LOCATION DENTON TX+OKEstablished Series
TAXONOMIC CLASS: Fine-silty, carbonatic, thermic Udic
Calciustolls
TYPICAL PEDON: Denton silty clay-cropland. (Colors are for dry soil unless otherwise stated)
Ap--0 to 6 inches; dark brown (7.5YR 4/2) silty clay, dark brown (7.5YR 3/2) moist; moderate fine and very fine granular structure; soft, very friable, sticky and plastic; few fine and medium roots; few fine pitted concretions of calcium carbonate; strongly effervescent; moderately alkaline; clear smooth boundary. (4 to 8 inches thick)
A--6 to 13 inches; dark brown (7.5YR 4/2) silty clay, dark brown (7.5YR 3/2) moist; moderate fine and very fine subangular blocky structure; very hard, firm, sticky and plastic; few fine roots; many pressure faces; few small slickensides less than 1 inch across forming wedge-shaped peds; few fine pitted concretions of calcium carbonate; strongly effervescent; moderately alkaline; gradual wavy boundary. (6 to 16 inches thick)
Bw--13 to 19 inches; reddish brown (5YR 4/4) silty clay, dark reddish brown (5YR 3/4) moist; moderate fine and very fine angular blocky structure; very hard, firm, sticky and plastic; few fine roots; many pressure faces forming wedge-shaped peds; few fine pitted concretions of calcium carbonate; strongly effervescent; moderately alkaline; gradual wavy boundary. (0 to 14 inches thick)
2Bk--19 to 36 inches; reddish yellow (7.5YR 7/6) silt loam, reddish yellow (7.5YR 6/6) moist; common medium masses of strong brown (7.5YR 5/6); weak medium and fine subangular blocky structure; hard, firm, sticky and plastic; few fine roots; about 20 percent fine and medium concretions and soft masses of calcium carbonate; violently effervescent; moderately alkaline; clear irregular boundary. (6 to 24 inches thick)
2CBk--36 to 52 inches; strong brown (7.5YR 5/6) marly soil materials, massive; with about 5 percent reddish yellow (7.5YR 6/6) Bk material along root channels and fracture planes; few fine roots; 10 percent by volume limestone fragments 1 inch to 8 inches across and 2 to 4 inches thick, fragments form a discontinuous line mainly in the upper part of layer; about 25 percent coarse and very coarse soft masses and thin discontinuous strata of calcium carbonate; violently effervescent; moderately alkaline; abrupt wavy boundary. (0 to 20 inches thick)
2R--52 to 70 inches; indurated slightly weathered limestone bedrock; interbedded with marl or chalky limestone at vertical intervals of 6 to about 12 inches; bedrock has tight fractures spaced about 8 to 24 inches apart and cannot be excavated with backhoe machine.
TYPE LOCATION: Coryell County, Texas; from the intersection of Texas Highway 36 and Farm Road 929; 8.6 miles east and north on Farm Road 929 to intersection with county road, 0.3 mile east on Farm Road 929, 85 feet north in cultivated field.
RANGE IN CHARACTERISTICS: Solum thickness ranges from 22 to 40 inches and the depth to limestone bedrock ranges from 40 to 60 inches. Common to many films, threads or soft masses of calcium carbonate are within a depth of 15 to 28 inches of the surface. The upper part of the control section is clayey with 35 to 56 percent clay. The calcium carbonate equivalent is 10 to 30 percent and COLE values range from 0.07 to 0.1. The lower part of the control section is loamy and has carbonatic mineralogy with silicate clay content of 15 to 25 percent. The calcium carbonate equivalent ranges from 40 to 80 percent and COLE values are 0.02 to 0.06. The average silicate clay content of the control section is 25 to 35 percent and the average calcium carbonate equivalent is 40 to 65 percent. The soil cracks when dry, and the cracks range from less than an inch up to about 2 inches wide in the surface layer but are commonly less than 0.4 of an inch wide at a depth of 20 inches. The COLE in the upper 50 inches or to bedrock ranges from 0.02 to 0.1 but the soil lacks a layer 20 inches or thicker with COLE of 0.07 or more.
The A horizon or mollic epipedon ranges from 7 to 20 inches thick. It has hue of 7.5YR, 10YR or 2.5Y, value of 3 or 4, and chroma of 2 or 3. The texture is silty clay or clay but the range includes silty clay loam. The clay content ranges from 35 to 57 percent with 0 to 5 percent as clay size carbonates.
