Geophysical indicators of controls on soil salinisation and implications, Longford Basin, Northern Tasmania

Abstract

A SIROTEM survey and experimental petrophysical data from drillcores have enabled a study of apparent conductance anomalies in and around the Longford Basin of northern Tasmania. Within the basin depocentre, conductance anomalies due to the thickness irregularity of highly conductive layers reflect stacking and migration of fluvial systems. Outside the basin margins, conductance anomalies reflect changes in the conductivity of drainage bedload which is a function of watershed lithology. The anomalously conductive Tertiary sediments have three possible sources for stored salt: inheritance from erosion of conductive Triassic red bed sequences in the basement below the Tertiary sequence; relict meteoric salt from proximity to a drowned estuary; or ions released from extensive lateritisation of lavas after a period of Eocene to Miocene basaltic volcanism.