Rhi McKeon

Madsen Building (F09), Room 412
Phone: +61 2 9036 6545
Fax: +61 2 9351 3644
Email: rmck4894@usyd.edu.au

PhD Candidate

Supervisors


Prof Dietmar Müller
Dr Gabriele Morra
Dr Maria Seaton
Dr Jo Whittaker

PhD title: 100Ma Global Scale, Plate Tectonic Reorganisations

Plate tectonics characterises the complex and dynamic evolution of the Earth in terms of the rigid plates that form the outer shell of the Earth. Even though links between plate tectonics and the Earth’s convecting mantle underneath are becoming more evident – notably through subsurface tomographic images and advances in mineral physics and geodynamic modeling – there is still no generally accepted mechanism that consistently explains plate tectonics in a framework of deep Earth dynamics. All we have to go by is fragmentary observational evidence suggesting a dependence of plate motions on interactions of the convecting upper and lower mantle.

Several global plate tectonic reorganizations post-dating the assembly of the supercontinent Pangaea have been identified at around 300, 250, 220, 150, and 50 million years ago (Ma) (Torsvik et al., 2008). Some of these events are contemporaneous with major organic extinctions, catastrophic climate change, and major phases of natural resource formation such as ore deposits. Prominent plate reorganization at about 100 Ma is well known from a major bend in the fracture zones in the Indian Ocean (Müller et al., 2000; Veevers, 2000), as well as from a change in Pacific plate motion (Wessel et al., 2006). Thus, major plate tectonic punctuations, often associated with major environmental change on Earth, appear to be relatively frequent, but their driving forces are unknown. An understanding of these forces will shed light on passive margins and their associated petroleum bearing sedimentary basins.

The most intriguing aspects of rapid global tectonic events are the feedbacks between surface processes, such as uplift/ subsidence and erosion/sedimentation, with crustal processes such as faulting and fluid flow with convection in the Earth’s interior. To unravel these feedbacks, we will combine an innovative numerical approach based on so-called Boundary Elements, recently developed by the PI of this proposal (Morra et al., 2007) with a global plate model, reconstructed ocean floor, mid ocean ridges and subduction plate boundaries through time (Müller et al., 2008a; Müller et al., 2008b).

Recent events have increased the price of oil to unprecedented levels and have given rise to concerns about the environmental impact of the use and long-term exploitation of petroleum resources. Resources lying in Australia’s continental crust and its vast unexplored continental shelves provide great opportunities, however an erroneous estimation of their real amount would produce dramatic consequences for the next generations of Australians, making it imperative to develop modeling tools for the estimation and possible discovery of all oil and gas resources located in the shallow and deep crust and in close or remote basins.

Immediately following the 100 Ma geodynamic reorganization event, subduction along the Eastern Gondwanan margin ceased and continental rifting and break-up initiated along much of the Southern and Eastern Australian passive margins. Break-up lead to the formation of the Southern Ocean and the Tasman Sea and also many extensional basins, such as the Fairway and New Caledonia Basins. Extensional sedimentary basins located on passive continental margins are a major focus for oil and gas exploration. This project aims to model the geodynamic forces driving the 100 Ma reorganization event via the coupling of plate kinematic models to continental margin basin formation. An improved understanding of the 100 Ma reorgansiation event and it's influence on passive margin formation in Australia will enable additional constraints to be placed on the formation of extensional sedimentary basins of the Eastern and (in particular) the Southern Australian passive margins.

www.earthbyte.org

• Morra, G., Chatelain, P., Tackley, P., and Koumoutsakos, P., 2007, Large Scale Three-Dimensional Boundary Element Simulation of Subduction, Computational Science – ICCS 2007, p. 1122-1129.
• Müller, R.D., Gaina, C., Tikku, A., Mihut, D., Cande, S., and Stock, J.M., 2000, Mesozoic/Cenozoic tectonic events around Australia, in Richards, M., and Gordon, R., eds., The History and Dynamics of Global Plate Motions, Volume 121: American Geophysical Union Monograph, American Geophysical Union, p. 161-188.
• Müller, R.D., Sdrolias, M., Gaina, C., and Roest, W.R., 2008a, Age, spreading rates and spreading asymmetry of the world's ocean crust: Geochemistry, Geophysics, Geosystems, v. in press.
• Müller, R.D., Sdrolias, M., Gaina, C., Steinberger, B., and Heine, C., 2008b, Long-term sea level fluctuations driven by ocean basin dynamics: Science, v. in press.
• Torsvik, T., Müller, R.D., Van der Voo, R., Steinberger, B., and Gaina, C., 2008, Global Plate Motion Frames: Toward a unified model: Reviews in Geophysics, v. in press.
• Veevers, J.J., 2000, Change of tectono-stratigraphic regime in the Australian plate during the 99 Ma (mid-Cretaceous) and 43 Ma (mid-Eocene) swerves of the Pacific: Geology, v. 28, p. 47-50.
• Wessel, P., Harada, Y., and Kroenke, L.W., 2006, Toward a self-consistent, high-resolution absolute plate motion model for the Pacific: Geochemistry Geophysics Geosystems, v. 7.