Late-Holocene shoreline changes related to palaeoseismic events in the Ionian Islands, Greece (original) (raw)
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Late-Holocene shoreline changes related to palaeoseismic events in the Ionian Islands
A systematic multidisciplinary survey on the coasts of the Ionian Islands, founded on 26 new radiocarbon accelerator mass spectrography (AMS) dates, has revealed the occurrence of sectors which were uplifted (seismo)tectonically during the late Holocene. In Corfu, two uplift movements of about 0.8m each took place in the central part of the island: one of them around 790-400 cal. BC, and also at a more recent, undetermined date. In Levkas, up-and-down tectonic movements of metric order governed late-Holocene relative sea-level changes, at least in the northern part of the island; submergence of at least 2.5 m occurred since 2400 years ago, with a possible spasmodic subsidence around cal. AD 500-700. In Cephalonia, two vertical displacements affected most of the island, around cal. AD 350-710 and in AD 1953; both movements resulted in uplift in the southeastern part of the island. Submergence seems to predominate round Ithaca. Lastly, in Zante, clear evidence of a Holocene crustal block movement is limited to the southeastern peninsula, where an uplift of 0.95 ± 0.15 m took place, probably coseismically, around the period cal. AD 200-500. The time ranges of uplift in Cephalonia and Zante, and of possible subsidence in Levkas, correspond with a period of regional tectonic paroxysm, between the middle of the fourth century AD and the middle of the sixth century AD; this has already been documented in several areas of the eastern Mediterranean, notably in the Gulf of Corinth, the southern Hellenic arc, Turkey, Cyprus, the Lebanon and Syria.
Episodic uplift deduced from Holocene shorelines in the Perachora Peninsula, Corinth area, Greece
Tectonophysics, 1994
Four raised shorelines, between + 1.1 m and +3.5 m, have been identified at two localities on the Perachora Peninsula and were dated by AMS 14C to between 6400 and 1500 calibrated years ago. Uplift movements seem to have occurred in increments of 0.8 k 0.3 m, with a return period of about 1600 years. The last uplift coincided with a regional tectonic paroxysm, which has already been documented in several areas of the eastern Mediterranean. The average uplift rate was probably faster during the Holocene than the average since the Last Interglacial period. No important vertical displacement occurred in this area at the time of (or after) the 1981 earthquake, but a new episode of coseismic uplift may be in preparation.
International Journal of Earth Sciences, 2014
An underwater geomorphological survey along the coasts of six Cycladic islands (Sifnos, Antiparos, Paros, Naxos, Iraklia and Keros) revealed widespread evidence of seven submerged tidal notches. At least seven former shorelines were identified at depths between 280 ± 20 and 30 ± 5 cm below modern sea level. The vertical succession of several submerged notches suggests the occurrence of rapid subsidence events, potentially of seismic origin. Comparison with other sea-level indicators from Naxos and Delos islands indicates that these relative sea-level changes took place after 3300 BP and provides a rough estimate of the time of development of several submerged shorelines. The submergence of the uppermost notch at -30 ± 5 cm is ascribed to effects of the recent global sea-level rise occurred during the last two centuries and, at least in part, to effects of recent earthquakes. Potential effects of the 1956 Amorgos earthquake with regard to coseismic and post-seismic vertical displacement have been recently investigated using a modellistic approach. According to the above, the lower shorelines should result from repetitive subsidence events and not from gradual subsidence.
Historical coseismic uplift on Euboea Island, Greece
Earth and Planetary Science Letters, 1992
In the Aegean region it is usually accepted that uplift is confined to the southern areas, near the outer island arc, whereas subsidence prevails in the inner basin areas. However, we give evidence of elevated notches and Lithophaga shells, dated by AMS 14C, showing that Holocene coseismic uplift of the order of about a metre occurred in inner Aegean areas too and affected parts of the coasts of north and central Euboea Island between 510 and 380 B.C. and also possibly between 1050 and 900 B.C.
