Slabs with inverted sedimentary sequences are present in the chaotic terranes (argille scagliose) of the Apennines. Previous investigators suggested that the inversion of the sequences took place during the gravity sliding of the argille scagliose. The working hypothesis presented herein postulates two episodes of deformation. Recumbent folds were formed during the early Tertiary. The inverted slabs originally were a part of the inverted limb of the folds. An erosional interval ensued, during which erosion removed the upper limbs of some recumbent folds. Late Tertiary deformation was characterized by more pervasive shearing, i.e., the land-slipping movement. The previously formed recumbent folds were fragmented during this movement. Large fragments of the limbs of the fol s are now preserved as slabs enclosed by the argille scagliose. Slabs which originally constituted the inverted limb contain thus only inverted sedimentary sequences; other slabs contain only normal sequences.

Geologic observations of the Monghidoro region in North Tuscany clearly indicate two episodes of deformation separated by an erosional interval. The early Tertiary recumbent folding hypothesis also helps clarify the geologic interpretations of East Liguria.