Development and deformation of marine terraces: Constraints to the evolution of the Campania Plain Quaternary coastal basin (Italy)

Raised paleoshorelines were detected in the eastern margin of the Campania Plain, which is one of the largest coastal basins in the Tyrrhenian back-arc basin system associated with the Neogene to Quaternary Apennine orogen. The paleoshoreline remnants crop out at variable elevations at several sites, including quarry cuts, which provide excellent 3D exposures of the coastal landforms and deposits, the associated continental sediments and faults dissecting those landforms and deposits. Based on the integration of geomorphological, stratigraphic, micropaleontological and facies analyses with structural data, we reconstructed shoreline development in response to erosional/depositional processes governed by relative sea level change in the framework of coeval extensional tectonics. Most of the paleoshoreline remnants are assigned to three displaced marine terraces that, based on new U-series dating, are related to the late part of the Middle Pleistocene. The faults offsetting the marine terraces (namely, E-W striking normal faults and NNW striking transfer faults) are interpreted as part of a single, segmented extensional fault system controlled by roughly N-S to NNW-SSE horizontal extension. The identified extensional system, being consistent with the regional structure imaged by seismic data, represents the first field evidence of the tectonics controlling the formation of the Campania Plain basin. Our results, providing new direct evidence that effectively complements the large amount of existing subsurface datasets, allow for a significant step forward in the understanding of the tectonic and sedimentary processes governing the Quaternary development of the Tyrrhenian back-arc basin margin.