New insights in the lithospheric configuration of the Ligurian-Provençal Basin derived from gravity field interpretation

Abstract

<p>The area of the western Mediterranean between the French and Italian coasts and Corsica-Sardinia is still of great interest in terms of its structural development, which remains incompletely understood. The resolution of geophysical data was not always high enough to explore detailed structures in the lithosphere. After completion of the new AlpArray gravity maps, a high-resolution gravity field is available. The intended 3D modelling of the lithosphere requires the search for reliable constraints for the density/susceptibility models (seismic, bathymetry, gravity fields, gradients). The calculation of residual gravity fields is difficult due to uncertainties in the calculation of regional fields which are characterized by pronounced gravity highs and lows in a very limited spatial area. The residual fields calculated here provide new insights into the lithospheric structure and suggest that the mass distribution in the Ligurian-Provençal Basin does not monotonously follow the known major geological units. A broad belt of local gravity highs (25 - 40 x 10<sup>-5</sup> m/s<sup>2</sup>) extends off the French coast to the northwest of the basin where it merges with NW-SE directed gravity highs (up to 45 x 10<sup>-5</sup> m/s<sup>2</sup>) near the Italian coast. Hitherto unknown is the residual field anomaly south of Marseille with max. 100 x 10<sup>-5</sup> m/s<sup>2</sup>. Euler deconvolution and correlations with maps of focal depths of earthquakes resulted in source depths that lie in the mantle. The results of further processing techniques (curvature calculations, third derivative of potential, terracing and cluster analysis) were superimposed on geological maps to make visual correlations clear. Results of dynamic modelling of the surrounding subduction zones, as well as newly inferred Moho and LAB depths, are also available for interpreting gravity field components of deeper regions of the Earth's mantle in the study area. Previously performed investigations (magnetic field modelling and recent seismic campaigns, e.g., LOBSTER and AlpArray seismic tomography models) were also added to the research.</p>