A major debate in Geoscience is centred on the hypothesis that a massive pulse of rapid seafloor spreading occurred during the mid-Cretaceous (~120-80 Ma). It has been suggested that such a pulse caused prolonged magnetic field stability, large igneous provinces, a sea-level highstand, variations in atmospheric CO2 and anoxia, but doubts have been raised about its existence. We propose to test this hypothesis by creating complete palaeo-seafloor age grids for the last 130 m.y. They will serve as input for 3-D spherical convection models, whose output will be groundtruthed by plate kinematics, results from mantle tomography and by the uplift-subsidence history of cratons.
We are integrating palaeo-age grids, including synthetic plates for restoring oceans which are entirely subducted now, with 3-D spherical convection models. The non-uniqueness of restoring lost ocean floor will be overcome by allowing subduction geometries and age-area distribution of subducted ocean crust to vary within reasonable limits. The model output includes (1) histories of subsidence and uplift though time due to dynamic topography, (2) a mantle density distribution for the present and (3) a predicted plate kinematic history. All model outputs can be tested using geological/geophysical observations. This approach is novel, and will lead to a new generation of dynamic Earth models. It will allow us to unravel the connections between global changes in seafloor-spreading rates, and thus mid-ocean ridge volumes, the history of subduction, dynamic topography, and regional versus global long-term sea-level changes. Our results will be relevant for separating eustatic from tectonic controls on basin sedimentation, and thus enhance our fundamental understanding of how stratigraphic cycles in basins form and aid in source rock and reservoir evaluation in frontier basins.
Large ARC Grant (1999-2001)
Dr R. D. Müller, The University of Sydney
Prof Michael Gurnis, California Institute of Technology
Dr Carmen Gaina, The University of Sydney, Research Fellow
Dr Dona Mihut, The University of Sydney, Research Associate
Stuart Clark, The University of Sydney, Honours student