strati.ch - Lexique lithostratigraphique de la Suisse

Représentation et statut

Variantes historiques: kalkig-tonige Bündnerschieferserie des oberen Val Antabbia N Pianascione (Günthert 1958), Pianasciom calcschist (Matasci et al. 2011 p.264)

Unités sus-jacentes

Définition: Matasci Battista, Epard Jean-Luc, Masson Henri (2011) : The Teggiolo zone: a key to the Helvetic–Penninic connection (stratigraphy and tectonics in the Val Bavona, Ticino, Central Alps). Swiss J. Geosci. 104, 257–283

p.264: 3.4.3 The Pianasciom calcschist

This formation is characterized by thick layers of calcschists rich in large blasts of plagioclase that give them a very typical ‘‘bumpy’’ appearance. Its basal contact with the Piano delle Creste sandstone is transitional. Thinner layers of various sandstones and more rarely of limestones are intercalated. Near the top it can also contain intercalations of micaschists with blasts of plagioclase, garnet and locally amphibole. The mineralogy of these rocks has been studied in detail by Allaz (2008) who calculated peak metamorphic conditions around T = 570C and P = 7 kb, presumably 20–22 Ma ago. This formation forms large outcrops on the Pianasciom shelf in Val Antabia that we choose as type locality. It becomes much thinner at Campo and for this reason has been omitted on Figs. 2 and 10. It also seems to vanish on the Italian side of the Kalberhorn (pt. 2805 on the boundary crest).