Aluminium substitution in goethites in soils from alluvium, Gippsland, Victoria

Abstract

The nature of the iron oxides associated with a chronosequence of soils on silty sediments in Gippsland was investigated. The soils range from 5 000 to approximately 763 000 years in age. Iron is present in the unaltered sediments, as represented by the younger soils, mainly as hematite. As the soils develop, this is replaced by goethite, which becomes more aluminous with increasing age. Thus there is continuing pedogenic development throughout the time scale investigated. In the A and B horizons of the older soils, small, coarse-sand sized hematite or maghemite concretions develop in the clay B horizons, and remain as a constituent of the light-textured A horizons as these develop through loss of the clay component of the soil by eluviation and lateral transport.