LOCATION DARBONNE LA+TXEstablished Series
TAXONOMIC CLASS: Fine-loamy, siliceous, active, thermic Typic Paleudalfs
TYPICAL PEDON: Darbonne loamy fine sand--on a 3 percent convex east-facing slope in mixed hardwoods and pine.
(Colors are for moist soil unless otherwise stated.)
A--0 to 5 inches; dark grayish brown (10YR 4/2) loamy fine sand; weak fine granular structure; very friable; many fine and medium roots; few coarse roots; small, angular, flattened and slightly rounded fragments of ironstone make up about 10 percent of the volume; about 10 percent of the fragments are larger than 3/4-inch in diameter; slightly acid; clear smooth boundary. (3 to 7 inches thick)
BE--5 to 13 inches; yellowish red (5YR 5/6) loamy fine sand; weak medium subangular blocky structure; very friable; common fine and medium roots; few coarse roots; some of the root channels are filled with A material; small, angular, flattened, and slightly rounded fragments of ironstone make up about 5 percent of the volume; about 10 percent of the fragments are larger than 3/4-inch in diameter; slightly acid; clear wavy boundary. (4 to 17 inches thick)
Bt1--13 to 23 inches; red (2.5YR 5/8) fine sandy loam; weak medium subangular blocky structure; friable; common fine and medium roots; a few of the roots channels are filled with A and E material from above; few thin patchy clay films mostly on vertical faces of peds; angular, flattened, and slightly rounded fragments of ironstone make up about 10 percent of the volume; about 10 percent of the fragments are larger than 3/4-inch diameter; medium acid; clear wavy boundary. (5 to 12 inches thick)
Bt2--23 to 35 inches; red (2.5Y 4/6) gravelly sandy clay loam; moderate medium and fine subangular blocky structure; firm; few fine roots; common thick continuous clay films on faces of peds; angular and flattened fragments of ironstone make up about 25 percent of the volume; about 40 percent of the angular fragments are larger than 3/4-inch in diameter; flattened fragments are 1/4 to 8 inches thick and 1/2 to 3 inches long; thick coatings of clay are on surfaces of some fragments; strongly acid; clear smooth boundary. (8 to 15 inches thick)
Bt3--35 to 45 inches; red (2.5YR 4/8) gravelly sandy clay loam; moderate medium subangular blocky structure; friable; few fine roots; thin patchy clay films on faces of peds; many fragments of ironstone that are flattened and angular, 1/2 to 4 inches thick, 1 to 8 inches long, and make up about 30 percent of the volume of the horizon. Some of the fragments lie end-to-end and appear as a discontinuous layer; few pockets and common thick coatings on ironstone fragments of yellowish brown (10YR 5/6) fine sandy loam; strongly acid; clear smooth boundary. (6 to 12 inches thick)
B/C1--45 to 57 inches; yellowish red (5YR 5/6) sandy clay loam (Bt) and yellowish brown (10YR 5/8) fine sandy loam (C); weak coarse and medium subangular blocky structure; the Bt part is firm; the C part is slightly hard and slightly brittle and makes up 20 percent of the volume; flattened and angular fragments of ironstone make up less than 5 percent of the volume; few fine and medium pockets and horizontal seams of light brownish gray (10YR 6/2) clay; few vertical and horizontal seams and peds coatings of red (2.5YR 4/8) clay; strongly acid; gradual wavy boundary. (6 to 15 inches thick)
B/C2--57 to 70 inches; red (2.5YR 5/6) and yellowish red (5YR 5/6) sandy clay loam (Bt) and yellowish brown (10YR 5/8) weakly cemented sandstone; (C); the Bt part has weak coarse and medium subangular blocky structure and firm consistence; the C part is hard and brittle and can be easily cut with a spade; the C part is in small pockets and strata and makes up about 30 percent of the cross-section; few fine roots are concentrated in the Bt material; thick coatings of red (2.5YR 4/8) clay are on some vertical faces of peds; common medium pockets of light brownish gray (10YR 6/2) clay; strongly acid.
TYPE LOCATION: Claiborne Parish, Louisiana; 3 miles east and 2 miles south of Lisbon, 475 feet north and 200 feet east of the southwest corner of sec. 28, T. 21 N., R. 4 W.
RANGE IN CHARACTERISTICS: The thickness of solum ranges from 50 to 80 inches. The base saturation is greater than 50 percent in the upper part of the solum and decreases with depth. Typically, fragments of ironstone are scattered throughout the solum and at least one subhorizon of the argillic horizon contains many fragments that make up from 15 to 60 percent of the volume. Fragments of ironstone make up from 5 to 35 percent of the volume of the particle-size control section. The volume of coarse fragments decreases with depth in most pedons. The caly content of the series control section averages 18 to 35 percent.
The A horizon has hue of 10YR, value of 4 or 5, and chroma of 2 or 3. It is loamy fine sand, fine sandy loam, sandy loam, loam, or their gravelly counterparts. Reaction ranges from very strongly acid to slightly acid.
The BE horizon has hue of 2.5YR, 5YR, 7.5YR or 10YR, value of 4 to 6, and chroma of 3 to 8. It is loamy fine sand, fine sandy loam, or their gravelly or very gravelly counterparts. Reaction ranges from very strongly acid to slightly acid.
