A puzzling, slightly submerged, single tidal notch has been reported from the carbonate coasts of the northeastern Adriatic Sea. This paper attempts to explain the origin and the recent evolution of this marine erosion feature and the reasons for its uniqueness in the late Holocene. After reviewing how tidal notches are usually formed, a comparison of recent measurements of bioerosion rates carried out in the area show that when the contribution of dissolution processes can be neglected, bioerosion rates of the deepening of tidal-notch profiles appear to be very low (often <0.1 mm/y) along the coasts of Istria, in contrast to higher rates (between 0.2 and 1.0 mm/y) generally reported in other Mediterranean areas. Such a low rate of bioerosion implies a long period favourable to tidal-notch development. Several glacial isostatic adjustment computations show that relative sea level changes in the area during the last few millennia may correspond to a period of equilibrium between the regional tectonic subsidence and hydro-isostatic emergence during which relative sea level changes were limited, permitting development of the tidal notch observed. The submergence of the notch is consistent with a coseismic subsidence in late Roman time. After this, a new tidal notch could not form at the present sea level because of the limited amount of local bioerosion and the relatively large rate of sea level rise.

Important earthquakes are often accompanied by vertical-land displacements. Therefore in coastal areas they may result in rapid changes of the relative sea level. An essential tool for the study of coastal paleoseismicity is the identification of fossil paleoshorelines, paying special attention to sea-level indicators that are consistent or provide evidence of rapid relative sea-level change.Here, different types of sea-level indicators that are often used in literature in order to determine changes in fossil shorelines are summarized. Information is also provided regarding four case studies of important earthquakes that occurred in Greece (in AD 365, 1953, and 1956) and in Japan (in 1923).

In this paper we attempt to map erosion and deposition zones in the island of Samos (Greece). The relief of Samos is characterized by hilly and mountainous geomorphology mantled by surface sediments and soils. The processes of erosion depends mainly on the frequency and magnitude of precipitation, surface water flow, slope characteristics, rock’s susceptibilitiy to erosion, vegetation and human impacts. The aim of this paper is to study these dynamic processes using easily updated spatial mapping processes in order to design structures to minimize erosion.

In the scope of the France-Greek program PLATON n° 30409XH “EMerChanCy”, this work focuses on the beachrocks of Paros and Naxos Islands, in central Cyclades, Aegean Sea, Greece, in an attempt to study their geochemistry and interpret their palaeoenvironmental significance. Beachrocks are coastal sedimentary formations, consisting of beach sediments that are relatively quickly cemented through the precipitation of CaCO3. However, debate still exists concerning their depositional environment, and therefore, their use as indicators for sea-level changes. For the aim of the present study, representative bulk samples from both islands were analyzed for their mineralogical (XRD) and chemical compositition (SEM). Chemical analyses were performed by XRF . The cement agent and the fine sand/clay fraction of the samples mainly consist of authigenic magnesian calcite, which commonly precipitates in shallow marine environments, especially in high concentration of Ca2+(>4 mol% CaCO3 or 1.2 wt.%). Furthermore, a series of clastic silicate and alumino-silicate minerals are detected. The predominant coarse fragments hosted within cement material are quartz, albite and K-feldspar. The texture of the beachrock samples varies from almost homogeneous sandstone to a mixture of lithologies, such as massive gravel, sandstone and claystone. Most of the grains are flattened and only rarely angular pieces of siliceous rocks occur, hosted in the fine-grained Mg-calcite cement. This grain size and shape is indicative of the genetic environment of beachrocks, implying the maturity level of cementation from early stage to modern situation. The beachrock samples derived from various depositional periods and depths, from the front and end slabs. The beachrocks were also correlated with stratigraphical material from boreholes and archaeological remains from the study area in an attempt to understand the coastal changes during the late Holocene in Central Cyclades.

Tidal notches are a well-known sea-level indicator, marking clearly former shorelines, which have often been used to deduce Quaternary tectonic trends and sea-level changes, mainly in uplifting areas. If raised notches have often been used to estimate past changes in sea level and tectonic movements, submerged notches, which are more difficult to observe, have been studied mainly occasionally by a few authors. Nevertheless, Holocene tectonics may include more than a single episode and it may be useful to extend underwater observations below the first submerged notch. In this context, this work focuses in the Aegean region, an area characterized by extensional tectonics, where subsidence prevails, related to the subduction of the Mediterranean floor below the Hellenic arc, where Quaternary uplift trends tend to prevail. In some islands of Cyclades and Sporades, there is evidence of the occurrence of repeated rapid subsidences during the Late Holocene. In this paper, the shape of tidal notches that may well be preserved underwater is recalled in order to reconstruct sequences of coseismic subsidences and other relative sea-level changes that occurred during at least the last few millennia. A re-analysis of already published measurements of submerged tidal notches in several islands reveals that subsidence trends in many areas of the Aegean are not continuous and gradual, but the result of repeated coseismic vertical subsidences of some decimetres at each time. The estimated average return times are of the order of approximately some centuries to one millennium. Although the results cannot be used for short-term predictions of earthquakes, they may provide useful indications about the long-term tectonic trends that are active in the Aegean region.

