LOCATION CORKSTONE TXEstablished Series
TAXONOMIC CLASS: Clayey, mixed, active, thermic, shallow Udic Argiustolls
TYPICAL PEDON: Corkstone clay loam, on a 3.5 percent slope, in rangeland.
(Colors are for dry soil unless otherwise stated.)
A1--0 to 4 inches; very dark grayish brown (10YR 3/2) clay
loam, very dark brown (10YR 2/2) moist; moderate fine granular and very fine subangular blocky structure; hard, firm; many fine
roots; common fine pores; few siliceous pebbles up to 2 cm across; mildly alkaline; clear wavy boundary. (3 to 8 inches thick)
B21t--4 to 8 inches; brown (7.5YR 4/2) clay, dark brown
(7.5YR 3/2) moist; moderate very fine subangular blocky and blocky structure; hard, firm; few fine roots; few fine pores; thin clay films on faces of peds; few siliceous pebbles; neutral; clear wavy boundary. (0 to 5 inches thick)
B22t--8 to 12 inches; reddish brown (5YR 4/4) clay, dark
reddish brown (5YR 3/4) moist; moderate fine and medium blocky structure; very hard, firm; few fine roots; few fine pores; few
seams of darker material between peds; few clay films on faces of peds; about 5 percent siliceous pebbles, including spiculite; neutral; clear wavy boundary. (4 to 9 inches thick)
B23t--12 to 18 inches; reddish brown (2.5YR 4/4) very cobbly clay; dark reddish brown (2.5YR 3/4) moist; moderate fine and
medium blocky structure; very hard, firm; few fine roots; few fine pores; few stains of darker material on some peds; few clay films
on faces of peds; about 40 percent spiculite fragments up to 5 cm thick and 10 cm across; few quartz pebbles; neutral; abrupt wavy boundary. (0 to 6 inches thick)
Cr--18 to 36 inches; pink (7.5YR 8/4) spiculite or porous
sponge residuum, pink (7.5YR 7/4) moist; platy, with plates mostly
5 to 15 cm thick and 30 to 90 cm across; hardness of less than 3
Mohs scale; about 10 percent reddish brown clay between plates; neutral; gradual wavy boundary. (4 to 48 inches thick)
R--36 to 60 inches; gray, fractured limestone, with a
hardness of more than 3 Mohs scale.
TYPE LOCATION: San Saba County, Texas; from the intersection of Texas Highway 16 and U. S. Highway 190 in San Saba, 4.5 miles west
on U. S. Highway 190, 9.0 miles southwest on Farm Road 2732, 0.8
mile south on county road, and 180 feet west in rangeland.
RANGE IN CHARACTERISTICS: The solum is 12 to 20 inches thick and corresponds to depth to spiculite, or sponge residuum from
spiculose limestone. The mollic epipedon ranges in thickness from
7 to 12 inches. Depth to hard limestone ranges from 20 to more
than 60 inches. Reaction of the A and Bt horizons is neutral or mildly alkaline.
The A horizon has a hue of 5YR through 10YR, value of 3 or 4, and chroma of 2 or 3. Texture is clay loam or loam. The A horizon contains 0 to 10 percent coarse fragments.
The B21t horizon has a hue of 5YR or 7.5YR, value is 3 or 4, and chroma from 2 to 3. The B22t horizon has a hue of 2.5YR through 7.5YR, value of 4 or 5, and chroma of 3 through 6. The B21t and
B22t horizons contain from 3 to 20 percent coarse fragments. The B23t horizon has a hue of 2.5YR or 5YR, value of 4 or 5, and
chroma of 4 through 6. It contains from 30 to about 65 percent spiculite fragments 1 to 8 cm thick and 2 to 25 cm across the long axis. The fine-earth fraction clay content of the Bt horizon
ranges from 55 to 75 percent.
The Cr horizon consists of yellowish, brownish, or pink porous spiculite with a hardness of 2 to 3 on Mohs scale. It is platy to flaggy, 5 to 20 cm thick and 15 cm to 1.5 m across. It contains
up to about 10 percent of fine earth in the interstices.
The R layer is grayish, hard, fractured limestone many feet thick.
COMPETING SERIES: This is the only series in the same family.
Other competing series include the
Anocon,
Bexar,
Comfort,
Frankirk,
Roughcreek,
Rumple,
Spicewood, and
Tarpley seres.
Anocon, Bexar, and Frankirk soils are less clayey and are moe than
20 inches deep. Comfort, Roughcreek, and Tarpley soils are
underlain at shallow depths by hard limestone, and in addityon, Comfort and Roughcreek soils contain more than 35 percent
limestone fragments. Rumple soils are more than 20 inches thick
and contain more than 35 percent chert gravel. Spicewood soils developed over the same material, but are more than 20 inches
thick.
GEOGRAPHIC SETTING: Corkstone soils are on gently sloping ridges, plateaus, and hill tops. This soil developed from the weathering
of limestone that has formed a layer of spiculite sponge residuum. This material is light and porous and has undergone considerable leaching of calcium and now consists of finely disseminated
silicate dioxide. The climate is dry subhumid. The average
annual rainfall ranges from 26 to 34 inches. The mean annual temperature ranges from 64 degrees to 67 degrees F., and the Thornthwaite P-E indices from 38 to about 54.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing
Roughcreek,
Rumple,
Spicewood, and
Tarpley series and the
Cho and
Mereta series. Cho and Mereta soils are on broader ridges, lack argillc horizons, and are underlain by cemented caliche.
Roughcreek and Tarpley soils occur in similar positions. Rumple
and Spicewood soils occur on broader ridges.
DRAINAGE AND PERMEABILITY: Well drained. Surface runoff is
medium. Permeability is slow.
USE AND VEGETATION: Used almost exclusively as rangeland. A few small aeras are cultivated. Some areas are mined for the
spiculite sponge residuum. Native vegetation now growing on most areas is sideoats grama, little bluestem, cane bluestem, Arizona cottontop, buffalograss, Texas wintergrass, white indiangrass,
forbs, Texas persimmon, liveoak, and mesquite.
DISTRIBUTION AND EXTENT: Central Texas. These soils are minor in extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: San Saba County, Texas; 1980.
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