LOCATION GRAYROCK TXEstablished Series
TAXONOMIC CLASS: Fine-silty, mixed, active, nonacid, thermic Typic Udorthents
TYPICAL PEDON: Grayrock silty clay loam--pasture.
(Colors are for moist soil unless otherwise stated.)
Ap--0 to 7 inches; dark grayish brown (l0YR 4/2) silty clay loam; grayish brown (l0YR 5/2) dry; moderate fine granular and very fine subangular blocky structure; hard, very friable; few medium and common, fine and very fine roots; about 2 percent by volume lignite and shale fragments 1/4 to 1/2 inch in diameter; few mica flakes; neutral; clear wavy boundary. (4 to 10 inches thick)
C1--7 to 28 inches; dark grayish brown (10YR 4/2) silty clay loam; grayish brown (10YR 5/2) dry; massive; hard, friable; few medium and many fine roots; about 6 percent by volume fragments of lignite and 12 percent fragments of shale from 1/2 inch to 6 inches across; few reddish clayey spots less than 1 percent by volume; few mica flakes; neutral; clear wavy boundary. (4 to 50 inches thick)
C2--28 to 37 inches; olive brown (2.5Y 4/4) silty clay loam, massive; hard, friable; few medium and many fine roots; about 25 percent by volume fragments of lignite and less than 2 percent fragments of shale 1/2 inch to 10 inches across; few mica flakes; medium acid; clear wavy boundary. (0 to 40 inches thick)
C3--37 to 80 inches; olive gray (5Y 4/2) silty clay loam; massive; hard, friable; few medium and many fine roots; about 12 percent by volume fragments of lignite and 4 percent fragments of shale 1/2 inch to 10 inches across; few mica flakes; mildly alkaline.
TYPE LOCATION: Titus County, Texas; from intersection of Interstate Highway 30 in Mt. Pleasant; about 7 miles west on Farm Road 1734 to entrance of TUGCO General Plant; about 0.7 mile southwest on haul road; 100 feet southeast; site is 36 feet north by northeast of tree test plot.
RANGE IN CHARACTERISTICS: Rooting depth is more than 80 inches. Mining operations have mixed the materials from 30 to about 150 feet deep. The reaction is commonly neutral but ranges from medium acid to mildly alkaline. Fragments of ironstone and sandstone mainly from less than 1 inch to 15 inches across the long axis range from 0 to 3 percent by volume. Fragments of diagnostic horizons range from 0 to less than 2 percent by volume. Fragments of lignite and shale commonly less than 3 inches in diameter that range to 15 inches across make up 2 to 35
percent by volume. Some of these fragments slake in water, most fragments break down readily when rubbed wet. The others break down with difficulty when rubbed. Most pedons contain micacous material throughout.
The A horizon has hue of 10YR or 2.5Y, value of 4 or 5, and chroma of 1 through 4. Reddish and brownish splotches range from none to a few. It is silty clay loam or clay loam.
The C horizon has hue of 10YR, 2.5Y, or 5Y, value of 3, 4, or 5, and chroma of 1 through 4. Splotches of these colors, as well as yellow, brown, and red range from none to common. It is silty clay loam, clay loam, or loam. The control section is commonly 20 to 35 percent clay, 50 to 65 percent silt, and less than 15 percent fine sand or coarser.
COMPETING SERIES: There are no competing series in the same family. Similar soils are the Barge, Bragg, Brilliant, Kanima, and Palmerdale series. Barge and Kanima soils have fragments of diagnostic horizons within the control section. Bragg soils are acid with siliceous mineralogy. Brilliant and Palmerdale soils have loamy-skeletal control sections. All of these soils are forming in spoil materials or they have been mechanically reworked.
GEOGRAPHIC SETTING: Grayrock soils are on gently sloping to strongly sloping areas of smoothed strip mine spoil materials. Slopes range from 2 to 12 percent with plain or convex surfaces. The soils are being reclaimed immediately after mining operations are completed. Mining operations, to some degree, are mixing soil materials from the surface to a depth of about 30 to 150 feet. The lignite seams are mainly in the Wilcox formation of Tertiary age. However, in some areas, Quaternary age materials are part of the overburden and are therefore intermixed. The mean annual temperature ranges from about 63 to 68 degrees F. Average annual precipitation ranges from about 40 to 48 inches, and the Thornthwaite P-E indices range from about 64 to 80.
GEOGRAPHICALLY ASSOCIATED SOILS: These are mainly the Annona, Freestone, and Woodtell series. These soils have Bt horizons and are on nearby undisturbed areas.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderate permeability for a few years after reclamation. The permeability may become slower with time and settling.
USE AND VEGETATION: Most areas are reestablished to improved pastures of bermudagrasses and legumes such as arrowleaf clovers. Other areas are in various stages of vegetative establishment.
DISTRIBUTION AND EXTENT: Northeast and East Texas. The series is of minor extent but the acreage is increasing as mining operations continue. The series is expected to be at least moderately extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Titus County, Texas; 1984.
REMARKS: Characterization data from the NSSL, S80TX-449-001. The site location was mined in 1974 and coastal bermudagrass established in 1975. Based on organic carbon levels, the soil could be classified in a fluventic subgroup. The irregular distribution of organic carbon is probably related to the amount of lignite in each layer; therefore, the soil is classified in a typic subgroup. Warren Lynn's comments on the characterization data support this classification.