Some pedons have an E horizon. Where present, it has hue of 7.5YR or 10YR, value of 5 or 6, and chroma of 2 to 4. Texture is loamy fine sand, fine sandy loam, or their gravelly counterparts. Reaction of the E horizon ranges from very strongly acid to slightly acid. The combined thckness of the A and E or A and BE horizons ranges from 7 to 20 inches where the texture is loamy fine sand and from 7 to 24 inches where the texture is fine sandy loam.
The Bt horizon has hue of 2.5YR, 5YR, or 7.5YR, value of 4 or 5, and chroma of 4 to 8. Mottles in shades of yellow, red, and brown range from none to common. Texture is fine sandy loam, loam, sandy clay loam, clay loam, or their gravelly or very gravelly counterparts. Individual subhorizons contain fragments of ironstone that can make up as little as 1 percent of the volume or as much as 60 percent. One or more discontinuous to nearly continuous layers of fractured ironstone are in the Bt horizon of some pedons. Where present, the layers range in thickness from 1/4 to 8 inches. The lateral distance between fractures in the layers ranges from 2 to 10 inches and averages 2 to 4 inches. Pockets and streaks of grayish or whitish clay and yellowish loamy or sandy material range from none to common. Reaction ranges from very strongly acid to medium acid.
The B/C1 horizon consists of reddish loamy material (Bt) and yellowish loamy or sandy material (C). The Bt part has colors similar to those of the Bt horizon, except that hue of 10R is included. Its texture is fine sandy loam, loam, sandy clay loam, or clay loam. The consistence of the Bt part ranges from friable to firm and it is slightly brittle in some pedons. The C part has hue of 10YR or 7.5YR, value of 4 to 6, and chroma of 4 to 8. It makes up 20 to 40 percent of the horizon. Texture is loamy fine sand, loamy sand, fine sandy loam, or sandy loam. Consistence of the C part typically is slightly hard or hard and slightly brittle or brittle, and it is friable to loose in some pedons. Small to large pockets or layers of weakly cemented sandstone make up the C part in some pedons. Small pockets, streaks, and strata of grayish or whitish clay range from few to common. Fragments of ironstone make up from less than 1 percent to as much as 5 percent of the horizon. The reaction of the B/C horizon ranges from very strongly acid to medium acid.
The B/C2 horizon is similar to the B/C1 horizon, except that the C part of the B/C2 horizon has more weakly cemented sandston that makes up from 30 to 50 percent of the volume. The C part is hard and brittle, but it can be easily cut with a spade. The C part is in small to large pockets and strata. Few to common fine and medium roots are concentrated in the Bt material. The Bt part is mainly narrow to wide, vertically oriented clay flows. Thin or thick clay films are on some ped faces of the Bt material Small to large pockets and streaks of grayish or whitish clay or shaly clay range from few to common.
Some pedons have a BC horizon. Where present, it has hue of 7.5YR to 10R value of 4 or 6, and chroma of 6 or 8. Mottles in shades of yellow or brown range from none to common. Texture is sandy clay loam, clay loam, or loam. Reaction ranges form very strongly acid to medium acid. COMPETING SERIES: These are the Attoyao, Caledonia, Elrose, Petal, and Sallisaw series in the same family and the Cuthbert, Kirvin, Ruston, and Vaucluse series. None of the competing soils formed in materials high in content of siderite. The Attoyao, Caledonia, Petal, Ruston, and Sallisaw soils do not contain fragments or layers of ironstone in the solum. In addition, the Petal soils have a clayey lower Bt horizon and the Sallisaw soils have a gravelly lower 2B horizon. The Elrose and Vaucluse soils contain fragments of ironstone that make up less than 15 percent by volume of the argillic horizon. In addition, the Elrose soils contain fragments of glaucontie within the solum. The Cutherbert and Kirvin soils are clayey and have a base saturation of less than 35 percent at a depth of 50 inches below the top of the argillic horizon.
GEOGRAPHIC SETTING: These soils are on ridgetops and upper side slopes in the uplands of the Western Coastal Plain. Slopes range from 1 to 8 percent. The soils formed in iron-rich, loamy, marine sediments. The primary source of iron is siderite. The typical pedon is forming in sediments of the Cockfield or Cook Mountain Formation, Claiborne Group, Eocene series. The mean annual temperature is 64 degrees F, and the mean annual precipitation is 51 inches near the type location.
GEOGRAPHICALLY ASSOCIATED SOILS: These are Bowie, Cuthbert, LaRue, Kirvin, and Sacul soils. The Bowie soils are in similar positions, have a hue of 10YR or 7.5YR in the argillic horizon, and have a subhorizon within 60 inches of the soil surface that has more than 5 percent plinthite. The LaRue soils are in similar positions and have a sandy epipedon that is 20 to 40 inches thick. The Cuthbert, Kirvin and Sacul soils are in similar positions as Darbonne soils, and have a clayey argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained; moderately slow permeability; medium runoff.
USE AND VEGETATION: Most areas of Darbonne soils are in woodland. Some areas are used for pasture and cultivated crops. Loblolly pine is the main commercially grown tree species. Coastal bermudagrass and bahiagrass are the principal pasture plants grown. Native vegetation was mainly hardwood trees.
DISTRIBUTION AND EXTENT: Western Coastal Plain in Louisiana and Texas. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Temple, Texas
SERIES ESTABLISHED: Claiborne Parish, Louisiana, 1986.
ADDITIONAL DATA: The pedon was sampled for complete characterization analyses by Louisiana Agricultural Experiment Station, sample S84LA-027-004(1-7). Data for a similar soil included with the Darbonne soils in mapping was provided by NSSL, sample No. S82LA027-012(1-6).