San Bernardino Stream

Along the San Bernardino stream there is a large cliff face where the ‘Scisti dei Laghi’ outcrop; this is a geological unit consisting mainly of mica schists derived from regional metamorphism of amphibolite facies (500–600 °C) of marine schists, likely dating from the Cambrian period.

This metamorphism, linked to a Carboniferous orogeny (the Hercynian or Variscan orogeny), has not completely obliterated the original sedimentary features (sandstone layers interbedded with clay-rich layers). The cliffs have a typically rounded morphology, due to glacial abrasion (roches moutonnées) and the presence of a number of so-called ‘giants’ kettles’.

The mineralogical composition of the rocks is dominated by quartz and micas (muscovite, biotite), with plagioclase, garnet, kyanite and staurolite. The widespread white quartz veins are typical of metamorphic rocks derived from clay-rich terrigenous sediments. Multiple stages of plastic folding can be observed (‘similar folds’, thickened at the hinges and thinned at the flanks).