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The chemistry and mineralogy of ’’lateritic’ materials in southern Australia reflect various modes of formation and the different facies of ferricretes may indicate environmental conditions during their formation. Consequently, the detailed characteristics of different ferricretes may represent ’tape recordings’ of their epigenetic histories.

Former uniform blankets of ’laterite’ may not have existed over large areas, but different types of ferricrete, mottled arid bleached zones may have developed in specific sites in response to local environments. Ferricretes are relatively rare and are often absent above pallid and/or mottled zones, suggesting the erosional truncation of former complete ’laterite profiles’. However, it may be that the crusts had never developed.

No reliable indication of age appears to derive from the morphology, chemistry or mineralogy of the ferricretes or their component parts, as similar ranges of weathering and ferruginous materials occur on lowland and summit surfaces. However, ferricretes with the greatest mineralogical diversity appear to have much more complex and lengthy histories of evolution than do ferricretes and mottles with simple iron oxide mineralogies.

Weathering of a landsurface of some relief could have led to considerable lateral variations in environmental conditions, causing bleaching of iron from some higher parts of the landscape and accumulation in adjacent lower-lying areas, forming ferricreted sediments and bedrock, and slabby and vesicular ferricretes. Within the zone of water table fluctuation, primary iron minerals in bedrock were degraded under reducing conditions, forming ferrous iron that was redistributed and segregated within the weathered and partly kaolinised rock to form ferric iron-rich mottles under oxidising conditions.

As surface weathering and erosion proceeded the hematitic mottles were progressively exposed at the surface, where they hardened, disintegrated, transformed partially to goethite, and formed lags. No thick residual lags formed on steep slopes, but only thin layers of pisoliths developed, on and within soils that directly overlie the mottled material. Pisolith evolution in these areas occurred during physical transport from higher to lower parts of the landscape. Pisolitic to nodular ferricretes required variable, lateral physical transport of the nodules and pisoliths, their accumulation and cementation.