Bight sea-floor study may aid mineral exploration
	Ship shape: Dr Ted Lilley (centre) with ANU graduates Drs Graham Heinson (left) and Steven Constable on the R.V. Fanklin
By Julian Lee The results of an unusual exploration of the sea floor in the Great Australian Bight will improve understanding of the history and evolution of the Australian continent and help future mineral exploration, an ANU scientist said. Coinciding with International Year of the Ocean, Dr Ted Lilley of the Research School of Earth Sciences and colleagues Drs Antony White and Graham Heinson at Flinders University, are investigating an anomaly in the earth's crust they believe may have been created when Australia separated from Antarctica 160 million years ago. "The anomaly, which is seen as a disturbance in the electrical conductivity, begins some two hundred kilometres inland, runs across the Eyre Peninsula in South Australia before hitting the coast and evidently heading out to sea where its characteristics are unknown," Dr Lilley said. Having successfully gained 20 days (valued at $500,000) on the Australian oceanographic vessel R.V. Franklin, Dr Lilley and colleagues were for the first time able to trace the structure out to sea. "The experiment involved the largest array of sea floor electromagnetic instruments ever assembled for a single experiment in the Southwest Pacific area - a total of 28 separate sea-floor deployments were made. "The experiment also involved setting up an equivalent array on land to record simultaneously with the marine array. "We are now in the process of downloading and analysing the data," he said. Taking advantage of the valuable ship time, Dr Lilley also tested a new sea-surface magnetometer which records the magnetic signals generated by waves. "The Great Australian Bight proved to be rich with magnetic signals due to ocean swells rolling in from the Southern Ocean," Dr Lilley said. The magnetometer will assist in understanding how these signals are created, and improve the accuracy of sea-floor surveys which are limited by the "static" produced by waves. Two ANU graduates, Dr Graham Heinson of Flinders University and Dr Steven Constable of the Scripps Institution of Oceanography (California), also tested new instruments on the research cruise. Dr Heinson trialed a new open-ocean instrument for measuring natural voltages in sea-water, while Dr Constable experimented for the first time in Australian waters with a high-frequency marine electromagnetic recorder. Dr Lilley said the electromagnetic recorder will help determine the structure of sedimentary basins on continental shelves and has direct applications in oil exploration. "Such research provides background knowledge which is essential in refining geophysical methods in the search for natural resources, especially as the search pushes out onto Australia's expanse of continental shelf," Dr Lilley said.