The overprint of the Alpine tectono-metamorphic evolution on the Hercynian orogen: an example from the Apuane Alps (Northern Apennines, Italy)

The Apuane Alps represent a tectonic window in the nappe structure of the Northern Apennines. In its lowermost part the Apuan Metamorphic Complex (i.e. "Autochthonous" Auct. and Massa Unit) reveals a polyphase structural pattern, as the result of two main Alpine events of Tertiary age. The first event is responsible for intense isoclinal folding and the development of a pervasive schistosity in greenschist facies, the second is connected with the subsequent late stage uplift. The pre-Triassic rocks in the core of the main isoclinal anticlines were severely tectonized, completely transposing a pre-existing foliation and a greenschist pre-Alpine synkinematic metamorphism, the traces of which are obvious and widespread. Hercynian structures of megascopic, mesoscopic and microscopic size are outlined here.