Assessing the Influence of Orogenic Inheritance on the Architecture, Time Evolution and Magmatic Budget of Hyper-extended Rift Systems: a Combined Mapping and Numerical Modelling Approach

Abstract:

The aim of this PhD thesis is to assess the influence of inherited structures and heterogeneities on the architecture and tectonic evolution of hyper-extended rift systems, with special focus on the North Atlantic. We propose a new mapping approach using simple and robust observation-based criteria to identify key features of rift systems, namely: 1) structural elements of rift domains; 2) age of the major rift events; and 3) key structures and heterogeneities inherited from previous orogenic phases.

We distinguish between 3 major rift domains: 1) the not or barely thinned proximal domain; 2) the unequivocal oceanic domain characterized by steady-state seafloor spreading; and, between them 3) the hyper-extended domain concentrating most of the deformation using gravity, magnetic and reflection and refraction seismic data. Previous studies mapped these domains along the magma-poor Iberia-Newfoundland and Bay of Biscay. One objective of this PhD is to extend this mapping further to the North, along the Irish, Scottish and Norwegian margins, into domains with polyphase rifting and magmatic additions.

In addition, we assign an age to the two most important events in the development of rifted margins, namely the necking and the breakup. This approach requires us to determine how these two events are recorded in the stratigraphy and how they can be mapped in seismic sections.

In order to highlight potential links between both rift domain architecture and timing of rifting and orogenic inheritance we map the structures and heterogeneities inherited from previous collision events that may have influenced significantly subsequent rifting. We consider features that: 1) are important enough to have had a potential impact on subsequent deformation; 2) are preserved through time; and 3) bear the potential to be reactivated.

Based on these data, we try to link the architecture and evolution of the North Atlantic rift system with the nature and in-depth location of weak features initially present within the lithosphere in the light of minimal numerical modelling experiments and use these results as a basis for designing more comprehensive numerical models for the North Atlantic rifting.