FORMATION AND PEDOLOGY OF DUPLEX SOILS

The term 'duplex' was first used by Northcote (1960) in his classification 'A Factual Key for the Recognition of Australian Soils' to describe soils which have an abrupt textural contrast between the surface soil horizons and the subsurface. Chemical, mineralogical and physical properties other than the textural contrast are not diagnostic. It is not suprising therefore, that duplex soils exhibit great diversity in their properties, particularly their genesis and mode of development. Many theories-chemical, physical, biological-have been proposed to explain the origin of duplex soils and the processes responsible for the development of their dominant morphological characteristic, the texture contrast. These theories, and some of the implications for an understanding of soil development, are reviewed.