Mantle dynamics of continentwide Cenozoic subsidence and tilting of Australia

Abstract

Australia is distinctive because it experienced first-order, broad-scale vertical motions during the Cenozoic. Here, we use plate-tectonic reconstructions and a model of mantle convection to quantitatively link the large-scale fl ooding history of the continent to mantle convection since 50 Ma. Subduction-driven geodynamic models show that Australia undergoes a 200 m northeast downward tilt as it approaches and overrides subducted slabs between Melanesia and the proto–Tonga-Kermadec subduction systems. However, the model only produces the observed continentwide subsidence, with 300 m of northeast downward tilt since the Eocene, if we assume that Australia has moved northward away from a relatively hot mantle anomaly. The models suggest that Australia's paleoshoreline evolution can only be reproduced if the continent moved northward, away from a large buoyant anomaly. This results in continentwide subsidence of ~200 m. The additional progressive, continentwide tilting down to the northeast can be attributed to the horizontal motion of the continent toward subducted slabs sinking below Melanesia.

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