Finetti, I. R., Calamita, F., Crescenti, U., Del Ben, A., Forlin, E., Pipan, M., Prizzon, A., Rusciadelli, G., and Scisciani, V.
Geological, geophysical and new CROP seismic data have been used to reconstruct and discuss a new crustal setting for the Central Apennines. The Apenninic chain of the Italian peninsula is formed by two main arcs (that of the Central-Northern Apennines and that of the Southern Apennines), decoupled along the Sangro-Volturno line. In the central sector of the Apennine chain, prominent folds and thrusts involve the Triassic-Miocene carbonate succession of the Adria continental margin and of the foreland and foredeep Neogene-Quaternary basins (Apennine Units s.s.). To the SE of the Sangro-Volturno line, the Molise Allochthonous Units, related to the Neogene-Quaternary closure of the Ionian Neotethys, overthrust the Apennine Units s.s. In the westernmost zone (Tuscan-Latium area), the Apennine Units remained below the internal allochthonous ones (Alpine Tethydes on Ligurian Units) connected to the closure of the Alpine Neotethys. In the peri-Adriatic area, the frontal zone of the chain is buried by the Quaternary succession. The main tectono-stratigraphic units outcropping east of the Quaternary volcanic deposits and the Pliocene-Quaternary deposits of the peri-Tyrrhenian area are formed by the Sibillini Mts.--Antrodoco-Olevano thrust (Sabine Units), the Gran Sasso (Latium-Abruzzi Units) and Mt. Morrone thrusts, and by the Teramo and Maiella thrusts (external units of the Messinian and Pliocene foredeeps). These thrusts have project out, and are locally conditioned by the Mesozoic distribution of the pelagic basins and carbonate platforms established since the Triassic-Liassic rifting processes. The architecture of the paleomargin has also constrained the physiography of the Neogene foredeep basins, whose depocenters are in many cases located in correspondence with the pelagic paleobasins. The Pliocene thrusts located on the Marchean-Abruzzi Apennine mountain front (M.gna dei Fiori-Gran Sasso--Mt. Morrone, Maiella) have produced a structural elevation of the top of the carbonate succession of about 10 km and horizontal displacements of about 45 km. Southward, these thrusts are joined to the NE-SW-oriented Sangro-Volturno dextral transpressive oblique ramp. An analogous kinematic role characterizes the Sibillini Mts.--Antrodoco-Olevano thrust, the southern segment of the Ancona-Anzio (Auct.) thrust system. The Sangro-Volturno oblique ramp constrains to the south the Central-Northern Apennine arc, which is segmented into the Northern and Central Apennine arcs by the Sibillini Mts.--Antrodoco-Olevano oblique ramp. The structural elevation of the Apennine Units s.s. within the Central-Northern Apennines is due to a greater shortening than in to the Southern Apennines, where the allochthonous units outcrop, whereas the latter are eroded in the Marchean-Abruzzi Apennines. The axial culminations of the arcs of the Northern Apennines (the Sibillini Mts. area) and the Central Apennines (the Gran Sasso area) correspond to the apex zones of their arcs where maximum shortening took place. In the Central-Northern Apennines axial zone, NW--SE trending normal faults with Quaternary activity are present, characterized by a SE-ward increase in the down-throw of up to 1000 m in the Abruzzi area. They are generated by gravity sliding of the sedimentarycover over the eastward sloping basement of the major composed thrust block of the Northern Apennines. Sliding and combined inversion of previous thrust faults of the piled cover stack constitute the basic mechanism of the high active shallow seismicity in the area. Deep compressive events derive directly from major thrust faults. New CROP data (lines M-15 and M-37), integrated with other geological and geophysical data, were used to reconstruct a lithospheric section across Central Italy, from the Corsica Basin to the Adriatic Sea (Plate-2). The reconstructed section leads to new observations on the evolution of the Central Apennines.… [ABSTRACT FROM AUTHOR]