Geology of the Pontinvrea area (Ligurian Alps, Italy): structural setting of the contact between Montenotte and Voltri units

Abstract

This geological map at the 1:10,000 scale shows the structural setting of two poly-deformed metaophiolite units, with different metamorphic peak conditions, i.e. the blueschist facies Montenotte Unit and the eclogite facies Voltri Unit, in a selected area of 8.2 km² within the Ligurian Alps (northern Italy). This study focuses on the tectonic contact between the two tectono-metamorphic units and on their relationships with the Oligocene sediments of the Tertiary Piedmont Basin. The map is a composite report of our field and laboratory study of structures and metamorphism, that explains our interpretation of the tectonic history of the study area. It shows that the two units were coupled during their exhumation path, along a blueschist facies mylonitic contact. This contact has been later involved in thrust faults that caused the superposition of the metamorphic basement on top of the Oligocene sediments.

Keywords:

• HP metaophiolite
• structural mapping
• Montenotte Unit
• Voltri Unit
• Ligurian Alps

Acknowledgements

Thanks are due to Gian Mario Dabove, Michele Piazza, Eugenio Poggi and Andrea Vigo for field assistance during geological mapping. Base of data come from the geological mapping project 212 'Spigno Monferrato' quadrangle, funded by the Regione Liguria (Project Manager Gianna Gorziglia), that is gratefully acknowledged. Funding for this research was also provided by COFIN-MIUR 2010–2011 project entitled ‘Birth and death of oceanic basins: geodynamic processes from rifting to continental collision in mediterranean and circum-mediterranean orogens’.