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Testing the Olympia Tsunami Hypothesis (OTH) – new results from tsunami modeling and palaeotsunami studies in the lower Alpheios River valley (Peloponnese, Greece)

Andreas Vött1, Peter Fischer1, Hanna Hadler1, Mathias Handl1, Peter Henning1, Franziska Lang2, Konstantin Ntageretzis2, Björn Röbke2, Timo Willershäuser2
1 Geographisches Institut, Johannes Gutenberg-Universität Mainz
2 Department of Classical Archaeology, Technische Universität Darmstadt

Key Note 6.1 in Quartäre Landschaftsentwicklung - ein Schlüssel zum Verständnis aktueller Georisiken

19.09.2012, 14:00-14:30, H8

The cult site of Olympia is situated where the Kladeos River, coming from the upper Lalas mountains, flows into the Alpheios River some 21 km inland from the Gulf of Kyparissia near the town of Pyrgos (western Peloponnese, Greece). It was the place of the Panhellenic Olympic games between the 8th century BC and the late 4th century AD when they were finally forbidden by the Romans. Since the end of the 19th century AD, Olympia has been excavated under the auspices of the German Archaeological Institute (Deutsches Archäologisches Institut, DAI) which, in 2009, initiated the interdisciplinary research project “Olympia und seine Umwelt” aiming to reconstruct local landscape changes as a palaeogeographical and palaeoenvironmental base for archaeological and historical issues.

Our studies, embedded in this project, were realized to find out the reasons for the rapid burial of the cult site by 4-6 m of sandy and silty sediments in the form of the so called “Olympia terrace” and the subsequent incision of the Kladeos River by 8-10 m since early medieval times, i.e. within some 1500 years only. Geomorphological studies revealed strong discrepancies between the present hydraulic potential of the Kladeos River and the dimension and structure of the Olympia terrace. For decades, the Olympia or Kladeos valley infill and erosion history has been one of the most intriguing geomorphological questions to be solved in the Mediterranean.

Since 2010, we have drilled 37 vibracores both in the lower and middle Kladeos River and in the lower Alpheios valleys. Core stratigraphies were analysed in detail by geomorphological, sedimentological and geochemical parameters. Stratigraphical correlations between vibracores and spatial variabilities of subsurface conditions were investigated along more than 140 earth resistivity transects. Selected sediment samples were analysed for their microfaunal content. A local geochronology was established based on diagnostic ceramic fragments and radiocarbon ages.

Our data show five phases of catastrophic, rapid flooding of the Kladeos River valley since the mid-Holocene. High-energy flood sediments can be clearly discriminated from more or less gradually deposited fluvial sediments of the Kladeos River. Potential climatic, tectonic and seismological reasons for the catastrophic flood events are discussed. However, sedimentary, geochemical and faunal traces found along the coast of the Gulf of Kyparissia, in the lower Alpheios River valley and in the adjacent Basin of Flokas-Pelopio show that the region has been repeatedly affected by tsunami impact. As stratigraphical fingerprints and correlations along the Kladeos River beyond the Ridge of Flokas-Platanos, that means in and around the site of Olympia, were found to be identical with palaeotsunami signatures found further towards the coast, we set up the Olympia Tsunami Hypothesis (OTH, Vött et al. 2011a). This hypothesis says that the shallow saddles of the Ridge of Flokas-Platanos were repeatedly overflowed by tsunami waters causing the cult site Olympia being flooded and finally destroyed by tsunami and not by river water. Moreover, we found out that, during historical times, freshwater lakes existed in the middle part of the Kladeos valley.

Geoarchives along the coasts of the Gulf of Kyparissia have revealed high values of maximum palaeotsunami runup, namely up to 18 m above present mean sea level (= m a.s.l.) at Pheia, an ancient harbour of Olympia, up to 25 m a.s.l. near Epitalio and up to 10 m a.s.l. near Kato Samiko (Vött et al. 2011b). Together with tsunami landfall modeling results obtained for the gulf itself (Röbke et al. 2012), these results strengthen the idea of strong inundation of the lower Alpheios River valley far inland during mega-tsunami events and thus fit well with the overall OTH.

Finally, implications of the OTH for modern geomorphological research in the coastal Mediterranean are discussed.

 

References

Röbke, B.R., Schüttrumpf, H., Wöffler, T., Hadler, H., Willershäuser, T., Vött, A. (2012): Tsunamis in the Gulf of Kyparissia (western Peloponnese, Greece) - risk assessment based on numeric simulation and field evidence. – 5th International Short Conference on Applied Coastal Research, RWTH Aachen (in press).

Vött, A., Fischer, P., Hadler, H., Handl, M., Lang, F., Ntageretzis, K., Willershäuser, T. (2011a): Sedimentary burial of ancient Olympia (Peloponnese, Greece) by high-energy flood deposits – the Olympia Tsunami Hypothesis. – In: Grützner, C., Pérez-Lopez, R., Fernández Steeger, T., Papanikolaou, I., Reicherter, K., Silva, P.G., Vött, A. (eds.): Earthquake Geology and Archaeology: Science, Society and Critical facilities. Proceedings of the 2nd INQUA-IGCP 567 International Workshop on Active Tectonics, Earthquake Geology, Archaeology and Engineering, 19-24 September 2011, Corinth (Greece), pp. 259-262. ISBN: 978-960-466-093-3.

Vött, A., Bareth, G., Brückner, H., Lang, F., Sakellariou, D., Hadler, H., Ntageretzis, K., Willershäuser, T. (2011b): Olympia’s harbour site Pheia (Elis, western Peloponnese, Greece) destroyed by tsunami impact. – Die Erde 142/3: 259-288.



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Letzte Änderung 13.07.2012