Relative Sea Level Changes by using archaeological markers: the INTERREG Italia-Slovenia Project "Alto Adriatico"

We studied the last 2 ka sea level change along the Italian, Slovenian and Croatian coastlines (Eastern Adriatic Sea) using archaeological and geomorphological markers surveyed between Duino and S. Simonov, along the eastern part of the Gulf of Trieste. Moreover, we present 14C AMS analyses provided on lagoonal fossil shells compraised between 9.7 an 4.6 ka BP at altitude between -1.3 and -4.5 m in Istria. Many Authors (Pirazzoli, 1980; Fouache et al., 2000; Benac et al., 2004) published geomorphological, archaeological and sismotectonic research works between the coast of Duino (Trieste) up to the central coast of Croatia (Zadar). Along the limestone coast, the Authors revealed a quasi-continous occurence of a submerged marine notch at a depth between –0.5 m and –1.0 m. In addition, Roman age archaeological markers were measured at depths lower than –0.5 m and often lower than –1.0 m. Antonioli et al. (2004) provided geomorphogical observations on marine notches in the Gulf of Trieste between –0.7 m and –2.55 m. Since the northern part of the Gulf is dominated by highly conservative limestone rocks, we provide new detailed geomorphological measurements, surveying a continous marine notch in 11 different sites. In this area there are no archaeological remains related to sea level changes. On the contrary, since the southern coast between Stramare (Italy) and Izola (Slovenija) is dominated by Flysch, there are no notches but 5 submerged archaeological sites. The altitude of the marine notch vary between –0.65 m on the Miramare olistoliths and –0.9 m in Canovella de’ Zoppoli. The depth of the notch increases in direction of Duino, from –1.3 m close to the Sistiana Harbour to –2.55 m below the castle of Duino. This situation highlights a clear SE-NW tilting versus in the Gulf of Trieste. Braitenberg et al. (2005), on the basis of tidal gauge data (over 110 years) and the movement of the last 30 years of the Grotta Gigante pendulum, hypothesized that NW movements could still be active. In the southern part of the Gulf, the mean values of the tide and pressure-corrected archaeological measurements (all provided by harbour stones) indicate a depth of -1.6±0.5 m for the 2 ky Bp sea level (Roman age – I sec. A.D., dated with an amphora at the base of the stones), assuming the top of the wall of the harbours at an altitude of about -0.9 m.