Abstract

A tentative interpretation of the structure of the south-eastern part of the Voltri Group, at a regional scale, is presented from field data collected during regional mapping. The new interpretation implies that the Voltri Group lherzolites, serpentinites and metasediments were folded in large isoclinal folds (F <sub>1</sub> -F <sub>2</sub> events) and subsequently refolded into a megafold with a NNE-SSW horizontal axis. The eastern part of the Voltri Group could represent the sub-vertical (slightly overturned towards the W) limb of a megasynform, while its western part would be the sub-horizontal limb of the same megastructure. The regional scale implications of this hypothesis are discussed, and compared with the structural setting of the surrounding units. A structural stacking, with the Voltri Group in the highest position, overlying the Cravasco-Voltaggio-Montenotte complex, the Triassic-Liassic unit, the Valosio crystalline massif and a Brianconnais crystalline massif (Savona and probably Arenzano) is proposed; this hypothesis about the structural stacking is also based on data from other areas (the contact between the Voltri Group and the Savona crystalline massif). The consistency of the new interpretation with geophysical data from the area under investigation is checked and some field aspects which disagree with the proposed megastructure are discussed.

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