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Abstract: The Lefkada–Preveza coastal zone, NW Greece, is characterised by an active barrier system and related extensive beachrock sequences. Besides the gradual coastal processes of longshore drift and spit evolution, the presence of active tectonics and the occurrence of tsunamis have been documented in previous studies and are part of the coastal geomorphological system. In this paper, we present the results of detailed multi-proxy sedimentological and geomorphological investigations carried out along the northern part of the barrier system and in back-beach positions. Our findings suggest that extreme wave events contributed to coastal and environmental changes and involved temporary breakdown of the barrier system. Sedimentary findings suggest that one generation of event deposits may be related to the 365AD Crete earthquake and associated tsunami. According to our results, the Lefkada coastal system formed by the interaction of both long-term, gradual and sudden, impulsive littoral geomorphodynamics. Extreme wave events are assumed to have played a significant role in the evolution of the present coastline, acting as recurrent impulsive disturbances of the coastal system. Subsequently, the onset of long-term gradual coastal processes, such as longshore drift, re-established a state of natural coastal balance by re-arranging the coastal sediments. [Copyright &y& Elsevier]

Abstract: This paper presents, for the first time, detailed geomorphological, sedimentological, geoarchaeological, geophysical and geochemical evidence of a strong tsunami impact on the Bay of Aghios Nikolaos and its environs (NW Greece) during Classical–Hellenistic times. Tsunamigenically dislocated beachrock slabs found on top of the Santa Maura beach ridge complex are closely interrelated to adjacent coarse-grained washover fan deposits encountered in vibracores and detected by earth resistivity measurements. Based on detailed topographic surveys and geomorphometric investigations, it was possible to localize areas of high intensity overflow. Underwater studies revealed that the central and northern parts of the former Plaka beach ridge were completely destroyed by tsunami impact. Loose littoral deposits were flushed into the Bay of Aghios Nikolaos and mega blocks of the underlying beachrock structure were dislocated landwards. Tsunami landfall occurred all along the eastern and northern shores of the bay where deposits, partly weathered and associated to archaeological findings, were found. Runup was estimated to minimum values between 2–3m and 4–6m a.s.l. Crosschecking the results of radiocarbon analyses with archaeological ages from five sites allowed to date the strong tsunami event to the time period between 395calBC and 247calBC. Due to the funnel-like contour of the coastline, the area is extremely sensitive to tsunami events of mid to high magnitude and high frequency. [Copyright &y& Elsevier]