GAB deep water geological and benthic ecology program

Voyage Number

IN2015_C01

Voyage Dates

25 Oct, 2015 to 25 Nov, 2015

Voyage Location

Hobart to Port Lincoln

Chief Scientist

Dr Andrew Ross

Institution

CSIRO

View the full voyage

Voyage summary

Charter voyage to the Great Australian Bight (GAB) to conduct geological and bioogical surveys of the Ceduna sub-basin.

The Ceduna sub-basin is the product of rifting followed by the subsequent Southern Ocean seafloor spreading between Australia and Antarctica, with the rifting created a narrow seaway between Australia and Antarctica. There are key knowledge gaps in understanding the fundamental geology of the Ceduna sub-basin and its benthic biological communities.

The objective of this voyage is to survey outcrops of sedimentary rocks, potential areas of hydrocarbon seepage and deep water seamounts in this region. The survey will include seafloor mapping and use of a deep tow camera to characterise the sea floor, and water column characterisation using CTD and acoustic systems. Sampling operations will be undertaken to survey the seafloor geology and benthic (seafloor) biota using various sledges and dredges.

Voyage impact

The voyage involved 37 researchers from seven research organisations undertaking 128 operations in water depths ranging from 700 m to 5,437 m. The voyage deployed a diverse collection of instrumentation fully utilising RV Investigator's capabilities. Of note, deployment of some of the equipment types was significantly deeper than previous deployments either in Australia or worldwide.

The data and samples collected significantly augment the sparse data and samples within the deep water of the Great Australian Bight (GAB) to date. This voyage collected 25,553 biological specimens (including the likely first records for Australia of a number of species), as well as 1.3 tons volcanic and sedimentary rocks. The volcanic rocks had never been sampled previously in the GAB. Overall, the collection of data and samples in this poorly studied region will allow a more detailed understanding of the geological evolution and biological communities of the southern margin of Australia.

Nearly 29,000 km² of seafloor was mapped using multibeam sonar, over 10,000 km² of which was at high resolution. This led to the discovery of several previously unmapped deep water canyons and ten previously unmapped volcanic seamounts, and revealed a complex deep water sedimentary environment.

Detailed analysis and interpretation of the geological and biological samples will be integrated with the processed voyage data to better inform the processes that have formed the Great Australian Bight and describe the present-day environment and fauna.