THE SUTURE BETWEEN THE ALPS AND APENNINES IN THE LIGURIAN SECTOR BASED ON GEOLOGICAL AND GEOMAGNETIC DATA

A ground magnetic survey was carried out over a wide area of northwestern Italy, including western and central Liguria, the southeastern Piedmont and a part of the Ligurian Sea. Several cross-sections, cutting the main structural elements (the Ligurian Sea, the Ligurian Alps, the Monferrato Hills) have been performed and magnetic models have been developed. The interpretation of the most characteristic cross-section (A1-NNW), is presented in this paper. A model involving the presence of a major suture between the Ligurian Alps and the Monferrato Hills fits the positive magnetic anomaly running from the surroundings of Turin towards Asti. This model implies that slabs of upper mantle or lower continental crust were trapped in the suture, as in the internal zone of the Western Alps, where the Ivrea body comes in contact at depth with the Pennidic nappes. To the south, this suture line does not appear throughout the Ligurian Sea, probably owing to the recent crustal thinning, which is revealed by both the magnetic and the gravimetric features.