ABSTRACT
Available geological and geophysical data do not yet provide a clear picture of the deep crustal structure beneath Central Italy. The National Research Project CROP, and specifically the CROP 11 sub-Project will focus on the crustal structure of Central Italy.
Gravimetric studies have already been performed. By a new interpretation of already exist data, they have allowed the development of a two-dimensional model of the crustal and upper mantle setting, along a cross section from Tyrrhenian to Adriatic Sea (corresponding to the acquisition trace of the CROP 11 seismic line).
This model suggests the existence of a Tyrrhenian lithospheric sector having lower densities with respect to the Adriatic sector. These two sectors are separated by an intermediate zone, where a lighter wedge of the upper mantle has been hypothesized. It has been interpreted as part of a slab of Adriatic crust underneath the Tyrrhenian Moho.
On this basis, for the comprehension of the regional deep setting, a 3D extension of the 2D previous model is now necessary. This will provide better evaluation of the lateral development of the identified structures. The first step of this process is the subject of this report. It consists in the study of the areal development of the residual gravimetric anomalies, exclusively due to deep structures. We started from the Bouguer anomaly map (2.67 g/cmJ) and removed the effects of superficial structures applying the stripping-off method to the topographic surface.
In this way, a new residual map for the Central Italy has been obtained. A prominent N-S direction can be recognised in the northern-central part of the study area, related to the flexed part of the Adriatic slab. It characterises the crustal portion and confirms that the CROP 11 deep seismic line is oriented properly. A more complex deep structure seems to be localized in the central-southern part of the region investigated, suggesting an important change going from north to south in the lower crust and upper mantle (these data also agree with the DSS and tomography data). Finally, the residual map shows that isolines trend W-E in the middle of the study area, in both Tyrrhenian and Adriatic side, as well as in the core of the Apenninic chain. It is difficult, at the moment, to find a real geological correspondence for these sets of isolines including the existence of important W-E structures, as the 41° parallel or the meso-adriatic belt, and they constitute an interesting theme for debate.
