Geodynamic modelling of aspects of the Bowen, Gunnedah, Surat and Eromanga Basins from the perspective of convergent margin processes

Abstract

Geodynamic modelling of selected aspects of the Bowen, Gunnedah, Surat and Eromanga Basins provides possible explanations of the mechanisms that were operating during their formation. For the Bowen and Gunnedah Basins, a quantitative analysis of the early Late Permian to Middle Triassic foreland loading phase examined the relative roles of static loading vs dynamic loading associated with the convergent plate margin. Subsidence in the initial foreland phase in the early Late Permian is consistent with platform tilting due to corner flow in the mantle associated with west-directed subduction. Later in the Late Permian, platform tilting probably continued to be the dominant cause of subsidence, but increasing amounts of subsidence due to foreland loading occurred as the thrust front in the New England Orogen migrated westward. In the latest Permian and Early Triassic, static flexural loading due to foreland loads is dominant and may be the sole cause for basin subsidence. For the Surat and Eromanga Basins, the tectonic subsidence across an east–west transect is modelled to assess the contribution of dynamically induced platform tilting, due to viscous mantle corner flow, in basin subsidence. The modelling suggests that subsidence was again controlled by dynamic platform tilting, which provides a mechanism for both the near-field and far-field effects. Uplift of the Eastern Highlands in the mid-Cretaceous may also be related to viscous corner flow driven by west-directed subduction beneath eastern Australia, with the uplift being due to rebound of the lithosphere after the cessation of subduction.

Key Words:

• Bowen Basin
• convergent margin
• Eromanga Basin
• geodynamics
• Gunnedah Basin
• Surat Basin

Acknowledgements

This paper presents some results of the Tectonic Framework of Eastern Australia project carried out within the Australian Geodynamics Cooperative Research Centre (AGCRC). PW and CB thank the AGCRC for financial support to work in Australia during part of this study, and the hospitality of RJK. CB also acknowledges the support of the Inco Fellowship of the Canadian Institute for Advanced Research. Part of this project utilised data compiled in the NGMA project Sedimentary Basins of Eastern Australia, and we wish to thank members of this project from Geoscience Australia, Geological Survey of Queensland and Geological Survey of New South Wales, particularly Jennie Totterdell and Malcolm Nicoll for their contribution. We thank Martin Norvick and Robert Langford for their thorough reviews of the manuscript, which significantly improved it; and Joe Mifsud, Shannon Muir, Mika Miller-Mitrany and Neale Jeffery for drafting the final figures. RJK publishes with permission of the Chief Executive Officer, Geoscience Australia.