Analogue modelling of the interplay between gravity gliding and spreading across complex rift topography in the Santos Basin

Leonardo Muniz Pichel, Oriol Ferrer, Christopher Aiden-Lee Jackson , Eduard Roca

The Santos Basin presents a complex and controversial evolution and distribution of salt tectonics domains. The controversies revolve mainly around the kinematically- linked Albian Gap and São Paulo Plateau. The Albian Gap is a ~450 km long and 60 km wide feature characterized by a post-Albian counter-regional rollover overlying depleted Aptian salt and in which the Albian is absent. The São Paulo Plateau is defined by a pre-salt structural high with significant base-salt topography and overlain by ~2.5 km thick salt. Another prominent feature is the Merluza Graben, a rift depocentre that underlies the southern portion of the Albian Gap and displays significant (3-4 km) of base-salt relief. Two competing hypotheses have been proposed to explain the origin and kinematics of these provinces. One invokes post- Albian extension within the Albian Gap and contraction in the Sao Paulo Plateau. The other invokes post-Albian salt expulsion in the Albian Gap and salt inflation in the São Paulo Plateau without significant lateral deformation. A recent study shows these processes contribute equally to the evolution of these domains, also demonstrating the importance of the previously neglected base-salt relief. We apply 3D physical modelling to test these new concepts and understand the interplay between laterally- variable base-salt relief, gliding and spreading on salt tectonics. Our results show a remarkably-similar salt and post-salt evolution and architecture to the Santos Basin as proposed in recent studies. They improve the understanding on the distribution and interaction of salt-related structural styles and gravity-driven processes, being also applicable to other salt-bearing margins.