LOCATION SOMERVELL TX+OKEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, carbonatic, thermic Typic Calciustolls
TYPICAL PEDON: Somervell very gravelly clay loam--rangeland.
(Colors are for dry soil unless otherwise stated.)
A--0 to 16 inches; very dark grayish brown (10YR 3/2) very gravelly clay loam, very dark brown (10YR 2/2) moist; strong very fine granular structure; hard, firm; contains 55 percent by volume
of limestone gravel and cobbles; many fine grass roots;
calcareous; moderately alkaline; gradual smooth boundary. (10 to
20 inches thick)
Bk--16 to 32 inches; light brownish gray (10YR 6/2) very gravelly clay loam, dark grayish brown (10YR 4/2) moist; strong
very fine granular structure; hard, firm, contains 80 percent by volume of limestone gravel and cobble fragments; common soft
masses of calcium carbonate; fragments have thin calcium carbonate coatings; common fine grass roots; calcareous; moderately
alkaline; abrupt wavy boundary. (10 to 20 inches thick)
R--32 to 40 inches; hard limestone bedrock with the upper 2 inches being weakly cemented.
TYPE LOCATION: Erath County, Texas; from the Erath County
Courthouse in Stephenville, Texas, 18.4 miles southeast on U.S. Highway 67 to its junction with Texas Highway 220; then south on Texas Highway 220, 4.9 miles; then 1.3 miles south on an unpaved county road and 100 yards east of road just upslope from a mott of Spanish oak trees in rangeland pasture.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 20 to 40 inches. The soil is calcareous and moderately alkaline
throughout.
The A horizon is brown (10YR 5/3, 4/3), dark brown (10YR 3/3), grayish brown (10YR 5/2), dark grayish brown (10YR 4/2), or very dark grayish brown (10YR 3/2). It is very gravelly clay loam,
very gravelly loam, gravelly loam, or gravelly clay loam with 15
to 85 percent gravel and cobble size limestone fragments.
The Bk horizon is light gray (10YR 7/2; 2.5Y 7/2), light brownish gray (10YR 6/2; 2.5Y 6/2), pale brown (10YR 6/3), light yellowish brown (10YR 6/4; 2.5Y 6/4), grayish brown (10YR 5/2, 2.5Y 5/2),
brown (10YR 5/3, 4/3), or yellowish brown (10YR 5/4). It is very gravelly loam or very gravelly clay loam, with 35 to 85 percent gravel and cobble size limestone fragments.
COMPETING SERIES: These include the
Bolar,
Dev,
Doss,
Engle,
Hubert,
Real, and
Venus series. Bolar, Engle, and Venus soils
have less than 35 percent coarse fragments in the control section. Dev soils lack calcic horizons. Doss and Real soils have sola
less than 20 inches thick. Hubert soils have mixed mineralogy and have mean annual soil temperatures of less than 59 degrees F.
GEOGRAPHIC SETTING: Gently sloping to steep uplands. Slope gradients are mainly 5 to 15 percent, but range from 1 to 45
percent. The soil formed in very gravelly loamy sediments, mainly derived from receding limestone scarps. The average annual precipitation ranges from 26 to 37 inches, Thornthwaite annual P-E indices are about 40 to 58 and mean annual temperature is about 64
to 68 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Bolar
and
Venus series, as well as the
Aledo,
Brackett,
Dugout,
Maloterre, and
Tarrant series. Aledo, Brackett, Dugout,
Maloterre, and Tarrant soils rest on limestone bedrock at less
than 20 inches depth.
DRAINAGE AND PERMEABILITY: Well drained; rapid runoff; moderate permeability.
USE AND VEGETATION: Used for native range. Native vegetation is dominantly midgrasses, including little bluestem and sideoats
grama. Woody vegetation consists mainly of Texas oak, juniper,
and live oak.
DISTRIBUTION AND EXTENT: Mainly in the Grand Prairie area of
central and north central Texas. The soils are of moderate
extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Erath County, Texas; 1970.
REMARKS: The Somervell soils were classified formerly in the Lithosol great soil group.