Evidence for a large-magnitude eruption from Campi Flegrei caldera (Italy) at 29 ka

The 40 ka caldera-forming eruption of Campi Flegrei (Italy) is the largest known eruption in Europe during the last 200 k.y., but little is known about other large eruptions at
\nthe volcano prior to a more recent caldera-forming event at 15 ka. At 29 ka a widespread
\nvolcanic ash layer, termed the Y-3 tephra, covered >150,000 km2
\n of the Mediterranean. The glass compositions of the layer are consistent with Campi Flegrei being the source, but no
\nprominent proximal equivalent in the appropriate chrono-stratigraphic position had been
\npreviously identified. Here we report new glass chemistry data and 40Ar/39Ar ages (29.3 ±
\n0.7 ka [2σ]) that reveal the near-source Y-3 eruption deposit in a sequence at Ponti Rossi
\nand a nearby borehole (S-19) in Naples. The dispersal and thickness of the deposits associated with this eruption, herein named the Masseria del Monte Tuff, were simulated using a
\ntephra sedimentation model. The model indicates that ~16 km3
\n dense rock equivalent of the
\nmagma erupted was deposited as fall. This volume and the areal distribution suggest that
\nthe Masseria del Monte Tuff resulted from a magnitude (M) 6.6 eruption (corresponding to
\nvolcanic explosivity index [VEI] 6), similar to the 15 ka caldera-forming Neapolitan Yellow
\nTuff (M 6.8) eruption at Campi Flegrei. However, the lack of coarse, thick, traceable, nearvent deposit suggests peculiar eruption dynamics. Our reconstruction and modeling of the
\neruption show the fundamental role that distal tephrostratigraphy can play in constraining
\nthe scale and tempo of past activity, especially at highly productive volcanoes.