Parna in the riverine plain of south-eastern Australia and the soils thereon

Abstract

This study of Widgelli parna, aeolian material derived from soils during a previous arid period, shows that there is a relationship between particle size and the distance leeward from the dune zones. Within 1 or 2 miles of the dunes the modal size of the non-clay fraction is 150 to 200 µ, and this value changes to 40 µ at a distance of 150 miles leeward. The clay content varies inversely, being about 36 per cent. near the dunes and 70 per cent. 150 miles leeward. The non-clay fraction is highly graded. Within the dune zones, and particularly in the dune itself, the parna is mixed with coarser sand. The size and clay-content relationships for the parna sheet also hold in the dune zones with the modal size at the crest about 400 µ. The landscapes and soils to be related to the parna include the riverine plains, the adjoining hills, and the dune landscape of the Mallee. Highly differentiated soils occur on the parna layer, and these include brown solonized soils in the dune zones, red-brown earths on the hills, and red-brown earths and grey and brown soils of heavy texture on the riverine plains. Soil differentiation is largely caused by drainage differences.