summary Wind action has modified relics of river systems which drained the southern and central parts of Western Australia. Dunes of both coarse crystalline and fine floury gypsum and lunettes of sand, silt, or clay size material are common near to the leeward margin of salt lakes. Further removed, materials, blown out from the lake areas as aggregates of clay, silt, and sand, are deposited as sheets which are medium‐textured and have a high lime content. The latter deposits have been termed lake parnas.
Abstract The micromorphology of a yellow earthy sand profile (P549) from the Western Australian sand plains, originally reported in the Handbook of Australian Soils (Stace et al., 1968, pp. 48–50), has been re‐examined in more detail and compared with samples of indurated lateritic mottled‐pallid zone material. The evidence, based on field relationships, and on a comparison of the fabric of the lateritic material with the glaebules in the yellow sand profile, strongly supports the hypothesis that the upper zone of the sand plains consists of a transported sedimentary (colluvial) deposit derived by erosion from an older lateritic profile. The profile examined is derived from indurated mottled‐pallid zone material. It is unnecessary to postulate repeated episodes of erosion and deposition to explain the ‘sandy’ nature of the profile which, in fact, contains a high proportion of argillaceous glaebules. The profile is ‘young’ at least in the sense of profile development.
Abstract The distribution of remnants of a system of conglomeratic sediments is described in the Harvey district of southwestern Australia. A study of their relationship to the major physiographic elements and to laterite gives rise to certain suggestions regarding landscape development in the southwestern margin of the Western Australian Precambrian Shield. A tentative correlation, based largely on comparable lithology and physiographic setting, places these materials in the Mesozoic. The distribution of sediments bears only slight relationship to the present drainage. They were emplaced in a prior valley system and have been dismembered in the development of the present drainage system. All major elements of the landscape, including parts of the Darling Scarp, have been subjected to deep lateritic weathering. Lateritized remnants of the sediments progress from the upland surface to well down into the valleys and onto the Ridge Hill Shelf, which flanks the Darling Scarp. Caution is needed in placing laterite development in a chronological framework, or in using it as an indicator of very low relief. Thus it is not clear whether laterite development is related to a long period of time encompassing several major phases of landscape development or took place after all major physiographic elements had developed.
Abstract Over much of arid Western Australia a red and brown hardpan occurs on broad plains; it may lie either on the surface or buried beneath a shallow mantle of soil. It is proposed that, because of its lithological character and its considerable thickness and extent, it should be given the name of Wiluna Hardpan. The proposed type section is north of Wiluna, near Bulloo Downs homestead, where headward erosion of the Ashburton River is exposing sections 30 m deep. Although both ferruginous and calcareous cement may be present, Wiluna Hardpan is largely indurated with silica. It is younger than laterite, but broadly contemporaneous with calcrete and Robe Pisolite. Initially it was probably geographically restricted by a coincidence of suitable conditions of low relief and a climate resulting in episodic flooding and desiccation. Its present distribution is partly controlled by current erosional and depositional processes.
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