The crust - mantle boundary in the Ligurian area: geological and geodynamic implications

The configuration of the crust-mande boundary in tbc transition zone between tbc Western Alps and tbc Northern Apennines is examinated. Some recent Moho contour maps are discussed from a geological standpoint, and their paleogeographie and geodynamic implications are considered. It is assumed that three principal Moho surfaces exist in tbc examined area. Most authors agree that two of them (tbc European and Adriatic Mohos) belong Io tbc pre-collisional Europe and Adria continental plates, while tbc appurtenance of tbc third ("Ligurian-Tuscan" Moho) is debated. On tbc basis of various arguments, tbc present work suggests that tbc Ligurian-Tuscan Mobo should be considered as forming part of tbc Adria Moho. Tbc deepest surface is tbc Europe Moho, which generafly dips Io the E under tbc Ligurian Tuscan Moho. The Adria Moho (locally called Po Plain-Adriatic Mobo) dips Io the W or to tbc SW under tbc Ligurian-Tuscan Moho, which is the shaflowest crust-mantle boundary. The overlap of tbc Ligurian Tuscan Moho on the Adriatic one is considered Io be a major intracontinental embrication, which is connected chronologically and dynamically to the Oligo-Miocene opening of the Ligurian-Balearie basin (in turn linked to tbc counterclockwise rotation of tbc Corso-Sardinian block) and to tbc subsequent Mio-Pliocene opening of the Tyrrhenian basin. The opening process has been accompanied cither by crustal attenuation or by the creation of a new, occanic type crust, hence generating new Moho surfaces (Ligurian-Balearic and Tirrhenian) which replace the older ones (European and Adrian, respectively). Two SW-trending crustal sections of the Maritime Alps and Corsica-Tuscany regions illustrate the two alternative geodynamic models that may explain tbc structural evolution of tbc area.