CONTINENTAL BREAK-UP ON REGIONAL AND GLOBAL SCALE: INSIGHTS FROM 3D NUMERICAL MODELING

Rifting and the break-up of continents are first order features of plate tectonics. We use three dimensional thermo-mechanical simulations to evaluate the necessary tectonic forces to induce break-up. Our finite element model SLIM3D includes a free surface and allows for treatment of realistic elasto-visco-plastic rheology. We present the results of two distinct models that have been conducted on regional and global scale:

On regional scale, we investigate oblique continental rifting which has been involved at several locations during continental break-up between South America and Africa, as well as North America and Europe. We evaluate the force that is required to maintain prescribed extensional boundary velocities in dependence on the angle of obliquity. We find that obliquity reduces the force that is required to initiate break-up.

Presently, we extend our modeling technique to global scale simulations of lithosphere deformation and plate motion. We implement a spherical version of SLIM3D to model a 300 km thick upper layer of the Earth with a non-linear temperature- and stress-dependent visco-elastic rheology combined with Mohr-Coulomb frictional plasticity. The mantle below 300 km depth is modeled using the mantle convection model TERRA which solves for the momentum and energy balance of convection at infinite Prandtl number. The upper layer and mantle modeling domains are coupled by continuity of tractions and velocities across the 300 km boundary. We present our first results on directions and magnitudes of extensional forces at the rift zones, taking into account the lithospheric structure of Gondwana as well as the accurate paleo-positions of subduction zones around the supercontinent.