Some tectonic influences on the Croatian shoreline evolution in the last 2000 years

Abstract

Working on the evolution of the Croatian shoreline (FOUACHE et al. 2000) we try to correlate geomorphological and archaeological markers. A submerged notch was found 0.5 m below the present sea level on many diving points, between Porec and Zadar, as well as on the islands of Rab and Pag. A number of submerged archaeological remnants on the Istria and Kvarner area give evidence that the notch corresponds to the sea level in Roman times, 2000 years ago. From the Zadar-Sibenik area the submerged archaeological remnants point to a submersion of at least 1.5 m. Those results could not be correlated with a geomorphological marker due to the lack of a notch. Continuing further to the south till the Prevlaka area neither geomorphological, nor appropriate archaeological markers, have been found. These facts raise the problem of tectonic influence on the above observations. In this study we present the recent structural relations in the studied area and discuss some aspects of tectonic influence on sea level change. The existence of the three sections of the Adriatic microplate, with a different size and a different rate of movement together with the major rock masses in the Dinarides that resist the movement of the microplate, determines the present seismotectonicaly active zones (ALJINOVIC, 1984, KUK et al., 2000) in the area. According to geomorphologic, archaeological, structural, seismic, positioning (GPS) and tide-gauge data we distinguish three main areas showing some homogenous properties. The Istria and Kvarner region shows a predominance of the eustatic component in the relative sea level change, while the Zadar-Sibenik and Sibenik-Prevlaka areas point to tectonic movements on which fluctuations in eustatic sea level are superimposed.