Fig. 7

Microphotos of thin sections. Note that as few metamorphic or sheared examples as possible are shown. Qz quartz, Qp polycrystalline quartz, P plagioclase, Musc muscovite, Bio biotite, Dolo dolomite lithoklast, Ech Echinoderm fragment, Fe-Cc iron-bearing calcite. A Quartz-bearing limestone bed of the Klus Formation; thin section stained for carbonate under normal light; echinoderm fragments (brownish-red) in iron-bearing sparitic calcite cement (blue); uncoloured grains are corroded quartz. B Spongy limestone from the Klus Formation under normal light. C Relatively coarse-grained sandstone from the Valzeina Formation (+ Nicols) consisting of quartz, plagioclase and muscovite; brownish grains are dolomite clasts. D Coarse sandstone in the lower part of the Sassauna Formation; besides quartz and corroded plagioclase, the calcite-cemented sandstone is rich in muscovite; + Nicols. E Thin section stained for feldspars from the Pfävigrat Formation; + Nicols; pinkish plagioclase is visible next to dominant quartz. F Carbonate-stained sandstone from the Pfävigrat Formation with similar characteristics as shown in A; here brownish-grey fine-sparitic to micritic dolomite lithoclasts can be seen. G Coarse arkose sandstone coloured for feldspars from the Fadura Formation; polarised light; plagioclase appears greyish pink, quartz is uncoloured; the matrix is siliceous and an incipient formation of fibrous beards is visible in the pressure shadows of the quartz grains. H Sublitharenite from the Gyrenspitz Formation; quartz dominates among the terrigenous grains, plagioclase and polycrystalline lithoclasts make up about 10% each; sparitic ferruginous cement; + Nicols. I Globotruncana linneiana in a sandstone of the Gyrenspitz Formation (pers. comm. M. Caron, Université de Fribourg, 2021). J Arkose from the Eggberg Formation, stained for carbonate under normal light; ferrous calcite cement (blue) and fibrous beards in the pressure shadows of the quartz grains. K Subarkose from the upper part of Oberälpli Formation; + Nicols. L Quartz-rich feldspathic litharenite of the Ruchberg Formation; stained for feldspar and under crossed Nicols. Quartz grains (grey to white) and plagioclase (pink) embedded in sparitic calcite cement