Superimposed cycles of composite marine terraces: the example of Cutro terrace (Calabria, Southern Italy)

Marine terraces are a valuable archive of information in the reconstruction of uplift and sea-level history of coastal areas, especially when they can be correlated with specific highstands of the eustatic curve. Usually, the correlation is based on the assumption that any morphological terrace is the result of a single sea-level fluctuation. However, if the surface of a terrace is reoccupied during successive transgressions, the result may be a single morphological terrace which has in fact been generated by several superimposed sea-level fluctuations. This study illustrates what type of stratigraphic architecture may be recorded in the deposits of such composite marine terraces, focusing on identification and interpretation of discontinuity surfaces and facies analysis. The examined example is the marine terrace of Cutro, the highest and most extensive of five terraces preserved in a step-like sequence along the coast of the Crotone Peninsula (Calabria, Southern Italy). The sedimentary cover of the Cutro marine terrace had generally been regarded as the result of a single sea-level oscillation, but stratigraphic analysis and correlation of several sections has enabled the recognition of three distinct transgressive–regressive sequences. These cycles display an overall shallowing trend from shelf deposits, represented in the first cycle by algal carbonate buildups, to shoreface and alluvial deposits in the younger cycles. The succession is now interpreted as a response to high-frequency sea-level fluctuations occurring during a long-term interglacial, such as those documented during marine isotope stage (MIS) 7.