@article {11942, title = {Comment on "Relative sea level change in western Istria (Croatia) during the last millennium" by Sanja Faivre, Eric Fouache, Matthieu Ghilardi, Fabrizio Antonioli, Stefano Furlani and Vladimir Kovacic.}, journal = {Quaternary International}, volume = {271}, year = {2012}, pages = {130-131}, abstract = {
The paper Faivre et al. (2011) presents an interpretation of\ results deduced from two coastal cores that are trying to date the\ period of formation of a slightly submerged tidal notch often
reported from the coasts of Istria.\ The development of a tidal notch in carbonate coasts is usually\ made possible by intertidal bioerosion processes during periods of\ relative sea-level stability (Pirazzoli, 1986). The inward depth of the\ tidal notch profile, that in Istria is often of about half a meter, may\ be used for a rough estimation of the duration of the period of\ relative sea-level stability, with assumptions on the bioerosion\ rates, that in the Mediterranean have been reported to vary\ generally between about 0.2 and 1.0 mm/y (Evelpidou et al., 2012).\ The profile of the Istrian tidal notch shows a well preserved roof,\ evidence that the notch was submerged by a rapid subsidence,\ probably coseismic (Evelpidou et al., 2011a, 2011b).\ Several publications, some of them co-signed by the same\ authors for the area between Porec and Zadar (Fouache et al., 2000;\ Faivre and Fouache, 2003), have reported, from correlation with\ archaeological remains, that the submerged notch corresponds,\ more or less, to the sea level in Roman times. Other data by Faivre\ et al. (2010), mention a tidal notch submerged by 0.5e0.7 m and\ a sea level rise from the first century AD that cannot have highly\ exceeded 1.0 m. Finally according to Fouache et al. (2011), the sea\ level rise indicated by archeological remains can be estimated at\ 1.0+-0.48 m since Roman times.
Faivre et al. (2011) provide a new interpretation from the two\ cores, which is in complete contradiction with previous results,\ suggesting that the notch formed much later, between 1000 and\ 1500 AD. These two dates correspond to radiocarbon ages of two\ shells collected by the cores. However, apart from the depth of\ sampling, that nearly coincides to the base of the notch, not before\ but after its submergence, there is no clear evidence that the dated\ shells are really related to the sea level at which the notch developed\ before its submergence. Also, the assertion that the sample\ from one core would have been deposited at the beginning of the\ notch formation, while the sample at the same depth from the\ other core would just have preceded the coseismic subsidence,\ seems unconvincing. In fact, after the rapid subsidence of the area,\ the relative sea level became several decimeters higher in the areas\ of the Mirna River valley and of the Santa Marina Cove, permitting
an acceleration in marine sediment deposition at the levels where\ they have been recently cored.\ In addition, the period between 1000 and 1500 AD seems too\ short for the development of the tidal notch considered, more\ specifically that this period seems very unfavorable to tidal notch\ development because the global sea-level rise that occurred until at\ least 1350 AD, at a rate of 0.6 mm/y (Kemp et al., 2011), has probably\ limited the possibilities of local bioerosion.\ Seismic evidence in the period around 1500 AD is also missing. If\ the rapid subsidence had a coseismic origin, the event is likely to\ have produced a tsunami in the northern Adriatic. It is hardly\ believable that a tsunami occurring about 1500 AD could escape\ notice in Venice and in the other lagoons and harbors of the\ western coast of the Adriatic. In short, a late Roman date, e.g. 361\ AD, as suggested by Benac et al. (2004), seems more likely than\ a date around 1500 AD.\ As to the relative sea level stability necessary for the notch\ formation, it could have occurred in a period of balance for relative\ sea level changes between the eustatic, isostatic and tectonic factors\ (Pirazzoli, 2005), i.e. before and during Roman times, possibly in\ accordance with relative sea-level variations of the type of those\ predicted with the modelm-2byAntonioli et al. (2007, Fig. 9C or 9D).
}, author = {Pirazzoli, P. and Evelpidou, N.} }