Fig. 4

Field aspect of the meta-sediments within the Pinerolo Unit: graphite-rich conglomerate-sandstone succession (a–c, 44° 56′ 24.8′′ N–7°9′ 18.2′′ E) and graphite-rich siltstone succession (d–f, 44° 58′ 11.9′′ N–7° 10′ 28.7′′ E) (si = meta-siltstones, sa = meta-sandstones, co = meta-conglomerates). In the stratigraphic log the reported thickness of the layers is the one measured on the outcrop and, thus, represents the thickness after the Alpine strain. a Graded meta-conglomerate layer with an upward polarity. b Interbedded meta-conglomerates and meta-sandstones in decimetre-thick layers. Meta-sandstones preserve a cross-bedding lamination. c Centimetre-sized pebbles of garnet-bearing micaschist, felsic gneiss and quartz in polygenic meta-conglomerates. d, e Graphite-poor meta-sandstone layers interbedded with graphite-rich meta-siltstones. f Meta-siltstones with a millimetre-thick lamination defined by the occurrence of albite-rich laminae