Evolution of the Iberia-Adria-Europe plate boundary revealed by the Meso-Cenozoic thermal history of the European paleomargin in SE France

Plate kinematic reconstructions of the boundary between Iberia, Adria microplates and Europe during Mid-Late Cretaceous deformation is disputed. At this time the collision in the Pyrenees-Provence, the Eo-Alpine phase of subduction, and far-field inversion in Western Central Europe occurred when Africa began to converge northward. The tectonic relationships between these compressional features and the structure of the Alpine Tethys (Adria-Europe) and the Pyrenean-Valaisan rift (Iberia-Europe) are still uncertain. Here, we reconstruct the thermal histories of the European paleomargin of the Western Alps, in SE France, by combining the analysis of numerous low-temperature thermochronometers and U-Pb dating on zircon, apatite and calcite in the Vocontian basin and in the Pelvoux and Maures-Tanneron massifs. After a period of exhumation of the Variscan basement during the late Paleozoic well identified in the Pelvoux massif, we find evidence of a thermal event in the Maures-Tanneron massif around 200 Ma, which is consistent with increased heat flux linked to the Central Atlantic Magmatic Province (CAMP). This is followed by a regionally significant heating event that results from the combined effect of depositional burial and crustal thinning associated with Alpine Tethys rifting during the Early Jurassic and the Cretaceous Vocontian-Valais rifting event, with a peak temperature reached around 90 Ma. This confirms the central role played by extension between Iberia and Europe in SE France, north of Corsica-Sardinia. A pre-Priabonian phase of cooling/exhumation is identified in both massifs between 80 and 50 Ma associated to N-S oriented Pyrenean shortening. A distinctive late Cenozoic cooling pattern in the Maures-Tanneron between 30-15 Ma is interpreted to reflect the opening of the Western European rift and the Liguro-Provençal basin. The onset of this phase, around 30 Ma, appears coeval with the Alpine collision marked by foreland basin deposition and the activation of the Penninic Frontal Thrust, which led to the burial of the Pelvoux massif. Brittle normal faulting in the Vocontian Basin dated between 34 and 7 Ma using calcite U-Pb geochronology suggests that the basin was impacted by the opening the Liguro-Provençal like the rest of Provence and Maures-Tanneron massif, whereas the Pelvoux massif recorded compression at this time. This study confirms that N-S compression between Iberia and Europe resulted in the inversion of the Cretaceous rift system during the Late Cretaceous. Both the age and the scale of the tectonic inversion in Europe suggest that both Iberia and Adria collided with the European paleomargin at this time, which in turn impacts the reconstruction of the boundary between Iberia and Adria. The impact of the Oligocene-Miocene extension in SE France seems to be significantly greater than previously thought. It might have played a role in isolating the developments of Provence and Vocontian basin from the Western Alps.