Measuring magnitude and rate of vertical movements in the offshore Capo Vaticano (W Calabria) using lowstand coastal prisms and wavebuilt terraces

Abstract

The magnitude and rate of vertical movements have been measured in the offshore Capo Vaticano (western Calabria) for the Late Pleistocene - Holocene on the basis of the depth of submerged coastal prism and associated wave-built terrace formed during the sea-level lowstand of the Last Glacial Maximum (LGM). Uplifted and submerged terraces have proved to be valuable recorders of vertical motion in many locations around the world (e.g. DICKINSON, 2001; WEBSTER et alii, 2004) as the depth of their tops appear to be controlled by the sea-level. In the eastern Tyrrhenian margins, depending on the hydraulic energy conditions (i.e. waves and wind-induced currents), the average water depth of terraced surface of lowstand coastal prisms was probably 15-20 m (CHIOCCI & ORLANDO, 1996). A series of LGM lowstand coastal prisms and associated wave-built terraces were identified on a new set of very highresolution reflection seismic profiles acquired along the continental shelf and upper slope of the western Calabria continental margin. Data processing included time-depth conversion and the interpretation of the resulting seismic lines was performed using a GIS-based software package. Seismic interpretation highlight that along the offshore Capo Vaticano the slope-breaks associated with wave-built terraced formed during the LGM deepens from ~130 m (cluster A) to ~170 m (cluster B) below sea level (bsl) as one moves from southwest to the northeast, over a distance of ~21 km (Fig. 1). Farther to the north, along the western flank of the Calabrian Arc, an average depth for the slope-breaks of ~165 m is measured. Removal of the non tectonic component of vertical changes using an ice-volume equivalent eustatic sea-level compilation (LAMBECK et alii, 2011) indicates ~15 (± 5) m of uplift and ~25 (± 5) m of subsidence during the post-LGM for the southern and northern sectors offshore Capo Vaticano, respectively. The resulting average uplift and subsidence rates (both regional and local components) for the last 20 (± 2) k.y. are 0.75 (±0.325) mm/y and 1.25 (±0.375) mm/y, respectively. The integration of the new data with those available in the literature (e.g. TORTORICI et alii, 2003; CUCCI & TERTULLIANI, 2010; FERRANTI et alii, 2011) may provide information on fault kinematics and constraints on slip rates of tectonic structures that are relevant for earthquake hazard analysis of western Calabrian margin. REFERENCES CHIOCCI, F. L. & ORLANDO L. (1996) - Lowstand terraces on Tyrrhenian Sea steep continental scope. Marine Geology, 134, 127-143. CUCCI, L. & TERTULLIANI A. (2010) - The Capo Vaticano (Calabria) coastal terraces and the 1905 M7 earthquake: the geomorphological signature of regional uplift and coseismic slip in southern Italy. Terra Nova, 22, 378–389. doi: 10.1111/j.1365-3121.2010.00961.x DICKINSON, W.R. (2001)- Paleoshoreline record of relative Holocene sea levels on Pacific islands. Earth-Science Reviews, 55, p. 191–234. doi: 10.1016/S0012-8252 (01)00063-0. FERRANTI L., SCICCHITANO G., SPAMPINATO C. R., ANTONIOLI F., MONACO C. (2011) - Holocene coastal uplift at Capo Vaticano, Calabria: implications for differential deformation rates. Riassunti VIII Forum FIST Geoitalia 2011, 19-23 Settembre 2011, Torino. Epitome, 4, 153. LAMBECK, K., F. ANTONIOLI, M. ANZIDEI, L. FERRANTI, G. LEONI, G. SCICCHITANO & S. SILENZI (2011) - Sea level change along the Italian coast during the Holocene and projections for the future. Quaternary International, 232, 250-257. WEBSTER, J.M., WALLACE, L., SILVER, E., APPLEGATE, B., POTTS, D., BRAGA, J.C., RIKER-COLEMAN, K. & GALLUP, C. (2004) - Drowned carbonate platforms in the Huon Gulf, Papua New Guinea. Geochemistry Geophysics Geosystems, 5, p. Q11008, doi: 10.1029/2004GC000726. TORTORICI, G., BIANCA, M., DE GUIDI, G., MONACO, C. & TORTORICI, L. (2003) - Fault activity and marine terracing in