SESS 1_160211.pub Il Quaternario Italian Journal of Quaternary Sciences 24, (Abstract AIQUA, Roma 02/2011), Congresso AIQUA Il Quaternario Italiano: conoscenze e prospettive Roma 24 e 25 febbraio 2011 NEW ARCHAEOLOGICAL AND GEOMORPHOLOGICAL MARKERS ALONG THE ISTRIAN COASTS (CROATIA) AND THEIR RELATIONS WITH RELATIVE SEA LEVEL CHANGES Stefano Furlani1,2, Sara Biolchi2,3, Rita Auriemma4, Giorgio Tunis2, Franco Cucchi2 & Fabrizio Antonioli5 1Dipartimento di Geografia “G. Morandini”, Università degli Studi di Padova, Italy 2Dipartimento di Geoscienze, Università degli Studi di Trieste, Italy 3Dipartimento di Scienze della Terra, Università degli Studi di Modena e Reggio Emilia, Italy 4Dipartimento di Beni Culturali, Università di Lecce, Italy 5ENEA, ACS, Roma, Italy Corresponding author: S. Furlani ABSTRACT: Furlani S. et al., New archaeological and geomorphological markers along the Istrian coasts (Croatia) and their relations with relative sea level changes. (IT ISSN 0349-3356, 2011) New data on archeological remains and coastal morphologies have been used to refine published data on the Late- Holocene relative sea-level change along the Northeastern Ardriatic coasts. Data have been compared with predicted curves, in order to detail the tectonic evolution of the studied area. RIASSUNTO: Furlani S. et al., Segnalazione di nuovi indicatori archeologici e geomorfologici lungo la costa istriana (Croazia) e correlazione con le variazioni relative di livello marino. (IT ISSN 0349-3356, 2011) Le variazioni di livello marino tardo-oloceniche lungo le coste nordorientali dell’Adriatico sono state dedotte da una serie di nuove misure effettuate su indicatori archeologici e geomorfologici sommersi. I dati raccolti sono stati comparati con le curve predette di risalita del livello del mare. Key words: sea level changes, late-Holocene, geoarchaeology, Istria, Northeastern Adriatic Parole chiave: variazioni di livello marino, tardo-olocene, geoarcheologia, Istria, Adriatico nordorientale The Gulf of Trieste and the Istrian coasts have been extensively studied during the last decade (FOUACHE et al., 2000; ANTONIOLI et al., 2004, 2007; FAIVRE and FOUACHE, 2003; FAIVRE et al., 2011; FURLANI et al., 2011). Neverthless, many sites remain unstudied from the point of view of sea level changes. Cited Authors reported along the limestone coasts between the Gulf of Trieste (Italy) and Istria (Croatia) the quasi-continuous occurence of a submerged marine notch at a depth ranging between –0.5 m and –2.8 m, while Roman age archaeological remains were measured at depths usually deeper than the altitude of the notch. We aim at detailing the late-Holocene, in particular since Roman-age, tectonic behaviour of the studied area following the methodological steps suggested first by ANTONIOLI et al. (2007). 1. STUDY AREA From a geodynamical point of view, the study area belongs to the External Dinarides. It is characterized by a diffuse NW-SE orientation of the tectonic structures. Along the Northeastern Adriatic coast crop out limestones belonging to the Adriatic Carbonate Platform and spanning in time from Lower Jurassic Fig. 1. The study area and the surveyed sites L’area di studio con i siti indagati 35 - 37 36 (Toarcian) to Eocene (VLAHOVIĆ et al., 2005). Previous works recognized the occurrence in the NE Adriatic sector of a NW tilting along different geological time scales: pendulum data (BRAITENBERG et al., 2005), geomorphological markers (ANTONIOLI et al., 2004, 2007), archeological markers (DEGRASSI et al., 2008) are evidence of recent tilting, while geophysical data (BUSETTI et al., 2010), structural data (CARULLI et al., 1980) and gravity modeling (COREN et al., 2006), indicate that the tilting is regional and long lasting. Moreover, the dataset suggests that the southern side of the gulf has subsided, at least since Roman time (about 0.6 mm/y), while the northern side has subsided during the Holocene, probably faster than the southern side (up to 1.99 mm/y, even if probably this value is mainly due to high sedimentation rates), following the aforementioned tilting (FURLANI et al., 2011). 