Structural inheritance and style of reactivation at mid-crustal levels: A case study from the Apuane Alps (Tuscany, Italy)

Structural analyses of the geometries and strain patterns of regional-scale folds in the Alpi Apuane, northwest Tuscany, Italy, show that the analyzed structures formed at mid-crustal conditions during the Oligocene– Miocene continental subduction of the Adria distal margin, and show evidence of structural inheritance in terms of: a) minor thrusts derived from fully inverted normal faults, local examples of inversion structures and their reactivation at mid-crustal depth; b) kilometer-scale variations in facies and thickness changes in the stratigraphic successions closely related with structural positions within large scale folds; c) formation of regional recumbent folds by initiation of fold nucleation and buckling on the site of former Jurassic faults and related lateral layer heterogeneities; d) relationship between rotated fold-segments or cross-folds and the primary shape of sub-basins, its original fault segmentation and the presence of transfer zones. The overall data set underline the importance of structural heritage in shaping overall architecture and kinematic development also in the internal metamorphic zones of orogens.