LOCATION RIOLOMAS TXEstablished Series
TAXONOMIC CLASS: Coarse-loamy, mixed, superactive, calcareous, thermic Typic Udorthents
TYPICAL PEDON: Riolomas fine sand, on a weakly convex mounded area adjacent to the Colorado River in pastureland. (Colors are for moist soil unless otherwise stated.)
A--0 to 8 inches; dark brown (7.5YR 4/4) fine sand, brown (7.5YR 5/4) dry; single grained; loose, few fine roots; strongly effervescent, moderately alkaline; abrupt wavy boundary.
C1--8 to 26 inches; strong brown (7.5 YR 5/6) sandy clay loam, pink (7.5YR 6/6) dry; few fragments 5 to 20 mm in diameter of yellowish red (5YR 5/6) sandy clay loam; single grained; soft, very friable, few fine roots; few fine pores; few fine calcium carbonate concretions; violently effervescent, moderately alkaline; gradual smooth boundary.
C2--26 to 32 inches; light brown (7.5YR 6/4) fine sandy loam, pink (7.5YR 7/4) dry; few fragments 5 to 20 mm in diameter of yellowish red (5YR 5/6) sandy clay loam; single grained; soft, very friable, loose, few fine calcium carbonate concretions; violently effervescent, moderately alkaline; abrupt smooth boundary.
C3--32 to 44 inches; pale brown (10YR 6/3) fine sand, very pale brown (10YR 7/3) dry; single grained; loose, few fine white concretions; strongly effervescent, moderately alkaline; abrupt smooth boundary.
C4--44 to 52 inches; dark yellowish brown (10YR 4/4) loamy fine sand, light yellowish brown (10 YR 6/4) dry; single grained; loose, nonsticky and nonplastic; few fine calcium carbonate concretions; violently effervescent, moderately alkaline; gradual smooth boundary.
C5--52 to 80 inches; light yellowish brown (10YR 6/4) fine sand, very pale brown(10YR 7/4) dry; single grained; loose, few fine calcium carbonates concretions; strongly effervescent, moderately alkaline.
TYPE LOCATION: Matagorda County, Texas; from the intersection of Texas Highway 35 and Farm Road 1468 south of Markham, 8.7 miles south on Farm Road 1468 to ranch entrance, 0.57 miles northeast on ranch road to ranch headquarters, 2.4 miles east-northeast on ranch road to mounds across the Colorado River from the Celanese Plant barge docks, 500 feet northwest in pasture.
RANGE IN CHARACTERISTICS: Rooting depth is more than 80 inches. Dredging or dragline operations have mixed the materials which have been randomly deposited and smoothed with a dozer into a layer that ranges from 5 to 10 feet thick. These soils are made up of sandy and loamy materials. The weighted average clay content of the control section ranges from 3 to 18 percent. The control section has more than 50 percent sand that is fine or coarse sand. Reaction is mildly to strongly alkaline and is slightly to strongly effervescent. Most pedons contain few to common hard concretions of calcium carbonate, black concretions and micro flakes. Some pedons contain 2 to 15 percent by volume siliceous pebbles.
The A horizon has hue of 5YR to 10YR, value of 3 to 5, and chroma of 4 to 6. The textures are variable and mixed, but composite textures are fine sand, loamy fine sand, fine sandy loam or sandy clay loam.
The C horizons have hue of 5YR to 5Y; value of 3 to 7; and chroma of 3 to 6. Texture is loamy fine sand, fine sand, fine sandy loam or sandy clay loam. Thin strata and fragments of clayey materials are in some horizons.
COMPETING SERIES: There are no competing series in the same family. Similar soils are the Grayrock and Marklake series. Grayrock soils have a fine-silty control section. Marklake soils have fine-loamy control sections. These soils are forming in deposits that have been reworked during lignite mining operations.
GEOGRAPHIC SETTING: Riolomas soils are on convex areas bordering dredged river and creek channels. These soils are forming in dredged deposits from sandy and loamy alluvium. Slopes range from 1 to 5 percent with convex or undulating surfaces. The mean annual temperature ranges from about 68 to 70 degrees F. Average annual precipitation is about 36 to 46 inches. The Thornthwaite P-E indices range from about 48 to 66.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Asa, Brazoria, Clemville, and Norwood series. The Asa and Brazoria soils are higher in the landscape. Brazoria soils have very-fine control sections. The Asa, Clemville, and Norwood soils have fine-silty control sections and the Asa soils have dark colored surface layers. Clemville and Norwood soils are in similar positions in the landscape but have smoother surfaces.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff; moderately rapid permeability. Permeability may be slower in areas where clayey strata are nearer the surface.
USE AND VEGETATION: Mainly used for pastureland. These areas have been mechanically smoothed and seeded to pasture grasses or sodded to bermudagrass.
DISTRIBUTION AND EXTENT: Mainly along the lower reaches of the Colorado River and possibly along the Brazos River in Texas. The series is of minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Matagorda County, Texas 1991.
REMARKS: These soils were formerly included in the Ijam series. Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon: from the surface to a depth of 10 inches.
Orthent feature: less than 5 percent diagnostic horizon fragments are recognized.
Calcareous reaction feature: effervescent in 25 to 50 cm control section.
Additional Data: NSSL mineralogy data from type location: Very fine sand; 81 percent resistant, fine sand; 89 percent resistant.