Neogene rejuvenation of the Pyrenees – Py-10

Relief and altitude of mountain ranges decrease after convergence has stopped, as does CO2 uptake - an important input into global climate models. However, the reduction in relief is not necessarily monotonous and may involve what we call relief rejuvenation, i.e. increase in relief and erosion renewal. Mechanisms for such rejuvenation may be climatic, geomorphic or geodynamic. Here, we will consider the Pyrenees. They have the advantage of of not having been significantly reworked by Quaternary glaciers. Moreover, the post-orogenic history is extensive (at least since the Oligocene), with an important erosion rejuvenation at ~10 Ma. Also, the range is small and therefore relatively easy to study, and furthermore, it has been the site of numerous recent studies that have provided a valuable body of data. The findings from the Pyrenees will be tested in other mountain ranges such as the Rockies. Beyond geomorphology and geodynamics, such rejuvenation may be of interest for its feedbacks with climate and evolution of species.
This project aims to better understand this post-orogenic phase initiated about 10 Ma ago and its impact on the present state of the orogen. In doing so, we propose to focus the discussion on the state of the range about 10 Ma ago, and not to analyse the range based on the present state, which is traditionally done. In this way, we should be able to answer the main questions: (1) What is the driver for the transition at 10 Ma? (2) Can rates of evolution from the more recent geological history (last few million years) be extrapolated over the last 10 million years? (3) How uniform is the post-orogenic history of the range? (4) Can our conclusions be generalised to other orogens?
These questions will be addressed by a combination of three approaches: (i) a geodynamic analysis of the range since 30 Ma; (ii) an analysis of the state of the range 10 Ma ago; and (iii) a comparison of the evolution of the range between 10 and 3 to 1 Ma.