Stratigraphic correlations and structural setting of the pre-neoautochthonous sedimentary sequences of northern Latium

The stratigraphic/structural setting of the "Tuscan', "Umbrian' and "Ligurian' Units, buried beneath the broad Quaternary volcanic "covers' of Northern Latium, has been defined at the end of the Tortorian "compressive' phases. It can be shown by the piling up, from W to E, of four main Triassic-Eocene "Tuscan' type Units separated by structural "depressions' characterized by strong thickness of "Ligurids' (even exceeding 3000 m). These "Tuscan' Units, displaying a well-defined arc-shaped feature congruent with the well-known "virgation' recognized in the Northern Apennines, are superposed on the "Umbrian' Series. The Tertiary terrigenous covers of the identified "Tuscan' Units are detached from the Mesozoic substratum and translated eastward. The overthrust surfaces between the different Units seem to verticalize at the front of the principal structural belts. During the Mio-Pliocene and Quaternary tensional tectonic phases, such discontinuity surfaces may have interacted with the deep NW-SE feeding magma features, affecting the local-distribution of the volcanic activity.