Soil studies at Swan Hill, Victoria, Australia. II. Dune moulding and parna formation

Abstract

The study involving a granulometric examination of the sedimentary nature of layers of aeolian material at Swan Hill, Vic., shows that the wind erosion of soils leading to the sorting of the components can result in the formation of a dust or suspended component and a saltation or dune-sand component. The former material, parna, contains most of the clay and lime of the original soil material. This is considered to be composed of fine aggregates associated with a companion sand which, in the neighbourhood of the dunes, has a diameter range of 70 to 90 µ. This material is normally separated from the saltation sand by wind action. However, under conditions of accession of parna at a site where saltation sand is in motion the parna becomes mixed with the saltation sand in a graduated manner, least being deposited at the crest. The periodic moulding of the dunes by local erosion and deposition and accession of regional parna is discussed.