Kinematics of the Helminthoid Flysch–Marguareis Unit tectonic coupling: consequences for the tectonic evolution of Western Ligurian Alps

Abstract

We investigated the kinematics of the coupled Helminthoid Flysch–Marguareis Unit outcropping in the High Tanaro Valley in order to constraint the tectonic evolution of the Western Ligurian Alps. Field mapping highlights a tectonic pile composed of, from top to bottom: the Marguareis Unit (Briançonnais Domain); the Helminthoid Flysch Unit (Ligurian Domain) and several continental-derived tectonic slices (Chambeuil Slices) showing affinity to the Briançonnais Domain. Each unit recorded different deformation histories represented by pre-, syn- and post-stacking structures. The syn-stacking structures are represented by thrusts and folds, both responsible for the coupling of the units and for their current structural relationships. In other sectors of the Alpine chain previous authors have highlighted similar structural architectures. We maintain that syn-stacking deformation events played a key role in the tectonic evolution of the Western Ligurian Alps.

Keywords

• Ligurian Alps
• Kinematics
• Tectonic evolution
• Low-grade units
• Late Eocene
• Early Oligocene
• Ligurian Alps