The tectono-sedimentary evolution of the Lechaion Gulf, the south eastern branch of the Corinth graben, Greece

The Gulf of Corinth is the second most active continental rift in the world and thus a much-studied natural laboratory for analyzing details of rift history. A new detailed offshore seismic survey combined with previously acquired data in its least studied part, the Lechaion Gulf, shed light on the tectono-sedimentary evolution of the eastern end of the Corinth rift. This study shows that: (i) the Lechaion Gulf is the submerged northern part of the onshore Corinth-Nemea basin, (ii) they are both bounded to the south by the north dipping Klenia and Kenchreai faults, which are considered at present inactive, (iii) both the Corinth-Nemea basin and the Lechaion Gulf were formed at around between 3.6 and 4 Ma BP (middle to late Pliocene), at the same time with the Megara basin, and (iv) the Lechaion Gulf was submerged and took its present shape at around between 0.7 and 1.7 Ma BP, at the same time with the Gulf of Corinth and the Alkyonides Gulf. Furthermore, sequence stratigraphy interpretation of seismic profiles from the Lechaion Gulf revealed: (i) a total post-alpine sediment thickness of almost 3 km below the Lechaion Gulf, (ii) at least 400 m of sediments accumulated during the last 245 ka, corresponding to a mean sedimentation rate of 1 m/ka for the last 245 ka and 2.3 m/ka for the Holocene, and (iii) differential vertical movement, in the order of 4.5 km, between the bedrock under the Lechaion Gulf and the adjacent mountains yields an accumulative average slip rate of 0.9 m/ka or less, over the last 4 Ma. Therefore, for estimating more accurately the slip rates, the uplift rates, the extensional rates and the earthquake recurrence interval over the eastern end of the Corinth rift, the presently mentioned tectono-sedimentary evolution of the Lechaion Gulf must be taken into consideration.