An example of positive inversion. Tectonic evolution of Lagonegro Units (Central Lucanian, Italy) [Un esempio di inversione positiva. Evoluzione tettonica delle Unità Lagonegresi (Lucania Centrale, Italia)]

The Lucanian Apennines of Southern Italy are an arcuate fold- and-thrust belt developed as a result of imbrication of different tec- tonic units, namely the Ligurian, Apenninic Platform and Lagonegro Units, onto the Apulian Foreland. These tectonic units, differentiated since Triassic time, were originated in distinct palaeogeographical domains that are, from west to east: the Ligurian Basin, the Apen- ninic Carbonate Platform, the Lagonegro Basin and the Apulian Platform. Differentiation of the palaeogeographical domains was controlled by syn-sedimentary, pre-orogenic normal faults developed during the rifting stage that led to the Mesozoic Neothethys Ocean and to drifting of the African (i.e. Adria) and European continental margins. From Eocene time onwards (KNOTT, 1994) the palaeogeo- graphical domains experienced contraction related to the closure of the Neotethys Ocean and to the contraction of the Adria continental margin, with development and imbrication of the main tectonic units. Mesozoic, pre-orogenic normal faults were overprinted by Ter- tiary thrusts and related folds during this episode of positive tectonic inversion. A wide literature has long suggested that the contractional geometry and kinematic evolution of the Lagonegro Units were largely controlled by Mesozoic, pre-orogenic normal faults (MAZZOLI et alii, 2001); however, these faults have mainly been inferred from the stratigraphic variations of syn-rift Mesozoic sediments across them (BERTINELLI et alii, 2005). Indeed, surprisingly little documen- tation has been provided so far, though with rare exceptions, to con- strain the local attitude and kinematics of pre-orogenic extensional structures within the Lagonegro Units. The results of recent research carried out in Val d'Agri, in the central part of the Lucanian Apen- nines, made it possible to recognise a macroscopic, pre-orogenic normal fault, whose occurrence within the template effectively con- trolled the geometry and kinematic evolution of the subsequent con- tractional structures. It appears significant to emphasize that this history of structural inheritance during positive tectonic inversion did not involve reverse fault reactivation, as it has been assumed for this part of the Lucanian Apennines.