Field relationships of ferricretes and weathered zones in southern South Australia: a contribution to 'laterite' studies in Australia

Abstract

Terrestrial landscapes have existed in parts of southern South Australia since the Carboniferous to Permian Gondwanaland glaciation. Widespread weathered zones and ferricrete horizons and crusts on present highland surfaces in the region have been ascribed by various workers to Mesozoic or early Tertiary weathering phases. A critical examination of field relationships, however, points instead to complex reworking and continuous weathering of relic landscapes since early Mesozoic times, leading to the intricate patterns of sediments and soils forming the present regolith. Ferricrete crusts sporadically distributed on the highland surfaces are interpreted dominantly as remnants of iron-impregnated sediments of ancient valleys or depressions. The great but variable thickness of kaolinized bedrock beneath the highland surfaces, regarded by other workers as the mottled and pallid zones of a 'laterite' profile, is the integrated product of leaching and weathering throughout the Mesozoic and Cainozoic and cannot be assigned to separate and distinct climatic events. The use of weathered landsurfaces and ferricretes as morphostratigraphic markers in such landscapes is questionable.