Submerged notches on the coast of Skyros Island (Greece) as evidence for Holocene subsidence
Geomorphology, 2012
Detailed mapping along the coasts of Skyros Island (Aegean Sea) provided new evidence concerning the rates and the modality of subsidence in the area. The results are provided through the study of the shape and the dimensions of the two submerged notches detected around the carbonate coasts of the island. It is apparent that the island has been submerged not only due to the global sea-level rise during the last two centuries (1.8± 0.3 mm/year between 1950 and 2000), but also because of tectonic events testified by the type of the submerged notches. Some of these tectonic events seem to be of gradual and some of co-seismic origin. The transition of MSL from the retreat point of the lower notch to the retreat point of the upper notch seems to have been produced by co-seismic subsidence of about 55 cm at slightly less than 850 years BP. (N. Evelpidou), vassilopoulos@geoenvi.org (A. Vassilopoulos), pirazzol@cnrs-bellevue.fr (P.A. Pirazzoli). 0169-555X/$see front matter
Quaternary Science Reviews, 2007
This study presents relative sea level (RSL) curves for seven coastal areas in Akarnania and the northwestern Peloponnese (NW Greece) since the mid-Holocene. RSL fluctuations are deduced from 48 14 C-AMS dated sedimentological sea level markers from 27 vibracores drilled in near-coast geological archives as well as from six geoarchaeological sea level indicators of known ages. Seven palaeo sea level curves including uncertainty bands are reconstructed for a coastal zone spanning a distance of 150 km. Considerable intraregional differences in sea level evolution exist. These differences are mainly due to tectonic reasons. In general, RSL in northwestern Greece has never been higher than today. Rates of local sea level rise were highest until 5500-5000 cal BC (up to 12.3 m/ka) and lowest during 4000-500 cal BC (0.2-1.4 m/ka). During the past 2500 or so years, RSL has accelerated anew (0.7-2.7 m/ka). Calculating differences between local mean sea level curves provides quantitative information on intra-regional differences of tectonic activity. The coastal plains of Palairos and Elis show signs of uplift, whereas the Mytikas and Boukka plains are strongly subsiding. Compared to other areas of the eastern Mediterranean, northwestern Greece has been subject to significant net long-term subsidence. Regional tectonic events (RTEs) were detected for the time around 4000, 2500, 500 and 250 cal BC as well as around 250 and 1250 cal AD. RTEs are characterized by changes of uplift/subsidence rates or by the redirection of local tectonic movements. The question if some of the RTEs were of a supra-regional nature is still open. From a geodynamic point of view, the results presented show that Akarnania's southwestern fringe is being downwarped while the tectonic block as a whole is moving towards the southwest. Strongest subsidence rates are observed for central Akarnania. At Akarnania's fringes, subsidence is reduced by the influence of strong uplift of adjacent areas such as around Preveza and the northern Peloponnese.
2007
The westernmost part of the Gulf of Corinth (Greece) is an area of very fast extension (~15 mm/yr according to geodetic measurements) and active normal faulting, accompanied by intense coastal uplift and high seismicity. This study presents geomorphic and biological evidence of Holocene coastal uplift at the western extremity of the Gulf, where such evidence was previously unknown. Narrow shore platforms (benches) and rare notches occur mainly on Holocene littoral conglomerates of uplifting small fan deltas. They are perhaps the only primary paleoseismic evidence likely to provide information on earthquake recurrence at coastal faults in the specific part of the Rift system, whereas dated marine fauna can provide constraints on average Holocene coastal uplift rate. Using geomorphic and biological indicators of coastal uplift for the evaluation of paleoseismicity and Holocene uplift rate at the footwall of a normal fault (western Corinth Gulf, Greece) N. Palyvos (1)(*), F. Lemeille (2), D. Sorel (3), D. Pantosti (1), K. Pavlopoulos (4)
Geologica Acta, 2016
Fossil shorelines produced by recent co-seismic movements were identified throughasubmarine survey along the coasts of Ithaca and Fiscardo (Greece).In both areas a tidal notch-slightly submerged below present Mean Sea Level (MSL) was observed at various sites. This “modern” notch is known to have been submerged by the global sea-level rise during the 19th and 20th centuries. The depth after tide and air-pressure correction of the vertex of the “modern” notch (that owes its submergence to the current rapid sea level rise) was measured between -20 and -30±5cm at Fiscardo and between -36 and -45±6cm at Ithaca. This “modern” notch at the same depth on east and west sides of the Ionian Thrust suggests that both areas were not affected by the co-seismic vertical movements that occurred in 1953 (in the wider area). On the other hand, a greater depth in Ithaca could be an effect of co-seismic subsidence. Over the long term, the tectonic behavior of Ithaca differs from Fiscardo. At Ithaca no...