Intermittenza e struttura della caldera risorgente attiva dell'Isola d'Ischia

Abstract

The island of Ischia (Bay of Naples, Italy) is a highly-exposed, ongoing resurgent caldera. The stages of development of the uplift are linked to a dome-like monocline-bounded structure and piston-like fault-bounded structure. During the piston-like stage, on the western and eastern flanks of the resurgent core, uplift occurred along NNW-striking faults, that have inclination from sub-vertical to vertical (>85°) and outward dips. In an ENE-WSW section, the geometry of these faults suggests a negligible extensional deformation. Along the northern flank, uplift was accomplished by ENE-striking normal faults. They have inclination of 60°-85°, dip northwards (outward) and show striae which indicate almost pure dip-slip. The southern flank is characterized by a monocline with hinge lines trending ENE associated with vertical faults. In a NNW-SSE section, the resulting resurgence has a wedge shape. This structure can be reconciled by the contemporaneous regional extension along NE to E-W striking normal faults, whose motion creates space for uplift with no deformation of the surrounding caldera floor.