Tracing 430,000 Years of Explosive Volcanism in Central Italy: Tephrostratigraphy and Tephrochronology of the Fucino Basin

The Fucino Basin in central Italy hosts a thick, continuous lacustrine sedimentary succession documenting the environmental history from the Early Pliocene to recent historical times. This distinguishes it as a unique archive within the Central Apennines and an extraordinary record within the Mediterranean region and on a global scale. Over the past decade, drilling operations have recovered several sediment successions from the Fucino Basin to ascertain the viability of the sediment archive for palaeoenvironmental, palaeoclimatic, tectonic and volcanic studies. The overarching ambition is to initiate an ICDP deep-drilling campaign (MEME project) recovering the complete basin history. The basin is located downwind of most Italian volcanic districts (< 150 km). This promotes its potential to explore the past explosive volcanic activity of the peri-Tyrrhenian volcanoes and to establish an outstanding tephrostratigraphic and tephrochronological record for the Central Mediterranean region. Here tephrostratigraphic and -chronological results from two drill sites (F1-F3, F4-F5) of the central part of the basin are presented, whose composite record comprises more than 140 tephra layers identified within the last 430 ka. The geochemical fingerprint of 116 of these tephra layers was successfully characterized by major and minor element glass compositions and extended for specific tephra layers by trace element and isotope data of glass and/or mineral phases. The geochronology of the Fucino tephra record is constrained by 47 radioisotopic ages, of which 18 represent ⁴⁰Ar/³⁹Ar ages directly obtained from tephra layers within the Fucino succession. This makes the Fucino record currently the most precisely dated Mediterranean Middle-Upper Pleistocene tephra archive. The combination of geochemical, stratigraphic and chronological data facilitates the unravelling the volcanic origin of tephra layers and the establishment of a robust tephrostratigraphic framework integrating proximal volcanic, but also other (mid)distal sedimentary tephra records. The Fucino tephra record provides unique insights into the different active phases of the respective Italian volcanic districts and centres, identifying prominent known and many previously unknown eruptions. Most tephra layers originate from the Latium volcanoes, which underwent their prime activity during the Middle Pleistocene, while, after 200 ka the main explosive activity of the Neapolitan volcanoes is also recorded.

The overall resulting tephrochronological information allows the construction of a comprehensive age-depth series of the Fucino sedimentary succession. This facilitates a reassessment of existing eruption ages and provides ages for previously undated tephra layers. Based on the improved chronology and more complete knowledge of volcanic activity, volcanic recurrence rates can be refined, but also climate-volcano interactions may be investigated. Furthermore, the Fucino tephrochronology provides a robust and independent chronology for the multiproxy series, allowing the Quaternary paleoclimatic-environmental dynamics to be explored independent of any a priori assumptions on response times to climate forcing and feedback.