Bathymetry mission sounds out limits of continental shelf

By on 10 March, 2020

The research team deploying the seismic source over the stern of the RV Investigator. Image: David Dieckfoss.

A team of scientists led by the University of Tasmania’s IMAS has returned to shore in Perth after a two-month voyage on Australia’s blue water research vessel RV Investigator.

The main objective of the voyage was to analyse the forces leading to the break up of two tectonic plates in the Indian Ocean — and in doing so, the scientists mapped over 100,00km2 of the Southern Ocean, much of it for the first time.

Data and rock samples collected on the mission could inform the United Nations Commission on the Limits of the Continental Shelf (CLCS) on the issue of Australia’s entitlement to a continental shelf that lies over 200 nautical miles from the Heard and McDonald islands.

The contested area is approximately the size of Switzerland, according to material released by IMAS.

Seafloor mapping of Williams Seamount on the Drygalski Ridge. Image: CSIRO.

Voyage Chief Scientist, IMAS Professor Mike Coffin, said that the commission’s previous findings did not consider the area justified to be considered within Australia’s marine estate, in part because the data Australia submitted to the process gave only indirect evidence of the feature known as William’s Ridge.

Professor Coffin said that the acquisition on this mission, which included seismic reflection, sub-bottom profile, gravity, and magnetics data, would demonstrate the processes that led to the current configuration of these major features on the Indian Ocean’s seafloor.

“The Kerguelen Plateau and adjacent William’s Ridge were once contiguous with Broken Ridge, which is now 2,700 kilometres to the north after separating 43 million years ago,” Professor Coffin said.

“We mapped along the entire length of William’s Ridge, defining both its continuity with the Central Kerguelen Plateau and its southeastern terminus for the first time. This information, along with results from shore-based petrological and geochemical analyses of the rock samples we have collected, will be important criteria for any future submissions to the UN Commission.”

A researcher photographs rock samples on board RV Investigator. Image: David Dieckfoss.

The voyage included scientists and students from Geoscience Australia, Macquarie University, University of Queensland, GFZ German Research Centre for Geosciences, James Cook University, University of Western Australia, College of the Atlantic, and Institute of Oceanology, Chinese Academy of Sciences.

The project also involves shore-based researchers from the Alfred Wegener Institute for Polar and Marine Research, University of Cambridge, Oregon State University, Natural History Museum of Denmark, and GEOMAR Helmholtz Centre for Ocean Research Kiel.

“The research we have undertaken during this voyage will help us to better understand the fundamental tectonic, volcanic, and geodynamic processes involved in the evolution of this part of the ocean,” Professor Coffin said.

“After we return to port our exceptional multidisciplinary international team of shore-based scientists will begin analysing our data and samples from areas that have never before been studied in this level of detail.”

OCCOM float ‘Krakow Dragon’ being prepared for deployment. Image: David Dieckfoss.

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