LOCATION TILVERN TX+OKEstablished Series
TAXONOMIC CLASS: Fine, mixed, active, thermic Vertic Haplustepts
TYPICAL PEDON: Tilvern clay loam--rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 5 inches; brown (7.5YR 4/2) clay loam, dark brown (7.5YR 3/2) moist; moderate fine and medium subangular blocky structure; very hard, firm; many fine and medium roots; few worm channels and casts; slightly alkaline; clear wavy boundary. (2 to 8 inches thick)
Bw--5 to 12 inches; reddish brown (5YR 4/4) clay, dark reddish brown (5YR 3/4) moist; moderate coarse angular blocky structure parting to moderate fine angular blocky; very hard, firm; common fine and medium roots; few worm channels and casts; dark coatings on surfaces of coarse peds; few fine concretions of calcium carbonate; noncalcareous; moderately alkaline; gradual wavy boundary. (6 to 14 inches thick)
Bk1--12 to 28 inches; reddish brown (5YR 5/4) silty clay, reddish brown (5YR 4/4) moist; moderate coarse angular blocky structure parting to moderate fine and medium angular blocky; very hard, firm; few fine and medium roots; few worm channels and casts; common old crack fills contain loamy material; common large pressure faces; common fine and medium concretions of calcium carbonate; strong effervescence; moderately alkaline; diffuse wavy boundary. (13 to 22 inches thick)
Bk2--28 to 46 inches; reddish brown (2.5YR 5/4) silty clay, reddish brown (2.5YR 4/4) moist; many wedge shaped peds tilted at 15 to 35 degrees from horizontal parting to moderate fine and medium angular blocky structure; very hard, firm; few fine roots; common fine and medium concretions of calcium carbonate; strong effervescence; moderately alkaline; gradual wavy boundary. (12 to 18 inches thick)
BCk--46 to 53 inches; reddish brown (2.5YR 5/4) silty clay, reddish brown (2.5YR 4/4) moist; moderate coarse subangular blocky structure parting to moderate fine and medium subangular blocky; very hard, firm; few fine roots; few medium distinct light olive gray (5Y 6/2) iron depletions; common pockets of crystals of gypsum and masses of calcium carbonate; common fine and few medium concretions of calcium carbonate; few weathered claystone fragments in lower part; strong effervescence; moderately alkaline; gradual wavy boundary. (0 to 8 inches thick)
Cd--53 to 80 inches; reddish brown (2.5YR 4/4) weakly consolidated claystone; dark reddish brown (2.5YR 3/4) moist; rock-like structure composed of wedge shaped aggregates that part to fine angular blocks; very hard, firm; common strata and mottles of light greenish gray (5GY 7/1); few thin red (2.5YR 5/6) loamy strata; few masses of calcium carbonate in upper part; common masses of gypsum crystals; slight effervescence; moderately alkaline.
TYPE LOCATION: King County, Texas; from the courthouse in Guthrie, Texas; 11.7 miles south on U.S. Highway 83; 0.62 mile east on Croton Creek Ranch entrance road; 0.1 mile south on pipeline road and 120 feet west in rangeland. (Latitude 33N, 27, 05; Longitude 100W, 15, 42)
RANGE IN CHARACTERISTICS: Solum thickness and depth to weathered redbed claystone ranges from 40 to 60 inches. Weighted average clay content of the particle-size control section ranges from 40 to 55 percent. During most years cracks 1/4 to 3/4 inch wide extend to a depth greater than 20 inches. Depth to wedge-shaped peds ranges from 24 to 35 inches. Linear extensibility ranges from 6.0 to 6.5 cm in the upper 40 inches of the soil.
The A horizon has color with hue of 2.5YR to 7.5YR, value of 4 or 5, and chroma of 2 to 4. Moist color value is 3 or 4. Surface layers with mollic color average less than 7 inches thick. Reaction ranges from slightly alkaline to moderately alkaline and is non-effervescent to strongly effervescent.
The Bw horizon has color with hue of 2.5YR or 5YR, value of 4 or 5 and chroma of 4. Texture is clay loam, clay or silty clay. Very fine or fine concretions of calcium carbonate range from very few to common. Reaction is moderately alkaline and is non-effervescent to strongly effervescent.
