Pre-collisional architecture of the European distal margin: Inferences from the high-pressure continental units of central Corsica (France)

The Lower Units of Alpine Corsica, France, are fragments of continental crust strongly deformed and metamorphosed under high-pressure metamorphic conditions. Three slices of Lower Units are well exposed in the area between the Asco and Tavignano valleys, Central Corsica. Despite their complex structural setting, they provide the opportunity for a reconstruction of the pristine stratigraphic setting of the Lower Units. In our reconstruction, these units consist of a Paleozoic basement topped by Triassic to Early Jurassic sedimentary rocks unconformably covered by Middle to Late Eocene foredeep deposits. However, the three units exposed in the study area display strong differences mainly in the thickness of the Mesozoic sequence. These differences are here interpreted as acquired during the first stage of the rifting process in a setting controlled by normal faults. During the collision-related tectonics and the accretion of the Lower Units to the Alpine orogenic wedge, these normal faults were probably reactivated with a reverse kinematics. The stratigraphic logs of the Lower Units strictly resemble those of the Pre-Piedmont Units from Western Alps. This similarity indicates a common origin of the Lower Units and the Pre-Piedmont Units from the same domain (i.e., the European distal continental margin).