LOCATION TARPLEY TXEstablished Series
TAXONOMIC CLASS: Clayey, smectitic, thermic Lithic Argiustolls
TYPICAL PEDON: Tarpley clay loam, stony--rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 7 inches; very dark grayish brown (10YR 3/2) clay loam, very dark brown (10YR 2/2) moist; moderate medium and fine subangular blocky structure; very hard, firm; common very fine and fine roots; few very fine pores; 15 percent limestone fragments from 1/8 inch to 15 inches in diameter on the surface; few chert fragments 5 inches to 15 inches in diameter on the surface; vertical cracks 1/2 to 1 inch wide extend through the horizon; neutral; clear smooth boundary. (3 to 8 inches thick)
Bt--7 to 18 inches; reddish brown (5YR 4/4) clay, dark reddish brown (5YR 3/4) moist; strong, medium subangular blocky and angular blocky structure; extremely hard, very firm; common very fine and fine roots; few very fine pores; thin continuous clay films on surfaces of peds; few fragments of chert mostly less than 1/4 inch; vertical cracks 1/2 inch to 1 inch wide extend to the bedrock; neutral; abrupt smooth boundary. (10 to 15 inches thick)
R--18 to 22 inches; pale yellow, coarsely fractured, indurated limestone bedrock.
TYPE LOCATION: Mills County, Texas; from the Mills County Courthouse in Goldthwaite, Texas, 14.5 miles southeast on Farm Road 572; north 1.4 miles on an unpaved road to a private pasture road; east on pasture road 200 yards to the top of a flat mountain and 400 yards southeast on the plateau in rangeland.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 13 to 20 inches and corresponds to the depth of limestone bedrock. Soil reaction ranges from slightly acid to mildly alkaline. Coarse fragments of cobbles and stones range from none to about 30 percent on the surface and in the soil. Cobbles and stones are of limestone or chert.
The A horizon has hue of 5YR, 7.5YR or 10YR, value of 2 to 4, and chroma of 2 or 3. It is clay loam or clay, excluding the coarse fragments. Clay content ranges from 30 to 50 percent.
The Bt horizon has hue of 2.5YR, 5YR, or 7.5YR, value of 3 or 4, and chroma of 2 to 4. It is clay, with the clay content ranging from 60 to 80 percent.
COMPETING SERIES: There are no other soils in this family. Similar soils are Bexar, Caradan, Lenapah, Hensley, Purves, Rumple, Speck, and Tarrant series. Lenapah soils have Bt horizons in hue of 10YR and 2.5Y and have less than 60 percent clay in the control section. Bexar, Caradan, and Rumple soils have sola more than 20 inches thick. Hensley soils lack mollic epipedons and have less than 60 percent clay in the Bt horizon. Purves and Tarrant soils lack Bt horizons and have calcic horizons. Speck soils have mixed mineralogy and less than 60 percent clay in the Bt horizon.
GEOGRAPHIC SETTING: Tarpley soils are nearly level to sloping and occur on upland plateaus and low ridges. Slope gradients range from 0 to 8 percent but are mostly less than 4 percent. The soil formed in clayey residuum over limestone bedrock of Lower Cretaceous age. Mean annual precipitation ranges from 28 to 35 inches and mean annual temperature ranges from 64 to 70 degrees F. Frost-free days range from 220 to 250 days and elevation ranges from 1000 to 2,000 feet. Thornthwaite P-E indices range from 42 to 54.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Caradan and Tarrant series, and Denton, Eckrant, Evant, Oglesby and Real series. Denton soils have sola thicker than 20 inches and lack Bt horizons. Eckrant and Real soils lack Bt horizons and have less than 60 percent clay in the control section. Evant soils are on similar positions and are underlain by petrocalcic horizons. Oglesby soils are on similar positions and do not have argillic horizons.
DRAINAGE AND PERMEABILITY: Well drained. Runoff is low on 0 to 1 percent slopes, medium on 1 to 5 percent slopes and high on 5 to 8 percent slopes. Permeability is slow.
USE AND VEGETATION: A few small areas are cultivated to oats or other small grains. Mostly used for rangeland. Native vegetation consists mostly of Texas wintergrass, sideoats grama, little bluestem, and Indiangrass. Woody vegetation is white shin oak, live oak, post oak, mesquite, catclaw, and pricklypear.
DISTRIBUTION AND EXTENT: Central Texas, mainly in the southern part of the Grand Prairie and the eastern part of the Edwards Plateau. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Mills County, Texas; 1975.
REMARKS: Tarpley series was formerly included as a shallow phase of the Crawford series. Diagnostic horizons and features recognized in this pedon are:
Mollic epipedon - 0 to 7 inches (A horizon)
Argillic horizon - 7 to 18 inches (Bt horizon)
Lithic contact - soil/limestone interface at 18 inches