The Magnetic Anomaly Map of Australia

Abstract

The Bureau of Mineral Resources has been routinely acquiring airborne magnetic surveys over the land area of Australia since 1951 to record and map anomalies in the earth's magnetic field attributable to geological structures and lithologies. In forty years, over four million line kilometres of survey data have been flown, while the technology of survey practice has passed through various stages of development. About 83 per cent of the land area has now been covered with so-called reconnaissance surveys flown 150 m above terrain at line spacing between 1.5 and 3.2 km. Located profile data for these surveys have been gridded using a minimum curvature technique, to 15 second of arc (approximately 400 m) and, where necessary, micro-levelled. Data for much of the remaining areas ? particularly the inland sedimentary basins covered by surveys of lower specifications ? were obtained from digital data on an approximately 2-km grid (72 seconds of arc) published in 1976; these have also been interpolated to 15 second of arc. The data were first assembled for each of over five hundred 1:250 000 map sheets. The 1:250 000 sheets were linked by minimizing the discrepancies along their common boundaries (which were often also survey boundaries) and reducing remaining mis-ties through Laplacian smoothing to minimize the visibility of boundaries between surveys acquired separately. While the data quality varies with instrumentation and survey parameters, it is almost everywhere good enough to provide a useful synoptic view of rnagnetic anomaly patterns, which can be expected to give important new insights into geology and tectonics at a continental scale, and to provide a regional framework within which to interpret more local magnetic anomalies. The purpose of this short paper is to report the latest progress on compilation of the Magnetic Anomaly Map of Australia, which is scheduled for publication late in 1992.