Hanna Hadler

Beachrock-type calcarenitic tsunamites along the shores of the eastern Ionian Sea (western Greece) – case studies from Akarnania, the Ionian Islands and the western Peloponnese

Th is paper presents geo-scientifi c evidence of beachrock-type calcarenitic tsunamites from three study areas in western Greece, namely from the Bays of Aghios Nikolaos (Akarnania), Langadakia (Cefalonia Island) and Aghios Andreas (Peloponnese). Geomorphological, sedimentological, micromorphological and geochemical studies were conducted to clarify depositional processes and the post-sedimentary evolution. Calcarenitic and locally conglomeratic carbonate crusts were studied in natural outcrops along the seafront and in vibracores. High-resolution topographic surveys and 3D-visualisation were carried out by diff erential GPS and LIDAR measurements. Tsunami impact was dated by a combined approach of radiocarbon, OSL and archaeological age determination and compared to local tsunami and earthquake chronologies. We found sedimentary structures such as basal unconformities, rip-up and intra-clasts, evidence of fi ning upward, thinning landward and upward increase in sorting as well as bi-to multimodal deposits and injection structures all of which are described as features typical of recent or historic tsunami deposits. Typically non-littoral sedimentary features such as load casts and convolute bedding further indicate gravity driven processes in water-saturated sheets of allochthonous deposits and are well known from, for example, turbidites. Moreover, thin section analyses revealed highenergy shockand impact-borne cracking and shearing eff ects. Our results show that cementation of tsunami deposits may occur by post-depositional pedogenetic decalcifi cation of higher sections and subsequent secondary carbonate precipitation in lower sections of tsunami deposits provided that they were deposited above sea level. Th e calcarenitic tsunamites encountered in the three study areas match the defi nition of beachrock sensu stricto. Th is is thus the fi rst paper giving examples of beachrock sequences that are interpreted as partially cemented tsunami deposits. Consequently, beachrock is recommended not to be used as sea level indicator in future studies unless a tsunamigenic formation can be defi nitely excluded. Dating results brought to light young, mostly Holocene ages of tsunami sediments. In the Bay of Aghios Andreas, western Peloponnese, we found spectacular traces that Olympia’s ancient harbour site Pheia was destroyed by tsunami impact in the 6th cent. AD and covered by a rapidly cemented, up to 3 m-thick beachrock-type tsunami deposit.

Tracing the Alkinoos Harbor of ancient Kerkyra, Greece, and reconstructing its paleotsunami history

1Institute ofGeography, Johannes Gutenberg-UniversitätMainz,Mainz, Germany 2Aix-Marseille Université, CNRS, CCJUMR 7299, Aix-en-Provence, France 3Ephorate of Antiquities of Corfu, Kerkyra, Greece Correspondence ClaudiaFinkler, Institute forGeography, JohannesGutenberg-UniversitätMainz, Johann-Joachim-Becher-Weg21, 55099Mainz, Germany. Email: c.finkler@geo.uni-mainz.de Scientific editingbyMartaPappalardo Abstract In this study, theAlkinoosHarborof ancientCorfuwas investigatedbymeansof geomorphological and sedimentologicalmethods in order to reconstruct the ancient harbor’s construction, its period of use and spatial extent, and local paleoenvironmental changes.Wepresent sedimentological evidence for the Alkinoos Harbor that shows distinct signs of dredging activities. Although the harbor must have been in use from the Archaic period onwards, a set of paleoenvironmental proxies based on vibracoring, geophysical prospection, electrical conductivity logging, microfaunal studies, and geochemical analyses revealed typical sediments of a closed, protected Roman harbor that was in use between the 1st and 6th century A.D. In addition, sedimentological and microfaunal evidence allowed us to differentiate between different parts of the Roman harbor. In contrast, the pre-Roman harbor and its shipsheds were built on a sandy seashore. Our data revealed two distinct stratigraphic disruptions related to tsunamigenic impact. These paleotsunamis were dated between the 3rd and 6th century A.D. and between the 5th and 6th century A.D., most probably correlating with the A.D. 365 (Crete) and 6th century A.D. (Peloponnese) supraregional events, respectively. The Alkinoos Harbor turned out to be an outstanding geoarchive to reconstruct human-environment interactions during the late Holocene.