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Geochemical traces of historical Eastern Mediterranean tsunamis in the sediments of Öüdeniz lagoon, sw Turkey.

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2020,
Yeniçeri, Murat Toygar
Tsunami is flooding of huge wave of sea water over the land that has the potential to cause destruction and devastation on the coastal regions. They are the result of large subaqueous mass movements possibly related to earthquakes, landslides and volcanic eruptions. More than 44 tsunamis having intensities higher than 6 have been recorded historically in the Mediterranean and connected seas. In order to reveal their sedimentological traces, we investigated Ölüdeniz Lagoon, a depositional environment which has the potential to preserve the tsunami records. For this purpose, three piston cores, ca. 3.5 m-long, were collected at three different locations in the lagoon. The cores were analyzed using ITRAX-micro XRF scanner to obtain high-resolution radiographic and optical images, and element constituents of sediments as well. Six pinus branches were picked from the cores for radiocarbon dating. Eight sedimentary events are recognized along the cores based on visual inspection and interpretation of elemental profiles. These sedimentary events show [Ti, Fe, Zn]/Ca anomalies, which imply sudden sediment influx from land into the lagoon, probably from the sand spit of the lagoon. Three of these events clearly correspond to well-known tsunamis in the eastern Mediterranean, which took place in 1609 CE, 1303 CE and 365 CE. The other four depositional events temporally correlate with less-known tsunamis in 746 CE, 148 CE and 142/143 BCE. Although sudden terrigenous sediment influx into the lagoon can be due to environmental events other than tsunamis, e.g. floods (from inland) or storm surges (from sand spit), tsunamis were accepted as “usual suspects” responsible for the sedimentary events ([Ti, Fe, Zn]/Ca anomalies) in Ölüdeniz Lagoon due to two main reasons: 1) They temporally correlate with wellknown historical tsunamis, and 2) Tsunamis, rather than storms, make up the 90% of all extreme wave events in the Mediterranean for the period 1902-2017. An important observation is that all events detected in three cores do not contain any mollusk shells or gravel/pebble size materials. This means that tsunamis that hit Ölüdeniz Lagoon were not strong enough to carry coarse material even for 300-400 m from the sand spit to the middle parts of the lagoon (coring locations). It seems that tsunamis in the eastern Mediterranean Sea are not as catastrophic as the ones in the Indian and Pacific oceans.