Micromorphological evidence of clay translocation in poorly dispersible soils

Abstract

Clay translocation is an important pedogenic process. Field and laboratory studies are used herein to evaluate the process in some Ultisols and Oxisols having horizons with poor dispersion characteristics. Surface areas measured by ethylene glycol monoethyl ether (EGME) and micromorphological studies confirmed the presence of argillic horizons in the Ultisols. Two of the Oxisols also have illuviation argillans, but most of these are below oxic horizons. Staining and cementation by Fe and Al oxides in soils in the oxidic families appear to have masked evidence of clay accumulation except in lower horizons. Because overlying horizons do not disperse well, we conclude that either environmental conditions changed or else weathering became more intense following development of the argillic horizons. Climatic shifts and continued intense weathering apparently are responsible for formation of the low-activity clays, and the iron and aluminum oxide cementation causing the poor dispersion.