Tephrochronological study in the Maccarese lagoon (near Rome, Italy) : Identification of Holocene tephra layers

This study deals with explosive activity of southern italian volcanoes recorded in the roman region since ca. 8,000 years. It presents chemical analyses performed on volcanic glass shards from a core (LM2 core) collected in the Maccarese lagoon, near Rome’s Fiumicino Airport, in February 2010. Rome is surrounded by volcanic complexes which recent activity is regularly discussed. Alban Hills and Sabatini are the two main volcanic complexes in the South and North Rome. The last traces of Sabatini volcanic activity are dated by 40Ar/39Ar at 251 ± 8 ka. The known youngest activity of the Alban Hills is dated at 7.5 ky, according to deposits observed at the bottom of the crater lake later. However, in 2003, Funiciello et al. have described pyroclastic and lahars deposits separated by a palaeosoil dated at 5.1 ± 0.1 14C ka BP. Historical accounts also relate volcanic activity during Bronze Age, but no volcanic deposits related to this recent activity have been described. Search of tephras related to Campanian, Sicilian and Eolian volcanic activity has been extended to recent explosive events from the Roman magmatic region. Three tephra levels have been observed in the LM2 core. Their chemical analyses, as well as Radiocarbon dating performed along the core, allow the identification of (1) the Agnano-Monte-Spina eruption dated at 3.99 ± 0.03 14C ka BP, (2) probably the last eruption from the Albans Hills, dated at ca. 5 ka, and (3), for the first time in northern Italy, a tephra associated with Phlegrean Fields volcanic activity but younger than the Agnano-Monte-Spina eruption. The increase in population around the Albans Hills volcanic complex and Rome exposes a growing number of people to various volcanic hazards. Increasing the number of studied sites in this area will provide a precise chronology of the recent volcanic eruptions and a better estimate of their environmental consequences