Geological pecularities
Among the rocks and faults of the Alps
The Morobbia Valley is set along the contact between the root zone of the Central Alps and the crystalline basement of the Southern Alps, marked by a major fault with a highly inclined plane and oriented east-west: the Insubric Line. This structure extends from Valtellina to Piedmont and was formed from the Oligo-Miocene 25 million years ago (Ma), along which a lateral slip of more than 60 km has been recognized.
North of the Insubric Line, on the right bank of the Morobbia Valley, is the Tonale Zone and the Melirolo Gneisses, the latter derived from rocks of the Bergell (30 Ma), deformed due to movements along the fault. Immediately south of the Insubric Line are lenses of unmetamorphized Triassic dolomite (225 to 180 ma). The southern flank of the Morobbia Valley is entirely set in the Crystalline Sluice of the Southern Alps (Strona Ceneri Zone), which consists of gneisses, micaschists and basic rocks, Paleozoic in age (2500 - 300 ma). Iron-containing "veins" affect only the left side of the Valley and belong to the vast mining district that includes Dongo and Val Cavargna in Italy and some neighboring valleys in Ticino.
