Structural features of south-western Sardinian shelf (Western Mediterranean) deduced from aeromagnetic and high-resolution reflection seismic data

Abstract

This paper presents the continuation of an integrated geophysical and geological study of the continental shelf of western Sardinia in its southern part. The study which was conducted because of the presence of a set of very strong elongated magnetic anomalies that have never been quantitatively interpreted, consists of an integrated interpretation of high-resolution reflection seismic and magnetic data. Thanks to Sparker high-resolution seismic data interpretation, it was possible to reconstruct the main structural features of the upper part of the south-western continental margin. In the geological and structural contexts of the studied area, the aeromagnetic data was interpreted by a combination of two-dimensional Werner and Euler deconvolutions and by a delineation technique based on the maxima of the radial horizontal derivative, which proved to be very effective. The results of these techniques combined with those of high-resolution reflection seismics were used as constraints for a three-dimensional magnetic modelling. Thanks to the study, which was carried out in the laboratory on rock samples from the most representative lithotypes outcropping on land, and to the application of a special processing on pole reduced data, it was possible to ignore the effect of remanent magnetisation. From the geological meaning of the 3D magnetic interpretation it was possible to improve our knowledge of the structure of the upper part of the continental margin and of new elements in volcano-tectonic evolution. In particular it was evidenced the presence of crustal faults that caused the lowering of the blocks of the south-western continental margin. The extensional tectonics that produced the block faulting also produced andesitic and ignimbritic volcanism during the Lower and Middle Miocene time span.