Depositional System, Petrography and Facies Analysis of Pleistocene Travertine in Southern MarcheE, Central Italy

Two major arcs can be distinguished in the Apenninic chain: the Northern Apenninic Arc, NE verging, which from Monferrato (NW Italy) extends to the Lazio–Abruzzi region (Central Italy), and the Calabrian Arc, SE verging, which extends from the Southern Apennines to Sicily.
The two arcs are separated by the Ortona-Roccamonfina line (Locardi, 1982), a Late Pliocene dextral strike-slip fault according to Patacca et al. (1990). To the east, the foreland is represented by the Ionian–Adriatic domain and the foreland flexure is regionally drawn by the deepening gradients of the base of the Pliocene isobaths (Royden et al., 1987; Bigi et al., 1990), a feature which is particularly evident in the Northern Apenninic Arc.

Further south, the flexure of the Molise Arc foreland ends abruptly at the Ofanto valley. From this point on, the foreland flexure is clearly evident only around the Gulf of Taranto (Bigi et al., 1990). Inward, to the west, the Tyrrhenian basin represents the main structure. In addition, high-K volcanoes dating from the Late Pleistocene to the Present, whose apparatuses follow structural alignments, occur inward of the Apenninic chain. In the Lazio–Toscana central-­‐western Italian regions they are NW–SE aligned, while in Campania (SW Italy) they follow an E–W trend.

In the Southern Tyrrhenian Sea a calc-alkaline volcanic arc (the Aeolian Arc) is also present. The two arcs are also different in shape and tectonic style. The northern Apenninic arc is an open arc dominated by imbricate thrusts in piggy-back sequences, which propagate towards the foredeep axis (Bally et al., 1986; Oldow et al., 1993).
High-angle NW–SE-trending normal faults and NNW–SSE-trending sinistral strike-slip faults are superposed on pre-­‐existing contractional structures. In Umbria and Tuscany regions, these faults border graben and half-­‐graben structures filled with Plio-Pleistocene continental and marine deposits (Ambrosetti et al., 1978).

The Southern Apennine represents a narrow isoclinal arc whose tectonic style is dominated by duplex compressive structures (Mostardini and Merlini, 1986; Patacca and Scandone, 1989). Thrust fronts, fold and piggy-back basin axes are NNW–SSE trending, roughly en echelon to the Bradanic foredeep axis. Along the Bradanic trough, borehole data (cf. profiles nos. 1–15 in Mostardini and Merlini, 1986) show that, below the Apenninic thrust belt, the Plio-Quaternary sediments of the Apulia plate occur at a different distance from the thrust front. To the west of the chain, the present Tyrrhenian margin of the Southern Apennines was dissected by Early Pleistocene normal faults attributed to a NE–SW trending fault system (‘anti-Apenninic system’) as well as to a NW–SE trending one (‘Apenninic system’) by Ortolani (1978) and Ortolani and Pagliucca (1988).