The distribution, nature and origin of some red sesquioxidic materials in Southeastern Queensland, Australia

Abstract Eight deep sections of the red materials and the highly weathered basalt underlying these red soils were sampled and described from seven sites in the Main Range volcanic province of southeastern Queensland. Chemical and mineralogical analyses were performed on sub-samples representative of each type of material. The highly weathered basalts could be discriminated from the red materials on the basis of gross elemental composition and on the mineral assemblages of the fine sand and clay. The differences between these materials, however, were not of the magnitude that would suggest that lateritisation or bauxitisation had been important processes in their development. The red materials studied may be discriminated in the field on morphological criteria and these are described and evaluated. Several hypotheses for their origin are considered, and it is proposed that the red materials sampled are weathered basaltic tephras of similar chemical composition to the associated basalt lavas.