Main structural domains of the central Mediterranean region and their Neogene tectonic evolution

The Central Mediterrancan area is composed of several structural domains which extend along an orocline belt from Tunisia to the Southern Apennines, through Sicily and Calabria. These domains originated during orogenic processes induced by the Europe-Africa convergence. In the present-day configuration of the region tbc following domains can be distinguished: the foreland domain, which is divided into three major sub-domains; the orogenic beh domains, consisting of three distinct tectonically superimposed "chains"; and the hinterland domains, represented by the European fragment of the Sardinian Block and by the Tyrrhenian Sea. Each domain originated in a distinct period corresponding to a stage in the polyphasic deformation of tbc region. The present-day outlines derived from the late orogenic tectonic events (post-Tortonian) which gave rise to tbc youngest domains and modified the pre-existing ones. The foreland domain is composed of two continental blocks: the Pelagian Block, which extends from eastern Tunisia Sahel io southeastern Sicily (Hyblean Plateau), and is mostly submerged, and the Apulian Block, facing the Southern Apennines. The two blocks are made up of a 20-30 km thick continental crust underlying a very thick Meso-Cenozoic carbonate sequence. They are separated by a thinned crustal area (10-15 km), the Ionian Basin, which faces towards the Calabrian Arc. Two major fault escarpments connect the continental blocks with tbc basin. These features probably originated during Mesozoic times and have controfied the palacogeography of the domain. The fault escarpment bounding the Pelagian Block to the casi, the Malta Escarpment, was reactivated by prevalently normal movements during the Plio-Pleistocene. The foreland edge facing the orogenic belt contains very narrow and discontirmous foredeep basins (the Bradanic Foredeep and Gela Foredeep) which are interrupted where the foreland-chain boundary is represented by Plio-Pleistocene transcurrent zones (N-S Axis in Tunisia, Nameless Bank in the Sicily Channel). The most external and deepest structural domain of the orogenic belt is the External Thrust System, a gently deformed thrust belt which has developed since the Tortonian. This domain involves sequences similar to those outeropping in tbc foreland sub-domains which are characterized by the lack of flysch-type terrigenous cover. In Sicily the External Thrust System developed on the margin of the Pelagian Block giving rise to the Sicanian Chain, a thrust belt which extends westwards in the Sicily Channel (Adventure Bank) as far as the Sardinia Straits (Egadi thrust belt) and the Atlas Mts. in Tunisia. The Sicanian Chain outerops extensively in Western Sicily, where it dips to the north under the more internal Maglirebian Chain. In Eastern Sicily the Sicanian Chain forms a duplex structure buried under the more internal units at a depth of about 7000 m. In tbc Southern Apennines, the External Thrust System, corresponding to the Apulian Chain, has developed since the Upper Miocene by tbc deformation of the most internal Apulian carbonate sequences and forms a duplex structure mostly buried under the more intemal domains. The southern continuation of this duplex structure has also been detected from subsurface data below the units of the Calabrian Arc. The intermediate domain of the orogenie belt is represented by the Apenninic-Maghrebian Chain, a strongly deformed thrust belt created since the Early Miocene. This domain is composed of allochthonous units involving Meso-Cenozoie sequences deriving from several palaeodomains. The chain is characterized by a huge bulk of Early Miocene to Upper Miocene syn-orogenie flysch-type terrigenous cover which is mostly detached from the original substratum and migrated foreward to the front of the chain. The Apperminic- Maglirebian Chain formed mostly before the Tortonian and progressively overthrust, as a whole, the more external domains during the late orogenic tectonie events. In that period tbc chain suffered further deformations and was involved in a continuous passive tectonic transport over tbc foreland areas, due io duplexing processes in the substrata. The most internal and uppermost domain of the orogenic belt is represented by the Kabilo-Calabride Chain, a highly deformed thrust belt, involving basement nappes mostly composed of Hercynian crystalhne rocks and their Meso Cenozoic sedimentary covers. This domain shows Upper Eocene- Early Miocene syn-orogenie flysch-type deposits. The Kabilo-Calabride Chain outerops on the northern coast of Africa and in the Calabrian Arc.