Journal of Coastal Research 853-863 West Palm Beach, Florida Summer 2000 Geomorphological Observations in the Coastal Zone of Kyllini Peninsula, NW Peloponnesus-Greece, and their Relation to the Seismotectonic Regime of the Area Hampik Maroukian'[, Kalliopi Gaki-Papanastassiou'[, Dimitris Papanastassiouj and Nikolaos Palyvos] tDepartment of Geography­ :j:lnstitute of Geodynamics Climatology National Observatory of University of Athens Athens GR-15784 Athens, Greece GR-11810 Athens, Greece ABSTRACT . MAROUKIAN, H.; GAKI-PAPANASTASSIOU, K.; PAPANASTASSIOU, D., and PALYVOS, N., 2000. Geomorpholog­ .tflllllllt. ical observations in the coastal zone of Kyllini Peninsula, NW Peloponnesus-Greece, and their relation to the seis­ ~ motectonic regime of the area. Journal of Coastal Research, 16(3), 853-863. West Palm Beach (Florida), ISSN 0749­ ~. 0208. ---- ~ ~ --~a-.__+; 1&--- The Kyllini Peninsula comprises an isolated hilly region and occupies the western part of the alluvial plain ofPeneios River. It owes its morphology to a Triassic salt dome intrusion active since Miocene times. During the Quaternary it was covered by the sea, became an island and was finally joined to Peloponnesus with the alluvial deposits ofPeneios River. In this study an attempt is made to correlate the coastal landforms with the seismotectonic regime of the broader area of Kyllini Peninsula. Raised Tyrrhenian shorelines occur at elevations ranging from sea-level up to 60 m. Holocene uplifted shorelines, wave cut benches, abrasion platforms and notches have been observed, at heights between 0.3 to 3 m. Furthermore, the coastal zone is characterized by beachrock and a series of dunes of two different generations as well as raised aeolianite. Geophysical investigations of the deep geological structure of the region have also revealed the offshore presence of salt diapirism as well as large faults in the area of Zakynthos Straits. The seismicity of the area is known to be high, with the epicenters of many earthquakes located mainly along the Zakynthos Straits. Examples of such activity are the five shallow earthquakes with magnitudes greater than 5.5 on the Richter scale, that have been recorded in this century. Based on the study of the coastal landforms, radiocarbon dating and the seismotectonic regime of the area, it is concluded that the uplift is primarily the result of neotectonism and secondarily, diapirism. INTRODUCTION of pre-Classical archaeological sites in the Holocene Peneios floodplain suggests that Kyllini Peninsula could have been The peninsula of Kyllini comprises an isolated hilly region an island at those times. Subsequent progradation of the Pe­ of about 130 km 2 and is located at the westernmost end of neios delta joined Chelonatas to the Eleian seaboard. RAPHA­ Peloponnesus (Figure 1). It is formed by a morphological rise EL (1973) estimates rates of coastal accretion as high as 1.85 (244 m at Kastron, the highest point) connected to mainland m1yr during the Roman occupation. From the writings of Peloponnesus in the east by the floodplain of Peneios River Strabo, it is known that the Peneios River emptied into the (plain of Elis), North of Kyllini extends the gulf of Kyllini, gulf of Kyllini in antiquity, whereas today it debouches to the south of it the Chelonitis gulf and in the west the straits of south-east of Chelonatas. The shift probably took place in the Zakynthos. late 18th century. The Kyllini promontory was called 'Chelonatas' in ancient The ancient harbor of Kyllini prospered in classical times times, probably due to its form, resembling the back of a tur­ as the seaport of nearby Elis, the city-state responsible for tle ('Chelona' = turtle). The broader area of the plain of Elis the organization of the festivities in honor of the Olympian has been inhabited since prehistoric times and the earliest Zeus, part of which were the well-known Olympic games. The signs of human occupation are placed in the palaeolithic pe­ exact location of ancient Kyllini is unknown, since finds re­ riod (Mousterian finds at Kastron, CHAVAILLON et al., 1967, lated to the city are scarce. 1969). According to RAPHAEL (1973), the conspicuous absence Based on relative and absolute dates of the coastal features an attempt is made to correlate the coastal landforms of the 98019 received 19 February 1998; accepted in revision 17 December Kyllini Peninsula with the seismotectonic regime of Western 1998; final figures accepted 12 December 1999. Peloponnesus in order to draw conclusions on whether the 854 Maroukian et at. ~,..- ~''-- ; "'0_ ~"'~:: ~ , ..-':t-,;, \ ....~\" ( • " ",... , ,,' LECHAINA , ' ...'", . \ CI) , ...,--, .. -""" o I: " " \, I I t ... - ... :t ~I ~ h.. 1/ ~ ~.,- e I //A/.s~ )... II 1/,-' i!'