An interdisciplinary approach to constructing models of the lithosphere across the Australia-Antarctica conjugate margin

Terrane boundaries that define orogens separating the West and South Australian Cratons are evident in a number of datasets, including geological, geochemical, geomagnetic anomalies, gravity anomalies and seismic tomography maps. Understanding this architecture is important in constraining the evolution of Proterozoic Australia. It also impacts on the lateral variations of rheology of the underlying lithosphere and asthenosphere of Australia’s former neighbour in Gondwana, East Antarctica, and hence on geothermal heat flux, glacial isostatic adjustment and other global climate system observables. Better understanding such systems has the potential to improve national preparedness and international resilience to global changes such as sea-level rise.

This research brings together diverse and disparate datasets that all inform, in different ways, the boundaries and deep structure of ancient cratons and orogens of western and southern Australia. These are constructed in the context of their disposition during the time of the southern hemisphere continents being configured together in the Gondwana supercontinent, i.e. with the overprint of the Pan African orogeny. The datasets that provide the foundation for the new models are seismic tomography maps from Australia and Antarctica. As these are smoothed models, our methodology is to add terrane boundaries informed by the geology and geochemistry of surface observations. We also incorporate information from airborne geophysics and remote sensed data. The methodologies used include changepoint detection and other informatics-based approaches. We thus extract new knowledge from the patterns and changes that occur across the layers in this high-dimensional dataset. We also guide the reconstruction of these boundaries across continental conjugate margin using well-informed plate-reconstructions, including recognition of the diverse Continent- Ocean-Boundary transitional crust along the Australian-Antarctic margin.

We produce families of alternate models of the lithosphere, accessible through a visualisation framework. These provide focus for discussions on alternate tectonic hypotheses, and are also made available for continent scale rheological and seismological simulations. This approach allows a variety of information to be included in a single model, with differently constrained parts of the model being handled with quantitative rigor. Applications of the new candidate models include heat flux calculations, glacial isostatic adjustment studies and will also be of value in sensitivity testing prior to new instrument deployments focussed on continental deep structure. Model suites will be made available to the research communities in interoperable data formats.