Deciphering the Cenozoic exhumation history of the Eastern Pyrenees
along a crustal-scale normal fault using low-temperature
thermochronology
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 afterwards. In the footwall,
cooling subsequently propagated westward along the fault during
Priabonian (35-32 Ma), upper Oligocene and lower Miocene (26-19 Ma), and
Serravalian-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 towards 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.