LOCATION OZONA TXEstablished Series
TAXONOMIC CLASS: Loamy, mixed, superactive, thermic, shallow Petrocalcic Calciustolls
TYPICAL PEDON: Ozona silty clay loam--rangeland. (Colors are for dry soil unless otherwise stated)
A1--0 to 2 inches; brown (10YR 5/3) silty clay loam, dark brown (10YR 3/3) moist; moderate fine and medium granular structure; slightly hard, friable; common very fine and fine roots; common fine and medium interstitial pores; about 2 percent weathered limestone fine gravel; slightly effervescent; moderately alkaline; clear smooth boundary. (2 to 10 inches thick)
A2--2 to 10 inches; brown (7.5YR 4/3) silty clay loam, dark brown (7.5YR 3/3) moist; weak coarse prismatic structure parting to moderate medium and coarse subangular blocky; hard, firm; common very fine and fine roots; common very fine and fine interstitial pores; about 2 percent weathered limestone fine and medium gravel; slightly effervescent; moderately alkaline; clear smooth boundary. (4 to 10 inches thick)
Bk--10 to 16 inches; brown (7.5YR 5/3) silty clay loam, brown (7.5YR 4/3) moist; weak coarse prismatic structure parting to moderate medium and coarse subangular blocky; hard, firm; common very fine and fine roots; common very fine and fine interstitial pores; about 2 percent fine threads and concretions of calcium carbonate; about 10 percent weathered caliche fragments; strongly effervescent; moderately alkaline; abrupt wavy boundary. (0 to 10 inches thick)
Bkm--16 to 24 inches; very pale brown (10YR 8/2) caliche, very pale brown (10YR 7/3) laminar cap about 1 cm thick on upper surface; strongly cemented, massive; few thin laminae streaks of very pale brown (10YR 7/3); few solution channels filled with brown (7.5YR 5/3) silty clay loam material; violently effervescent; moderately alkaline; abrupt wavy boundary. (4 to 12 inches thick)
Bk'--24 to 80 inches; very pale brown (10YR 8/2) weakly cemented calcareous loamy materials that has distinct layers of weathered material; 1 to 2 percent soil material between plates that is discontinuous horizontally; violently effervescent; moderately alkaline.
TYPE LOCATION: Crockett County, Texas; from the intersection of Business Loop 466 and Texas Highway 163 in Ozona; 14.4 miles north on Texas Highway 163; 4.6 miles west on U. S. Highway 190; 0.9 mile north on ranch road; 80 feet east in rangeland. (Latitude: 30N, 55, 24; Longitude: 101W, 14, 15)
RANGE IN CHARACTERISTICS: Solum thickness and depth to the petrocalcic horizon is 6 to 20 inches. The texture above the petrocalcic horizon is silty clay loam or clay loam. Total clay content ranges from about 28 to 40 percent, and silicate clay content ranges from 25 to 35 percent.
The A horizon has hue of 7.5YR or 10YR, value of 3 to 5, and chroma of 2 or 3.
The Bk horizon has hue of 7.5YR or 10YR. value of 3 to 5, and chroma of 3 to 5. Fragments of caliche, from 1/4 to 3 inches across, range from few in the upper part to as much as 45 percent just above the petrocalcic horizon.
The Bkm horizon ranges from strongly cemented to indurated. The upper 1 to 2 cm is laminar.
The Bk' horizon is weakly to moderately cemented with calcium carbonate and contains degrading caliche gravel and limestone gravel and cobbles.
COMPETING SERIES: These include the Carbine, Espy, Kimbrough, Pitzer, and Queeny series in the same family, and the Amistad, Boracho, Cho, Eola, Kavett, Mailtrail, Mereta, Noelke, and Zorra series in similar families. Carbine soils have a petrocalcic horizon thicker than 20 inches and receive significant winter precipitation. Espy soils are formed in loamy over gravelly igneous materials. Kimbrough soils have a mollic epipedon to the indurated petrocalcic horizon. Pitzer and Queeny soils are in more moist climates and have a gravelly substrata containing siliceous and limestone fragments. Amistad, Boracho, Eola, Mailtrail, Noelke, and Zorra soils have more than 35 percent coarse fragments in the particle-size control section. Cho, Eola, and Mailtrail soils have more than 40 percent calcium carbonate equivalent in the particle-size control section. Kavett and Mereta soils have a clayey particle-size control section.
GEOGRAPHIC SETTING: Ozona soils are on nearly level to gently sloping plains of the Edwards Plateau. Slopes are mainly less than 2 percent, but range to 3 percent. The soil formed in calcareous loamy eolian sediments and sediments derived from marl and limestone of the Cretaceous age Buda Limestone Formation. Mean annual precipitation ranges from 15 to 22 inches. Mean annual temperature ranges from 67 to 69 degrees F. Frost-free season ranges from 220 to 260 days. Elevation ranges from 2,000 to 2,700 feet. Thornthwaite P-E index ranges from 24 to 36.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Kavett, Mailtrail, and Noelke series, and the Angelo, Ector, Irion, Tarrant, Texon, and Tobosa series. Kavett soils are on similar landscape positions. Mailtrail soils are on footslope fan positions. Noelke soils are on slightly higher positions. Angelo soils are very deep and are in smooth valley fill positions. Ector and Tarrant soils are underlain by limestone bedrock within 20 inches and are on rims above slope breaks. Irion and Tobosa soils are in slight concave positions and have a clayey particle-size control section. Texon soils are on similar landscapes and are very deep. Noelke and Texon soils are mapped in a complex with Ozona soils in some areas.
DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderate above the petrocalcic horizon, very slow in the petrocalcic, and moderately slow below the petrocalcic. Runoff is low on slopes of 0 to 1 percent and medium on 1 to 3 percent slopes.
USE AND VEGETATION: Used mainly for rangeland. Native grasses are buffalograss, tobosagrass, Hall's panicum, and curly mesquite. Native woody plants are mesquite, prickly pear, tasajillo, and cholla.
DISTRIBUTION AND EXTENT: Western Edwards Plateau of Texas (MLRA 81A). The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas.
SERIES ESTABLISHED: Crockett County, Texas; 2002.
REMARKS: The Ozona series was established with a special survey of the Texas Range Station in Crockett County in 1938. In 1974 the Ozona series was placed on the inactive list and combined with the Kavett and Mereta series. The series was reactivated with the 1998 survey of Crockett County, Texas to define soils that are very similar to the original concept of the Ozona series.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon--0 to 10 inches (A1 and A2 horizons).
Cambic horizon--10 to 16 inches (Bk horizon).
Petrocalcic horizon--16 to 24 inches (Bkm horizon).
ADDITIONAL DATA: TAMU Soil Characterization Laboratory data for the type location in Crockett County (S96TX-105-001).
TAXONOMIC VERSION: Soil Taxonomy, 2nd edition, 1999.