Summary
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.
Outcomes
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.
Participants
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