(a) General context of the French Massif Central. (b) Sketch map of the Variscan basement of the Pontgibaud region showing the spatial distribution of LGU, UGU and PAU units, and localities where these nappes were defined (Sioule Series, Artense Dome and Haut Allier). Modified after Chantraine et al., (2003). (c) Geological map of the Pontgibaud region. The dashed black line represents the UGU/LGU contact proposed by Chantraine et al. (2003). Note that paragneiss are either attributed to LGU (north-west of Gelles granite) or UGU (south-east of Gelles granite). Modified after Hottin et al., (1989).