engleski

Indicators of the 2 000 years sea level change on the island of Vis

The island of Vis belongs to the group of the Central Dalamatian Islands. According to its size (90, 3 km2) it is the tenth island in the Adriatic Sea located far from the land and therefore strongly influenced by the sea. Its relief can be simply described through three main hilly ranges between which two main valley-like structures are situated. The northern one is relatively tight, it relates Vis and Komiža, while the southern one is wider and is represented by a row of poljes. Theses forms are mainly east-west oriented as a consequence of spreading of the main geological structures. Structurally the island represents an anticline which roughly spreads east-west and which sinks toward the east 10 in average. The core of the anticline is made of clastites with gypsum and igneous rocks while the limbs are made of Cretaceous carbonates: limestone and dolomites. In the depth below the Lower Cretaceous the anhydrites can be found on the larger area of the island of Vis. This anticline is completely cut by faults which are parallel with the hinge line of the anticline. The whole area is therefore characterized with strong compression which resulted in numerous fissures and intensive karstification. (Terzić, 2003). The deformation of structure directly depends on the stress orientation. According to Prelogović et al. 2001 the orientation of the regional stress is 18-198. The transversal orientation of the stress direction in relation to the spreading of structures points to the compression of the area as well. In those circumstances the reverse movements along faults of opposite vergences occurred and pop-up like structures occurred. The island of Vis represents a very interesting area for the investigation of the 2000 years sea level change due to the existence of the submerged antique port of Issa. The archaeological prospection made by Čargo (2002) suggest that the port have been built in the 4. century B.C. On the southern part of the peninsula of Prirovo this port is very well preserved. It is made of great stone blocks built without mortar. Two rows of blocks are preserved today in the length of 24 m. The coast line of the time was slightly curved and follows the natural coastline. Generally, the blocks are today 1, 5 m under the sea level. Those archaeological remains represent a very good sea level indicator. Furthermore, investigating the cost of the island of Vis submerged tidal notches were found on few places along the faults, like in the bay of Oključna and in the bay of Parja. Local shore platforms were also identified which are mainly structurally predisposed, like in the bay of Stončica for example. They represent a good today sea-level indicator. On the island of Biševo the beautiful algal trottoirs have been prospected. They develop in close connection with the sea level and can be the precise (± 10 cm) sea level indicator.

tidal notch; sea level change; Vis; Croatia

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