Cool-water carbonate mounds at the shelf break of the Great Australian Bight

Cool-water carbonate mounds at the shelf break of the Great Australian Bight

Associate professor Mads Huuse, Ph.D., Department of Geology and Petroleum Geology, University of Aberdeen

Within the past decade there have been discoveries of several examples of carbonate banks/reefs in deep waters at high latitudes, where the water temperature is typically below 10 degrees. These reefs contain important information on the reef-building organisms and their eco-systems, as well as on the currents on the seabed and the climatic conditions that obtained during the formation of the reefs. The chalk deposits the coast of South Australia tells us much about the sea currents and changing climatic conditions in the area during the past two million years, during which ice ages and inter-ice ages alternated with high frequency. The chalk deposits were surveyed as part of ODP (Ocean Drilling Programme) expedition 182. The survey showed that a considerable portion of the chalk deposits form banks, and it was considered the most likely explanation that the banks had been formed by reef-building bryozoans in the course of the ice ages when a low sea level and rising currents on the seabed favoured bryozoan growth. However, there remains substantial doubt about the validity of this model.

The project here proposed aims at researching an alternative hypothesis, according to which the formation of the banks are viewed as forms of deposits associated with the strong (>1m/s) Leeuwin Current, which flows along coasts of Western and Southern Australia. The understanding of the formation of the banks is important for understanding the currents and their variations through the past couple of million years, during which ice ages and inter-ice ages alternated with high frequency. In addition, the banks are important for the understanding of analogue banks, which were recently discovered in the Danish white chalk and Danien limestone deposits. They are found on land, along the rim of the North Sea basin and contain the main part of the Danish oil reservoirs in the North Sea.

The surveys will encompass seismic tests, extraction of drilling cores, measuring of currents, water samples, as well as video recordings of the conditions on the seabed.