MISURE DEL SOLCO TIRRENIANO (MIS 5.5) NELL’ISOLA DI CAPRI: VALUTAZIONE DI ATTIVITÀ TETTONICA DURANTE IL PLEISTOCENE SUPERIORE

Abstract

L. Ferranti & F. Antonioli, Subtle tectonic displacements and active structural blocks in the last 124 ka BP revealed by
measurements of the MIS 5.5 tidal notch, Capri Island, Southern Italy (IT ISSN 0394-3356, 2007).
Capri Island, located on the western side of Southern Italy, Central Mediterranean Sea, is considered tectonically stable during the Late
Pleistocene based on the nearly eustatic (6±3 m a.s.l) elevation, along its rocky coastline, of the tidal notch attributed to the Last
Interglacial and dated at 124 ka. In this study, we present detailed (cm-scale) measurements of the notch elvation, which ranges
between 5.2 and 8.0 m a.s.l. The change in elevation of the notch is not random, but rather decreases progressively from a southeastern high sector along the westen and southern coasts to reach a minimum in the north-western sector. We argue these changes in elevations are caused by minor tectonic slips along previously mapped faults. The pattern of down-dropping of the tidal notch is consistent with the active subsidence occurring in the Gulf of Naples and Salerno, located north and south of Capri Island, respectively. Within these basins, which are part of a belt of basins flooring the continental shelf of the western, Tyrrhenian flank of Italy (periTyrrhenian basins), the largest subsidence was controlled by a ~NW-SE extension during Pliocene-Quaternary. The NW-SE extension is also active today along with a ~NE-SW directed extension, that characterizes the main seismogenic belt of the Apennines Mountains further east, as documented by seismicity, bore-hole breakouts and active fault studies. The very-low vertical displacement rates (~0.01 mm/a) averaged over the Late Pleistocene of the faults inferred at Capri, which are an order of magnitude lower than the displacement rates of the main seismogenic faults of the Apennines, suggest asesimic or microseismic, slow motion. Fault slips may be
controlled by deep mechanical surfaces which were either inherited by the pre-Late Tertiary thrust imbrication, or formed during
Pliocene-Quaternary extensional development of the peri-Tyrrhenian basins.