New investigations about three young volcano-sedimentary systems of Velay-Vivarais (France) and co-evolution humans-volcanoes in the background

After presenting the geographical framework of this region on the south-eastern edge of the Massif Central which saw the birth of volcanology and still fuels debates on the contemporaneity of man and extinct volcanoes, we recall the general context and chronology of recent volcanic activity in the Velay-Vivarais, known as the “Young Volcanoes of Ardèche”. We insist on the contra- dictory results provided by the different dating methods used in recent decades (14C, OSL, TL, K/Ar and 40Ar/39Ar) and provide new results about three localities: the Grand Suc de Breysse (Présailles, Haute-Loire), the Suc de Bauzon whose flow dammed the Palaeo-Loire at Rieutord (Usclades-et-Rieutord, Ardèche) and the Issarlès maar (Le Lac d’Issarlès, Ardèche) with lacustrine sedi- mentary archives preserved below a 108.5 m waterbody. The eruption of the Grand Suc de Breysse began with a phreatomagmatic phase during MIS 5 (OSL, TL, K/Ar). The filling of the Rieutord volcanic dam paleo-lake fossilises a basaltic flow dated at 85 ± 4 ka (K/Ar) and continues during MIS 3: in its central part, the upper part of the preserved deposit is dated between 41.7 and 18.2 ka (14C and OSL); in its upstream part, deltaic deposits of the paleo-Loire are dated between 52 ± 2 and 35 ± 3 ka (OSL). The eruption of the Issarlès maar is dated at 54 ± 8 ka (TL), confirming that it belongs to a recent phase of the volcanism of the “Young Volcanoes of Ardèche”. At the moment, no Palaeolithic vestiges are directly associated with these three volcano-sedimentary complexes.