Unravelling the architecture and evolution of the inverted multi-stage North Iberian-Bay of Biscay rift

Patricia Cadenas (1) , Gianreto Manatschal (1) , Gabriela Fernández-Viejo (2)

1 IPGP (UMR_7154) - Institut de Physique du Globe de Paris
2 University of Oviedo

Current rift models propose polyphase rift evolutions that develop with the same kinematic framework and accommodate continuous and sequential extension, through the stacking of deformation modes. Several rifted margins show, however, evidence for multiple and out of sequence rift events, which developed within different kinematic frameworks, with a complex spatial and temporal evolution. In this work, we address the problem of multi-stage rift systems based on the study of the central North Iberian margin, located at the southern Bay of Biscay triangular oceanic domain. This magma-poor rifted margin recorded three major Mesozoic rift events and a subsequent Alpine compressional reactivation, representing a unique setting to study the architecture of a multi-stage rift system and the exerted control on subsequent reactivation. Relying on a dense set of 2D seismic reflection profiles, boreholes, and published velocity models, we map and describe structural domains and major extensional and compressional structures, and we construct depth and thickness maps of syn-rift units. These new maps display the geometry and spatial distribution of major rift basins and bounding structures. Distinctive scenarios resulting from this tectono-stratigraphic approach led us to define three rift systems. A first, diffuse and widespread Triassic system, with classical fault-bounded half-graben basins; a second, narrow, deep and localised Late Jurassic to Barremian transtensional system, including laterally confined pull-apart basins; and a third, widely distributed Aptian to Cenomanian hyperextended system. Our results show that each rift system controlled the successive extensional and compressional events, resulting in a complex 3D template. Deciphering the tectono-stratigraphic architecture of such, multi-stage systems provide key insights on the spatial, temporal, and thermal evolution of divergent plate boundaries. It is likewise indispensable to propose and test kinematic plate deformable models on conjugate rifted margins and to comprehend the implications for their reactivation.

Mots clés: multi-stage extension; rift system; strike-slip; hyperextension; compressional reactivation; 3D structural segmentation

Domaines: Géophysique [physics.geo-ph]

Patricia Cadenas, Gianreto Manatschal, Gabriela Fernández-Viejo. Unravelling the architecture and evolution of the inverted multi-stage North Iberian-Bay of Biscay rift. Gondwana Research, In press, ⟨10.1016/j.gr.2020.06.026⟩. ⟨insu-02921549⟩