Résumé
The French Massif Central is a key basement relief subject to an intense alkaline volcanism starting with the Cantal Stratovolcano at 11 Ma and ending at 3 Ma. To quantify the palaeoelevation of the Cantal Stratovolcano, and to replace it in the frame of the uplift history of the Massif Central, we first reconstructed the vegetation and the climate based on a detailed pollen analysis, following the botanical approach, of the Murat diatomites deposited in a maar lake. The vegetation was organised in three different belts with a Glyptostrobus swamp around the lake, a mixed forest with evergreen and deciduous trees and, at higher altitude, a conifer forest. The climate estimated using the 'climatic amplitude method' indicates mean annual temperatures between 11.4 and 17°C. Using these estimates and the comparison with contemporaneous sites situated at sea level, we inferred a palaeoelevation between 710 and 930 m.a.s.l. of the Murat site (1058 m.a.s.l. today). During the Early Pliocene, the site of Murat has thus uplifted by 130 to maybe 350 m that led to a reorganisation of the drainage pattern and to the capture of rivers coming from the northern edge of the Massif Central towards the Atlantic Ocean. Moreover, using pollen floras, mean annual temperature estimates and the vertical shift of the vegetation belts in relation to latitude, our study confirms that the Cantal Stratovolcano was a very high volcano (>2500 m) before its progressive dismantling due to glacial phases of the Pleistocene.