Structural map of Ligurian Briançonnais sheath folds (Pamparato-Murialdo unit, Bormida valley, Liguria, Italy)

We performed a careful geometric analysis of minor structural details of curvilinear hinge geometries exposed in blueschist rocks from the Pamparato-Murialdo unit of the central Ligurian Alps. The data collection resulted in a new structural map and related cross-sections, which elucidate the relationships and evolution of the associated large-scale sheath folds of the Ligurian Brianconnais.We measured and collected the geometric parameters of minor fold shape, vergence, lineation obliquity and structural facing pattern, in order to define the large-scale fold structure. The synthesis of the small-scale data results in a coherent structure showing several orders of magnitude of parasitic folds. The meticulous definition of the relationships between facing and fold hinge/lineation obliquity at small scales is the only tool to reconstruct the large-scale structure and to define the sheath fold vergence and transport direction. On the whole, the new map and related cross-sections supply new insights on the three-dimensional structure and evolution of sheath folds generated by the ductile deformation of the Brianconnais rocks during the Alpine subduction.