The Carnic Alps, the summit-ridge of which is the frontier between Austria and Italy, are famous for their Palaeozoic formations, which contain large and beautiful faunas of Ordovician, Silurian, Devonian, Upper Carboniferous, and Permian age. The Carnic Alps form a very important part of the whole Alpine region, because they display clear evidence of Palaeozoic orogenesis; for example, the Taconic orogenesis between Ordovician and Silurian (which is of relatively little importance), and some phases of the Variscan orogenesis (between Devonian and Upper Carboniferous, and between the limestone of Trogkofel, which is equivalent to the stage of Artinsk, and the Lower Permian).