Unveiling “too-old” radiocarbon ages at Serapeo (Pozzuoli) enhances understanding of the present unrest crisis at Campi Flegrei caldera, Italy

Abstract The Campi Flegrei caldera, west of Naples, Italy, is currently experiencing volcanic unrest, a process that started 75 years ago. The magmatic origin of past uplift crises has been questioned by studies based on 14C data from marine organisms, suggesting three rapid uplifts; only the last, in the fifteenth century, was followed by the Monte Nuovo eruption (1538 CE). New 14C dating and water composition analyses from the thermal spring in the Roman Macellum of Pozzuoli (Serapeo) show that the two supposed non-eruptive medieval unrest phases are unreliable, because they are based on two-old ages due to absorption of deep 14C-depleted CO2 by marine fauna. The implication of this finding is that the current unrest has a high probability of being linked to the resumption of magma supply to the shallow plumbing system of the caldera, and that this process could result in a renewal of volcanic activity in the area.