Fig. 2

a Rhyolite pebble from slump of marlstones of Morbio Formation (upper Pliensbachian) in Rosso Ammonitico Lombardo (Toarcian), Molinello, Arzo, scale bar: 8 mm; b rhyolite pebble from the Molino Member, Pliensbachian, Val Molinaccio, Varese, polished surface, scale bar: 1 cm; c quartzite pebble, Rosso Ammonitico Lombardo (Toarcian), Molinello, Arzo; d Rounded and angular clasts of rhyolite in matrix of crinoidal lime grainstone, Broccatello Formation, Sinemurian, Gozzano; the Liassic Gozzano High where the Broccatelo Formation unconformably overlies the Permian rhyolite succession is the probable source area of the dropstones, scale bar: 2 cm; e. Wood fragment, Rosso Ammonitico Lombardo (Toarcian), ancient cement factory, Ponte Chiasso, scale bar: 2 cm; f. Thin-section of e showing the well-preserved wood texture, Nicols parallel