Thursday 29 April 2010, 11:30 AM (AAD Theatrette)

Dr Phil O'Brien

Geosciences Australia

Insights into sea floor habitats, processes and geology on a rocky Antarctic coast from multibeam bathymetry: Davis sea bed mapping survey 2009/2010

With Ian Atkinson (GA), Ross Bowden, Dean Forrest, Jade Paddison and Steve Swanson (Deployable Geospatial Support Team, Royal Australian Navy).

This summer saw the first use in the AAT of a high resolution multibeam echosounder by an Australian project. We mapped the Vestfold Hills coast around Davis. The GA system was mounted on the AAD workboat Howard Burton and provides a minimum density of 1 sounding every 40 cm. It provides highly detailed maps of sea floor character that can be used with video and sample data to greatly enhance our understanding of the marine environment. The Royal Australian Navy is also using the data to improve the charts for safer navigation. This talk presents some early results.

The Vestfold Hills have a complex coast of shallow bays, fjords and islands. The multibeam data reveal a similar terrain to that onshore with basement outcrops and sediment covered depressions. Unlike the onshore sediment areas, ice scours of various types are widespread. Sediment areas are predominantly covered in muddy sand to sandy mud, though scour channels around bedrock highs and islands contain muddy sand. Rippled sands are present in coastal embayments which lacks iceberg scours but features current –constructed sand ribbons. Isolated boulders are common and are visible on the high resolution data. The data provide a physical framework for understanding benthic habitats. Rocky outcrops are readily delineated as are regions of sediment substrates, high sedimentation and strong current activity. Rocky areas are mostly covered by macroalgae and commonly show clouds of water column reflections we believe come from gas bubble produced by algae transpiration. 

Bio: Phil joining Geoscience Australia's predecessor, BMR, in 1980. For 12 years he worked on a wide variety of resource and environmental geology projects. In 1992, he joined the new Antarctic CRC project. He has participated in 6 Antarctic surveys, including leading the 2000 the Ocean Drilling Program Leg to Prydz Bay and one of the 2001 Law of the Sea surveys to the AAT. He has been the Program Leader for Geosciences since 1999 and is Deputy Chair of the SCAR Geoscience Standing Group.