Evidence for Clay Translocation in Coastal Plain Soils with Sandy/Loamy Boundaries

Abstract

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 (>50 cm).

Assessing lithologic discontinuities and parent material uniformity within the Texas sandy mantle and implications for archaeological burial and preservation potential in upland settings

“…For many geologists and pedologists, uniformity of parent material is still in question for contrasting-textured Alfisols in many geomorphic settings of the Gulf Coastal Plain. As a result, identifying lithologic discontinuities, which include significant changes in particle-size distributions or mineralogy representing differences in lithology, is crucial to pedogenic interpretation (Chapman and Horn, 1968;Raad and Prozt, 1971;Cabrera-Martinez et al, 1989;Schaetzl, 1998;Hallmark and Franzmeier, 1999).…”

“…3a). Because of abrupt textural differences between the A-E and Bt horizons, archaeologists, pedologists, and geologists have differing views (pedogenic vs. geomorphic) on its origin, and the context in which artifacts became buried is the subject of controversy (Heinrich, 1986;Perttula et al, 1986;Mandel, 1987;Cabrera-Martinez et al, 1989;Collins and Bousman, 1992;Thoms, 1993;Hallmark and Franzmeier, 1999;Rogers, 1999;Bruseth and Martin, 2001;Frederick et al, 2002;Phillips, 2004Phillips, , 2007. A pedogenic viewpoint attributes the textural differences to pedogenic alteration of sandy and loamy Tertiary parent material, whereby clay formation and translocation resulted in the observed A-E-Bt horizon sequence (Fig.…”

Problems arising from fixed-depth assessment of deeply weathered sandy soils

“…Entisols on old landscapes, with albic horizons or with grain coatings dominated by resistant minerals, should be described as having E or Bw horizons. The issue raised here, however, is not whether the horizon is a C or E or Bw, or whether the sandy/loamy boundary is pedogenic or a lithologic discontinuity as addressed by some researchers (e.g., Carlisle, 1962;Gamble et al, 1970;Cabrera-Martinez et al, 1989). These questions should ultimately be resolved based on the scientific evidence at hand.…”

Genesis of Soils on Two Stream Terrace Levels on the Tennessee River

“…Particle-size distribution was determined by the pipette method (Gee and Bauder, 1986). Ratios of fine and very fine sand to total sand were plotted with depth to identify various depositional layers (Cabrera-Martinez et al, 1989).…”