Bündner schist

Alps portal The Bündner schist or Bündner slate (German: Bündnerschiefer; French: schistes lustrés) is a collective name for schistose rocks that form a number of geologic formations in the Penninic nappes of the Alps.

Bündner schists were originally marine sediments that underwent metamorphism at large depths.

They formed a kilometers thick monotonous layer of dark clays, marbles and sandy limestones.

The resulting metamorphism and deformation turned them into calcareous phyllites and schists, strongly foliated rocks rich in micas.

The Bündner schists can be found throughout the Penninic zone of the Alps, often forming zones of high strain between or large infolded synclines (so called Mulde or Mulden) in the crystalline nappes that are made of more competent gneiss.