LOCATION MOUNTAINBURG AR+AL GAEstablished Series
TAXONOMIC CLASS: Loamy-skeletal, siliceous, subactive, thermic Lithic Hapludults
TYPICAL PEDON: Mountainburg cobbly fine sandy loam, 20 percent slope, forested.
(Colors are for moist soil unless otherwise stated.)
A--O to 1 inches; very dark grayish brown (10YR 3/2) cobbly fine sandy loam; moderate medium granular structure; very friable; many fine and medium roots; about 30 percent by volume sandstone fragments 1/4 inch to 12 inches or more in diameter; moderately acid; clear smooth boundary. (1 to 6 inches thick)
E--1 to 6 inches; brown (10YR 5/3) cobbly fine sandy loam; weak medium subangular blocky structure; very friable; many fine and medium roots; about 30 percent by volume sandstone fragments 1/4 inch to 12 inches or more in diameter; strongly acid; clear smooth boundary. (0 to 8 inches thick)
Bt--6 to 18 inches; strong brown (7.5YR 5/6) very cobbly sandy clay loam, weak medium subangular blocky structure; friable; many fine and medium roots; about 40 percent by volume sandstone fragments 1/4 inch to 12 inches or more in diameter; strongly acid; clear smooth boundary. (6 to 14 inches thick)
R--18 to 20 inches; horizontally bedded, hard, sandstone bedrock.
TYPE LOCATION: Washington County, Arkansas; SE1/4SE1/4NE1/4, sec. 28, T. 15 N., R. 32 W.
RANGE IN CHARACTERISTICS: Solum thickness and depth to bedrock ranges from 12 to 20 inches. Sandstone fragments less than 3 inches in diameter range from 10 to 60 percent by volume and fragments greater than 3 inches in diameter range from 0 to 50 percent by volume in the A, E, and BE horizons. Total coarse fragment content ranges from 10 to 60 percent by volume. Sandstone fragments less than 3 inches in diameter range from 30 to 60 percent by volume and fragments greater than 3 inches in diameter range from 5 to 50 percent by volume in the B horizon. Total coarse fragment content ranges from 35 to 75 percent by volume in the B horizon. Reaction ranges from very strongly acid to moderately acid in the A, E, and BE horizons, and is very strongly acid or strongly acid in the B horizon.
The A horizon has hue of 10YR, value of 3 or 4, and chroma of 2 or 3. In cultivated area, the Ap horizon has hue of 10YR, value of 4 or 5, and chroma of 3 or 4, or with value of 4 and chroma of 2. Texture is sandy loam, fine sandy loam, very fine sandy loam, loam, or their gravelly, very gravelly, cobbly, very cobbly, stony or very stony analogs.
The E horizon has hue of 10YR, value of 4 through 6, and chroma of 3 or 4. Texture is sandy loam, fine sandy loam, very fine sandy loam, or their gravelly, very gravelly, cobbly, very cobbly, stony, or very stony analogs.
The BE horizon, where present, has hue of 10YR or 7.5YR, value of 4 or 5, and chroma of 6. Texture is sandy loam, fine sandy loam, very fine sandy loam, loam, or their gravelly, very gravelly, cobbly, very cobbly, stony, or very stony analogs.
The Bt horizon has hue of 10YR or 7.5YR, value of 5, and chroma of 4 or 6; or it has hue of 5YR, value of 4 or 5 and chroma of 4 or 6, or with value of 5, and chroma of 8. Texture is very gravelly fine sandy loam, very gravelly sandy loam, very gravelly loam, very gravelly sandy clay loam, or their extremely gravelly, very cobbly, extremely cobbly, or very stony analogs.
The R horizon is horizontally bedded, acid, hard, sandstone bedrock.
COMPETING SERIES: Mountainburg is the only series in this family. Series in closely related families include Basehor, Clebit, Hector, Linker, Ramsey, and Steprock. Basehor and Ramsey soils have mean annual soil temperatures of less than 59 degrees F; contain less coarse fragments, and do not have argillic horizons. Clebit soils do not have an argillic horizon and are formed in residuum of tilted and folded interbedded sandstone and shale bedrock. Hector soils do not have an argillic horizon and contains less coarse fragments. Linker soils contain less coarse fragments and are deeper to bedrock. Steprock soils are deeper to a paralithic contact.
GEOGRAPHIC SETTING: Mountainburg soils are on nearly level ridgetops and plateaus to very steep mountainsides. The slope gradients range from 1 to 65 percent. The soils formed in residuum of hard, massive, horizontally bedded sandstone. The mean annual temperature is about 59 degrees F. Average annual rainfall ranges from 42 to 52 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These include the competing Hector, Linker, and Steprock soils and Enders, Hartsells, Leesburg, and Nella soils. Enders, Leesburg, and Nella soils, which occur on similar landscapes have thicker sola and are deeper to bedrock.
DRAINAGE AND PERMEABILITY: Well drained, slow to rapid runoff; moderately rapid internal drainage; moderately rapid permeability.
USE AND VEGETATION: Most areas are in woodland. Vegetation is dominantly mixed hardwood forests of upland oaks, elms, and hickories, or is in mixed hardwood pine-forest. Minor areas have been cleared and are in pasture.
DISTRIBUTION AND EXTENT: Mountain plateaus, ridges, and mountainsides of the Boston Mountains of Arkansas and Oklahoma, and of the Cumberland and Sand Mountains of Alabama, Kentucky, and Tennessee. The soil is of large extent.
MLRA OFFICE RESPONSIBLE: Little Rock, Arkansas
SERIES ESTABLISHED: Washington County, Arkansas; 1970.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the surface to a depth of 6 inches.
Argillic horizon - The zone from 6 inches to 18 inches.
Loamy-skeletal - Particle size class - More than 35 percent by volume rock fragments larger than 2mm in diameter in the 6 to 18 inch zone.
Lithic contact - Boundary between soil and underlying coherent bedrock.