Desert-aeolian origin of late Cenozoic regolith in arid and semi-arid Southwestern Australia

Abstract

Using a sedimentary geology approach, the late Cenozoic regolith of Southwestern Australia is interpreted as basement saprock and saprolite unconformably overlain by sequences of continental sedimentary deposits. The sedimentary deposits which overlie saprock and saprolite are allochthonous, variously altered, and mainly, partly to wholly, desert-aeolian sediments. They include: aeolian and fluvial sandy clayrock facies (e.g. deposits which resemble the pallid and mottled zones of weathered Precambrian bedrock of the traditional “laterite profile”); altered aeolian sand and sandy dust facies (e.g. “hardpan”, lower parts of “duplex soils”, red sandy silt-claystone and calcrete valley fills); altered sandy duststones (e.g. “bauxite”, “laterite” and “ferricrete” of the traditional “laterite profile”); and bioturbated aeolian sand-sheets (e.g. “sandplain soils”, “lateritic sandplains” of the traditional “laterite profile”, and upper parts of “duplex soils”). The allochthonous and desert-aeolian views proposed here differ fundamentally from the traditional residual, colluvial, and erosional views. Consequently there is a need for both traditional and alternative views to be critically appraised from the perspective of sedimentary geology.