Tectonic setting of the Tuscan Nappe in the Turrite Cava valley, southeastern Alpi Apuane

In the Alpi Apuane region, the Tuscan Nappe is the lowermost tectonic unit in the tectonic cover on the Alpi Apuane Metamorphic Complex (Apuane Unit + Massa Unit), being in turn overthrust by the Subliguride and Liguride Units. Such a large scale structure resulted from the Tertiary orogenesis, that developed through a syn- to post-collisional compressive regime responsible for the stacking of all the tectonic units, and a successive extensional tectonics leading to a regional-wide uplift. To improve the knowledge of this evolution in the Alpi Apuane region, this paper describes the polydeformed structural setting of the Tuscan Nappe along the Turrite Cava valley in the southeastern Alpi Apuane. The analysis of this area confirms that both the two deformation events affected intensely the Tuscan Nappe: - the compressional tectonics developed a S1 foliation, mainly recognisable in the pelite-rich lithotypes of the sequence, and some, variably important tectonic laminations along the relatively more ductil sedimentary levels. The S1 foliation appears to be unrelated with a well formed fold structure, nevertheless the angular relationships between bedding and S1 foliation indicate the east-northeastward tectonic motion of this deformation event; - the extensional tectonics produced (1) east-northeast folding of the previous setting and reactivation of some tectonic surfaces as low-angle normal faults; (2) nucleation and development of dome -like kilometric structures; and (3) a final system of high angle normal faults. The general features of this tectonic framework recall those of the underlying Alpi Apuane Metamorphic Complex, apart from obvious differences linked to the diverse structural levels at which the two tectonic bodies experienced their Tertiaty tectono-metamorphic history.