~~~ G ~ I I I ', • Cape ;1/ I ANDRAVIDA ~-'S ~ ;V Melissa"~ "J .". • --, Traga~n ~ , , ' II " ( l-'\.-/1~ o ' <,,.. () I \, ," CI) h.. ~ i? £t \ Contour Interval: 20 m h.. \ .::, CI) I ( \ \ \ \ N "'. -- -20- 'CHELONITIS GULF o 1CXX> 2CXX> m A ·'$0,.---......... Figure 1. Topographic map of the Kyllini Peninsula based on 1:50.000 H.A.G.S. maps (Vartholomion sheet). Inset shows the location of the study area in Greece as well as the Hellenic trench. observed uplift movements are attributed to neotectonism or from sea-level to 60 m, a formation of Tyrrhenian calcareous local diapiric phenomena. sandstones overlies unconformally the Plio-Pleistocene se­ ries. KOWALCZYK and WINTER (1979) divided these Tyrrhe­ GEOLOGY nian terraces into two formations, Eu-Tyrrhenian and Neo­ Tyrrhenian. According to them the Neo-Tyrrhenian terrace In the peninsula of Kyllini post-alpine formations prevail, (Wurm 1111 interstadial age) has formed at elevations of 3-4 with only a few outcrops of the alpine basement present (Fig­ m in the coastal zone between Cape Glossa and Loutra and ure 2). The alpine rocks belong to the Ionian geotectonic unit has a thickness of a few meters, while the Eu-Tyrrhenian and they include the white thin-bedded Cretaceous-Eocene terrace which is of Wurm-Riss interglacial age, reaches in­ limestones of Trypito, Kastron and Oros, as well as the dia­ land to its highest elevations in the northern part of Kyllini piric intrusions of Triassic evaporites which crop out at the Peninsula. MARIOLAKOS et at. (1991) report the same for­ western part of the peninsula (CHRISTODOULOU, 1969). The mation at an elevation of about 150 m (near Kastron), but diapirism has been active since Miocene times. this determination was not verified in the present study. Above the alpine formations are found the Lower Pliocene The recent formations consist of alluvial deposits occupying conglomerates and a Plio-Pleistocene series of sands, sand­ the lowlands made up of colluvium, talus, fluvio-torrential stones, clays and marls that is at least 400 m thick. This sediments, coastal dunes and beach material. series, which is dominant in the peninsula, is characterized by an alternating shallow marine, brackish and lacustrine TECTONICS facies. The area of western Peloponnesus is characterized by a Peripheral to the Chelonatas hills, at elevations ranging compressional regime undergoing the consequences of the Journal of Coastal Research, Vol. 16, No.3, 2000 Seismotectonic Regime- Peloponnesus-Greece 855 / / p /// //'<, Kafkalida lsi. \ , \ --i Cape Trypito (, t...... I '. I \ \ "\1" "I \I I \ I . ~ Neochotion I I \ \ \ N 2km Recent dunes mil Tyrrhenian deposits Cretaceous - Eocene limestones Holocene alluvial deposits D Plio-Pleistocene formations • Triassic evaporites Late Pleistocene talus --$-. Axis of anticline " Normal fault Figure 2. Geologic map of the Kyllini area (after CHRISTODOULOU, 1969; KOWALCZYK and WINTER, 1979, and field observations). subduction of the African plate beneath the Eurasian plate. In the Kyllini Peninsula, active salt diapirism since the The subduction is taking place along the Hellenic Trench lo­ Miocene is another tectonic factor. The pressure of the over­ cated offshore. The compressional regime is well documented lying sediments and the lateral eastward compression have by the reports of different researchers (SOREL, 1976; Mc­ triggered off diapiric phenomena in the basement evaporites KENZIE, 1978; ANGELIER et al., 1982; HATZFELD et al., 1990). (UNDERHILL, 1988). The evaporite intrusions are located On the contrary, the strait between the peninsula of Kyllini along a NNW-SSE axis, uplifting the Plio-Pleistocene sedi­ and the island ofZakynthos, is a linear submarine valley system mentary cover into an asymmetric anticline with the same of tectonic origin which runs parallel to the seaboard of Pelo­ trend and dipping NNW. Associated with diapirism, many ponnesus (Figure 3). This graben has been clearly mapped from normal faults and joints striking mainly N-S and E-W dissect geophysical investigations and it is bounded by two major nor­ the Plio-Pleistocene formations. Related to diapirism-induced mal faults (BROOKS and FERENTINOS, 1984). The valley floor is faulting, is the presence of hot springs in the south-western flat and it is about 7.5 km wide. The side walls are very steep, part of Kyllini (Loutra), with an average height of 300 m. The average slope is 1:5, but It is therefore evident that the area of Kyllini Peninsula in some places it is as steep as 1:2.5 (FERENTINOS et al; 1985). is mainly affected by the faults located in the Zakynthos The graben is considered to have been formed during the middle straits and the local ones formed during the process of dia­ Pleistocene (KoWALczyJ( and WINTER, 1979). pirism. Journal of Coastal