High energy marine flood deposits on Astypalaea Island, Greece: possible evidence for the AD 1956 southern Aegean tsunami

High energy marine sediments are described from Livadia and Stavros, Astypalaea Island, Greece, which are tentatively interpreted to be associated with the southern Aegean tsunami of 9th July AD 1956. At Livadia, the marine provenance of imbricated pebble deposits (referred to here as the Imbricated Clast Unit, or ICU) are inferred from two observations. Firstly, the similarity between the clasts comprising the ICU and contemporary beach sediments, and secondly the inclusion of foraminiferal tests within the sediment matrix. Derivation from the AD 1956 tsunami, rather than from a storm surge, is inferred from the uniqueness of the deposits within the sedimentary record, their distinct imbrication, and Cs-137 and Pb-210 dating of overlying and underlying sediments. The top of the ICU occurs at + 2.00 metres above sea level (m a.s.l.) indicating a minimum flood level at this location. At Stavros, a gravel with rounded clasts incorporating marine mollusca is found on exposed cliff surfaces up to an elevation of + 10.00 m a.s.l. These gravels are also interpreted as having been deposited by the AD 1956 tsunami. The elevation of the deposits and topographic observations indicate that previously reported run-up elevations were over-estimated. The results shown here represent the first systematic investigation into sedimentary deposits possibly associated with a modern tsunami within the Aegean Sea region of Greece. (C) 2000 Elsevier Science B.V. All rights reserved.