LOCATION OBEN                    TX

Established Series


The Oben series consists of shallow, well drained soils that formed in weakly cemented sandstone. These soils are on nearly level to moderately sloping backslopes, shoulders and summits of ridges.. Slope ranges from 1 to 8 percent. Mean annual air temperature is about 19 degrees C (66 degrees F), and mean annual precipitation is about 711 mm (28 in).

TAXONOMIC CLASS: Loamy, mixed, active, thermic, shallow Typic Haplustalfs

TYPICAL PEDON: Oben fine sandy loam--in rangeland. (Colors are for dry soil unless otherwise stated).

A--0 to 13 cm (0 to 5 in); 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, 2 to 75 mm, sandstone gravels, flat, angular, weakly cemented; neutral; clear smooth boundary. (Thickness of the A horizon is 10 to 18 cm [4 to 7 in])

Bt1--13 to 36 cm (5 to 14 in); 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, 12 to 38 mm, sandstone, flat, angular; neutral; abrupt wavy boundary.

Bt2--36 to 48 cm (14 to 19 in); 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, 25 to 51 mm thick and 100 to 250 mm long, sandstone, flat, weakly cemented,that can be easily cut with a spade when moist; neutral; abrupt wavy boundary. (Combined thickness of the Bt horizon is 12 to 41 cm [5 to 16 in] thick)

Cr--48 to 76 cm (19 to 30 in); 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; From the intersection of Highway 16 and Ranch Road 1323, approximately 14 miles north of Fredericksburg, 1.4 miles east on Ranch Road 1323, 0.2 mile north on Box Canyon Trail, and 50 feet west in rangeland. (Willow City USGS topographic quadrangle; Latitude: 30 degrees, 24 minutes, 45.5 seconds N; Longitude: 98 degrees, 42 minutes, 52.4 seconds W; NAD83.)

Solum thickness to sandstone: 23 to 50 cm (9 to 20 in)
Depth to paralithic contact: 23 to 50 cm (9 to 20 in)
Surface fragments: 0 to 15 percent by area, gravel to stone size.
Reaction: Slightly acid or neutral

Particle-size control section (weighted average)
Fragments: Amount-0 to 30 percent by volume, kind-weathered sandstone.
Clay content: 16 to 25 percent

A horizon
Hue: 5YR to 7.5YR
Value: 4 to 6, 3 to 5 moist
Chroma: 2 to 4, dry and moist
Texture: Loamy sand, sandy loam, or fine sandy loam
Other features: In pedons where moist value and chroma are 3 or less, the epipedon is not thick enough for a mollic epipedon.

Bt horizon
Hue: 5YR to 7.5YR
Value: 4 to 6, 3 to 5 moist
Chroma: 2 to 6, dry and moist
Texture: Fine sandy loam, loam, sandy clay loam, or clay loam; and extremely paragravelly, extremely parachannery, very paragravelly, very parachannery, paragravelly, and parachannery phases
Clay content: 16 to 30 percent
Coarse fragments: amount-0 to 35 percent, size-2-150 mm, kind-sandstone; in some pedons, the lower Bt horizon has 15 to 70 percent weakly cemented sandstone fragments.
Other notes: Some pedons have coarse mottles of hues 2.5YR to 7.5YR; values 4 to 6, 3 to 5 moist; chromas: 3 to 6, dry and moist.

Cr layer
Hue: 5YR to 10YR
Value: 3 to 6, 3 to 5 moist
Chroma: 2 to 6, dry and moist
Kind: noncalcareous sandstone
Cementation: weakly to strongly cemented
Hardness (Moh's scale): less than 3

COMPETING SERIES: There are no soils in the same family. Similar soils include the Cosh (TX), Exray (TX), Hye (TX), Jolly (TX), and Nebgen (TX) soils.
Cosh and Exray soils: have argillic horizons redder than 5YR.
Exray soils: have a clayey control section.
Hye soils: are 50 to 100 cm (20 to 40 in) to sandstone bedrock.
Jolly soils: have siliceous mineralogy.
Nebgen soils: do not have argillic horizons.

Parent material: Red sandstone that contains an appreciable amount of glauconite such as the Hickory Formation of the Cambrian Age.
Landscape: dissected plateaus
Landform: backslopes, shoulders and summits of ridges
Slope: 1 to 8 percent
Slope shape: plane to convex
Climate: Dry subhumid
Soil moisture: Typic ustic moisture regime
Precipitation Pattern: The majority of the yearly amount occurs during the fall and spring months. The winter and summer months are normally drier.
Mean annual temperature: 18 to 19 degrees C (65 to 67 degrees F)
Mean annual precipitation: 610 to 762 mm (24 to 30 in)
Frost-free period: 215 to 235 days
Elevation: 305 to 671 m (1,000 to 2,200 ft)
Thornthwaite P-E indices: 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 50 cm (20 in) to sandstone.
Campair, Loneoak, and Matilo soils: have sandy surface layers.
Campair soils are on footslopes, backslopes and shoulders of ridges underlain by Cambrian sandstone
Hye soils: are on footslopes of ridges underlain by Cambrian sandstone.
Loneoak and Matilo soils: are on undulating plains and footslopes of ridges underlain by Cambrian sandstone.
Nebgen soils: are on similar or slightly higher positions.

DRAINAGE AND PERMEABILITY: Well drained. The permeability is moderate. Runoff is negligible on slopes less than 1 percent, low on 1 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 post oak, live oak and mesquite trees.

DISTRIBUTION AND EXTENT: Central Texas; LRR-I; MLRA 82ATexas Central Basin. Central Great Plains Winter Wheat and Range Region, LRR-H: MLRA 78C-Central Rolling Red Plains, Western Part. This series is of moderate extent.


SERIES ESTABLISHED: Gillespie County, Texas 1970.

Diagnostic horizons or features recognized in this pedon are:
Ochric epipedon: 0 to 13 cm (0 to 5 in). (A horizon)
Argillic horizon: 13 to 48 cm (5 to 19 in). (Bt horizons)
Paralithic contact: 48 cm (19 in) with sandstone


TAXONOMIC VERSION: Keys to Soil Taxonomy, 11th Edition, 2010.

National Cooperative Soil Survey