The Role of the Strain History on the Modes of Continental Extension

Abstract:

Continental rifts evolve through deformation episodes into a variety of diverse basins with complex structural styles, subsidence and thermal histories, which may include melting. Existing models have probed the role of initial lithospheric rheological layering, geothermal gradients and stretching rates on continental rifting, however continental rifts evolution often includes several extensional phases, which are not easily explained by a single rifting approach.

Here, we address the role of episodic stretching on the long-term evolution of continental rifts. By means of numerical modelling we investigate the development of rifting patterns as a consequence of distinct phases of lithospheric extension under different stretching rates, modifying the lithosphere’s rheological layering, and intervening cooling, during which the lithosphere regains its original thickness, and their effect on subsequent rifting.

The models show that the time-dependent boundary conditions have a fundamental control on lithospheric-scale strain localization/delocalization and, consequently, on the tectonic rifting style and its evolution, resulting in a variety of basins ranging from narrow to wide rifts to hyper-thinned and with diverse melt yield in time, reproducing the first-order features of major basins on Earth. On the base of the rifting history we propose a classification that support the interpretation of rift basins and passive margins.