Fig. 4

a–f Thin-section micrographs of Permian volcanic clasts in the Broccatello Formation, Sinemurian, Gozzano. a, b The rhyolithe sample, displaying subhedral quartz (qtz) and sanidine (san) in a devitrified felsitic matrix with fluidal texture, some volcanic lithic clasts (lithic), subordinate plagioclase phenocrysts, and variably altered biotite (bio) compares well with the rhyolite dropstone from Val Molinaccio (Sample 3, Fig. 3c, d). Small amounts of secondary calcite (cc) occur in the matrix. c, d Rhyolitic clasts cemented by sparry calcite (cc). The clasts are composed of subhedral quartz (qtz) and sanidine (san) with minor, partly altered biotite (bio and ex-bio). The very fine-grained, devitrified matrix shows some fluidal texture and minor welding. e, f The rhyolite clast with subhedral clear quartz (qtz) with embayments, simply twinned alkalifeldspar (Ak-fsp) and very minor and strongly altered plagioclase (plg) compares well with the rhyolite clast from Arzo (Sample 1, Fig. 3a, b). The clasts are set in a matrix of bioclastic lime grainstone. a, c, e Nicols parallel; b, d, f Nicols crossed