Universite de Savoie, France

Along the 50 km of coastline from Villa San Giovanni to Melito di Porto Salvo, fourteen marine terraces (so-called main terraces) form a staircase between the present sea-level and 520 m a.s.l. They were uplifted at a mean rate of 1.24 m/ka. Their minimum width is 60 m and their are often bounded landward by a former sea-cliff more than 10 m high. These major strandlines are distinguished from smaller terrace shorelines which are intercalated between the main terraces. Five of the main terraces (TM 10, TM 170, TM 290, TM 400 and TM 510) are correlated with interglacial stages 1, 5.5, 7.5, 9 and 11 corresponding to peaks of warmer climate on isotopic curves SPECMAP/ODP 677 or ODP 984. These correspond to a 100 ka return period. Considering the entire suite of fourteen main terraces the mean return period is 30 ka. Within the 0-170 m range of altitude, six main terraces the shorelines of which are uplifted at 8, 49, 71, 90, 119 and 167 m a.s.l. respectively, constitute major benchmarks within a population of thirty-one palaeoshorelines. Following the high-resolution isotopic curves Vostok, GRIP and GIPS2, the intercalated shorelines are correlated with second order climatic oscillations which momentarily reversed or briefly interrupted the tendency toward cooling which occurred after each major warm peak, during the period starting at the beginning of interglacial stage 5.5 and ending at glacial stage 2. In spite of important earthquakes occurrences in the study area, the palaeoshorelines are correlated with minor glacio-eustatic fluctuations or standstills which took place during the main marine regressions. Finally, a 3 ka mean return period appears suited to the rhythmic generation of the thirty-one shorelines. This time interval corresponds to a frequency 10 to 33 times shorter than the double periodicity responsible for shaping the main terraces. These terraces associate abrasion platforms with the second order shorelines. They represent a geomorphologic response to the dissymmetry which opposes an abrupt sea-level rise of great magnitude occurring every 30 ka to a subsequent sea-level lowering during a longer interval, interrupted by minor fluctuations or standstills with a 3 ka return period.