Age and geochemistry of tephra layers from Ischia, Italy: constraints from proximal-distal correlations with Lago Grande di Monticchio

Unraveling the eruptive history of the Island of Ischia (southern Italy) is problematic due to its burial, caldera collapse, resurgent uplift and erosion. Here, we present new major and trace element glass data for 39–75ka proximal tephra deposits, including those of the caldera-forming Monte Epomeo Green Tuff (MEGT) eruption. Correlations with the distal tephra archive preserved at Lago Grande di Monticchio (LGdM) are used to constrain the timing of as yet undated eruptive events. Out of 13 LGdM tephras analysed from the 39–104ka time window, glass geochemical data show that all are compositionally consistent with the explosive volcanic eruptions of Ischia, whilst 5 of them can be correlated with specific proximal deposits. Pre-MEGT pyroclastic sequences comprise three compositional groups, these groups occur repeatedly in sucessive eruptions. Proximal-distal correlations indicate that the Porticello eruption occurred at 59±2ka and the Tisichiello eruption probably occurred at 76±3ka. The MEGT eruption is correlated with LGdM TM-19, which has been directly dated at 55±2ka. Post-MEGT tephras form compositional groups that overlap with the pre-MEGT but are displaced to lower FeO and TiO2 and lower incompatible element contents. Proximal-distal correlations indicate that the Schiappone and Pietre Rosse eruptions occurred at 50.6±2.0ka and 45±6ka, respectively. Tephra from the MEGT eruption span a wide compositional range, broadly overlapping the three pre-MEGT compositional groups but are displaced to higher Nd and Y and contain an additional less evolved glass population. Glass geochemistry is used to recognise and confirm distal equivalents of the MEGT at LGdM (TM-19) and in the Ionian (Y-7), Adriatic (PRAD 1870) and Tyrrhenian (C-18, MD 28) seas. Distal occurences of MEGT tephra define a dispersal axis to the south-southeast and are found as far as 540km from Ischia, making the MEGT one of the most widely dispersed late Quaternary pyroclastic deposit erupted in the Campanian region. We estimate a volume of approximately 40km3 for the fallout portion of the MEGT pyroclastic sequence on the basis of proximal and distal deposit thicknesses. •We provide major and trace element micron-beam data 39–75ka Ischia tephra.•We correlate 5 distal tephras with proximal deposits.•High resolution ages are provided the varved distal stratigraphy of Lago Grande di Monticchio.•Isopach maps are provided for the caldera-forming MEGT eruption.•MEGT fall is dispersed to the SSE