The F2 folds in the Verrucano as records of extensional tectonics in the Northern Apennines (Italy)

Preliminary structural data from three localities where Verrucano sequences outcrop in the Northern Apennines (Italy) are reported. After a syn-collisional related D1 deformation phase, a D2 phase has been recognized. D2 causes prevailing recumbent symmetric folds (F2), whose geometric features imply vertical shortening and horizontal extension in NE-SW direction of steeply dipping sedimentary beds or tectonic layering, originated by the earlier D1 phase. The widespread occurrence of such structures in the outcrops of the Massa Unit of the Northern Apennines, suggests a general pure shear regime of deformation related to extensional tectonics.