Evidence for clay translocation in coastal Plain soils with sandy/loamy boundaries
1989
Cabrera-Martinez, F. | Harris, W.G. | Carlisle, V.W. | Collins, M.E.
Soils of the Atlantic Coastal Plain commonly have thick sandy epipedons overlying loamy subsurface horizons. The origin of these sandy/loamy boundaries is often uncertain, due to frequent lack of visible indications of clay translocation. Five soils, which varied in depth to a sandy/loamy boundary, were analyzed for evidences of lithological discontinuity and clay translocation. Four of these soils occurred in close landscape association; the fifth soil, formed in an obviously stratified parent material, was included to test the sensitivity of the methods used. No evidence of a discontinuity was found for the four associated soils. Ratios of dominant sand subfractions to total sand were relatively uniform with depth, as was heavy mineral content of very fine sand. The stratified soil, however, exhibited considerable fluctuation in these parameters. Clay translocation was indicated by (i) the presence of oriented clay coatings on ped surfaces in the Btg horizon of one soil, as verified by micromorphological techniques; and (ii) significantly higher fine-clay to total-clay ratios below the sandy/loamy boundary than above. Results suggest that clay illuviation is a factor in the formation of sandy/loamy boundaries in some Coastal Plain soils even when the boundary is relatively deep (greater than 50 cm).
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