2. THE INVESTIGATED SITES AND THEIR SIGNIFICANCE ON LOCAL TECTONICS Six new submerged archaeological and geomorphological markers have been surveyed, one in Italy and the remnants in Istria (Croatia). In particular: 1) submerged structure at Sistiana (Trieste, Italy). The functionality of the structure is not completely understood yet, since it is inclined toward the sea. Since the presence of quarries, which are active since Roman age, located just near the site, it could be a “slide” to charge limestone blocks on the ships. Its altitude ranges between -1.0 m and - 5.0 m; 2) coastal quarry at Palud (Pula, Croatia). The structure shows the proofs of human quarrying on limestone blocks. The base level of the quarry is covered by cementitium (maybe used to level off the pavement) and it is at about -0.2/-0.3 m m.s.l. Fig. 2,Submerged dock at Barbariga Il molo sommerso di Barbariga S. Furlani et al. 37 Ms. received: Testo ricevuto il Offshore there is another human-made basement; 3) submerged “path” at Kolone (Bale, Croatia). A submerged path, at about -1.5 m m.s.l., connects the coast to a small island. It is about 100 m long; 4) submerged dock at Barbariga (Croatia). The state of conservation is bad. The altitude of the structure is about -1.5 m; 5) submerged beachrock at Brijuni. Its depth ranges between about -5.0 and about -1.5 m. Its morphology suggests that the structure is a beachrock; 6) coastal quarry at Sekovac (Premantura, Croatia). The structure evidences the proofs of human quarrying on limestone blocks. The altitude is similar to the quarry located at Palud. The comparison between published and these new data refines the knowledge on late Holocene sea level change in Istria. The large number of structures already surveyed in the area allows to usefully integrate the available data, despite the bad state of conservation of the studied markers and the large uncertainty on their functionality. The most useful sea level marker is the roman dock at Barbariga. The mean values of the tide and pressure-corrected archaeological measurements suggest a depth of -1.6±0.5 m for the 2 ky Bp sea level (Roman age – I sec. A.D.). Considering the recent position of the submerged road at Bale, the same relative sea level rise rate seems to affect even the area located toward North. The altitude of the quarries represents an upper limit for the Roman Age sea level, however values agree with the other considerations. Comparison between the position of the submerged markers and the predicted values of sea level rise for the Northern Adriatic Sea details data collected by previous Authors and confirms the negative tectonic rate (-0.7/-0.8 mm/yr) for the whole studied area. ACKNOWLEDGEMENTS We are kindly grateful to Dr. Sandro Duijmović and Eduard Kolić of the Brijuni National Park (Croatia) for the surveyings along the coasts of the park. REFERENCES ANTONIOLI F., CARULLI G.B., FURLANI S., AURIEMMA R. & MAROCCO R. (2004) - The enigma of submerged marine notches in northern Adriatic Sea. Quaternaria, 8, 27–36. ANTONIOLI F., ANZIDEI M., LAMBECK K., AURIEMMA R., GADDI D., FURLANI S., ORRU’ P., SOLINAS E., GASPARI A., KARINJA S., KOVACIC V. & SURACE L. (2007) - Sea level change during Holocene from Sardinia and northeastern Adriatic (Central Mediterranean sea) from archaeological and geomorphological data. Quaternary Science Reviews, 26, 2463–2486. BRAITENBERG C., NAGY I., ROMEO G. & TACCETTI Q. (2005) - The very broad-band data acquisition of the long-base tiltmeters of Grotta Gigante (Trieste, Italy), Journal of Geodynamics, 41, 164-174. 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FURLANI S., BIOLCHI S., CUCCHI F., ANTONIOLI F., BUSETTI M. & MELIS R. (2011) - Tectonic effects on Late- Holocene sea level changes in the Gulf of Trieste (NE Adriatic Sea, Italy). Quaternary International. In press. VLAHOVIC I., TISLJAR J., VELIC I. & MATICEC D. (2005) - Evolution of the Adriatic Carbonate Platform: paleogeography, main events and depositional dynamics, Palaeogeography, Palaeoclimatology, Palaeoecology, 220, 333-360. New archaeological and geomorphological markers along ... January 15, 2011 15 gennaio 2011