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


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Whittaker, JM, Goncharov, A, Williams, SE and Muller, RD 2012 , 'Crustal velocity and sediment thickness asymmetries along and between the conjugate Australian-Antarctic margins', paper presented at the Eastern Australasian Basins Symposium IV, 10-14 September 2012, Brisbane, QLD.

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The Australian-Antarctic conjugate margins are remarkably
symmetric in comparison to other magma-poor rifted continental
margins, particularly in the central Great Australian Bight section.
Here, we use two datasets derived from seismic refraction data to
investigate the pre-rift crustal structure of the conjugate Australian-
Antarctic margins. We analyse two datasets for the conjugate
Australian-Antarctic margins, (i) seismic velocity data derived
from a synthesis of seismic refraction and sonobuoy data, and (ii)
estimates of total sediment thickness from seismic refraction data
calibrated against stacking-derived seismic velocities from seismic
reflection profiles along each margin. Using a novel approach
involving plate reconstruction and 3D visualistion we utilize these
datasets to map the 3D lithospheric structure of the Australian-
Antarctic margins. Our approach enables accurate juxtaposition
of the Australian-Antarctic conjugate margins at the approximate
time of breakup (~83 Ma). We find that the distribution of
sediment along and across the conjugate Australian-Antarctic
margins is highly asymmetric and that observed asymmetries in
crustal structure are predominantly due to the patterns of sediment
loading. Our results also indicate that total sediment thicknesses
have been significantly underestimated from seismic reflection
profile data for large sections of both margins. Underestimations
of total sediment thickness appear particularly severe on the
Antarctic margin. A significant insight this analysis provides is
that the velocity information from seismic refraction data has been
grossly under-utilised.

Item Type: Conference or Workshop Item (Paper)
Authors/Creators:Whittaker, JM and Goncharov, A and Williams, SE and Muller, RD
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Copyright 2012 PESA

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