THE EVOLUTION OF THE SOLID EARTH OVER THE PAST 200 MILLION YEARS: CONSTRAINTS FROM MANTLE STRUCTURE, PLATE TECTONIC HISTORY, AND SURFACE GEOLOGY

In the past years our increasing ability to synthesise observations in paleogeographic information systems and to link them to high-performance computing models has resulted in major improvements in models of mantle convection and plate tectonic cycles. However, most current models are restricted to analysing only about 3% of Earth's history, typically staring in the Early Cretaceous (140 Ma). Even for this geologically short period of time, opinions diverge on whether we know enough to push solid earth models back this far. Analogous to unravelling poorly preserved geological processes, any given observable by itself is insufficient to completely reconstruct either surface plate motions or mantle convection. In terms of the plate tectonic history, the main unknowns concern the reconstruction of now subducted ocean basins and absolute plate motions. Here seismic mantle tomography provides a missing link, because subducted slabs imaged in the mantle reflect the history of the geometry and migration of convergent plate boundaries over the mantle as well as the time-dependence of plate convergence rates. Mantle tomography models, on the other hand, are plagued by regional and depth-dependent uncertainties, which are usually not easy to discern for “end-users”. Nevertheless, many recent global tomography models have reached a level of detail that offer the prospect of establishing a “subduction reference frame”, in which global plate motions and plate boundary geometries through time are anchored by matching subducted slab volumes in the deep mantle back to 200 million years ago. An intriguing prospect of the model iteration involved is that the structure of the deep mantle can ultimately be used to differentiate between alternative plate models, both in a global and regional context. In addition surface geological data can be used to put further constraints on such coupled plate kinematic-mantle convection models. Key geological observables include geological and palaeomagnetic data from the margins and terranes associated with now closed ocean basins, geological remnants of mid-ocean ridge subduction such as adakites, global and regional sea level records, reflecting both changes in the volume of the ocean basins as well as mantle-driven dynamic topography and long-term chemical cycles in the ocean basins.