Precise dating of middle to late Villafranchian mammalian paleofaunae from the Upper Allier River valley (French Massif Central) using U–Pb geochronology on volcanic zircons

Abstract

The French Massif Central represents one of the rare occurrences in Europe where lower Pleistocene fossil deposits are associated to a substantial volcanic activity. Thanks to the abundance of volcanic zircons in the differentiated products of the Monts-Dore/Guéry stratovolcano, we were able for the first time to use U/Pb geochronology on zircon to precisely date lower Pleistocene fossil deposits. Zircon, a weathering-proof heavy mineral, was dispersed over the landscape through Plinian eruptions, and quickly reworked in fossil-bearing sedimentary deposits. Five Villafranchian fossil sites in the Upper Allier River valley (French Massif Central) have been precisely dated: Chilhac (MNQ17b, 2.285 ± 0.046 Ma), Mont Coupet (2.274 ± 0.032 Ma), Senèze (reference locality for MNQ18, 2.100 ± 0.029 Ma, confirming the previously determined 2.18–2.10 Ma 40Ar/39Ar ages), Blassac-La Girondie (MNQ19, 1.946 ± 0.029 Ma), and Vazeilles (1.843 ± 0.028 Ma). These new chronological data constrain the duration of the MNQ18 in central France to about 200 ka. The confirmation of an old age for the Blassac-La Girondie deposit indicates that the MNQ19 biozone started significantly earlier than previously thought.