LOCATION DELASSUS MOEstablished Series
TAXONOMIC CLASS: Fine-loamy, mixed, active, mesic Typic Fragiudults
TYPICAL PEDON: Delassus silt loam - on a north facing convex slope of 3 percent under mixed hardwoods at 975 feet elevation. (Colors are for moist soil unless otherwise stated.)
A--0 to 3 inches; brown (10YR 4/3) silt loam, pale brown (10YR 6/3) dry; moderate fine and very fine granular structure; friable; many very fine and few fine roots; neutral; abrupt smooth boundary. (2 to 7 inches thick)
E--3 to 7 inches; yellowish brown (10YR 5/4) silt loam with about 10 percent mixing of brown (10YR 4/3) A horizon material; weak fine granular structure; friable; common very fine and few fine roots; moderately acid; clear wavy boundary. (2 to 7 inches thick)
BE--7 to 13 inches; brown (7.5YR 5/4) silt loam; moderate medium and fine subangular blocky structure; friable; common fine and few very fine roots; strongly acid; clear wavy boundary. (0 to 8 inches thick)
Bt--13 to 26 inches; brown (7.5YR 4/4) silty clay loam; moderate medium and fine subangular blocky structure; firm; few faint reddish brown clay films on faces of peds; common fine and few medium and very fine roots; very strongly acid; clear smooth boundary. (7 to 24 inches thick)
2E--26 to 31 inches; light yellowish brown (10YR 6/4) silt loam; many coarse faint dark yellowish brown (10YR 4/6) masses of iron accumulation; weak thin and medium platy structure; firm; common fine and very fine roots along horizontal plates; extremely acid; abrupt smooth boundary. (0 to 10 inches thick)
2Btxl--31 to 45 inches; light brownish gray (10YR 6/2) loam; common medium distinct dark yellowish brown (10YR 4/6) masses of iron accululation; moderate very coarse prismatic structure, ped interiors massive; very firm; brittle, very hard; few very fine roots along faces of prisms; few faint dark brown clay films and flows on vertical faces of prisms; extremely acid; gradual wavy boundary.
2Btx2--45 to 61 inches; reddish yellow (7.5YR 6/6) loam; many coarse distinct light brownish gray (10YR 6/2) iron depletions; weak very coarse prismatic structure, ped interiors massive; very firm; brittle, very hard; few faint brown clay films and flows on vertical faces of prisms; 2 percent granite fragments - one small stone and a few pebbles; extremely acid; abrupt wavy boundary. (Combined thickness of the 2Btx horizons is 20 to 60 inches.)
2R--61 inches; red granite.
TYPE LOCATION: St. Francois County, Missouri; about 6 miles south of Farmington; 1980 feet south and 2210 feet west of the northeast corner, sec. 2, T. 34 N., R. 5 E; USGS Wachita Mountain quadrangle, lat. 37 degrees 40 minutes 57 seconds N. and long. 90 degrees 26 minutes 49 seconds W.
