I. Fountoulis

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.

Surface faulting caused by the Kalamata (Greece) earthquakes (13.9.86)

A great number of neotectonic faults traverse the Messinian gulf and its geological prolongation on the continent towards the north, which forms the Kalamata-Kyparissia tectonic graben. On the 13th September 1986, the whole Messinia area was shaken by an earthquake (M = 6.2); it caused much damage, mainly in the city of Kalamata. Catastrophes were limited to a relatively small area, in the form of a triangle. The striken area is a second-order tectonic graben (called the Dimiova-Perivolakia graben) which is developed on the eastern margin of the greater Kalamata-Kyparissia tectonic graben. Alpine and post-Alpine (Neogene and Quaternary) formations outcrop in the graben. The recent earthquakes caused small fractures (4–5 m long) and small-scale reactivation of neotectonic faults. Both have been observed in almost all formations. The seismic fractures form a zone or zones. They consist of small parallel fractures arranged en echelon, which allows us to conclude that in some places the fracture zones are of right-lateral and in others of left-lateral character. This, in fact, coincides with the kinematics of the main neotectonic fault-zones of the graben. This, in conjunction with other morphotectonic observations, suggests that the deformation of the area is connected with coupling or even torsion phenomena.

Intensity Distribution and Neotectonic Macrostructure Pyrgos Earthquake Data (26 March 1993, Greece)

We present a number of data for the Pyrgos (W.Peloponnessos, Greece), which took place on 26 March1993 and caused considerable damage in the town ofPyrgos and the surrounding area. The local geologicaland neotectonic conditions are also outlined; they aremainly characterized by complex stratigraphicstructure and outcrop pattern, together with a largenumber of large active fault zones and/or isolatedfaults. The detailed damage recording in themeizoseismal area, which was based on the EMS-92,showed significant differentiation of damage from oneurban unit to another, regardless of the foundationformation. The correlation of the existing dataconfirmed the decisive impact of faults and fault zoneon intensity distributions. It was also clear that,the larger a fault zone, the greater was thedifference in intensity across that structure.

Quaternary neotectonic configuration of the southwestern Peloponnese, Greece, based on luminescence ages of marine terraces

This project studies marine terraces in western Messenia, southwestern Peloponnese, Greece, to propose a model of neotectonic configuration and paleogeographic evolution of western Messenia during the Quaternary. GIS analysis of topographic data and geological mapping revealed flanks of raised terraces created on Quaternary marine deposits. Luminescence ages of sediments from the three westernmost marine terraces tend to be consistent OIS-5, OIS-7 and OIS-9, respectively, thus agreeing with the three latest warm stages of the Pleistocene. Moreover, the type and the extent of deformation of the dated marine terraces allowed us to reflect on the neotectonic configuration of western Messenia as well as to conclude that progressive differential uplift over the last 300 ka has induced a dome-like structure to the upper crust of western Messenia.

Detection and Monitoring of Active Faults in Urban Environments: Time Series Interferometry on the Cities of Patras and Pyrgos (Peloponnese, Greece)

Monitoring of active faults in urban areas is of great importance, providing useful information to assess seismic hazards and risks. The present study concerns the monitoring of the potential ground deformation caused by the active tectonism in the cities of Patras and Pyrgos in Western Greece. A PS interferometric analysis technique was applied using a rich data–set of ERS–1 & 2 SLC images. The results of the interferometric analysis were compared with the tectonic maps of the two cities. Patras show clearer uplift–subsidence results due to the more distinct fault pattern and intense deformation compared to the Pyrgos area, where more diffused deformation is observed, with no significant displacements on the surface.

Flash flood event of Potamoula, Greece: Hydrology, geomorphic effects and damage characteristics

The geoenvironmental setting is a determinative factor in catchments’ response during heavy precipitation events. In this work, the flash flood of 2008 in Potamoula (Aetoloakarnania, Greece) is investigated in terms of hydrologic and geomorphologic features. The study area is a relatively small, partly forested, rural catchment situated in western Greece with steep mountainous topography and with flysch being the prevailing lithology. In 2nd of October 2008 a storm of high intensity (measured up to 280 mm in 24 hours) produced noteworthy quantities of runoff which inundated the lower parts of the small valley, inflicting damage to a significant number of structures and killing two people. Field investigations were carried out to record the extent and characteristics of damage, the physical attributes of flooding such as the peak discharge, the geomorphic effects and the geological factors affecting the local hydrology. The results were investigated in comparison with geomorphological and geological evidence showing that this event, although extreme, corresponded very well to the geological record of the area. Finally, runoff response of the catchment was assessed with respect to the geology of the basin.

THE MORPHONEOTECTONIC STRUCTURE OF THE TRANSITIONAL ZONE BETWEEN THE GORTYNIA MT. HORST AND THE PYRGOS-OLYMPIA BASIN (CENTRAL -WESTERN PELOPONNESE, GREECE)

The present paper aims to the understanding of the neotectonic deformation in areas where no post-alpine sediment occurs. The study area is located at the transitional zone between the horst ofGortynia Mt. (Arcadia) and the Pyrgos-Olympia basin in the central-western Péloponnèse and is tectonically and seismically active. The studied neotectonic faults can be distinguished in low to mid angle faults and high angle faults. The majority of them present striation sets with significant horizontal component that causes the change in the direction and plunge of the fold axes of Pindos unit. The younger and with more active characteristics fault zones are the Lefkohori and Ohthia ones.