Pattern and rate of post-20 ka vertical tectonic motion around the Capo Vaticano Promontory (W Calabria, Italy) based on offshore geomorphological indicators

Abstract

The magnitude and rate of Late PleistoceneeHolocene vertical tectonic movements offshore of the Capo Vaticano Promontory (western Calabria, southern Italy) have been measured on the basis of the presentday depth variations of the edges of submerged depositional terraces (and associated abrasion platforms) that formed below the storm-wave base, during the sea level stillstand of the Last Glacial Maximum (LGM). These depositional features, represented by submerged prograding wedges and an associated terrace-shaped upper boundary, have been identified in high-resolution seismic reflection profiles acquired along the continental shelf and the upper slope of the promontory, and are referred to in this study as “Lowstand Infralittoral Prograding Wedges (LIPWs)”. Our new data and methods provide evidence that LIPWs can be used as geomorphological indicators of vertical movements in offshore settings with well controlled uncertainty. Removal of the non-tectonic component of vertical changes using an ice-volume equivalent eustatic sea level compilation indicates w11 ( 3.2) m of uplift and w25 ( 3.2) m of subsidence, from southwest to northeast, along the promontory, over a distance of w22 km, during the post-LGM. The resulting uplift and subsidence rates (including both regional and local components) for the last 20.350 ( 1.35) years are 0.54 ( 0.2) mm/y and 1.23 ( 0.25) mm/y, respectively. These results are consistent with longer-term estimates based on uplifted 215e82 ka old coastal terraces and Late Holocene shorelines. This integration of offshore and coastal markers indicates a pattern of vertical movements characterized by a marked asymmetry associated with a northeast down tilt of the Capo Vaticano Promontory. The calculated tilt rate increases by one order of magnitude during the post-LGM in respect to the time interval from 215 to 82 BP. Displacement associated with the NWeSE striking normal fault that bound the Capo Vaticano Promontory to the Gioia Tauro Basin ended in the (?) Pleistocene, and thus does not contribute to the tilt of the promontory at least during the last 215 ka.