RANGE IN CHARACTERISTICS:
Depth to the 2Btx: 20 to 36 inches
Solum thickness: 48 to 72 inches
Depth to bedrock: 48 to 100 inches
A or Ap horizon:
Hue of 7.5YR or 10YR
Value of 3 to 5
Chroma of 2 to 4
Fine earth-silt loam or loam
Rock fragments--0 to 27 percent
Reaction: very strongly acid to neutral
E horizon
Hue: 7.5YR or 10YR
Value: 3 to 6
Chroma: 2 to 6
Fine earth: silt loam or loam
Rock fragments: 0 to 27 percent
Reaction: very strongly acid to neutral
BE and Bt horizon (upper part)
Hue: 5YR to 10YR
Value: 4 to 6
Chroma: 3 to 6
Fine earth: silt loam, loam, or silty clay loam
Rock fragments: 0 to 27 percent
Reaction: very strongly acid to moderately acid
Bt horizon (lower part)
Hue: 5YR to 10YR
Value: 4 to 6
Chroma: 3 to 6
Fine earth: silt loam, clay loam, loam, or silty clay loam
Rock fragments: 0 to 27 percent
Reaction: extremely acid to strongly acid
2E horizon
Hue: 5YR to 2.5Y
Value: 4 to 7
Chroma: 2 to 6
Fine earth: silt loam or loam
Rock fragments: 0 to 35 percent
Reaction: extremely acid or very strongly acid
2Btx horizon
Hue: 5YR to 2.5Y
Value: 4 to 6
Chroma: 2 to 8
Fine earth: silt loam, loam, silty clay loam, clay loam, sandy loam, sandy clay loam, or coarse sandy loam
Rock fragments: 0 to 60 percent
Reaction: extremely acid to strongly acid
3Bt horizon (where present)
Hue: 2.5YR to 10YR
Value: 3 to 7
Chroma: 1 to 8
Fine earth: silt loam, loam, silty clay loam, or clay
Rock fragments: 5 to 60 percent
Reaction: extremely acid to strongly acid
COMPETING SERIES: These are the Annandale, Beltsville, Califon, Hanover, Meckesville, Monongahela, Tonti, Trego, and Watson series. Annandale soils have fragipans of gravelly sandy loam and formed in glacial till derived from gneiss. Beltsville soils are semiactive and formed in silty sediments over coastal plain gravelly and sandy sediments. Califon soils have formed in deeply weathered till or colluvium and rock fragments derived predominantly from granitic gneiss. Hanover soils have rock fragments dominated by sandstone. Meckesville soils have hues of 5YR or redder in the fragipan. Monongahela soils are semiactive and formed in alluvium. Trego soils have B horizons with more than 40 percent sand. Tonti soils formed in cherty residuum from limestone. Watson soils have formed in glacial till and contain rock fragments derived from sandstone and shale.
GEOGRAPHIC SETTING: Delassus soils are on broad smooth to undulating uplands, saddles, and on talus slopes. Slopes range from 2 to 15 percent. They formed in loess mixed with slope alluvium, and the underlying slope alluvium or residuum weathered from granite or similar igneous rocks. Mean annual temperature ranges from 52 to 57 degrees F, and mean annual precipitation ranges from 40 to 47 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Irondale, Knobtop, Loughboro, and Syenite soils. None of these soils have a fragipan. Irondale and Knobtop soils are associated with fine textured felsitic parent rock and are located at higher elevations and on steeper slopes. In addition, the Irondale soils are very stony and both Knobtop and Irondale soils are moderately deep to hard rock. Loughboro soils have colors of lower chroma and a clayey subsoil and are on nearly level uplands. Syenite soils are very bouldery and are on steeper upland side slopes.
DRAINAGE AND PERMEABILITY: Moderately well drained. Surface runoff is medium to high. Permeability is moderate above the fragipan, and very slow in the fragipan. The saturated hydraulic conducivity is moderately high above the fragipan, and low in the fragipan.
USE AND VEGETATION: The majority of the area remains in native hardwood forest dominated by upland oaks. Those areas that are cleared are used for hay, pasture, and row crops. Fescue, orchard grass, and native grasses are the principal hay and pasture plants and wheat, corn, and grain sorghum are the principal cultivated crops.
DISTRIBUTION AND EXTENT: The St. Francois Mountains of the eastern Ozarks area (MLRA 116C) of southeast Missouri. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Morgantown, West Virginia
SERIES ESTABLISHED: St. Francois County, Missouri, 1979.
REMARKS: Diagnostic horizons and features recognized in this series are:
ochric epipedon - the zone from the surface of the soil to a depth of 13 inches (A, E, and BE horizons);
argillic horizon above the fragipan - the zone from approximately 13 to 26 inches (Bt1 horizon);
fragipan and lower argillic horizon - the zone from approximately 31 to 61 inches (2Btx1 and 2Btx2 horizons).
ADDITIONAL DATA: Characterization data is available on two pedons: Sample Nos. S73MO-94 and S73MO-62, MTSC, Soil Survey Investigations Unit, April 1975.