LOCATION PURDHAM ARTentative Series
TAXONOMIC CLASS: Loamy-skeletal, mixed, semiactive, thermic Oxyaquic Hapludults
TYPICAL PEDON: Purdham gravelly loam, in red oak, post oak and hickory forest
(Colors are for moist soil unless otherwise stated.)
A--0 to 4 inches; very dark grayish brown (10YR 3/2) gravelly loam; moderate medium granular structure; friable; common coarse, common medium, and common fine roots; common fine and common medium pores; about 20 percent angular and subangular sandstone pebbles less than 3 inches in diameter; very strongly acid; clear smooth boundary.
BA--4 to 8 inches; brown (7.5YR 4/4) gravelly loam; weak fine subangular blocky structure; friable; common coarse, common medium and common fine pores; common fine and common medium pores; about 30 percent angular and subangular percent sandstone pebbles less than 3 inches in diameter; very strongly acid; clear smooth boundary.
Bt1--8 to 16 inches; strong brown (7.5YR 4/6) very channery loam; moderate medium and fine subangular blocky structure; friable; common fine, common medium and common coarse roots; common fine and common medium pores; few faint yellowish red (5YR 5/6) clay films on faces of peds and on surfaces along some pores; about 40 percent subangular sandstone channers less than 6 inches in length oriented 20 to 60 degrees from horizontal; very strongly acid; clear smooth boundary.
Bt2--16 to 25 inches; strong brown (7.5YR 5/6) very channery loam; moderate medium and fine subangular blocky structure; firm; common fine, common medium and few coarse roots; common fine and common medium pores; common distinct yellowish red (5YR 5/6) clay films on faces of peds and on surfaces along some pores; few medium prominent red (2.5YR 4/6) iron accumulations on faces of peds; few medium distinct yellowish brown (10YR 5/4) iron depletions on faces of peds; about 55 percent subangular sandstone channers less than 6 inches in length oriented 20 to 60 degrees from horizontal; very strongly acid; clear wavy boundary.
2Bt3--25 to 38 inches; yellowish red (5YR 5/6) very channery silty clay; moderate medium and fine angular blocky structure; firm; few fine and few medium roots; common very fine and common fine pores; many distinct yellowish red (5YR 5/6) and gray (10YR 6/1) clay films on faces of peds and on surfaces along pores; common medium and fine distinct red (10R 4/6) masses of iron accumulations on faces of peds and lining pores; common fine and common medium distinct strong brown (7.5YR 5/8) masses iron accumulations in matrix; common fine and medium gray (10YR 6/1) iron depletions on faces of peds and lining pores; about 40 percent shale channers less than 6 inches in length oriented 20 to 60 degrees from horizontal; very strongly acid; clear wavy boundary.
2Cr--38 to 45 inches; soft platy shale bedrock with black interiors and red, gray, brown and black exteriors tilted 20 to 90 degrees from horizontal.
TYPE LOCATION: Pulaski County, Arkansas; NW1/4 SE1/4 NE1/4 SE1/4, sec. 8, T. 3 N., R. 12 W., lat. 92 degrees, 18 minutes, 19 second, long. 34 degrees, 54 minutes, 22 seconds, Cato Quadrangle.
RANGE IN CHARACTERISTICS: Solum thickness and depth to shale or interbedded shale and sandstone bedrock ranges from 20 to 40 inches. Due to the wavy boundary between the 2Bt horizon and the underlying tilted bedrock, it is extremely variable within short distances. Reaction ranges from moderately acid to very strongly acid A, BA, horizons and from very strongly acid to extremely acid in the Bt and 2Bt horizons. Sandstone fragments less than 3 inches in diameter and/or less than 6 inches in length range from about 5 to 60 percent by volume in the A and BA horizons. Sandstone fragments less than 3 inches in diameter and/or less than 6 inches in length range from 35 to 60 percent in the Bt horizon. Shale and sandstone fragments less than 6 inches in length range from 20 to 60 percent by volume in the 2Bt horizon.
The A horizon has hue of 10YR, value of 4, and chroma of 3 or 4, or where the A horizon is less than 6 inches thick, it includes hue of 10YR, value of 3 and chroma of 2. Texture is fine sandy loam, silt loam, or their gravelly, or very gravelly analogs.
The BA horizon has hue of 7.5YR, value of 4, and chroma of 4 or 6, or value of 5 and chroma of 6 or 8. Texture is fine sandy loam, loam, silt loam, or their gravelly, or very gravelly analogs.
The Bt horizon has hue of 5YR through 7.5YR, value of 4 to 6, and chroma of 6 or 8. Some pedons contain iron accumulations and depletions in shades of brown, yellow and red. Texture is very gravelly loam, very channery loam, very gravelly clay loam, or very channery clay loam.
The 2Bt horizons have hue of 2.5YR or 5YR, value of 4 or 5, and chroma of 6 or 8, and iron accumulations and depletions in shades of red, brown, yellow and gray. Some pedons do not have dominant matrix hue and are variegated in shades of red, brown, yellow and gray. Texture is clay loam, silty clay loam, silty clay, clay, or their channery, very channery, or extremely channery analogs.
The 2Cr horizon is soft weathered shale bedrock, or interbedded shale and sandstone or siltstone bedrock in various shades of black, olive, gray, brown, red, and yellow. The beds have a dip of more than 20 degrees from horizontal.
COMPETING SERIES: Purdham is the only series in this family.
GEOGRAPHIC SETTING: Purdham soils are on level to moderately steep hills and ridges within valleys of the Ouachita Mountains. Slopes range from 0 to 15 percent. These soils formed in residuum from tilted, fractured, and folded interbedded sandstone and shale dominantly of Pennsylvanian age. Mean annual precipitation ranges from 41 to 56 inches with the highest amount being distributed in January to May. Mean annual temperature ranges from 60 degrees to 64 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cato, Littlefir, and Psyam series. Cato soils, which occur on toeslopes and valley floors, have a 40 to 60 inch solum, have a fine-loamy family and are moderately well drained. Littlefir soils, which occur on similar landscapes, have a 20 to 50 inch solum and are in a fine family. Psyam soils, which occur on drainageways and valley floors, have a solum over 60 inches, are in a fine-loamy family and are moderately well drained.
DRAINAGE AND PERMEABILITY: Purdham soils are moderately well drained. Runoff is low to high depending on slope. Permeability is slow. These soils are saturated above the bedrock for one month or more, most years.
USE AND VEGETATION: Used mainly for woodland. Native forest vegetation is post oak, blackjack oak, southern red oak hickory and shortleaf pine.
DISTRIBUTION AND EXTENT: Ouachita Mountains of Arkansas and possibly Oklahoma; MLRA 119. The series is minor extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Morgantown, West Virginia
SERIES PROPOSED: Pulaski County, Arkansas; 1998
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - The zone from the soil
surface to a depth of about 5 inches.
Argillic horizon - the zone from a depth of
about 5 to 40 inches.
Paralithic contact - boundary between the 2Bt3
horizon and the underlying soft shale bedrock (Cr).
These soils were formerly included in the Mountainburg series.
ADDITIONAL DATA: Characterization of the typical pedon by the University of Arkansas Soil Characterization Laboratory, NRCS sample number S98AR119-09-(1-5), additional supporting characterization data by the University of Arkansas Soil Characterization Laboratory, NRCS sample numbers S98AR119-03-(1-5) and S98AR1119-04-(1-5).