Crustal velocity and sediment thickness asymmetries along and between the conjugate Australian-Antarctic margins

• Main Authors: Whittaker, J, Goncharov, A, Williams, SE, Muller, RD
• Format: Conference Object
• Language: English
• Published: Petroleum Exploration Society of Australia 2012
• Subjects: Earth Sciences; Geology; Marine Geoscience; Antarctic; Antarc*
• Online Access: http://www.earthbyte.org/publications.html; http://ecite.utas.edu.au/84448

The Australian-Antarctic conjugate margins are remarkablysymmetric in comparison to other magma-poor rifted continentalmargins, particularly in the central Great Australian Bight section.Here, we use two datasets derived from seismic refraction data toinvestigate the pre-rift crustal structure of the conjugate Australian-Antarctic margins. We analyse two datasets for the conjugateAustralian-Antarctic margins, (i) seismic velocity data derivedfrom a synthesis of seismic refraction and sonobuoy data, and (ii)estimates of total sediment thickness from seismic refraction datacalibrated against stacking-derived seismic velocities from seismicreflection profiles along each margin. Using a novel approachinvolving plate reconstruction and 3D visualistion we utilize thesedatasets to map the 3D lithospheric structure of the Australian-Antarctic margins. Our approach enables accurate juxtapositionof the Australian-Antarctic conjugate margins at the approximatetime of breakup (~83 Ma). We find that the distribution ofsediment along and across the conjugate Australian-Antarcticmargins is highly asymmetric and that observed asymmetries incrustal structure are predominantly due to the patterns of sedimentloading. Our results also indicate that total sediment thicknesseshave been significantly underestimated from seismic reflectionprofile data for large sections of both margins. Underestimationsof total sediment thickness appear particularly severe on theAntarctic margin. A significant insight this analysis provides isthat the velocity information from seismic refraction data has beengrossly under-utilised.