Spatial and Temporal Evolution of Rift Systems: Implication for the Nature, Kinematics and Timing of the Iberian–European Plate Boundary

Abstract:

The mechanisms of continental lithosphere deformation that control the formation and evolution of rift systems leading to continental breakup and the creation of divergent plate boundaries represent a long-standing problem in tectonics. Studies conducted in present-day rifted margins and their onshore fossil analogues reveal variable crustal architecture emphasizing the complex spatial and temporal evolution of rift systems. The Bay of Biscay and Pyrenees, at the transition between the Iberian and European plates, correspond to a Late Jurassic to Mid Cretaceous rift system. The transition from preserved oceanic and rift domains to the West to their complete inversion in the East enables the investigation of seismically imaged, drilled and exposed parts of a rift system. We combine observations from seismic reflection data, gravity inversion results and field mapping to identify and map former rift domains from the Bay of Biscay margins to onshore fossil analogues preserved in the Pyrenean orogen. The results of this mapping emphasize the existence of spatially disconnected and strongly segmented rift systems preserved along the paleo Iberian-European plate boundary. Based on their restoration, subsidence and deformation history, we illustrate the evolution of strain partitioning between them and present the implications at the scale of the Iberian-European plate boundary. The deformation history suggested is more complex than previously assumed, highlighting the polyphased evolution of this plate boundary. We propose that the onset of the Late Jurassic to Early Cretaceous rifting was partitioned between a set of distinct left-lateral transtensional rift systems. A plate kinematic reorganization at Aptian-Albian time resulted in the onset of seafloor spreading in the Western Bay of Biscay and extreme crustal and lithosphere thinning in intra-continental rift basins to the east. Finally, the results of this work may provide insights on: (1) processes preceding break-up and the initiation of segmented and strongly oblique shear margins, (2) the deformation history of nascent divergent plate boundaries, and (3) the kinematics of the southern North Atlantic and Alpine domain in Western Europe.