Abstract
As high energy tsunami waves reach shallow near-shore environments, the height of the waves increases and sea water propagates towards the land. During this movement, significant amounts of sediment are transported inland from the nearshore, foreshore and beach. While a lagoon that is separated from the sea by a low, thin sand barrier has a relatively calm depositional environment under normal conditions, during a tsunami the sea water climbs over the sand barrier and deposits material from the nearshore, foreshore and sand barrier onto inner parts of the lagoon. This phenomenon is the reason why investigation of sedimentary sequences in lagoons reveals the sedimentary traces of past tsunamis. In this study, the physical and geochemical properties of sediments in two ca. 3.2 m-long cores collected from Karine Lagoon on the coast of Aydin-Soke (western Turkey) were investigated in order to determine the traces of past tsunamis in the Aegean Sea. An ITRAX micro-XRF scanner was used to obtain 0.2 mm-resolution radiographic images and 1mm-resolution XRF data from the cores. High-resolution analysis detected three heterogeneous and high-density intercalations within the relatively homogenous and occasionally laminated background sediments. XRF data revealed that these intercalations had significantly higher Ca/Ti values compared to the background sediments, i.e. they were rich in carbonates. Observation under a stereo-microscope determined that while the background sediments contained fresh bivalve shells smaller than 1 cm in diameter, the intercalations contained weathered/broken bivalve shells approximately 4 cm in diameter. Considering the physical and geochemical observations together, it was concluded that the intercalations containing relatively coarser and intensely-weathered bivalve shells are deposits that were transported from the sand barrier of the lagoon during tsunamis. Radiocarbon dating shows that three intercalations in the sequence of Karine Lagoon were deposited during the tsunamis, from AD 1956, 1650 and 1303.