Abstract

The Australian Bureau of Mineral Resources, Geology and Geophysics, completed a 15 year systematic reconnaissance gravity survey of Australia in 1974. Using helicopters, gravity stations were established at 11 km spacing over most of the continent, and at 7 km spacing in South Australia and Tasmania. Station elevations were measured barometrically and station positions were marked on aerial photographs and transferred to 1:250,000 photocenter base maps. Gravity and elevation controls were maintained by ties to specially established control networks. A Bouguer anomaly map of Australia has been compiled from the reconnaissance data, and from information from other gravity surveys by state governments, petroleum exploration companies, and academic institutions which together cover about 15 percent of the total area. The compilation uses a total of about 170,000 gravity observations. The accuracy of Bouguer anomaly values, taking account of errors in the gravity, elevation, and position measurements, is estimated to be better than ± 2.0 mgal.

The Bouguer anomaly fields over Australia are divided into nine regional gravity divisions, in each of which the gravity contour pattern has some degree of uniformity, or is such as to imply tectonic affinities between the sources of individual gravity features. The gravity divisions can be correlated with various metamorphic complexes and orogenic provinces, ranging in age from Archaean to Paleozoic, which also form the basements to extensive sedimentary platform covers.

The reconnaissance gravity results have been made public as the survey has progressed to assist in regional geologic studies and the search for petroleum and minerals. They have proved to be of considerable benefit in delineating regional structures and in providing leads for more detailed geophysical investigations. Predictions of the structures of sedimentary basins have been made and possible extensions to mineral provinces have been indicated. The results have also been used in deep crustal and upper mantle studies and in geodesy.

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