LOCATION OBEN TXEstablished Series
TAXONOMIC CLASS: Loamy, mixed, active, thermic, shallow Typic Haplustalfs
TYPICAL PEDON: Oben fine sandy loam--rangeland. (Colors are for dry soil unless otherwise stated).
A--0 to 5 inches; reddish brown (5YR 5/4) fine sandy loam, reddish brown (5YR 4/4) moist; weak fine subangular blocky structure and single grained; slightly hard, very friable; common roots; common fine tubes and pores; 10 percent of weakly cemented angular fragments of sandstone less than 3 inches thick; neutral; clear smooth boundary. (4 to 7 inches thick)
Bt1--5 to 14 inches; yellowish red (5YR 5/6) fine sandy loam, yellowish red (5YR 4/6) moist; weak medium subangular blocky structure; slightly hard, very friable, slightly sticky; common fine and medium roots; common fine tubes and pores; few clay films; 5 percent angular fragments of sandstone from 1/2 to 1 1/2 inches across; neutral; abrupt wavy boundary. (4 to 10 inches thick)
Bt2--14 to 19 inches; yellowish red (5YR 5/6) sandy clay loam, yellowish red (5YR 4/6) moist; weak very fine subangular blocky and granular structure; hard; friable, sticky; common fine roots; few pores; 65 percent fragments of soft sandstone, 1 to 2 inches thick and 4 to 10 inches long, that can be easily cut with a spade when moist; neutral; abrupt wavy boundary. (1 to 6 inches thick)
Cr--19 to 30 inches; brownish yellow (10YR 6/6) weakly cemented sandstone, less than 3 on Moh's scale; fractured and somewhat platy in upper part; neutral.
TYPE LOCATION: Gillespie County, Texas; About 14 miles north of Fredericksburg, Texas, from the intersection of U.S. Highway 290 and Texas Highway 16 in Fredericksburg, 13 miles north on Texas Highway 16 to the junction with Ranch Road 1323, 1.5 miles east on Ranch Road 1323, 0.5 mile north on private road, 100 feet east in rangeland.
RANGE IN CHARACTERISTICS: Solum thickness to sandstone ranges from 9 to 20 inches. The weighted average of coarse fragments in the solum ranges from a few to about 30 percent by volume. These are partially weathered sandstone of pebble to cobble or flagstone size. Coarse fragments on the surface range from none to 15 percent, and from pebble to stone size. Reaction is slightly acid or neutral.
The A horizon has hue of 5YR or 7.5YR, value of 4 to 6, and chroma of 4.
The Bt horizon has hue of 5YR or 7.5YR, value of 4 to 6, and chroma of 3 to 6. Texture is fine sandy loam or sandy clay loam with 16 to 25 percent clay. In the lower Bt horizon of some pedons is 2 to 6 inches that contains 15 to 70 percent by volume of weakly cemented fragments of weathered sandstone. It is coarsely mottled reddish brown (5YR 4/3), red (2.5YR 4/6), reddish yellow (7.5YR 6/6), or strong brown (7.5YR 5/6) material that easily crushes to sandy loam or sandy clay loam.
The Cr horizon is yellowish or reddish, weakly to strongly cemented, noncalcareous sandstone with a hardness of less than 3 on Moh's scale.
COMPETING SERIES: There are no soils in the same family. Similar soils include the Cosh, Exray, Hye, Jolly, and Nebgen soils. Cosh and Exray soils have argillic horizons redder than 5YR and moist values less than 4. In addition, Exray soils have a clayey control section. Hye soils have sola 20 to 40 inches thick. Jolly soils have siliceous minerology. Nebgen soils do not have argillic horizons.
GEOGRAPHIC SETTING: Oben soils are on undulating uplands having surfaces that are plane to covex. Slope gradients range from 1 to 8 percent. These soils developed in reddish sandstone that contains an appreciable amount of glauconite such as the Hickory Formation of the Cambrian Age. Mean annual precipitation ranges from 24 to 30 inches and, mean annual temperature ranges from 65 to 67 degrees F. Frost free period is 215 to 235 days, and elevation ranges from 1,000 to 2,000 feet. Thornthwaite P-E indices range from 36 to 46.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the Campair, Hye, Loneoak, Matilo, Nebgen and Pontotoc soils. Campair, Hye, Loneoak, Matilo and Pontotoc soils are deeper than 20 inches to sandstone. In addition Campair, Loneoak and Matilo soils have sandy surface layers. Campair, Hye, Loneoak, Matilo, and Pontotoc soils are on slightly lower positions. Nebgen soils are on similar or slightly higher positions.
DRAINAGE AND PERMEABILITY: Well drained. Permeability is moderate. Runoff is very low on 1 to 3 percent slopes, low on 3 to 5 percent slopes, and medium on 5 to 8 percent slopes.
USE AND VEGETATION: Used mainly as rangeland. Native vegetation consists of threeawns, little bluestem, sideoats grama, dropseed, windmillgrass, sand lovegrass, purpletop, and green sprangletop with a few postoak, liveoak and mesquite trees.
DISTRIBUTION AND EXTENT: South-central Texas. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Gillespie County, Texas 1970.
REMARKS: Diagnostic horizons or features recognized in this pedon are:
Ochric epipedon --0 to 5 inches (A horizon)
Argillic horizon --5 to 19 inches (Bt horizons)
Paralithic contact with sandstone at 19 inches
Soil Interpretation Record: TX0516; STONY TX0517