 4 inches; very dark grayish brown (10YR 3/2) clay, very dark grayish brown (10YR 3/2) moist: moderate fine subangular blocky structure; slightly hard, friable, very sticky, very plastic: common fine roots; few fine limestone pebbles; strongly effervescent; moderately alkaline; clear smooth boundary.
A2--4 to 14 inches; dark grayish brown (10YR 4/2) clay, very dark grayish brown (10YR 3/2) moist; moderate fine and medium angular blocky structure; very hard, very firm, very sticky, very plastic; few fine roots, few shiny ped surfaces; few fine and medium limestone pebbles; strongly effervescent; moderately alkaline; gradual smooth boundary. (Combined thickness of the A horizon is 8 to 24 inches)
Bss1--14 to 40 inches; dark grayish brown (10YR 4/2) clay, very dark grayish brown (10YR 3/2) moist; moderate medium prismatic structure parting to moderate fine and medium angular blocky; very hard, very firm, very sticky, very plastic; few fine roots on surface of peds; many prominent slickensides; few shiny ped surfaces; few fine and coarse limestone pebbles; strongly effervescent; moderately alkaline; gradual smooth boundary.
Bss2--40 to 54 inches; dark grayish brown (10YR 4/2) clay, very dark grayish brown (10YR 3/2) moist: weak medium prismatic structure parting to weak medium angular blocky; very hard, very firm, very sticky, very plastic; few fine roots on surface of peds; common prominent slickensides; few brown (10YR 4/3) stains on ped surfaces; few black concretions; common fine limestone pebbles; strongly effervescent; moderately alkaline; gradual smooth boundary. (Combined thickness of Bss horizons is 20 to 60 inches)
Bk--54 to 72 inches; grayish brown (10YR 5/2) clay, dark grayish brown (10YR 4/2) moist; weak medium prismatic structure parting to weak coarse angular blocky; very hard, very firm; common shiny ped surfaces; common brown (10YR 4/3) stains on ped surfaces; few fine limestone pebbles; few masses of calcium carbonate in lower part; strongly effervescent; moderately alkaline; abrupt smooth boundary. (0 to 28 inches thick)
R--72 to 75 inches; indurated platy limestone interbedded with thin layers of marl.
TYPE LOCATION: Crockett County, Texas; from the intersection of Texas Highway 137 and Texas Highway 163 about 1 mile north of Ozona; 5.4 miles north on Texas Highway 163; 3.7 miles east on Crockett County road 109; 1.7 miles east and 0.4 mile south on private ranch road; 510 feet southwest in rangeland. (Latitude: 30N, 49, 26; Longitude: 101W, 05, 18).
RANGE IN CHARACTERISTICS: Solum thickness and depth to indurated limestone is 60 to more than 80 inches. Slickensides begin at a depth of 8 to 24 inches. Gilgai microrelief on native rangeland have microlows that are 2 to 12 inches lower than the microhigh. Distance between microhighs and microlows ranges from 6 to 15 feet. Texture is clay or silty clay throughout. In any horizon, limestone cobbles, stones, and gravels comprise 0 to 15 percent by volume.
The A horizon has color with hue of 7.5YR, 10YR, or 2.5Y, value of 2 to 5, and chroma of 1 to 3. Color is the same on microhigh and microlows.
The Bss horizon has color with hue of 7.5YR or 10YR, value of 3 to 5, and chroma of 1 to 3.
The Bk horizon, where present, has color with hue of 5YR, 7.5YR, or 10YR, value of 4 to 6, and chroma of 2 to 4. Concretions and masses of calcium carbonate range from few to common.
The Bw horizon, where present, has color with hue of 7.5YR, 10YR, or 2.5Y, value of 4 to 6, and chroma of 1 to 3.
COMPETING SERIES: These are the Campwood, Hollister, Indiahoma, Leeray, Lockney, Roscoe, and Teagard series. All of these soils do not have limestone bedrock within 80 inches of the surface. In addition, Campwood soils formed in alluvium on terraces. Hollister soils formed in alluvial sediments on broad terraces and have cooler mean annual temperature. Indianhoma soils formed in Permian age sediments, have linear shaped microhighs and have cooler mean annual temperature. Leeray soils formed in alluvial sediments and have SAR of 8 to more than 15 within 40 inches of the surface. Lockney soils are moderately well drained, formed in eolian sediments of the High Plains, and have cooler mean annual temperature. Roscoe soils are on flats and are moderately well drained. Teagard soils have sola less than 40 inches thick over claystone.
GEOGRAPHIC SETTING: Iron soils are in slightly concave depressions. Slope ranges from 0 to 1 percent. These soils formed in clayey sediments over fractured limestone bedrock of the Buda Limestone Formation of Cretaceous age. Mean annual precipitation ranges from 13 to 22 inches. Mean annual temperature ranges from 64 to 69 degrees F. Elevation ranges from 2,200 to 2,800 feet. Frost-free days range from 220 to 240. The Thornthwaite PE index is 24 to 36.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Tobosa series and also Ector, Kavett, Noelke, Ozona, and Texon series. Tobosa soils are slightly higher in position on broad flats. Ector and Noelke soils are shallow to very shallow to bedrock and are in higher positions. Kavett soils are shallow to a petrocalcic and are in higher positions. Texon soils are very deep to limestone bedrock on higher positions.
DRAINAGE AND PERMEABILITY: Well drained. Permeability is very slow. Runoff is negligible. In about 1 year out of 10 ponding duration can be a month or more.
USE AND VEGETATION: Used mostly for rangeland but a few areas are cropped to cotton, grain sorghum, and wheat. Native vegetation is buffalograss, curly mesquitegrass, threeawn, buffalo bur, prickly pear, and mesquite trees.
DISTRIBUTION AND EXTENT: Texas in Western Edwards Plateau (MLRA 81A) and possibly Central Edwards Plateau (MLRA 81B). The series is of minor extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas.
SERIES ESTABLISHED: Crockett County, Texas: 2002. The series was proposed and established for a special survey of the Texas Range Station in 1938. The series was later deactivated and combined with the Lipan and Roscoe series. The series is reactivated to interpret soils originally proposed for the Irion series.
REMARKS: This soil was formerly included with the Roscoe and Lipan series.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon -- 0 to 14 inches (Al and A2 horizons)
Vertisol feature -- Slickensides from 14 to 54 inches (Bssl and Bss2
horizon) and cracks that open and close periodically.
Cambic horizon -- 54 to 72 inches (Bk horizon)
Lithic contact -- at 72 inches (R horizon)
Vegetative Site: Clay Flat, (081AY290TX) (081BY323TX)
ADDITIONAL DATA: None
TAXONOMIC VERSION: Soil Taxonomy, Second Edition, 1999.