Post‐orogenic evolution of the southern P yrenees: constraints from inverse thermo‐kinematic modelling of low‐temperature thermochronology data

The late‐stage evolution of the southern centralPyrenees has been well documented but controversies remain concerning potentialNeogene acceleration of exhumation rates and the influence of tectonic and/or climatic processes. A popular model suggests that thePyrenees and their southern foreland were buried below a thick succession of conglomerates during theOligocene, when the basin was endorheic. However, both the amount of post‐orogenic fill and the timing of re‐excavation remain controversial. We address this question by revisiting extensive thermochronological datasets of theAxialZone. We use an inverse approach that couples the thermo‐kinematic modelPecubeand theNeighbourhood inversion algorithm to constrain the history of exhumation and topographic changes since 40 Ma. By comparison with independent geological data, we identified a most probable scenario involving rapid exhumation (>2.5 km Myr−1) between 37 and 30 Ma followed by a strong decrease to very slow rates (0.02 km Myr−1) that remain constant until the present. Therefore, the inversion does not require a previously inferredPliocene acceleration in regional exhumation rates. A clear topographic signal emerges, however: the topography has to be infilled by conglomerates to an elevation of 2.6 km between 40 and 29 Ma and then to remain stable untilca. 9 Ma. We interpret the last stage of the topographic history as recording major incision of the southernPyrenean wedge, due to the Ebro basin connection to theMediterranean, well before previously suggestedMessinian ages. These results thus demonstrate temporally varying controls of different processes on exhumation: rapid rock uplift in an active orogen during lateEocene, whereas base‐level changes in the foreland basin control the post‐orogenic evolution of topography and exhumation in the centralPyrenees. In contrast, climate changes appear to play a lesser role in the post‐orogenic topographic and erosional evolution of this mountain belt.