Volcanism and faulting of the Campania margin (Eastern Tyrrhenian Sea, Italy): a three-dimensional visualization of a new volcanic field off Campi Flegrei

Abstract

By means of information technology, 3D digital geologic models are increasingly the best methods of constraining interpretations of geology at depth. Visualization in three dimensions has allowed us to develop solutions that explain the stratigraphic and structural complexity of the Campania margin of the Eastern Tyrrhenian Sea, especially the lateral relationships among volcanoes and underlying normal faults. Using seismic and sequence stratigraphy and structural geology approaches in a dedicated GIS environment, we interpreted a seismic grid and investigated a subsurface volcanic field in Gaeta Bay (off Campi Flegrei) located within the Campania margin. The Gaeta Bay basin fill is characterized by several volcanic units that were analyzed using 2D structure contour maps and isochron maps. These volcanoes are comparable in size to the edifices of Campi Flegrei, Vesuvius, and the submerged volcanoes of the Bay of Naples. Their age spans from the Lower Pleistocene for the isolated V0 volcano sited in Central Gaeta Bay to 0.4–0.1 Ma for the volcanic field of southern Gaeta Bay. The study of the interplay between volcanic units and faults allowed us to distinguish (1) the oldest fault buried by the Lower Pleistocene V0 volcano in Central Gaeta Bay; (2) a normal fault swarm NE–SW that in the Middle Pleistocene gave rise to a half-graben filled by the V1–V5 volcanic field in southern Gaeta Bay; and (3) post-0.4 Ma normal faults that downthrow the V1 and V3 volcanoes. We correlated the >1,500-m-thick Late Quaternary volcanoes of southern Gaeta Bay to the buried lava volcanoes interlayered with volcanoclastic deposits drilled at Campi Flegrei geothermal wells.