ALBERT

Description: We report detailed morphometric observations on several MIS 5.5 and a few older (MIS 11, 21, 25) fossil tidal notches shaped along carbonate coasts at 80 sites in the central Mediterranean Sea and at an additional six sites in the eastern and western Mediterranean. At each site, we performed precise measurements of the fossil tidal notch (FTN) width and depth, and of the elevation of its base relative to the base of the present tidal notch (PTN). The age of the fossil notches is obtained by correlation with biologic material associated with the notches at or very close to the site. This material was previously dated either through radiometric analysis or by its fossiliferous content. The width (i.e. the difference in elevation between base and top) of the notches ranges from 1.20 to 0.38 m, with a mean of 0.74 m. Although the FTN is always a few centimetres wider than the PTN, probably because of the lack of the biological reef coupled with a small erosional enlargement in the FTN, the broadly comparable width suggests that tide amplitude has not changed since MIS 5.5 times. This result can be extended to the MIS 11 features because of a comparable notch width, but not to the MIS 21 and 25 epochs. Although observational control of these older notches is limited, we regard this result as suggesting that changes in tide amplitude broadly occurred at the Early-Middle Pleistocene transition. The investigated MIS 5.5 notches are located in tectonically stable coasts, compared to other sectors of the central Mediterranean Sea where they are uplifted or subsided to ~100m and over. In these stable areas, the elevation of the base of the MIS 5.5 notch ranges from 2.09 to 12.48 m, with a mean of 5.7 m. Such variability, although limited, indicates that small land movements, deriving from slow crustal processes, may have occurred in stable areas. We defined a number of sectors characterized by different geologic histories, where a careful evaluation of local vertical land motion allowed the selection of the best representative elevation of the MIS 5.5 peak highstand for each sector. This elevation has been compared against glacial isostatic adjustment (GIA) predictions drawn from a suite of ice-sheet models (ICE-G5, ICE-G6 and ANICE-SELEN) that are used in combination with the same solid Earth model and mantle viscosity parameters. Results indicate that the GIA signal is not the main cause of the observed highstand variability and that other mechanisms are needed. The GIA simulations show that, even within the Mediterranean Basin, the maximum highstand is reached at different times according to the geographical location. Our work shows that, besides GIA, even in areas considered tectonically stable, additional vertical tectonic movements may occur with a magnitude that is significantly larger than the GIA.

Description: Published

Description: 600-623

Description: 5A. Ricerche polari e paleoclima

Description: JCR Journal

Description: Recent works (Evelpidou et al., 2012) suggest that the modern tidal notch is disappearing worldwide due sea level rise over the last century. In order to assess this hypothesis, we measured modern tidal notches in several of sites along the Mediterranean coasts. We report observations on tidal notches cut along carbonate coasts from 73 sites from Italy, France, Croatia, Montenegro, Greece, Malta and Spain, plus additional observations carried outside the Mediterranean. At each site, we measured notch width and depth, and we described the characteristics of the biological rim at the base of the notch. We correlated these parameters with wave energy, tide gauge datasets and rock lithology. Our results suggest that, considering ‘the development of tidal notches the consequence of midlittoral bioerosion’ (as done in Evelpidou et al., 2012) is a simplification that can lead to misleading results, such as stating that notches are disappearing. Important roles in notch formation can be also played by wave action, rate of karst dissolution, salt weathering and wetting and drying cycles. Of course notch formation can be augmented and favoured also by bioerosion which can, in particular cases, be the main process of notch formation and development. Our dataset shows that notches are carved by an ensemble rather than by a single process, both today and in the past, and that it is difficult, if not impossible, to disentangle them and establish which one is prevailing. We therefore show that tidal notches are still forming, challenging the hypothesis that sea level rise has drowned them.

Description: Published

Description: 66-84

Description: 6A. Monitoraggio ambientale, sicurezza e territorio

Description: JCR Journal

Description: restricted

Description: The coasts of Italy still preserve several remnants of coastal quarries built in antiquity, that now provide insights into the intervening sea-level changes occurred during the last millennia. In this paper, we show and discuss a new class of sea level indicator consisting of millstones carved along the rocky coast of southern Italy since 2500 BP, that are currently submerged. They were extracted from beachrocks, sandstones or similar sedimentary rocks, easier for carving by ancient carving tools. Our study focuses on 10 coastal sites located at Capo d’Orlando, Avola, and Letojanni, in Sicily; Soverato, Tropea, and Capo dell’Armi, in Calabria; Castellabate, Palinuro, and Scario, in Campania; and Polignano San Vito, in Apulia. Unfortunately, only limited archaeological information is available for these anthropic structures. Scario, one of these millstone quarries discussed here, has been dated through independent archaeological remains, allowing us to restrict the exploitation age to the end of XVII century. Present day elevations of these coastal sites were obtained through geo-archaeological surveys calibrated using the nearest tidal stations, together with geomorphological and tectonic interpretations. Data were compared against the latest sea level predictions based on glacio-hydro-isostatic models. Our results allow proposal of the age-range of these millstone quarries and to estimate the intervening relative sea level changes since the time when they were carved.

Description: Published

Description: 126-142

Description: 3A. Ambiente Marino

Description: JCR Journal

Description: restricted