THE CANNING BASIN GEOMAGNETIC INDUCTION ANOMALY

The results from a large scale magnetometer array study in the Canning Basin have revealed the existence of a substantial geomagnetic induction anomaly striking to the southeast from Broome right across the basin. The reversal in the vertical field fluctuation can be followed along the anomaly and indicates that the anomaly is essentially a line current. The anomaly appears to be associated with the Jurgurra and Barbwire Terraces of the Fenton Fault system. It is suggested that the anomaly may be caused by the pervasive halite deposits of th Silurian Carribuddy Formation, assuming that some moisture is available to enhance electrolytic conduction. A preliminary analysis of the effect of the induction anomaly on aeromagnetic survey data, suggests that it may introduce errors of tens of nanoTesla during magnetic quiet days and as large as hundred nanoTesla during periods of substorm activity.