Mesozoic-Tertiary carbonate platforms, slopes and basins of the external Apennines and Sicily

Abstract

Mesozoic and Tertiary limestones form the morphological backbone of the Apennines between Umbria and northern Calabria. They are also exposed in a number of tectonic windows below higher nappes along the Tyrrhenian margin of the Italian peninsula; that is, in the Tuscan nappe and in the exhumed metamorphic structural units of the Northern Apennines They further occur along the Adriatic foreland both in the subsurface and on the plateau of the Apulian peninsula. These limestones are the relics of a Mesozoic archipelago of Bahamian-type carbonate platforms, separated by deeper basins and plateaus, which originally were situated on the continental margin to the S and E of the Liguria—Piedmont segment of the (Neo-) Tethys ocean and extended over what is now the external fold-belts of the Apennines, Hellenides, Dinarides and Southern Alps and their Adriatic foreland (Figs 18.1, 18.2). Wherever the original substratum of these limestone successions is exposed or drilled, it is composed of upper Palaeozoic and Triassic elastics, limestones and evaporites, or of continental crust of Hercynian age. There exists a long-lasting discussion on whether the area was a promontory of the African continent throughout most of its Mesozoic history (Argand, 1924; Channell et al., 1979) or an independent microcontinent (Adria or Apulia, Dewey et al., 1973) that became separated from Africa in Permian (Stampfli et al.,1991; Vai, 1994), Triassic (Dewey et al., 1973) or Cretaceous time (Dercourt et al., 1986; Ricou, 1994). Nowadays there is convincing evidence that Adria was indeed separated from the North African margin by a deep oceanic basin that was connected to the Ligurian Tethys (Fig. 18.2; De Voogd et al.,1992). The Mesozoic and Tertiary limestones of Sicily were deposited along this North African margin and are now an important part of the nappes of central and southern Sicily and of their Hyblean (Iblei) foreland.