GNGTS 2015 - Atti del 34° Convegno Nazionale

12 GNGTS 2015 S essione 1.1 the Tertiary foreland of the Apenninic-Maghrebian Thrust Belt. NE–SW and NW–SE trending normal fault systems affect the outcropping Miocene terrain (Lentini et al. , 1984). In the studied area the main of these faults is the 20 km long, NE-striking E-dipping normal Avola Fault (AF in Fig. 1). The growth of this fault since 200-240 ky is hypothesized on geomorphological observation (Catalano et al. , 2008) but its recent activity has never been constrained. Active tectonics of the eastern sector of the Hyblean Plateau is scantly documented. The most recent evidence consist in joint sets and grid-lock fracture systems affecting Late Pleistocene terraced deposits (yellow sands and bioclastic calcarenites) documenting the existence of an extensional tectonic regime (De Guidi et al. , 2013). However, present day active tectonics has never been documented for lacking of deformed Holocene terrains. Historical data . The foundation of Avola, in an area previously inhabited by the Sicans, is perhaps connected to the history of the older town of Hybla Major (Di Maria, 1745) that was invaded by the Sicels in the 11th-9th centuries BC. The Greeks colonized the city in the 8th century BC. After the Syracuse domination (4th century BC), the Romans conquered Sicily in 227 BC. The Sicels’ age is testified by numerous finds, especially pottery and dishes, found in the oven-shaped tombs resembling a beehive and characterizing the surroundings of Avola Vecchia and the near site of Cavagrande di Cassibile. The cave houses are a type of dwelling cave carved into the rock that marks the ancientAvola urban centre. They date back to the Byzantine-medieval period (6th-9th centuryAD) and people lived there until the 1693 earthquakes (Gringeri Pantano, 1996). The caves of the Sicels’ necropolis along with the Byzantine-medieval cave houses are among the oldest testimony of civilization in the area. The older Hybla town disappeared in the early middle Ages, and the territory started to be repopulated during the Islamic domination of Sicily (9th-11th centuries AD). However, Avola Vecchia appeared only during the Norman or Hohenstaufen rule (12th-13th centuries), and persisted until the 1693, when two earthquakes destroyed it, as well as many of the southeastern Sicily towns. Not persisting more reasons to rebuild the city in an elevated site to protect themselves from the Saracens’ incursions and to favoured maritime trade, the old city was abandoned and rebuilt in a new location along the Fig. 1 – A) Geologic map (modified after Lentini et al. , 1984) and location of the studied area; AF is the Avola Fault; the yellow arrow marks the 1693 Mt. Ginisi landslide; B) Mt Aquilone and location of the caves with the mesostructural stations.