LOCATION PIDCOKE TXEstablished Series
TAXONOMIC CLASS: Loamy, carbonatic, thermic Lithic Calciustolls
TYPICAL PEDON: Pidcoke clay loam, on a convex 2 percent slope in rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 7 inches; dark grayish brown (10YR 4/2) clay loam, very dark grayish brown (10YR 3/2) moist; weak fine subangular blocky and granular structure; hard, friable; common very fine and fine roots; common fine concretions of calcium carbonate; about 5 percent by volume fossil shells from 1/8 inch to 1 1/2 inches across; strongly effervescent; moderately alkaline; clear smooth boundary. (4 to 12 inches thick)
Bk--7 to 13 inches; grayish brown (10YR 5/2) gravelly clay loam, dark grayish brown (10YR 4/2) moist; weak fine subangular blocky; hard, friable; common very fine and fine roots; common fine concretions and few films and threads of calcium carbonate; about 25 percent by volume fossil shells from 1/8 inch to 1 1/2 inches across; strongly effervescent; moderately alkaline; abrupt smooth boundary. (6 to 8 inches thick)
R--13 to 30 inches; indurated fossiliferous limestone; massive and unfractured; hardness of about 3 by Mohs scale.
TYPE LOCATION: Coryell County, Texas; from the intersection of Texas Highway 36 and Farm Road 2955 about 11 miles north of Gatesville; 0.4 mile northwest on Texas Highway 36; 0.6 mile south on county road; 75 feet northwest in rangeland.
RANGE IN CHARACTERISTICS: The solum ranges from 10 to 20 inches thick. Texture is clay loam, silty clay loam, or their gravelly counterparts. Silicate clay ranges from 20 to 35 percent. The calcium carbonate equivalent ranges from 40 to 60 percent. Fossil shells, mainly oyster, from 1/8 inch to 3 inches across range from a few to 25 percent by volume in the control section. The reaction is mildly or moderately alkaline and calcareous throughout.
The A horizon has hue of 7.5YR or 10YR, value of 3 or 4, and chroma of 2 or 3. Fossil shells range from a few to about 25 percent by volume.
The Bk horizon has hue of 7.5YR or 10YR, value of 4 to 6, and chroma of 2 to 4. Fossil shells range from 1 to 35 percent by volume.
The R layer is indurated limestone. The limestone is cemented beds of fossilized oyster shells. The beds are about 2 to 20 feet thick and have thin marl or shale seams at vertical intervals of about 1 to 3 feet.
COMPETING SERIES: There are no other series in this family. Closely similar soils include Cho, Doss, Maloterre, Purves, Real and Tarrant series. Cho, Doss, and Real soils are underlain by a paralithic contact, and in addition Real soils have skeletal control sections. Maloterre soils are very shallow soils that have an ochric epipedon. Purves and Tarrant soils are clayey, montmorillonitic. In addition, Tarrant soils have a skeletal control section.
GEOGRAPHIC SETTING: Pidcoke soils are on gently sloping uplands. Surfaces are typically convex with slopes of 1 to 3 percent. These soils are on summits of knolls and low hills. Pidcoke soils formed in the Walnut Clay Geologic Formation of the Lower Cretaceous Period. Mean annual precipitation is 26 to 34 inches. Mean annual temperature is 64 to 68 degrees F. Thornthwaite P-E indices range from 44 to 56.
GEOGRAPHICALLY ASSOCIATED SOILS: These include Brackett, Cho, Maloterre, and Topsey series. Brackett and Maloterre soils have light colored surfaces and are below or on similar positions. Cho soils are on ridgetops at lower elevations. Topsey soils are deep loamy soils on slopes below the Pidcoke soils.
DRAINAGE AND PERMEABILITY: Well drained, slow to medium runoff; moderately slow permeability.
USE AND VEGETATION: Mainly range. Native vegetation includes little bluestem, sideoats grama, Texas wintergrass, buffalograss and threeawn. Woody vegetation includes scattered live oak and juniper.
DISTRIBUTION AND EXTENT: Grand Prairie Land Resource Area in Central Texas. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Coryell County, Texas; 1983.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 7 inches
Calcic horizon - 7 to 13 inches
Lithic contact - Soil and limestone interface at 13 inches