Airborne Electromagnetic Surveys of the Regolith

Secondary salinity of once productive agricultural land is a widespread problem throughout the southern agricultural areas of Australia. Previous studies in Western Australia have shown that airborne electromagnetic surveys can assist in defining the location of high salt storage within the regolith by measurement of conductance of the near surface layers. A survey from the Eyre Peninsula in South Australia shows that this concept can be extended to other areas prone to salinity. Elevation data acquired in this area demonstrates that topography reveals the drainage pattern which has the overriding control on the salt storage. The geology, as indicated by aeromagnetics, shows structures within the geological basement that influence the salt storage pattern. It is believed that this relationship is similar to that seen in previous surveys in Western Australia, where the weathering of dolerites to a clay formed barriers of lower hydraulic conductivity within the regolith.