Some pedons do not have a Bw horizon. When present, it has hue of 5YR, 7.5YR or 10YR, value of 3 to 5, and chroma of 4 or 6. The texture is silty clay or silty clay loam.
The 2Bk horizon has hue of 7.5YR, 10YR or 2.5Y, value of 5 to 7, and chroma of 2 to 6. It is silty clay loam, silt loam or loam. Fragments of limestone from pebble to cobble size range from none to about 15 percent by volume. Concretions and soft masses of calcium carbonate range from 5 to 25 percent by volume. Most of the carbonates are secondary, however, some appear to be weathered in place from limestone.
The 2CBk horizon is absent in some pedons. When present, it has colors mainly in shades of brown or yellow. It is marly soil material mainly silty clay loam or silt loam. Limestone pebbles or cobbles range from a few to about 35 percent by volume. Limestone fragments typically occur in a discontinuous lag line in the 2Bk or 2CBk horizons. Large soft masses and discontinuous strata of calcium carbonate ranges from about 5 to 35 percent by volume. Some of the carbonates are secondary but most appear to have weathered in place from limestone.
The 2R layer is indurated limestone bedrock that is interbedded with marly soil materials or chalky limestone at vertical intervals of 4 to 20 inches. There are cracks or fractures spaced about 6 to 30 inches apart. Fractures are tight, but some range up to about 1 1/2 inches wide. In most pedons the bedrock cannot be excavated with conventional digging equipment such as a backhoe machine.
COMPETING SERIES: These are Brenham and Nuff series and the similar Krum, Mosheim, Purves, Set and Slidell series. Brenham, Krum, Nuff, Set and Slidell soils lack bedrock within a depth of 40 to 60 inches. In addition, Brenham soils formed in Tertiary age sediments and Set soils formed in Pennsylvanian age shales. Mosheim soils are members of a fine, montmorillonitic family. Purves soils are shallow to bedrock.
GEOGRAPHIC SETTING: Denton soils are on nearly level to gently sloping uplands. Slopes are mainly l to 3 percent but range from 0 to 5 percent. The soil formed in a mantle of clayey materials over limestone bedrock of Lower Cretaceous age. It is mapped mainly on the Denton clay, Fort Worth Limestone, Duck Creek Limestone and Georgetown Formations. The average annual precipitation ranges from 28 to 34 inches and the summer moisture deficit is about 7 to 9 inches. The average annual temperature ranges from 64 to 68 degrees F, Frost free days range from 220 to 250 and the elevation ranges from 700 to 1500 feet above sea level. The annual Thornthwaite P.E. indices range from 44 to 56.
GEOGRAPHICALLY ASSOCIATED SOILS: They include the competing Purves and Slidell series and Bolar, Crawford, and Eckrant series. Slidell soils are in lower position down slope. Purves and the fine-loamy Bolar soils are upslope on ridgetops. The clayey Crawford soils and the shallow Eckrant soils are down slope.
DRAINAGE AND PERMEABILITY: Well drained; medium surface runoff; slow permeability.
USE AND VEGETATION: Used mainly for cropland and pasture. Some areas are in rangeland. Small grain and grain sorghum are the principal crops. Bermudagrass and kleingrass are the major pasture grasses. Native grasses include bluestems, sideoats grama, indiangrass and Texas wintergrass with a few live oak and bois'd arc trees.
DISTRIBUTION AND EXTENT: Mainly in Central Texas in the Grand Prairie Land Resource Area. The series is of large extent.
MLRA OFFICE RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Denton County, Texas; 1918.
ADDITIONAL DATA: S63TX-50-1 (Coryell Co.) LSL Nos. 18152-18157; S63TX-50-3 (Coryell Co.) LSL Nos. 18165-18170; S62TX-246-90 (Williamson Co.) Sample Nos. K1471-1476 (TAES); S82TX-99-1 (TAES).
REMARKS: This revision recognizes that the lithic contact is deeper (40 to 60 inches) and that typically a lag line of limestone fragments occur within 20 to 40 inches of the surface. This lag line apparently was considered to be a lithic contact. Minimal change in interpretations will result due to the upper part being clayey.
Classification is changed 11/89 from fine-silty, carbonatic, thermic Typic Calciustolls to fine-silty, carbonatic, thermic Udic Calciustolls.
Diagnostic horizons and features recognized in this pedon:
Mollic epipedon - the zone from 0 to 13 inches.
Cambic horizon - the zone from 13 to 19 inches.
Calcic horizon - the zone from 19 to 52 inches. Calcium carbonate equivalent is more than 40 percent.
Lithic contact - occurs at 52 inches.