Abstract

The timing of transition between the contractional and extensional regimes along the Pyrenean range remains debated. Compared to its central and western parts, the eastern part of the chain was significantly affected by extensional tectonics mostly related to the opening of the Gulf of Lion. The Têt normal fault is the best example of this tectonic activity, with topographic reliefs above 2,000 m in its footwall. In this study, we synthetized previous thermochronological data and performed new (U-Th)/He and fission track dating in the Eastern Pyrenean massifs. Output apparent exhumation rate and thermal modeling in the hanging wall of the Têt fault highlight a rapid exhumation (0.48 km/Ma) and cooling (∼30°C/Ma) phase between 38 and 35 Ma, followed by slower exhumation/cooling afterward. In the footwall, cooling subsequently propagated westward along the fault during Priabonian (35–32 Ma), upper Oligocene and lower Miocene (26–19 Ma), and Serravallian-Tortonian times (12–9 Ma). These data and modeling outcomes suggest that the exhumation of the Têt fault hanging wall related to southward thrusting ended at 35 Ma, and was followed by different extensional stages, with a propagation of the deformation toward the West during the upper Miocene. We propose that the onset of extension in the Eastern Pyrenees occurred during the late Priabonian period, contemporaneously with the large-scale rifting episode recorded in Western Europe. After this event, the Têt fault activity and the westward propagation of the deformation appear mainly controlled by the opening of the Gulf of Lion.