In view of diverse understanding on the movement and accumulation of clay particles in Vertisols, a study on seven benchmark calcareous Vertisols representing a climosequence from sub-humid moist to arid dry climate was undertaken. The Vertisols have clay enriched slickensided horizons (Bss) (>=8 percent absolute increase from the eluvial horizon). The study indicates that the clay enrichment in the Bss horizons due to illuviation of clay particles and their subsequent accumulation in the Bss horizons have been possible because of the dispersion of the clay particles caused by Mg~(2+) and Na~+ ions when precipitation of soluble Ca~(2+) ions as calcium carbonate (CaCO_3) occurs. The formation of CaCO_3 and the illuviation of clay are two pedogenetic processes occurring simultaneously as comtemporary pedogenic events in drier climate since the late Holocene. Thus, the argilliturbation towards proisotropic pedoturbation has not been able to overtake the clay illuviation in Vertisols under study for thousands of years.
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