LOCATION TONKAVAR TXEstablished Series
TAXONOMIC CLASS: Loamy, siliceous, semiactive, thermic Grossarenic Paleudalfs
TYPICAL PEDON: Tonkavar sand--wooded. (Colors are for moist soil unless otherwise noted.)
A--0 to 5 inches; dark grayish brown (10YR 4/2) sand, light brownish gray (10YR 6/2) dry; weak coarse subangular blocky structure; loose; common fine and medium roots; few fine siliceous pebbles; slightly acid; clear smooth boundary. (2 to 12 inches thick)
E1--5 to 20 inches; light yellowish brown (10YR 6/4) sand, weak coarse subangular blocky structure; loose; common fine and medium roots; few siliceous pebbles; slightly acid; clear smooth boundary. (8 to 60 inches thick)
E2--20 to 38 inches; pale brown (10YR 6/3) sand with few fine prominent yellowish red (5YR 5/6) mottles; weak coarse subangular blocky structure; loose; common fine and medium roots; few siliceous pebbles; slightly acid; clear smooth boundary. (0 to 30 inches thick)
E and Bt--38 to 53 inches; pale brown (10YR 6/3) loamy sand; weak coarse subangular blocky structure; loose; common fine roots; few siliceous pebbles; few thin strong brown (7.5YR 5/6) lamella about 1 cm thick and comprise less than 5 percent of the horizon; slightly acid; abrupt smooth boundary. (0 to 30 inches thick)
Bt1--53 to 62 inches; yellowish red (5YR 5/6) sandy clay loam with few fine faint red (2.5YR 4/6) mottles; moderate medium subangular blocky structure; firm; few discontinuous clay films; few fine roots; slightly acid; clear smooth boundary. (6 to 20 inches thick)
Bt2--62 to 69 inches; red (2.5YR 5/8) sandy clay loam with common medium distinct grayish brown (10YR 5/2) mottles; weak medium subangular blocky structure; friable; few roots; thin patchy clay films; reduction along root channels; a 1 cm thick layer of clay at contact to Cr; strongly acid; abrupt wavy boundary. (0 to 20 inch thick)
Cr1--69 to 77 inches; light gray (10YR 7/2) weakly cemented sandstone with few medium prominent yellowish red mottles; extremely firm; few roots along fractures; strongly acid; abrupt smooth boundary. (0 to 12 inches thick)
Cr2--77 to 85 inches; yellowish red (5YR 5/6) weakly cemented sandstone with common medium prominent very pale brown mottles; extremely firm; few fine roots along fractures; very strongly acid.
TYPE LOCATION: Grimes County, Texas, from Texas Hwy. 90 in Roans Prairie, 2.8 miles west on Texas Hwy. 30 for then 300 feet south along private road, 100 feet west in wooded area.
RANGE IN CHARACTERISTICS: Solum thickness and depth to a paralithic contact of weakly cemented sandstone is 60 to 80 inches. The combined A and E horizons range from 40 to 72 inches thick.
The A horizon has hue of 10YR or 7.5YR, value of 4 to 7 and chroma of 2 or 3. It is loamy fine sand, loamy sand, fine sand or sand. Reaction is medium acid to neutral.
The E horizon has hue of 10YR or 7.5YR value of 6 to 8 and chroma of 2 to 4. It is loamy fine sand, loamy sand, fine sand or sand. A few thin lamellae of fine sandy loam are common in the lower part of most pedons, but is lacking in some pedons. The reaction ranges from strongly acid to slightly acid.
The Bt horizon has hue of 10R to 10YR, value 4 to 8 and chroma 4 to 8. Mottles range from few to many in hue of 2.5YR to 10YR, value 4 to 8 and chroma 3 to 8. The texture is fine sandy loam, sandy clay loam, or clay loam. It is very strongly acid to medium acid.
The Cr horizon has a hue of 7.5YR to 10YR, value of 5 to 7 and chroma of 2 to 6. It is weakly to strongly cemented fractured sandstone. It can be dug with hand auger when moist, but is hard when dry. Roots are present in fractures only. It is strongly acid or very strongly acid.
COMPETING SERIES: These are the Kenney, Landman, Latch, Lutterloh, and Pickton soils in the same family, and the similar Bienville, Boy, Catilla, Desan, Gunter, Padina, and Tonkawa soils. Kenney, Landman, Latch, Lutterloh, and Pickton soils lack a paralithic contact within 80 inches of the soil surface. Bienville and Tonkawa soils lack continuous argillic horizons within 80 inches. Boy and Gunter soils contain plinthite and in addition Gunter soils have less than 35 percent base saturation. Catilla, Desan and Padina soils occur in regions of less rainfall.
GEOGRAPHIC SETTING: Tonkavar soils are on upland ridges and hilltops. Slopes range from 1 to 12 percent mainly with convex or plain surfaces. The soil was formed from beds of weakly cemented sandstone and sand of the Jackson Geologic group. The mean annual temperature ranges from 64 to 70 degrees F. Average annual precipitation ranges from 38 to 44 inches, and Thornthwaite PE indices range from 62 to 70.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the Arol, Burlewash, Falba, Elmina, Gomery, and Shiro soils. Arol, Burlewash and Falba soils have fine sandy loam surface layers over clayey argillic horizons and are on lower positions. Elmina and Gomery soils are on similar positions and have loamy fine sand surface layers 20 to 40 inches thick. Shiro soils have loamy sand surface layers less than 20 inches thick and are on lower positions.
DRAINAGE AND PERMEABILITY: Well drained; very slow runoff; moderate permeability. A perched water table is present for short periods usually less than 30 days, following rains.
USE AND VEGETATION: Most areas are used for grazing livestock or for forest. Some cleared areas are used for improved pasture. Native vegetation includes shortleaf and loblolly pine, post oak, southern red oak, white oak, blackjack oak, hickory and sweetgum trees. The understory includes yapon, wax myrtle, sumac, grape and American beauty berry with tall and mid grasses.
DISTRIBUTION AND EXTENT: Tonkavar soils are moderate in extent in south-central Texas.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Grimes County, Texas, 1988.
ADDITIONAL DATA: TAMU Characterization Data from type location S83TX-185-02.
REMARKS: Diagnostic horizons and feature recognized in these pedons are:
ochric epipedon - 0 to 53 inches;
albic horizon - 20 to 53 inches;
argillic horizon - 53 to 69 inches;
grossarenic feature - 0 to 53 inches;
paralithic contact - at 69 inches.