Wind action has modified relics of river systems which drained the southern and central parts of Western Australia. Dunes of both coarse crystalline and h e 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 pamas.

The soil pattern in the Merredin district of Western Australia is closely related to a number of readily recognizable landscape features. An understanding of these relationships is proving useful in broad-scale mapping in semi-arid Western Australia and the units so obtained can be readily subdivided for more detailed mapping. Soil and topographic relationships of the five surfaces recognized are described in detail. These are an expression of erosional modifications of a mature Tertiary landscape resulting from changes in landscape stability. Deep lateritic weathering has influenced the chemistry and morphology of large areas of soils. Smaller areas of soils are developed from less weathered material exposed by complete removal of the lateritic profile, and from lake parna resulting from wind deflation of salinized alluvial sediments. The physical and chemical properties of samples from representative soils are summarized and discussed with reference to profiles which are arranged in groups on the basis of origin of parent material.

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Factors involved in increasing salinity, which has followed clearing in the Western Australian wheat belt, have been investigated in a typical valley. Field and laboratory studies show that salinity is associated with a three-component hydrologic system involving surface, soil, and aquifer waters. The amounts of surface and soil water have increased after clearing. The third component, which is not thus affected, consists of a confined and continuous fine-textured aquifer which extends under most of the area and which has its intakes adjoining rock outcrops. This aquifer is the major repository for water and salt in the landscape, and salinity of overlying soils results where capillary contact with the surface occurs in the valley bottoms. The increase in volume of surface water does not lead directly to increased salinity, but rather, ultimately, to a removal of salts from the system via the main drainage lines. Increased soil water, however, serves to affect salinity in two ways. Firstly, it increases the area and duration of capillary contact between the confined aquifer and the soil surface in valley floors. Secondly, it leads to the development of seepage spots in the coarse-textured soils on valley sides, thus resulting in the formation of saline patches. The main part of the salt in the landscape has accumulated through atmospheric accession.