The Bk1 and Bk2 horizons have color with hue of 2.5YR or 5YR, value of 4 or 5 and chroma of 4 to 6. Texture is clay or silty clay. Wedge-shaped aggregates are common below a depth of 26 to 35 inches. Fine and medium concretions and masses of calcium carbonate range from few to common. Crystals of gypsum range from none to common in the Bk2 horizon. Reaction is moderately alkaline and is slightly effervescent to strongly effervescent.
Where present, the BCk horizon has color with hue of 2.5YR or 5YR, value of 3 to 5 and chroma of 4 to 6. Texture is clay loam, clay, or silty clay. Mottles and stains in shades of gray and olive are common. These colors are inherited from the parent material. Concretions and masses of calcium carbonate and crystals of gypsum range from 5 to 15 percent. Weathered redbed claystone fragments are common in the lower part of the horizon. Reaction is moderately alkaline and is strongly effervescent to violently effervescent.
The Cd layer has color with hue of 10R to 5YR, value of 4 or 5 and chroma of 4 to 6. Gray, light gray, greenish gray and olive gray mottles and strata are common. It is redbed claystone stratified with clay, silty clay, or clay of the Permian age. Some pedons contain thin strata of gypsum or broken dolomitic limestone. Wedge shaped aggregates are common in some pedons. Masses and coatings of calcium carbonate range from none to common. Crystals of gypsum range from few to many. Reaction ranges from slightly alkaline to moderately alkaline and is non-effervescent to strongly effervescent.
COMPETING SERIES: These are the Mangum and Throck series in the same family and the similar Owens, Stamford, and Vernon series. Mangum soils are on floodplains and contain stratification. Owens and Vernon soils have sola less than 40 inches thick. In addition Owens soils have hues of 7.5YR to 5Y. Stamford soils are Vertisols and have smectitic mineralogy. Throck soils have hues of 7.5YR to 2.5Y.
GEOGRAPHIC SETTING: Tilvern soils are on gently sloping uplands. Slopes range from 1 to 3 percent. The soil formed in calcareous clays and redbed claystone mainly of the Permain age Blaine Formation. Mean annual precipitation ranges from 22 to 28 inches. The mean annual temperature ranges from 58 to 64 degrees F. Elevation ranges from 900 to 2000 feet. Frost free days range from 190 to 230. The Thornthwaite PE indices is 32 to 44.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the similar Vernon soils and the Aspermont, Cottonwood, Jaywi, Knoco, Quanah, Talpa, and Westill soils. Aspermont soils are on the same position as Tilvern soils and have fine-silty particle size control sections. Cottonwood, Knoco and Talpa soils are on higher positions and are underlain by bedrock at shallow or very shallow depths. Jaywi and Quanah soils are on stream terrace deposits or colluvial fans and have fine-silty particle size control sections. Westill soils are on higher positions mantled with Quaternary age deposits. Also, Westill soils have a mollic epipedon and a argillic horizon. Vernon soils are on more sloping positions than Tilvern soils.
DRAINAGE AND PERMEABILITY: Well drained. Permeability is very slow. Runoff is very high.
USE AND VEGETATION: Used mostly as rangeland, but some areas are cropped to wheat, cotton and forage sorghums. Native vegetation is buffalograss, tobosa grass, tall dropseed, sideoats grama, blue grama, threeawns, Texas grama, Texas wintergrass, mesquite, lote bush and prickly pear.
DISTRIBUTION AND EXTENT: Central Rolling Red Plains of western Oklahoma and northwestern Texas LRR H (MLRA 78B). The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas.
SERIES ESTABLISHED: King County, Texas; 1999.
REMARKS: This soil was formerly included with the Tillman and the Vernon series. Some data indicate these soils may classify as Vertisols. More study across the series province in the soil survey update will verify the classification.
Diagnostic horizons and features recognized with this pedon are:
Ochric epipedon - 0 to 5 inches (A horizon).
Cambic horizon - 5 to 53 inches (Bw, Bk, and BCk horizons).
Vertic features - Wedged shaped aggregates from 28 to 46 inches and cracks that open and close periodically. Local COLE data indicates a linear extensibility of slightly more than 6.0 cm within a depth 100 cm (Bk2 horizon).
The assignment of the cation-exchange activity class is based on lab data from King County, TX, and Jackson County, OK.
Range Site: Clay Prairie - 078BY090TX.
ADDITIONAL DATA: NSSL Data Sample No. S80TX-253-001 from Jones County, TX; S98OK-065-004 Jackson County, OK; and S98TX-269-001 King County, TX.
TAXONOMIC VERSION: Soil Taxonomy, Second Edition, 1999.