The initial propagation of the Western Alpine orogen was directed
northwestward, as shown by basement-involved and Mesozoic sedimentary
cover compressional structures and by the early foreland basins
evolution. The crystalline basement of the Dauphine zone recorded three
shortening episodes: pre-Priabonian deformation D1 (coeval with the
Pyrenean-Provence orogeny), and Alpine shortening events D2 (N-NW
directed) and D3 (W-directed). The early Oligocene D2 structures are
trending sub-perpendicular to the more recent, arcuate orogen and are
interfering with (or truncated by) D3, which marks the onset of westward
lateral extrusion. The NW-ward propagating Alpine flexural basin shows
earliest Oligocene thin-skinned compressional deformation, with
syn-depositional basin-floor tilting and submarine removal of the basin
infill above active structures. Gravity enhanced submarine erosion gave
birth locally to steep submarine slopes overlain by kilometric-scale
blocks slid from the orogenic wedge. The deformations of the basin floor
and the associated sedimentary and erosional features indicate a
N-NW-ward directed propagation, consistent with D2 in the Dauphine
foreland. The Internal zones represent the paleo-accretionary prism
developed during this early Alpine continental subduction stage. The
early buildup has been curved in the arc and rapidly exhumed during the
Oligocene collision stage. Westward extrusion and indenting by the
Apulian lithosphere allowed the modern arc to crosscut the western,
lateral termination of the ancient orogen from similar to 32 Ma onward.
This contrasted evolution leads to propose a palinspastic restoration
taking in account important northward transport of the distal passive
margin fragments (Brianconnais) involved in the accretionary prism
before the formation of the Western Alps arc.