LOCATION PURVES TX+OKEstablished Series
TAXONOMIC CLASS: Clayey, smectitic, thermic Lithic Calciustolls
TYPICAL PEDON: Purves clay--pasture. (Colors are for dry soil unless otherwise stated.)
A--0 to 8 inches; very dark grayish brown (10YR 3/2) clay, very dark brown (10YR 2/2) moist; strong very fine subangular blocky and granular structure; very hard, firm; many fine roots; calcareous; moderately alkaline; gradual smooth boundary. (6 to 12 inches thick)
Ak--8 to 12 inches; brown (10YR 4/3) clay, dark brown (10YR 3/3) moist; strong very fine subangular blocky and granular structure; hard, firm; common fine roots; few to common concretions and soft masses of calcium carbonate; calcareous; moderately alkaline; clear smooth boundary. (2 to 8 inches thick)
Bk--12 to 14 inches; brown (10YR 5/3) very gravelly clay dark brown (10YR 3/3) moist; strong fine granular structure; hard, firm; contains about 70 percent fragments of limestone 1 to 6 inches across the long axis; fragments have pendants and coatings of calcium carbonate 3 to 10 mm thick; many fine concretions; calcareous; moderately alkaline; abrupt smooth boundary. (0 to 5 inches thick)
R--14 to 20 inches; indurated limestone, with a hardness by Moh's scale of 3 or more; contains a few fractures.
TYPE LOCATION: Erath County, Texas; from the center of Purves, Texas, 0.5 mile southeast of Farm Road 219; 0.27 mile northeast on private road, and 120 feet northwest of road in native grass pasture. Latitude 32 degrees, 00 minutes 13 seconds N; Longitude 98 degrees, 15 minutes 33 seconds W.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 8 to 20 inches. Fragments of limestone that are 2 mm to 25 cm across the long axis range from none to 35 percent by volume of the material above the bedrock. Secondary carbonates occur as concretions and soft masses and as coatings and pendants on fragments. Calcium carbonate equivalent ranges from 5 to 45 percent, but averages 15 to 40 percent in the AK and BK horizons.
The solum has hue of 10YR or 7.5YR, value of 3 to 5 dry and 2 or 3 moist, and chroma of 1 to 3. It is clay loam, silty clay loam, silty clay, or clay with silicate clay content ranging from 35 to 55 percent, and includes textures with gravelly, cobbly, and stony textural class modifiers.
COMPETING SERIES: There are no competing series in the same family. Similar soils are the Eckrant, Ector, Harper, Kavett, Lueders, Maloterre, Mereta, Stephen, Talpa, and Tarrant series. Eckrant, Ector, Lueders, and Tarrant soils have skeletal control sections. Harper soils have vertic properties and are noncalcareous. Kavett and Mereta soils have petrocalcic horizons. Maloterre and Talpa soils are in loamy families. Stephen soils have a paralithic content.
GEOGRAPHIC SETTING: Purves soils are on gently sloping to steep upland divides with plane to convex surfaces. The slope gradient is commonly 1 to 5 percent, but the range is 1 to 40 percent. The soil formed in interbedded hard limestones and calcareous marls. Mean annual temperature ranges from 64 to 68 degrees F. and mean annual precipitation ranges from 27 to 37 inches. Frost free days range from 210 to 240 days and elevation ranges from 400 to 1800 feet. Thornthwaite annual P-E indices range from 40 to 60.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Eckrant. Maloterre, and Tarrant series and Denton, Dugout, and San Saba series. Denton and San Saba soils have sola thicker than 20 inches and are in lower, less sloping positions. Eckrant, Maloterre, Tarrant, and Dugout soils are on similar or slightly higher positions than Purves soils. In addition, Dugout soils have loamy control sections and lack dark colored A horizons.
DRAINAGE AND PERMEABILITY: Well drained. Runoff is slow to medium. Permeability is moderately slow.
USE AND VEGETATION: Used mainly as rangeland, with some areas cultivated to small grains. Vegetation in rangeland is predominantly mid grasses, with some live oak and mesquite trees.
DISTRIBUTION AND EXTENT: Mainly in the Grand Prairie, Edwards Plateau, Texas North-Central Prairies, and Texas Blackland Prairie of Central Texas. The soil is extensive.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Travis County, Texas; 1969.
REMARKS: Purves soils were formerly classified as a shallow phase of the Denton series.
Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - the zone from the surface to 14 inches. (A, AK and BK horizons)
Calcic horizon - the zone from 12 to 14 inches. (AK and BK horizons)
Lithic feature - the occurrence of hard limestone at a depth of 14 inches.