LOCATION LIGON TXEstablished Series
TAXONOMIC CLASS: Fine, mixed, superactive, thermic Typic Rhodustalfs
TYPICAL PEDON: Ligon loam--rangeland. (Colors are for dry soil unless otherwise stated.)
A--0 to 4 inches; reddish brown (5YR 4/4) fine sandy loam, dark reddish brown (5YR 3/4) moist; weak fine subangular blocky structure parting to moderate very fine granular; hard, friable, many fine and very fine roots; many fine and very fine discontinuous tubular pores; 10 percent pebbles of quartz; slightly acid; abrupt smooth boundary. (3 to 9 inches thick)
Bt1--4 to 7 inches; reddish brown (2.5YR 4/4) clay; dark reddish brown (2.5YR 3/4) moist; moderate fine subangular blocky structure; very hard, firm; common fine and few medium roots; patchy dark reddish brown (2.5YR 3/4) clay films on faces of peds and on coarse fragments; 15 percent cobbles; slightly acid; clear smooth boundary. (0 to 11 inches thick)
Bt2--7 to 18 inches; red (2.5YR 4/6) clay; dark red (2.5YR 3/6) moist; weak medium prismatic structure parting to moderate medium subangular blocky; very hard, firm; few fine and very fine roots; discontinuous dark red (2.5YR 3/6) clay films on faces of peds; neutral; gradual smooth boundary. (6 to 12 inches thick)
Bt/C--18 to 23 inches; red (2.5YR 4/6) sandy clay loam, dark red (2.5YR 3/6) moist; weak medium prismatic structure parting to weak medium subangular blocky; hard, firm; few fine and medium roots; 3 percent siliceous pebbles; patchy clay films; weakly consolidated reddish brown (5YR 4/4) schist fragments make up about 20 percent (C); neutral; gradual wavy boundary. (4 to 10 inches thick)
C--23 to 32 inches; reddish brown (5YR 4/4) weathered schist; few fine and very fine roots penetrating cleavage planes; neutral; gradual wavy boundary.
Cr--32 to 52 inches; tilted weakly cemented schist; few fine roots between plates and seams.
TYPE LOCATION: Llano County, Texas; About 11.5 miles southwest of Llano, Texas. From the intersection of Texas Highway 16 and Ranch Road 2323 in Llano, 11.6 miles southwest of Llano on Ranch Road 2323, 3.0 miles north on county road, 1.3 miles north on private road, 60 feet west in rangeland. Latitude 30 degrees-40 minutes-54 seconds north and Longitude 098 degrees-51 minutes-30 seconds west.
RANGE IN CHARACTERISTICS: Depth to schist or schistose gneiss bedrock ranges from 20 to 40 inches. Coarse fragments of angular schist and quartz up to 8 inches across range from 5 to 40 percent. Reaction of the solum ranges from medium acid to mildly alkaline.
The A horizon has hue of 2.5YR, 5YR or 7.5YR, value of 3 to 5 and chroma of 4 to 6. It is loam, fine sandy loam or clay loam. Gravelly, very gravelly and cobbly phases are included.
The Bt horizon has value of 2 or 4 and chroma of 4 to 6. Texture is sandy clay loam, clay loam or clay. The average clay content of the control section ranges from 35 to 45 percent. The boundary between the Bt horizon and C horizon ranges from gradual to abrupt, and from wavy to irregular.
Most pedons have a C horizon of weathered schist or schistose gneiss. These materials are not cemented when dry but grade into weakly cemented materials with depth.
The Cr horizon is mainly hornblende schist but ranges to schistose gneiss, and is tilted 30 to 60 degrees. The upper 1 inch to 12 inches of the Cr horizon contains reddish fine earth in pockets and along cleavage planes. It is weakly to strongly cemeneted when dry.
COMPETING SERIES: There are no soils in the same family. Similar soils include Exray, Hensley, and Cosh soils. Cosh soils have loamy control sections and are less than 20 inches thick to sandstone. Exray and Hensley soils have clayey control sections and in addition, Hensley soils are less than 20 inches thick to limestone and Exray are less than 20 inches thick to sandstone.
GEOGRAPHIC SETTING: Ligon soils occur on broad convex ridges. Slopes are dominantly less than 5 percent, but range from 1 to 15 percent. The surfaces are slightly ridged with outcrops of quartz dikes. The soil formed in a thin mantle of loamy residuum and colluvium over schist. The climate is dry subhumid. Mean annual temperature ranges from 65 to 67 degrees F. and mean annual rainfall ranges from 24 to 30 inches. Frost free days range from 215 to 235 days and elevation ranges from 1,000 to 2,250 feet. Thornthwaite P-E index ranges from 38 to 44.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Castell, Honey creek, Katemcy and Keese soils. Castell, Honey creek and Katemcy soils have solums 20 to 40 inches thick. Keese soils lack Bt horizons.
DRAINAGE AND PERMEABILITY: Well drained, runoff is medium; permeability is moderately slow.
USE AND VEGETATION: Used for rangeland. Originally prairie having scattered oak with climax dominants being mainly little bluestem, plains lovegrass, sideoats grama, and Arizona cottontop. Many areas are invaded by brushy species, mainly whitebrush, mesquite and black persimmon and shorter grasses, including threeawn, annuals and numerous forbs.
DISTRIBUTION AND EXTENT: In the Central Basin of Texas. The series is of moderate extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: McCulloch County, Texas; 1970.
REMARKS: Data are available in a thesis "A Study of Mineral Transformations and Weathering Process occurring during the Genesis of Two Soils developed from Gneiss and Schist in Llano County, Texas; May 1965" by Clyde Stanke for a Masters Degree, Texas Technological College, Lubbock, Texas.
Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - the zone from the surface of the soil to a depth of 4 inches. (The A horizon)
Argillic horizon - the zone from a depth of 4 inches to a depth of 18 inches. (The Bt horizon)
Paralithic contact at 32 inches.