Different types of sea level indicators, (e.g. geomorphological, biological and archaeological) have been used in the Eastern Mediterranean in order to assess Late Quaternary coastal evolution and relative sea level (RSL) changes. Among them, beachrocks have often been used to assess Holocene shoreline evolution and tectonically induced RSL changes in the Aegean sea. Open debate about the cementation environment and the accuracy of beachrocks as sea level indicators is still present in literature: However, in several recent studies beachrocks have been proven useful in the absence of other sea level indicators or when coupled with other available sea level indicators. In particular, the combined analysis of erosional (e.g. tidal notches) and depositional sea level indicators has great significance given the fact that erosional indicators, although more precise for RSL studies, rarely preserve dateable materials, which are more frequent in depositional landforms. In this context, we carried out a detailed mapping of beachrocks in Paros and Naxos islands (Cyclades, Central Aegean Sea). In most sites, multiple generations of beachrocks were identified, at depths varying between the present mean sea level and -6.3 m. Beachrock slabs were also sampled and thin sections were carried out for petrographic and microstratigraphic analyses, aiming to characterize the constituents, the presence of bioclasts as well as the type of the cements. In order to provide an age estimate for sea level changes in the study area during the late Holocene, beachrock samples were dated using the Optically Stimulated Luminescence (OSL) method. The study focused on both quartz and feldspar. The first OSL age estimates are presented in this study. In the last 15 years, a number of geomorphological and geoarchaeological investigations were carried out to assess the relative sea level changes in this area. Therefore, we correlated beachrocks with previously published data such as submerged tidal notches, cores on coastal lagoons and submerged archaeological remains. Here we present the results of this multiproxy study. Our results allowed both to identify the Holocene palaeoshorelines and to place a chronological framework to the sea level changes in the broad area of central Cyclades.

Remains of past sea levels, such as tidal notches, benches, beachrocks, etc. may provide valuable information for the investigation of relative sea level changes of eustatic and/or tectonic origin. Tidal notches are usually formed in limestone cliffs in the mid-littoral zone, are well known as precise sea-level indicators and they can attest to the modality of sea level change (rapid or slow) allowing to identify palaeoseismic events. In this framework, this work focuses on the eastern coasts of the Attica Peninsula (eastern Greece) in order to trace the palaeoshorelines of the Upper Holocene through the use of tidal notches and discuss their implication for the interpretation of the recent tectonic history in the area. A submarine geomorphological investigation took place in the coasts of eastern Attica, aiming to identify palaeoshorelines. Former sea-level positions were deduced from emerged and submerged tidal notches. An attempt was made to date past sea level positions, based on 14C datings from sedimentological data of drillings in nearby locations for the submerged tidal notches while one uplifted shoreline was dated with 14C based on a shell collected at a nearby location. Eight fossil shorelines were deduced in the study area; two emerged ones at about +24±6 and +40±6 cm, and six submerged ones at about -22±6 (modern), -40±6, -60±6, -80±6, -130±6 and -460±6 cm. It is worth mentioning that a rather different tectonic behavior may be distinguished between the south (AT1-AT5) and the north (AT10-AT28) part of the study area.

Because changes in sea level may have a great impact on the distribution of mineral resources, the exploration and exploiting of these resources should not ignore the changes in sea level that may have occurred in the past in the area considered. The study of relative sea-level changes is an essential element of ocean observation and technological advances are often necessary to improve this study that includes the determination of levels (elevation or depth), chronological estimations, and the identification of appropriate sea-level indicators.Indicators of fossil or present-day sea-level positions are the most important elements for a sea-level reconstruction, because they provide information not only on the former level but also on the accuracy of the reconstruction.A classification is proposed of the main criteria that can be used to deduce appropriate sea-level indicators from geomorphological, stratigraphical, biological or archeological coastal data. Two cases studies are used as examples of sea-level reconstructions that may be useful to clarify the geology in certain areas, or to coastal engineering and coastal protection: (1) on the impact of the recent sea-level rise in the interpretation of sea-level indicators; and (2) on the foreseeable impacts of the predicted near-future sea-level rise on the coasts of NE Italy.