| In the Bergamasc Alps we have observed one major unconformity between the Basement rock and the overlying Permian. The total absence of any recognisable Palaeozoic sedimentary rocks accentuates this unconformity, and moreover this enormous hiatus makes the dating of any Palaeozoic event impossible. However, by comparison with the Central Alps and Kärnten, we learned that the Asturian orogenitic phase precedes the deposition of the first volcanic sediments. In analogy with the Aar and Gotthard masses we presumed the intrusion of the less metamorphic ortho rocks of the Basement, the granodiorite and the gneiss chiaro, to be of Upper Carboniferous age. The close resemblance of the chemical composition and differentiation of the Permian volcanic rocks and the... |
