The southern Apennine Arc

The Southern Apennine Arc (SAA), stretching from Central Apennines to Sicily, is the southern Italian part of the Apennine-Maghrebian chain, important segment of the circum-Mediterranean Alpidic tem. It is a complex arcuate thrust belt, composed by minor arcs of different size and curvature, with general convexity and vergency towards the Adria-Apulia-Africa foreland. Like the other parts of the Apennine chain, the SAA developed through the deformation of two major palaeogeographic domains. The first one, internal, is of oceanic type and is represented by Upper Jurassic to Oligocene tectono-sedimentary successions of the Liguria-Piedmont Ocean, linked to the Neo-Tethyan sea. The second one, external, is represented by Triassic to lower Miocene sedimentary sequences deposited on deformed continental crust along the Adria-Apulia-Africa passive margin, and is featured by an extensive carbonate platform/basin system. The two main units represented contiguous palaeogeographic domains up to the end of Mesozoic. They were then progressively incorporated into the chain. The SAA fold-and-thrust belt developed from Late Cretaceous to early Pleistocene at the subduction-collisional boundary between the European and the westward subducted Ionian and Adria plates. Large parts of the Mesozoic oceanic crust were subducted during an Alpine phase from Late Cretaceous to Eocene, while the continental collision of the European margin against the Adria-Apulia-Africa margin probably occurred between late Oligocene and Langhian-Serravallian. The chain was built as an accretionary wedge over a sinking and roll-backing slab, which forced the opening of the Tyrrhenian back-arc basin. The frontal arcs of the SAA overthrust now the Miocene-lower Pliocene, prevailingly terrigenous sequence of the most recent and external foredeep (“Adriatic foredeep”) and the scarcely deformed margin of the Apulian foreland, while the stack of thrust sheets of the Maghrebian Sicily are verging toward the southern Hyblean foreland. The SAA appears composed of two main wings, Central-Southern Apennines to the North, and Sicily to the South, with the Kabylo-Calabride Arc as hinge. Mesozoic-Tertiary platform carbonates, and marly/siliceous pelagic deposits prevail in the northern and southern wing of the SAA, while Calabrian Arc mostly consists of metamorphic exotic terranes (Calabride units, part of the Kabylo-Calabride thrust belt). The Calabrian Arc is a composite terrane of likely Western Alpine origin, accreted on the back of the SAA. Within SAA, tectonic segmentation and variations in structural trend are controlled by thrust partitioning and strike-slip transfer along transverse discontinuities connected with thin-skinned differential rotations. The SAA shows in general much greater amount of shortening in respect of Northern Apennines. Its style is featured by duplexes and relevant out-of-sequence thrusts